"""
shapefile.py
Provides read and write support for ESRI Shapefiles.
authors: jlawhead<at>geospatialpython.com
maintainer: karim.bahgat.norway<at>gmail.com
version: 2.2.0
Compatible with Python versions 2.7-3.x
"""

__version__ = "2.2.0"

from struct import pack, unpack, calcsize, error, Struct
import os
import sys
import time
import array
import tempfile
import logging
import io
from datetime import date
import zipfile


# Module settings
VERBOSE = True

# Constants for shape types
NULL = 0
POINT = 1
POLYLINE = 3
POLYGON = 5
MULTIPOINT = 8
POINTZ = 11
POLYLINEZ = 13
POLYGONZ = 15
MULTIPOINTZ = 18
POINTM = 21
POLYLINEM = 23
POLYGONM = 25
MULTIPOINTM = 28
MULTIPATCH = 31

SHAPETYPE_LOOKUP = {
    0: 'NULL',
    1: 'POINT',
    3: 'POLYLINE',
    5: 'POLYGON',
    8: 'MULTIPOINT',
    11: 'POINTZ',
    13: 'POLYLINEZ',
    15: 'POLYGONZ',
    18: 'MULTIPOINTZ',
    21: 'POINTM',
    23: 'POLYLINEM',
    25: 'POLYGONM',
    28: 'MULTIPOINTM',
    31: 'MULTIPATCH'}

TRIANGLE_STRIP = 0
TRIANGLE_FAN = 1
OUTER_RING = 2
INNER_RING = 3
FIRST_RING = 4
RING = 5

PARTTYPE_LOOKUP = {
    0: 'TRIANGLE_STRIP',
    1: 'TRIANGLE_FAN',
    2: 'OUTER_RING',
    3: 'INNER_RING',
    4: 'FIRST_RING',
    5: 'RING'}


# Python 2-3 handling

PYTHON3 = sys.version_info[0] == 3

if PYTHON3:
    xrange = range
    izip = zip

    from urllib.parse import urlparse, urlunparse
    from urllib.error import HTTPError
    from urllib.request import urlopen, Request
    
else:
    from itertools import izip

    from urlparse import urlparse, urlunparse
    from urllib2 import HTTPError
    from urllib2 import urlopen, Request


# Helpers

MISSING = [None,'']
NODATA = -10e38 # as per the ESRI shapefile spec, only used for m-values. 

if PYTHON3:
    def b(v, encoding='utf-8', encodingErrors='strict'):
        if isinstance(v, str):
            # For python 3 encode str to bytes.
            return v.encode(encoding, encodingErrors)
        elif isinstance(v, bytes):
            # Already bytes.
            return v
        elif v is None:
            # Since we're dealing with text, interpret None as ""
            return b""
        else:
            # Force string representation.
            return str(v).encode(encoding, encodingErrors)

    def u(v, encoding='utf-8', encodingErrors='strict'):
        if isinstance(v, bytes):
            # For python 3 decode bytes to str.
            return v.decode(encoding, encodingErrors)
        elif isinstance(v, str):
            # Already str.
            return v
        elif v is None:
            # Since we're dealing with text, interpret None as ""
            return ""
        else:
            # Force string representation.
            return bytes(v).decode(encoding, encodingErrors)

    def is_string(v):
        return isinstance(v, str)

else:
    def b(v, encoding='utf-8', encodingErrors='strict'):
        if isinstance(v, unicode):
            # For python 2 encode unicode to bytes.
            return v.encode(encoding, encodingErrors)
        elif isinstance(v, bytes):
            # Already bytes.
            return v
        elif v is None:
            # Since we're dealing with text, interpret None as ""
            return ""
        else:
            # Force string representation.
            return unicode(v).encode(encoding, encodingErrors)

    def u(v, encoding='utf-8', encodingErrors='strict'):
        if isinstance(v, bytes):
            # For python 2 decode bytes to unicode.
            return v.decode(encoding, encodingErrors)
        elif isinstance(v, unicode):
            # Already unicode.
            return v
        elif v is None:
            # Since we're dealing with text, interpret None as ""
            return u""
        else:
            # Force string representation.
            return bytes(v).decode(encoding, encodingErrors)

    def is_string(v):
        return isinstance(v, basestring)


# Begin

class _Array(array.array):
    """Converts python tuples to lists of the appropriate type.
    Used to unpack different shapefile header parts."""
    def __repr__(self):
        return str(self.tolist())

def signed_area(coords, fast=False):
    """Return the signed area enclosed by a ring using the linear time
    algorithm. A value >= 0 indicates a counter-clockwise oriented ring.
    A faster version is possible by setting 'fast' to True, which returns
    2x the area, e.g. if you're only interested in the sign of the area.
    """
    xs, ys = map(list, list(zip(*coords))[:2]) # ignore any z or m values
    xs.append(xs[1])
    ys.append(ys[1])
    area2 = sum(xs[i]*(ys[i+1]-ys[i-1]) for i in range(1, len(coords)))
    if fast:
        return area2
    else:
        return area2 / 2.0

def is_cw(coords):
    """Returns True if a polygon ring has clockwise orientation, determined
    by a negatively signed area. 
    """
    area2 = signed_area(coords, fast=True)
    return area2 < 0

def rewind(coords):
    """Returns the input coords in reversed order.
    """
    return list(reversed(coords))

def ring_bbox(coords):
    """Calculates and returns the bounding box of a ring.
    """
    xs,ys = zip(*coords)
    bbox = min(xs),min(ys),max(xs),max(ys)
    return bbox

def bbox_overlap(bbox1, bbox2):
    """Tests whether two bounding boxes overlap, returning a boolean
    """
    xmin1,ymin1,xmax1,ymax1 = bbox1
    xmin2,ymin2,xmax2,ymax2 = bbox2
    overlap = (xmin1 <= xmax2 and xmax1 >= xmin2 and ymin1 <= ymax2 and ymax1 >= ymin2)
    return overlap

def bbox_contains(bbox1, bbox2):
    """Tests whether bbox1 fully contains bbox2, returning a boolean
    """
    xmin1,ymin1,xmax1,ymax1 = bbox1
    xmin2,ymin2,xmax2,ymax2 = bbox2
    contains = (xmin1 < xmin2 and xmax1 > xmax2 and ymin1 < ymin2 and ymax1 > ymax2)
    return contains

def ring_contains_point(coords, p):
    """Fast point-in-polygon crossings algorithm, MacMartin optimization.

    Adapted from code by Eric Haynes
    http://www.realtimerendering.com/resources/GraphicsGems//gemsiv/ptpoly_haines/ptinpoly.c
    
    Original description:
        Shoot a test ray along +X axis.  The strategy, from MacMartin, is to
        compare vertex Y values to the testing point's Y and quickly discard
        edges which are entirely to one side of the test ray.
    """
    tx,ty = p

    # get initial test bit for above/below X axis
    vtx0 = coords[0]
    yflag0 = ( vtx0[1] >= ty )

    inside_flag = False
    for vtx1 in coords[1:]: 
        yflag1 = ( vtx1[1] >= ty )
        # check if endpoints straddle (are on opposite sides) of X axis
        # (i.e. the Y's differ); if so, +X ray could intersect this edge.
        if yflag0 != yflag1: 
            xflag0 = ( vtx0[0] >= tx )
            # check if endpoints are on same side of the Y axis (i.e. X's
            # are the same); if so, it's easy to test if edge hits or misses.
            if xflag0 == ( vtx1[0] >= tx ):
                # if edge's X values both right of the point, must hit
                if xflag0:
                    inside_flag = not inside_flag
            else:
                # compute intersection of pgon segment with +X ray, note
                # if >= point's X; if so, the ray hits it.
                if ( vtx1[0] - (vtx1[1]-ty) * ( vtx0[0]-vtx1[0]) / (vtx0[1]-vtx1[1]) ) >= tx:
                    inside_flag = not inside_flag

        # move to next pair of vertices, retaining info as possible
        yflag0 = yflag1
        vtx0 = vtx1

    return inside_flag

def ring_sample(coords, ccw=False):
    """Return a sample point guaranteed to be within a ring, by efficiently
    finding the first centroid of a coordinate triplet whose orientation
    matches the orientation of the ring and passes the point-in-ring test.
    The orientation of the ring is assumed to be clockwise, unless ccw
    (counter-clockwise) is set to True. 
    """
    triplet = []
    def itercoords():
        # iterate full closed ring
        for p in coords:
            yield p
        # finally, yield the second coordinate to the end to allow checking the last triplet
        yield coords[1]
        
    for p in itercoords(): 
        # add point to triplet (but not if duplicate)
        if p not in triplet:
            triplet.append(p)
            
        # new triplet, try to get sample
        if len(triplet) == 3:
            # check that triplet does not form a straight line (not a triangle)
            is_straight_line = (triplet[0][1] - triplet[1][1]) * (triplet[0][0] - triplet[2][0]) == (triplet[0][1] - triplet[2][1]) * (triplet[0][0] - triplet[1][0])
            if not is_straight_line:
                # get triplet orientation
                closed_triplet = triplet + [triplet[0]]
                triplet_ccw = not is_cw(closed_triplet)
                # check that triplet has the same orientation as the ring (means triangle is inside the ring)
                if ccw == triplet_ccw:
                    # get triplet centroid
                    xs,ys = zip(*triplet)
                    xmean,ymean = sum(xs) / 3.0, sum(ys) / 3.0
                    # check that triplet centroid is truly inside the ring
                    if ring_contains_point(coords, (xmean,ymean)):
                        return xmean,ymean

            # failed to get sample point from this triplet
            # remove oldest triplet coord to allow iterating to next triplet
            triplet.pop(0)
            
    else:
        raise Exception('Unexpected error: Unable to find a ring sample point.')

def ring_contains_ring(coords1, coords2):
    '''Returns True if all vertexes in coords2 are fully inside coords1.
    '''
    return all((ring_contains_point(coords1, p2) for p2 in coords2))

def organize_polygon_rings(rings, return_errors=None):
    '''Organize a list of coordinate rings into one or more polygons with holes.
    Returns a list of polygons, where each polygon is composed of a single exterior
    ring, and one or more interior holes. If a return_errors dict is provided (optional), 
    any errors encountered will be added to it. 

    Rings must be closed, and cannot intersect each other (non-self-intersecting polygon).
    Rings are determined as exteriors if they run in clockwise direction, or interior
    holes if they run in counter-clockwise direction. This method is used to construct
    GeoJSON (multi)polygons from the shapefile polygon shape type, which does not
    explicitly store the structure of the polygons beyond exterior/interior ring orientation. 
    '''
    # first iterate rings and classify as exterior or hole
    exteriors = []
    holes = []
    for ring in rings:
        # shapefile format defines a polygon as a sequence of rings
        # where exterior rings are clockwise, and holes counterclockwise
        if is_cw(ring):
            # ring is exterior
            ring = rewind(ring) # GeoJSON and Shapefile exteriors have opposite orientation
            exteriors.append(ring)
        else:
            # ring is a hole
            ring = rewind(ring) # GeoJSON and Shapefile holes have opposite orientation
            holes.append(ring)
                
    # if only one exterior, then all holes belong to that exterior
    if len(exteriors) == 1:
        # exit early
        poly = [exteriors[0]] + holes
        polys = [poly]
        return polys

    # multiple exteriors, ie multi-polygon, have to group holes with correct exterior
    # shapefile format does not specify which holes belong to which exteriors
    # so have to do efficient multi-stage checking of hole-to-exterior containment
    elif len(exteriors) > 1:
        # exit early if no holes
        if not holes:
            polys = []
            for ext in exteriors:
                poly = [ext]
                polys.append(poly)
            return polys
        
        # first determine each hole's candidate exteriors based on simple bbox contains test
        hole_exteriors = dict([(hole_i,[]) for hole_i in xrange(len(holes))])
        exterior_bboxes = [ring_bbox(ring) for ring in exteriors]
        for hole_i in hole_exteriors.keys():
            hole_bbox = ring_bbox(holes[hole_i])
            for ext_i,ext_bbox in enumerate(exterior_bboxes):
                if bbox_contains(ext_bbox, hole_bbox):
                    hole_exteriors[hole_i].append( ext_i )

        # then, for holes with still more than one possible exterior, do more detailed hole-in-ring test
        for hole_i,exterior_candidates in hole_exteriors.items():
            
            if len(exterior_candidates) > 1:
                # get hole sample point
                # Note: all rings now follow GeoJSON orientation, i.e. holes are clockwise
                hole_sample = ring_sample(holes[hole_i], ccw=False)
                # collect new exterior candidates
                new_exterior_candidates = []
                for ext_i in exterior_candidates:
                    # check that hole sample point is inside exterior
                    hole_in_exterior = ring_contains_point(exteriors[ext_i], hole_sample)
                    if hole_in_exterior:
                        new_exterior_candidates.append(ext_i)

                # set new exterior candidates
                hole_exteriors[hole_i] = new_exterior_candidates

        # if still holes with more than one possible exterior, means we have an exterior hole nested inside another exterior's hole
        for hole_i,exterior_candidates in hole_exteriors.items():
            
            if len(exterior_candidates) > 1:
                # exterior candidate with the smallest area is the hole's most immediate parent
                ext_i = sorted(exterior_candidates, key=lambda x: abs(signed_area(exteriors[x], fast=True)))[0]
                hole_exteriors[hole_i] = [ext_i]

        # separate out holes that are orphaned (not contained by any exterior)
        orphan_holes = []
        for hole_i,exterior_candidates in list(hole_exteriors.items()):
            if not exterior_candidates:
                orphan_holes.append( hole_i )
                del hole_exteriors[hole_i]
                continue

        # each hole should now only belong to one exterior, group into exterior-holes polygons
        polys = []
        for ext_i,ext in enumerate(exteriors):
            poly = [ext]
            # find relevant holes
            poly_holes = []
            for hole_i,exterior_candidates in list(hole_exteriors.items()):
                # hole is relevant if previously matched with this exterior
                if exterior_candidates[0] == ext_i:
                    poly_holes.append( holes[hole_i] )
            poly += poly_holes
            polys.append(poly)

        # add orphan holes as exteriors
        for hole_i in orphan_holes:
            ext = holes[hole_i]
            # since this was previously a clockwise ordered hole, inverse the winding order
            ext = rewind(ext)
            # add as single exterior without any holes
            poly = [ext]
            polys.append(poly)

        if orphan_holes and return_errors is not None:
            return_errors['polygon_orphaned_holes'] = len(orphan_holes)

        return polys

    # no exteriors, be nice and assume due to incorrect winding order
    else:
        if return_errors is not None:
            return_errors['polygon_only_holes'] = len(holes)
        exteriors = holes
        # since these were previously clockwise ordered holes, inverse the winding order
        exteriors = [rewind(ext) for ext in exteriors]
        # add as single exterior without any holes
        polys = [[ext] for ext in exteriors]
        return polys

class Shape(object):
    def __init__(self, shapeType=NULL, points=None, parts=None, partTypes=None, oid=None):
        """Stores the geometry of the different shape types
        specified in the Shapefile spec. Shape types are
        usually point, polyline, or polygons. Every shape type
        except the "Null" type contains points at some level for
        example vertices in a polygon. If a shape type has
        multiple shapes containing points within a single
        geometry record then those shapes are called parts. Parts
        are designated by their starting index in geometry record's
        list of shapes. For MultiPatch geometry, partTypes designates
        the patch type of each of the parts. 
        """
        self.shapeType = shapeType
        self.points = points or []
        self.parts = parts or []
        if partTypes:
            self.partTypes = partTypes
        
        # and a dict to silently record any errors encountered
        self._errors = {}
        
        # add oid
        if oid is not None:
            self.__oid = oid
        else:
            self.__oid = -1

    @property
    def __geo_interface__(self):
        if self.shapeType in [POINT, POINTM, POINTZ]:
            # point
            if len(self.points) == 0:
                # the shape has no coordinate information, i.e. is 'empty'
                # the geojson spec does not define a proper null-geometry type
                # however, it does allow geometry types with 'empty' coordinates to be interpreted as null-geometries
                return {'type':'Point', 'coordinates':tuple()}
            else:
                return {
                'type': 'Point',
                'coordinates': tuple(self.points[0])
                }
        elif self.shapeType in [MULTIPOINT, MULTIPOINTM, MULTIPOINTZ]:
            if len(self.points) == 0:
                # the shape has no coordinate information, i.e. is 'empty'
                # the geojson spec does not define a proper null-geometry type
                # however, it does allow geometry types with 'empty' coordinates to be interpreted as null-geometries
                return {'type':'MultiPoint', 'coordinates':[]}
            else:
                # multipoint
                return {
                'type': 'MultiPoint',
                'coordinates': [tuple(p) for p in self.points]
                }
        elif self.shapeType in [POLYLINE, POLYLINEM, POLYLINEZ]:
            if len(self.parts) == 0:
                # the shape has no coordinate information, i.e. is 'empty'
                # the geojson spec does not define a proper null-geometry type
                # however, it does allow geometry types with 'empty' coordinates to be interpreted as null-geometries
                return {'type':'LineString', 'coordinates':[]}
            elif len(self.parts) == 1:
                # linestring
                return {
                'type': 'LineString',
                'coordinates': [tuple(p) for p in self.points]
                }
            else:
                # multilinestring
                ps = None
                coordinates = []
                for part in self.parts:
                    if ps == None:
                        ps = part
                        continue
                    else:
                        coordinates.append([tuple(p) for p in self.points[ps:part]])
                        ps = part
                else:
                    coordinates.append([tuple(p) for p in self.points[part:]])
                return {
                'type': 'MultiLineString',
                'coordinates': coordinates
                }
        elif self.shapeType in [POLYGON, POLYGONM, POLYGONZ]:
            if len(self.parts) == 0:
                # the shape has no coordinate information, i.e. is 'empty'
                # the geojson spec does not define a proper null-geometry type
                # however, it does allow geometry types with 'empty' coordinates to be interpreted as null-geometries
                return {'type':'Polygon', 'coordinates':[]}
            else:
                # get all polygon rings
                rings = []
                for i in xrange(len(self.parts)):
                    # get indexes of start and end points of the ring
                    start = self.parts[i]
                    try:
                        end = self.parts[i+1]
                    except IndexError:
                        end = len(self.points)

                    # extract the points that make up the ring
                    ring = [tuple(p) for p in self.points[start:end]]
                    rings.append(ring)

                # organize rings into list of polygons, where each polygon is defined as list of rings.
                # the first ring is the exterior and any remaining rings are holes (same as GeoJSON). 
                polys = organize_polygon_rings(rings, self._errors)
                
                # if VERBOSE is True, issue detailed warning about any shape errors
                # encountered during the Shapefile to GeoJSON conversion
                if VERBOSE and self._errors: 
                    header = 'Possible issue encountered when converting Shape #{} to GeoJSON: '.format(self.oid)
                    orphans = self._errors.get('polygon_orphaned_holes', None)
                    if orphans:
                        msg = header + 'Shapefile format requires that all polygon interior holes be contained by an exterior ring, \
but the Shape contained interior holes (defined by counter-clockwise orientation in the shapefile format) that were \
orphaned, i.e. not contained by any exterior rings. The rings were still included but were \
encoded as GeoJSON exterior rings instead of holes.'
                        logging.warning(msg)
                    only_holes = self._errors.get('polygon_only_holes', None)
                    if only_holes:
                        msg = header + 'Shapefile format requires that polygons contain at least one exterior ring, \
but the Shape was entirely made up of interior holes (defined by counter-clockwise orientation in the shapefile format). The rings were \
still included but were encoded as GeoJSON exterior rings instead of holes.'
                        logging.warning(msg)

                # return as geojson
                if len(polys) == 1:
                    return {
                    'type': 'Polygon',
                    'coordinates': polys[0]
                    }
                else:
                    return {
                    'type': 'MultiPolygon',
                    'coordinates': polys
                    }

        else:
            raise Exception('Shape type "%s" cannot be represented as GeoJSON.' % SHAPETYPE_LOOKUP[self.shapeType])

    @staticmethod
    def _from_geojson(geoj):
        # create empty shape
        shape = Shape()
        # set shapeType
        geojType = geoj["type"] if geoj else "Null"
        if geojType == "Null":
            shapeType = NULL
        elif geojType == "Point":
            shapeType = POINT
        elif geojType == "LineString":
            shapeType = POLYLINE
        elif geojType == "Polygon":
            shapeType = POLYGON
        elif geojType == "MultiPoint":
            shapeType = MULTIPOINT
        elif geojType == "MultiLineString":
            shapeType = POLYLINE
        elif geojType == "MultiPolygon":
            shapeType = POLYGON
        else:
            raise Exception("Cannot create Shape from GeoJSON type '%s'" % geojType)
        shape.shapeType = shapeType
        
        # set points and parts
        if geojType == "Point":
            shape.points = [ geoj["coordinates"] ]
            shape.parts = [0]
        elif geojType in ("MultiPoint","LineString"):
            shape.points = geoj["coordinates"]
            shape.parts = [0]
        elif geojType in ("Polygon"):
            points = []
            parts = []
            index = 0
            for i,ext_or_hole in enumerate(geoj["coordinates"]):
                # although the latest GeoJSON spec states that exterior rings should have 
                # counter-clockwise orientation, we explicitly check orientation since older 
                # GeoJSONs might not enforce this. 
                if i == 0 and not is_cw(ext_or_hole):
                    # flip exterior direction
                    ext_or_hole = rewind(ext_or_hole)
                elif i > 0 and is_cw(ext_or_hole):
                    # flip hole direction
                    ext_or_hole = rewind(ext_or_hole)
                points.extend(ext_or_hole)
                parts.append(index)
                index += len(ext_or_hole)
            shape.points = points
            shape.parts = parts
        elif geojType in ("MultiLineString"):
            points = []
            parts = []
            index = 0
            for linestring in geoj["coordinates"]:
                points.extend(linestring)
                parts.append(index)
                index += len(linestring)
            shape.points = points
            shape.parts = parts
        elif geojType in ("MultiPolygon"):
            points = []
            parts = []
            index = 0
            for polygon in geoj["coordinates"]:
                for i,ext_or_hole in enumerate(polygon):
                    # although the latest GeoJSON spec states that exterior rings should have 
                    # counter-clockwise orientation, we explicitly check orientation since older 
                    # GeoJSONs might not enforce this. 
                    if i == 0 and not is_cw(ext_or_hole):
                        # flip exterior direction
                        ext_or_hole = rewind(ext_or_hole)
                    elif i > 0 and is_cw(ext_or_hole):
                        # flip hole direction
                        ext_or_hole = rewind(ext_or_hole)
                    points.extend(ext_or_hole)
                    parts.append(index)
                    index += len(ext_or_hole)
            shape.points = points
            shape.parts = parts
        return shape

    @property
    def oid(self):
        """The index position of the shape in the original shapefile"""
        return self.__oid

    @property
    def shapeTypeName(self):
        return SHAPETYPE_LOOKUP[self.shapeType]

    def __repr__(self):
        return 'Shape #{}: {}'.format(self.__oid, self.shapeTypeName)

class _Record(list):
    """
    A class to hold a record. Subclasses list to ensure compatibility with
    former work and to reuse all the optimizations of the builtin list.
    In addition to the list interface, the values of the record
    can also be retrieved using the field's name. For example if the dbf contains
    a field ID at position 0, the ID can be retrieved with the position, the field name
    as a key, or the field name as an attribute.

    >>> # Create a Record with one field, normally the record is created by the Reader class
    >>> r = _Record({'ID': 0}, [0])
    >>> print(r[0])
    >>> print(r['ID'])
    >>> print(r.ID)
    """

    def __init__(self, field_positions, values, oid=None):
        """
        A Record should be created by the Reader class

        :param field_positions: A dict mapping field names to field positions
        :param values: A sequence of values
        :param oid: The object id, an int (optional)
        """
        self.__field_positions = field_positions
        if oid is not None:
            self.__oid = oid
        else:
            self.__oid = -1
        list.__init__(self, values)

    def __getattr__(self, item):
        """
        __getattr__ is called if an attribute is used that does
        not exist in the normal sense. For example r=Record(...), r.ID
        calls r.__getattr__('ID'), but r.index(5) calls list.index(r, 5)
        :param item: The field name, used as attribute
        :return: Value of the field
        :raises: AttributeError, if item is not a field of the shapefile
                and IndexError, if the field exists but the field's 
                corresponding value in the Record does not exist
        """
        try:
            index = self.__field_positions[item]
            return list.__getitem__(self, index)
        except KeyError:
            raise AttributeError('{} is not a field name'.format(item))
        except IndexError:
            raise IndexError('{} found as a field but not enough values available.'.format(item))

    def __setattr__(self, key, value):
        """
        Sets a value of a field attribute
        :param key: The field name
        :param value: the value of that field
        :return: None
        :raises: AttributeError, if key is not a field of the shapefile
        """
        if key.startswith('_'):  # Prevent infinite loop when setting mangled attribute
            return list.__setattr__(self, key, value)
        try:
            index = self.__field_positions[key]
            return list.__setitem__(self, index, value)
        except KeyError:
            raise AttributeError('{} is not a field name'.format(key))

    def __getitem__(self, item):
        """
        Extends the normal list item access with
        access using a fieldname

        For example r['ID'], r[0]
        :param item: Either the position of the value or the name of a field
        :return: the value of the field
        """
        try:
            return list.__getitem__(self, item)
        except TypeError:
            try:
                index = self.__field_positions[item]
            except KeyError:
                index = None
        if index is not None:
            return list.__getitem__(self, index)
        else:
            raise IndexError('"{}" is not a field name and not an int'.format(item))

    def __setitem__(self, key, value):
        """
        Extends the normal list item access with
        access using a fieldname

        For example r['ID']=2, r[0]=2
        :param key: Either the position of the value or the name of a field
        :param value: the new value of the field
        """
        try:
            return list.__setitem__(self, key, value)
        except TypeError:
            index = self.__field_positions.get(key)
            if index is not None:
                return list.__setitem__(self, index, value)
            else:
                raise IndexError('{} is not a field name and not an int'.format(key))

    @property
    def oid(self):
        """The index position of the record in the original shapefile"""
        return self.__oid

    def as_dict(self, date_strings=False):
        """
        Returns this Record as a dictionary using the field names as keys
        :return: dict
        """
        dct = dict((f, self[i]) for f, i in self.__field_positions.items())
        if date_strings:
            for k,v in dct.items():
                if isinstance(v, date):
                    dct[k] = '{:04d}{:02d}{:02d}'.format(v.year, v.month, v.day)
        return dct

    def __repr__(self):
        return 'Record #{}: {}'.format(self.__oid, list(self))

    def __dir__(self):
        """
        Helps to show the field names in an interactive environment like IPython.
        See: http://ipython.readthedocs.io/en/stable/config/integrating.html

        :return: List of method names and fields
        """
        default = list(dir(type(self))) # default list methods and attributes of this class
        fnames = list(self.__field_positions.keys()) # plus field names (random order if Python version < 3.6)
        return default + fnames 
        
class ShapeRecord(object):
    """A ShapeRecord object containing a shape along with its attributes.
    Provides the GeoJSON __geo_interface__ to return a Feature dictionary."""
    def __init__(self, shape=None, record=None):
        self.shape = shape
        self.record = record

    @property
    def __geo_interface__(self):
        return {'type': 'Feature',
                'properties': self.record.as_dict(date_strings=True),
                'geometry': None if self.shape.shapeType == NULL else self.shape.__geo_interface__}

class Shapes(list):
    """A class to hold a list of Shape objects. Subclasses list to ensure compatibility with
    former work and to reuse all the optimizations of the builtin list.
    In addition to the list interface, this also provides the GeoJSON __geo_interface__
    to return a GeometryCollection dictionary."""

    def __repr__(self):
        return 'Shapes: {}'.format(list(self))

    @property
    def __geo_interface__(self):
        # Note: currently this will fail if any of the shapes are null-geometries
        # could be fixed by storing the shapefile shapeType upon init, returning geojson type with empty coords
        collection = {'type': 'GeometryCollection',
                      'geometries': [shape.__geo_interface__ for shape in self]}
        return collection

class ShapeRecords(list):
    """A class to hold a list of ShapeRecord objects. Subclasses list to ensure compatibility with
    former work and to reuse all the optimizations of the builtin list.
    In addition to the list interface, this also provides the GeoJSON __geo_interface__
    to return a FeatureCollection dictionary."""

    def __repr__(self):
        return 'ShapeRecords: {}'.format(list(self))

    @property
    def __geo_interface__(self):
        collection =  {'type': 'FeatureCollection',
                        'features': [shaperec.__geo_interface__ for shaperec in self]}
        return collection

class ShapefileException(Exception):
    """An exception to handle shapefile specific problems."""
    pass

# def warn_geojson_collection(shapes):
#     # collect information about any potential errors with the GeoJSON
#     errors = {}
#     for i,shape in enumerate(shapes):
#         shape_errors = shape._errors
#         if shape_errors:
#             for error in shape_errors.keys():
#                 errors[error] = errors[error] + [i] if error in errors else []

#     # warn if any errors were found
#     if errors:
#         messages = ['Summary of possibles issues encountered during shapefile to GeoJSON conversion:']

#         # polygon orphan holes
#         orphans = errors.get('polygon_orphaned_holes', None)
#         if orphans:
#             msg = 'GeoJSON format requires that all interior holes be contained by an exterior ring, \
# but the Shapefile contained {} records of polygons where some of its interior holes were \
# orphaned (not contained by any other rings). The rings were still included but were \
# encoded as GeoJSON exterior rings instead of holes. Shape ids: {}'.format(len(orphans), orphans)
#             messages.append(msg)

#         # polygon only holes/wrong orientation
#         only_holes = errors.get('polygon_only_holes', None)
#         if only_holes:
#             msg = 'GeoJSON format requires that polygons contain at least one exterior ring, but \
# the Shapefile contained {} records of polygons where all of its component rings were stored as interior \
# holes. The rings were still included but were encoded as GeoJSON exterior rings instead of holes. \
# Shape ids: {}'.format(len(only_holes), only_holes)
#             messages.append(msg)

#         if len(messages) > 1:
#             # more than just the "Summary of..." header
#             msg = '\n'.join(messages)
#             logging.warning(msg)

class Reader(object):
    """Reads the three files of a shapefile as a unit or
    separately.  If one of the three files (.shp, .shx,
    .dbf) is missing no exception is thrown until you try
    to call a method that depends on that particular file.
    The .shx index file is used if available for efficiency
    but is not required to read the geometry from the .shp
    file. The "shapefile" argument in the constructor is the
    name of the file you want to open, and can be the path
    to a shapefile on a local filesystem, inside a zipfile, 
    or a url. 

    You can instantiate a Reader without specifying a shapefile
    and then specify one later with the load() method.

    Only the shapefile headers are read upon loading. Content
    within each file is only accessed when required and as
    efficiently as possible. Shapefiles are usually not large
    but they can be.
    """
    def __init__(self, *args, **kwargs):
        self.shp = None
        self.shx = None
        self.dbf = None
        self.shapeName = "Not specified"
        self._offsets = []
        self.shpLength = None
        self.numRecords = None
        self.numShapes = None
        self.fields = []
        self.__dbfHdrLength = 0
        self.__fieldLookup = {}
        self.encoding = kwargs.pop('encoding', 'utf-8')
        self.encodingErrors = kwargs.pop('encodingErrors', 'strict')
        # See if a shapefile name was passed as the first argument
        if len(args) > 0:
            if is_string(args[0]):
                path = args[0]
                
                if '.zip' in path:
                    # Shapefile is inside a zipfile
                    if path.count('.zip') > 1:
                        # Multiple nested zipfiles
                        raise ShapefileException('Reading from multiple nested zipfiles is not supported: %s' % args[0])
                    # Split into zipfile and shapefile paths
                    if path.endswith('.zip'):
                        zpath = path
                        shapefile = None
                    else:
                        zpath = path[:path.find('.zip')+4]
                        shapefile = path[path.find('.zip')+4+1:]
                    # Create a zip file handle
                    if zpath.startswith('http'):
                        # Zipfile is from a url
                        # Download to a temporary url and treat as normal zipfile
                        req = Request(zpath, headers={'User-agent':'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/35.0.1916.47 Safari/537.36'})
                        resp = urlopen(req)
                        # write zipfile data to a read+write tempfile and use as source, gets deleted when garbage collected
                        zipfileobj = tempfile.NamedTemporaryFile(mode='w+b', suffix='.zip', delete=True)
                        zipfileobj.write(resp.read())
                        zipfileobj.seek(0)
                    else:
                        # Zipfile is from a file
                        zipfileobj = open(zpath, mode='rb')
                    # Open the zipfile archive
                    with zipfile.ZipFile(zipfileobj, 'r') as archive:
                        if not shapefile:
                            # Only the zipfile path is given
                            # Inspect zipfile contents to find the full shapefile path
                            shapefiles = [name
                                        for name in archive.namelist()
                                        if name.endswith('.shp')]
                            # The zipfile must contain exactly one shapefile
                            if len(shapefiles) == 0:
                                raise ShapefileException('Zipfile does not contain any shapefiles')
                            elif len(shapefiles) == 1:
                                shapefile = shapefiles[0]
                            else:
                                raise ShapefileException('Zipfile contains more than one shapefile: %s. Please specify the full \
                                    path to the shapefile you would like to open.' % shapefiles )
                        # Try to extract file-like objects from zipfile
                        shapefile = os.path.splitext(shapefile)[0] # root shapefile name
                        for ext in ['shp','shx','dbf']:
                            try:
                                member = archive.open(shapefile+'.'+ext)
                                # write zipfile member data to a read+write tempfile and use as source, gets deleted on close()
                                fileobj = tempfile.NamedTemporaryFile(mode='w+b', delete=True)
                                fileobj.write(member.read())
                                fileobj.seek(0)
                                setattr(self, ext, fileobj)
                            except:
                                pass
                    # Close and delete the temporary zipfile
                    try: zipfileobj.close()
                    except: pass
                    # Try to load shapefile
                    if (self.shp or self.dbf):
                        # Load and exit early
                        self.load()
                        return
                    else:
                        raise ShapefileException("No shp or dbf file found in zipfile: %s" % path)

                elif path.startswith('http'):
                    # Shapefile is from a url
                    # Download each file to temporary path and treat as normal shapefile path
                    urlinfo = urlparse(path)
                    urlpath = urlinfo[2]
                    urlpath,_ = os.path.splitext(urlpath)
                    shapefile = os.path.basename(urlpath)
                    for ext in ['shp','shx','dbf']:
                        try:
                            _urlinfo = list(urlinfo)
                            _urlinfo[2] = urlpath + '.' + ext
                            _path = urlunparse(_urlinfo)
                            req = Request(_path, headers={'User-agent':'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/35.0.1916.47 Safari/537.36'})
                            resp = urlopen(req)
                            # write url data to a read+write tempfile and use as source, gets deleted on close()
                            fileobj = tempfile.NamedTemporaryFile(mode='w+b', delete=True)
                            fileobj.write(resp.read())
                            fileobj.seek(0)
                            setattr(self, ext, fileobj)
                        except HTTPError:
                            pass
                    if (self.shp or self.dbf):
                        # Load and exit early
                        self.load()
                        return
                    else:
                        raise ShapefileException("No shp or dbf file found at url: %s" % path)

                else:
                    # Local file path to a shapefile
                    # Load and exit early
                    self.load(path)
                    return
                    
        # Otherwise, load from separate shp/shx/dbf args (must be file-like)
        if "shp" in kwargs.keys():
            if hasattr(kwargs["shp"], "read"):
                self.shp = kwargs["shp"]
                # Copy if required
                try:
                    self.shp.seek(0)
                except (NameError, io.UnsupportedOperation):
                    self.shp = io.BytesIO(self.shp.read())
            else:
                raise ShapefileException('The shp arg must be file-like.')
            
            if "shx" in kwargs.keys():
                if hasattr(kwargs["shx"], "read"):
                    self.shx = kwargs["shx"]
                    # Copy if required
                    try:
                        self.shx.seek(0)
                    except (NameError, io.UnsupportedOperation):
                        self.shx = io.BytesIO(self.shx.read())
                else:
                    raise ShapefileException('The shx arg must be file-like.')
                
        if "dbf" in kwargs.keys():
            if hasattr(kwargs["dbf"], "read"):
                self.dbf = kwargs["dbf"]
                # Copy if required
                try:
                    self.dbf.seek(0)
                except (NameError, io.UnsupportedOperation):
                    self.dbf = io.BytesIO(self.dbf.read())
            else:
                raise ShapefileException('The dbf arg must be file-like.')
            
        # Load the files
        if self.shp or self.dbf:
            self.load()

    def __str__(self):
        """
        Use some general info on the shapefile as __str__
        """
        info = ['shapefile Reader']
        if self.shp:
            info.append("    {} shapes (type '{}')".format(
                len(self), SHAPETYPE_LOOKUP[self.shapeType]))
        if self.dbf:
            info.append('    {} records ({} fields)'.format(
                len(self), len(self.fields)))
        return '\n'.join(info)

    def __enter__(self):
        """
        Enter phase of context manager.
        """
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        """
        Exit phase of context manager, close opened files.
        """
        self.close()

    def __len__(self):
        """Returns the number of shapes/records in the shapefile."""
        if self.dbf:
            # Preferably use dbf record count
            if self.numRecords is None:
                self.__dbfHeader()
                
            return self.numRecords
        
        elif self.shp:
            # Otherwise use shape count
            if self.shx:
                # Use index file to get total count
                if self.numShapes is None:
                    # File length (16-bit word * 2 = bytes) - header length
                    self.shx.seek(24)
                    shxRecordLength = (unpack(">i", self.shx.read(4))[0] * 2) - 100
                    self.numShapes = shxRecordLength // 8
                    
                return self.numShapes
            
            else:
                # Index file not available, iterate all shapes to get total count
                if self.numShapes is None:
                    for i,shape in enumerate(self.iterShapes()):
                        pass
                    self.numShapes = i + 1
                    
                return self.numShapes
            
        else:
            # No file loaded yet, treat as 'empty' shapefile
            return 0 

    def __iter__(self):
        """Iterates through the shapes/records in the shapefile."""
        for shaperec in self.iterShapeRecords():
            yield shaperec

    @property
    def __geo_interface__(self):
        shaperecords = self.shapeRecords()
        fcollection = shaperecords.__geo_interface__
        fcollection['bbox'] = list(self.bbox)
        return fcollection

    @property
    def shapeTypeName(self):
        return SHAPETYPE_LOOKUP[self.shapeType]

    def load(self, shapefile=None):
        """Opens a shapefile from a filename or file-like
        object. Normally this method would be called by the
        constructor with the file name as an argument."""
        if shapefile:
            (shapeName, ext) = os.path.splitext(shapefile)
            self.shapeName = shapeName
            self.load_shp(shapeName)
            self.load_shx(shapeName)
            self.load_dbf(shapeName)
            if not (self.shp or self.dbf):
                raise ShapefileException("Unable to open %s.dbf or %s.shp." % (shapeName, shapeName))
        if self.shp:
            self.__shpHeader()
        if self.dbf:
            self.__dbfHeader()

    def load_shp(self, shapefile_name):
        """
        Attempts to load file with .shp extension as both lower and upper case
        """
        shp_ext = 'shp'
        try:
            self.shp = open("%s.%s" % (shapefile_name, shp_ext), "rb")
        except IOError:
            try:
                self.shp = open("%s.%s" % (shapefile_name, shp_ext.upper()), "rb")
            except IOError:
                pass

    def load_shx(self, shapefile_name):
        """
        Attempts to load file with .shx extension as both lower and upper case
        """
        shx_ext = 'shx'
        try:
            self.shx = open("%s.%s" % (shapefile_name, shx_ext), "rb")
        except IOError:
            try:
                self.shx = open("%s.%s" % (shapefile_name, shx_ext.upper()), "rb")
            except IOError:
                pass

    def load_dbf(self, shapefile_name):
        """
        Attempts to load file with .dbf extension as both lower and upper case
        """
        dbf_ext = 'dbf'
        try:
            self.dbf = open("%s.%s" % (shapefile_name, dbf_ext), "rb")
        except IOError:
            try:
                self.dbf = open("%s.%s" % (shapefile_name, dbf_ext.upper()), "rb")
            except IOError:
                pass

    def __del__(self):
        self.close()

    def close(self):
        for attribute in ('shp','shx','dbf'):
            try:
                obj = getattr(self, attribute)
            except AttributeError:
                # deepcopies fail to copy these attributes and raises exception during
                # garbage collection - https://github.com/mattijn/topojson/issues/120
                obj = None
            if obj and hasattr(obj, 'close'):
                try:
                    obj.close()
                except IOError:
                    pass

    def __getFileObj(self, f):
        """Checks to see if the requested shapefile file object is
        available. If not a ShapefileException is raised."""
        if not f:
            raise ShapefileException("Shapefile Reader requires a shapefile or file-like object.")
        if self.shp and self.shpLength is None:
            self.load()
        if self.dbf and len(self.fields) == 0:
            self.load()
        return f

    def __restrictIndex(self, i):
        """Provides list-like handling of a record index with a clearer
        error message if the index is out of bounds."""
        if self.numRecords:
            rmax = self.numRecords - 1
            if abs(i) > rmax:
                raise IndexError("Shape or Record index out of range.")
            if i < 0: i = range(self.numRecords)[i]
        return i

    def __shpHeader(self):
        """Reads the header information from a .shp or .shx file."""
        if not self.shp:
            raise ShapefileException("Shapefile Reader requires a shapefile or file-like object. (no shp file found")
        shp = self.shp
        # File length (16-bit word * 2 = bytes)
        shp.seek(24)
        self.shpLength = unpack(">i", shp.read(4))[0] * 2
        # Shape type
        shp.seek(32)
        self.shapeType= unpack("<i", shp.read(4))[0]
        # The shapefile's bounding box (lower left, upper right)
        self.bbox = _Array('d', unpack("<4d", shp.read(32)))
        # Elevation
        self.zbox = _Array('d', unpack("<2d", shp.read(16)))
        # Measure
        self.mbox = []
        for m in _Array('d', unpack("<2d", shp.read(16))):
            # Measure values less than -10e38 are nodata values according to the spec
            if m > NODATA:
                self.mbox.append(m)
            else:
                self.mbox.append(None)

    def __shape(self, oid=None, bbox=None):
        """Returns the header info and geometry for a single shape."""
        f = self.__getFileObj(self.shp)
        record = Shape(oid=oid)
        nParts = nPoints = zmin = zmax = mmin = mmax = None
        (recNum, recLength) = unpack(">2i", f.read(8))
        # Determine the start of the next record
        next = f.tell() + (2 * recLength)
        shapeType = unpack("<i", f.read(4))[0]
        record.shapeType = shapeType
        # For Null shapes create an empty points list for consistency
        if shapeType == 0:
            record.points = []
        # All shape types capable of having a bounding box
        elif shapeType in (3,5,8,13,15,18,23,25,28,31):
            record.bbox = _Array('d', unpack("<4d", f.read(32)))
            # if bbox specified and no overlap, skip this shape
            if bbox is not None and not bbox_overlap(bbox, record.bbox):
                # because we stop parsing this shape, skip to beginning of
                # next shape before we return
                f.seek(next)
                return None
        # Shape types with parts
        if shapeType in (3,5,13,15,23,25,31):
            nParts = unpack("<i", f.read(4))[0]
        # Shape types with points
        if shapeType in (3,5,8,13,15,18,23,25,28,31):
            nPoints = unpack("<i", f.read(4))[0]
        # Read parts
        if nParts:
            record.parts = _Array('i', unpack("<%si" % nParts, f.read(nParts * 4)))
        # Read part types for Multipatch - 31
        if shapeType == 31:
            record.partTypes = _Array('i', unpack("<%si" % nParts, f.read(nParts * 4)))
        # Read points - produces a list of [x,y] values
        if nPoints:
            flat = unpack("<%sd" % (2 * nPoints), f.read(16*nPoints))
            record.points = list(izip(*(iter(flat),) * 2))
        # Read z extremes and values
        if shapeType in (13,15,18,31):
            (zmin, zmax) = unpack("<2d", f.read(16))
            record.z = _Array('d', unpack("<%sd" % nPoints, f.read(nPoints * 8)))
        # Read m extremes and values
        if shapeType in (13,15,18,23,25,28,31):
            if next - f.tell() >= 16:
                (mmin, mmax) = unpack("<2d", f.read(16))
            # Measure values less than -10e38 are nodata values according to the spec
            if next - f.tell() >= nPoints * 8:
                record.m = []
                for m in _Array('d', unpack("<%sd" % nPoints, f.read(nPoints * 8))):
                    if m > NODATA:
                        record.m.append(m)
                    else:
                        record.m.append(None)
            else:
                record.m = [None for _ in range(nPoints)]
        # Read a single point
        if shapeType in (1,11,21):
            record.points = [_Array('d', unpack("<2d", f.read(16)))]
        # Read a single Z value
        if shapeType == 11:
            record.z = list(unpack("<d", f.read(8)))
        # Read a single M value
        if shapeType in (21,11):
            if next - f.tell() >= 8:
                (m,) = unpack("<d", f.read(8))
            else:
                m = NODATA
            # Measure values less than -10e38 are nodata values according to the spec
            if m > NODATA:
                record.m = [m]
            else:
                record.m = [None]
        # Seek to the end of this record as defined by the record header because
        # the shapefile spec doesn't require the actual content to meet the header
        # definition.  Probably allowed for lazy feature deletion. 
        f.seek(next)
        return record

    def __shapeIndex(self, i=None):
        """Returns the offset in a .shp file for a shape based on information
        in the .shx index file."""
        shx = self.shx
        if not shx:
            return None
        if not self._offsets:
            if self.numShapes is None:
                # File length (16-bit word * 2 = bytes) - header length
                shx.seek(24)
                shxRecordLength = (unpack(">i", shx.read(4))[0] * 2) - 100
                self.numShapes = shxRecordLength // 8
            # Jump to the first record.
            shx.seek(100)
            # Each index record consists of two nrs, we only want the first one
            shxRecords = _Array('i', shx.read(2 * self.numShapes * 4) )
            if sys.byteorder != 'big':
                 shxRecords.byteswap()
            self._offsets = [2 * el for el in shxRecords[::2]]
        if not i == None:
            return self._offsets[i]

    def shape(self, i=0, bbox=None):
        """Returns a shape object for a shape in the geometry
        record file.
        If the 'bbox' arg is given (list or tuple of xmin,ymin,xmax,ymax), 
        returns None if the shape is not within that region. 
        """
        shp = self.__getFileObj(self.shp)
        i = self.__restrictIndex(i)
        offset = self.__shapeIndex(i)
        if not offset:
            # Shx index not available so iterate the full list.
            for j,k in enumerate(self.iterShapes()):
                if j == i:
                    return k
        shp.seek(offset)
        return self.__shape(oid=i, bbox=bbox)

    def shapes(self, bbox=None):
        """Returns all shapes in a shapefile.
        To only read shapes within a given spatial region, specify the 'bbox'
        arg as a list or tuple of xmin,ymin,xmax,ymax. 
        """
        shp = self.__getFileObj(self.shp)
        # Found shapefiles which report incorrect
        # shp file length in the header. Can't trust
        # that so we seek to the end of the file
        # and figure it out.
        shp.seek(0,2)
        self.shpLength = shp.tell()
        shp.seek(100)
        shapes = Shapes()
        i = 0
        while shp.tell() < self.shpLength:
            shape = self.__shape(oid=i, bbox=bbox)
            if shape:
                shapes.append(shape)
            i += 1
        return shapes

    def iterShapes(self, bbox=None):
        """Returns a generator of shapes in a shapefile. Useful
        for handling large shapefiles.
        To only read shapes within a given spatial region, specify the 'bbox'
        arg as a list or tuple of xmin,ymin,xmax,ymax. 
        """
        shp = self.__getFileObj(self.shp)
        shp.seek(0,2)
        self.shpLength = shp.tell()
        shp.seek(100)
        i = 0
        while shp.tell() < self.shpLength:
            shape = self.__shape(oid=i, bbox=bbox)
            if shape:
                yield shape
            i += 1

    def __dbfHeader(self):
        """Reads a dbf header. Xbase-related code borrows heavily from ActiveState Python Cookbook Recipe 362715 by Raymond Hettinger"""
        if not self.dbf:
            raise ShapefileException("Shapefile Reader requires a shapefile or file-like object. (no dbf file found)")
        dbf = self.dbf
        # read relevant header parts
        dbf.seek(0)
        self.numRecords, self.__dbfHdrLength, self.__recordLength = \
                unpack("<xxxxLHH20x", dbf.read(32))
        # read fields
        numFields = (self.__dbfHdrLength - 33) // 32
        for field in range(numFields):
            fieldDesc = list(unpack("<11sc4xBB14x", dbf.read(32)))
            name = 0
            idx = 0
            if b"\x00" in fieldDesc[name]:
                idx = fieldDesc[name].index(b"\x00")
            else:
                idx = len(fieldDesc[name]) - 1
            fieldDesc[name] = fieldDesc[name][:idx]
            fieldDesc[name] = u(fieldDesc[name], self.encoding, self.encodingErrors)
            fieldDesc[name] = fieldDesc[name].lstrip()
            fieldDesc[1] = u(fieldDesc[1], 'ascii')
            self.fields.append(fieldDesc)
        terminator = dbf.read(1)
        if terminator != b"\r":
            raise ShapefileException("Shapefile dbf header lacks expected terminator. (likely corrupt?)")
        
        # insert deletion field at start
        self.fields.insert(0, ('DeletionFlag', 'C', 1, 0))

        # store all field positions for easy lookups
        # note: fieldLookup gives the index position of a field inside Reader.fields
        self.__fieldLookup = dict((f[0], i) for i, f in enumerate(self.fields))

        # by default, read all fields except the deletion flag, hence "[1:]"
        # note: recLookup gives the index position of a field inside a _Record list
        fieldnames = [f[0] for f in self.fields[1:]]
        fieldTuples,recLookup,recStruct = self.__recordFields(fieldnames)
        self.__fullRecStruct = recStruct
        self.__fullRecLookup = recLookup

    def __recordFmt(self, fields=None):
        """Calculates the format and size of a .dbf record. Optional 'fields' arg 
        specifies which fieldnames to unpack and which to ignore. Note that this
        always includes the DeletionFlag at index 0, regardless of the 'fields' arg. 
        """
        if self.numRecords is None:
            self.__dbfHeader()
        structcodes = ['%ds' % fieldinfo[2]
                        for fieldinfo in self.fields]
        if fields is not None:
            # only unpack specified fields, ignore others using padbytes (x)
            structcodes = [code if fieldinfo[0] in fields 
                            or fieldinfo[0] == 'DeletionFlag' # always unpack delflag
                            else '%dx' % fieldinfo[2]
                            for fieldinfo,code in zip(self.fields, structcodes)]
        fmt = ''.join(structcodes)
        fmtSize = calcsize(fmt)
        # total size of fields should add up to recordlength from the header
        while fmtSize < self.__recordLength:
            # if not, pad byte until reaches recordlength
            fmt += "x"
            fmtSize += 1
        return (fmt, fmtSize)

    def __recordFields(self, fields=None):
        """Returns the necessary info required to unpack a record's fields,
        restricted to a subset of fieldnames 'fields' if specified. 
        Returns a list of field info tuples, a name-index lookup dict, 
        and a Struct instance for unpacking these fields. Note that DeletionFlag
        is not a valid field. 
        """
        if fields is not None:
            # restrict info to the specified fields
            # first ignore repeated field names (order doesn't matter)
            fields = list(set(fields))
            # get the struct
            fmt, fmtSize = self.__recordFmt(fields=fields)
            recStruct = Struct(fmt)
            # make sure the given fieldnames exist
            for name in fields:
                if name not in self.__fieldLookup or name == 'DeletionFlag':
                    raise ValueError('"{}" is not a valid field name'.format(name))
            # fetch relevant field info tuples
            fieldTuples = []
            for fieldinfo in self.fields[1:]:
                name = fieldinfo[0]
                if name in fields:
                    fieldTuples.append(fieldinfo)
            # store the field positions
            recLookup = dict((f[0], i) for i,f in enumerate(fieldTuples))
        else:
            # use all the dbf fields
            fieldTuples = self.fields[1:] # sans deletion flag
            recStruct = self.__fullRecStruct
            recLookup = self.__fullRecLookup
        return fieldTuples, recLookup, recStruct

    def __record(self, fieldTuples, recLookup, recStruct, oid=None):
        """Reads and returns a dbf record row as a list of values. Requires specifying
        a list of field info tuples 'fieldTuples', a record name-index dict 'recLookup', 
        and a Struct instance 'recStruct' for unpacking these fields. 
        """
        f = self.__getFileObj(self.dbf)

        recordContents = recStruct.unpack(f.read(recStruct.size))
        
        # deletion flag field is always unpacked as first value (see __recordFmt)
        if recordContents[0] != b' ':
            # deleted record
            return None

        # drop deletion flag from values
        recordContents = recordContents[1:]

        # check that values match fields
        if len(fieldTuples) != len(recordContents):
            raise ShapefileException('Number of record values ({}) is different from the requested \
                            number of fields ({})'.format(len(recordContents), len(fieldTuples)))

        # parse each value
        record = []
        for (name, typ, size, deci),value in zip(fieldTuples, recordContents):
            if typ in ("N","F"):
                # numeric or float: number stored as a string, right justified, and padded with blanks to the width of the field. 
                value = value.split(b'\0')[0]
                value = value.replace(b'*', b'')  # QGIS NULL is all '*' chars
                if value == b'':
                    value = None
                elif deci:
                    try:
                        value = float(value)
                    except ValueError:
                        #not parseable as float, set to None
                        value = None
                else:
                    # force to int
                    try:
                        # first try to force directly to int.
                        # forcing a large int to float and back to int
                        # will lose information and result in wrong nr.
                        value = int(value) 
                    except ValueError:
                        # forcing directly to int failed, so was probably a float.
                        try:
                            value = int(float(value))
                        except ValueError:
                            #not parseable as int, set to None
                            value = None
            elif typ == 'D':
                # date: 8 bytes - date stored as a string in the format YYYYMMDD.
                if not value.replace(b'\x00', b'').replace(b' ', b'').replace(b'0', b''):
                    # dbf date field has no official null value
                    # but can check for all hex null-chars, all spaces, or all 0s (QGIS null)
                    value = None
                else:
                    try:
                        # return as python date object
                        y, m, d = int(value[:4]), int(value[4:6]), int(value[6:8])
                        value = date(y, m, d)
                    except:
                        # if invalid date, just return as unicode string so user can decide
                        value = u(value.strip())
            elif typ == 'L':
                # logical: 1 byte - initialized to 0x20 (space) otherwise T or F.
                if value == b" ":
                    value = None # space means missing or not yet set
                else:
                    if value in b'YyTt1':
                        value = True
                    elif value in b'NnFf0':
                        value = False
                    else:
                        value = None # unknown value is set to missing
            else:
                # anything else is forced to string/unicode
                value = u(value, self.encoding, self.encodingErrors)
                value = value.strip().rstrip('\x00') # remove null-padding at end of strings
            record.append(value)

        return _Record(recLookup, record, oid)

    def record(self, i=0, fields=None):
        """Returns a specific dbf record based on the supplied index.
        To only read some of the fields, specify the 'fields' arg as a
        list of one or more fieldnames. 
        """
        f = self.__getFileObj(self.dbf)
        if self.numRecords is None:
            self.__dbfHeader()
        i = self.__restrictIndex(i)
        recSize = self.__recordLength
        f.seek(0)
        f.seek(self.__dbfHdrLength + (i * recSize))
        fieldTuples,recLookup,recStruct = self.__recordFields(fields)
        return self.__record(oid=i, fieldTuples=fieldTuples, recLookup=recLookup, recStruct=recStruct)

    def records(self, fields=None):
        """Returns all records in a dbf file. 
        To only read some of the fields, specify the 'fields' arg as a
        list of one or more fieldnames.
        """
        if self.numRecords is None:
            self.__dbfHeader()
        records = []
        f = self.__getFileObj(self.dbf)
        f.seek(self.__dbfHdrLength)
        fieldTuples,recLookup,recStruct = self.__recordFields(fields)
        for i in range(self.numRecords):
            r = self.__record(oid=i, fieldTuples=fieldTuples, recLookup=recLookup, recStruct=recStruct)
            if r:
                records.append(r)
        return records

    def iterRecords(self, fields=None):
        """Returns a generator of records in a dbf file.
        Useful for large shapefiles or dbf files.
        To only read some of the fields, specify the 'fields' arg as a
        list of one or more fieldnames.
        """
        if self.numRecords is None:
            self.__dbfHeader()
        f = self.__getFileObj(self.dbf)
        f.seek(self.__dbfHdrLength)
        fieldTuples,recLookup,recStruct = self.__recordFields(fields)
        for i in xrange(self.numRecords):
            r = self.__record(oid=i, fieldTuples=fieldTuples, recLookup=recLookup, recStruct=recStruct)
            if r:
                yield r

    def shapeRecord(self, i=0, fields=None, bbox=None):
        """Returns a combination geometry and attribute record for the
        supplied record index. 
        To only read some of the fields, specify the 'fields' arg as a
        list of one or more fieldnames. 
        If the 'bbox' arg is given (list or tuple of xmin,ymin,xmax,ymax), 
        returns None if the shape is not within that region. 
        """
        i = self.__restrictIndex(i)
        shape = self.shape(i, bbox=bbox)
        if shape:
            record = self.record(i, fields=fields)
            return ShapeRecord(shape=shape, record=record)

    def shapeRecords(self, fields=None, bbox=None):
        """Returns a list of combination geometry/attribute records for
        all records in a shapefile.
        To only read some of the fields, specify the 'fields' arg as a
        list of one or more fieldnames. 
        To only read entries within a given spatial region, specify the 'bbox'
        arg as a list or tuple of xmin,ymin,xmax,ymax. 
        """
        return ShapeRecords(self.iterShapeRecords(fields=fields, bbox=bbox))

    def iterShapeRecords(self, fields=None, bbox=None):
        """Returns a generator of combination geometry/attribute records for
        all records in a shapefile.
        To only read some of the fields, specify the 'fields' arg as a
        list of one or more fieldnames. 
        To only read entries within a given spatial region, specify the 'bbox'
        arg as a list or tuple of xmin,ymin,xmax,ymax. 
        """
        if bbox is None:
            # iterate through all shapes and records
            for shape, record in izip(self.iterShapes(), self.iterRecords(fields=fields)):
                yield ShapeRecord(shape=shape, record=record)
        else:
            # only iterate where shape.bbox overlaps with the given bbox
            # TODO: internal __record method should be faster but would have to
            # make sure to seek to correct file location... 

            #fieldTuples,recLookup,recStruct = self.__recordFields(fields)
            for shape in self.iterShapes(bbox=bbox):
                if shape:
                    #record = self.__record(oid=i, fieldTuples=fieldTuples, recLookup=recLookup, recStruct=recStruct)
                    record = self.record(i=shape.oid, fields=fields) 
                    yield ShapeRecord(shape=shape, record=record)


class Writer(object):
    """Provides write support for ESRI Shapefiles."""
    def __init__(self, target=None, shapeType=None, autoBalance=False, **kwargs):
        self.target = target
        self.autoBalance = autoBalance
        self.fields = []
        self.shapeType = shapeType
        self.shp = self.shx = self.dbf = None
        if target:
            if not is_string(target):
                raise Exception('The target filepath {} must be of type str/unicode, not {}.'.format(repr(target), type(target)) )
            self.shp = self.__getFileObj(os.path.splitext(target)[0] + '.shp')
            self.shx = self.__getFileObj(os.path.splitext(target)[0] + '.shx')
            self.dbf = self.__getFileObj(os.path.splitext(target)[0] + '.dbf')
        elif kwargs.get('shp') or kwargs.get('shx') or kwargs.get('dbf'):
            shp,shx,dbf = kwargs.get('shp'), kwargs.get('shx'), kwargs.get('dbf')
            if shp:
                self.shp = self.__getFileObj(shp)
            if shx:
                self.shx = self.__getFileObj(shx)
            if dbf:
                self.dbf = self.__getFileObj(dbf)
        else:
            raise Exception('Either the target filepath, or any of shp, shx, or dbf must be set to create a shapefile.')
        # Initiate with empty headers, to be finalized upon closing
        if self.shp: self.shp.write(b'9'*100) 
        if self.shx: self.shx.write(b'9'*100) 
        # Geometry record offsets and lengths for writing shx file.
        self.recNum = 0
        self.shpNum = 0
        self._bbox = None
        self._zbox = None
        self._mbox = None
        # Use deletion flags in dbf? Default is false (0). Note: Currently has no effect, records should NOT contain deletion flags.
        self.deletionFlag = 0 
        # Encoding
        self.encoding = kwargs.pop('encoding', 'utf-8')
        self.encodingErrors = kwargs.pop('encodingErrors', 'strict')

    def __len__(self):
        """Returns the current number of features written to the shapefile. 
        If shapes and records are unbalanced, the length is considered the highest
        of the two."""
        return max(self.recNum, self.shpNum) 

    def __enter__(self):
        """
        Enter phase of context manager.
        """
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        """
        Exit phase of context manager, finish writing and close the files.
        """
        self.close()

    def __del__(self):
        self.close()

    def close(self):
        """
        Write final shp, shx, and dbf headers, close opened files.
        """
        # Check if any of the files have already been closed
        shp_open = self.shp and not (hasattr(self.shp, 'closed') and self.shp.closed)
        shx_open = self.shx and not (hasattr(self.shx, 'closed') and self.shx.closed)
        dbf_open = self.dbf and not (hasattr(self.dbf, 'closed') and self.dbf.closed)
            
        # Balance if already not balanced
        if self.shp and shp_open and self.dbf and dbf_open:
            if self.autoBalance:
                self.balance()
            if self.recNum != self.shpNum:
                raise ShapefileException("When saving both the dbf and shp file, "
                                         "the number of records (%s) must correspond "
                                         "with the number of shapes (%s)" % (self.recNum, self.shpNum))
        # Fill in the blank headers
        if self.shp and shp_open:
            self.__shapefileHeader(self.shp, headerType='shp')
        if self.shx and shx_open:
            self.__shapefileHeader(self.shx, headerType='shx')

        # Update the dbf header with final length etc
        if self.dbf and dbf_open:
            self.__dbfHeader()

        # Close files, if target is a filepath
        if self.target:
            for attribute in (self.shp, self.shx, self.dbf):
                if hasattr(attribute, 'close'):
                    try:
                        attribute.close()
                    except IOError:
                        pass

    def __getFileObj(self, f):
        """Safety handler to verify file-like objects"""
        if not f:
            raise ShapefileException("No file-like object available.")
        elif hasattr(f, "write"):
            return f
        else:
            pth = os.path.split(f)[0]
            if pth and not os.path.exists(pth):
                os.makedirs(pth)
            return open(f, "wb+")

    def __shpFileLength(self):
        """Calculates the file length of the shp file."""
        # Remember starting position
        start = self.shp.tell()
        # Calculate size of all shapes
        self.shp.seek(0,2)
        size = self.shp.tell()
        # Calculate size as 16-bit words
        size //= 2
        # Return to start
        self.shp.seek(start)
        return size

    def __bbox(self, s):
        x = []
        y = []
        if len(s.points) > 0:
            px, py = list(zip(*s.points))[:2]
            x.extend(px)
            y.extend(py)
        else:
            # this should not happen.
            # any shape that is not null should have at least one point, and only those should be sent here. 
            # could also mean that earlier code failed to add points to a non-null shape. 
            raise Exception("Cannot create bbox. Expected a valid shape with at least one point. Got a shape of type '%s' and 0 points." % s.shapeType)
        bbox = [min(x), min(y), max(x), max(y)]
        # update global
        if self._bbox:
            # compare with existing
            self._bbox = [min(bbox[0],self._bbox[0]), min(bbox[1],self._bbox[1]), max(bbox[2],self._bbox[2]), max(bbox[3],self._bbox[3])]
        else:
            # first time bbox is being set
            self._bbox = bbox
        return bbox

    def __zbox(self, s):
        z = []
        for p in s.points:
            try:
                z.append(p[2])
            except IndexError:
                # point did not have z value
                # setting it to 0 is probably ok, since it means all are on the same elevation
                z.append(0)
        zbox = [min(z), max(z)]
        # update global
        if self._zbox:
            # compare with existing
            self._zbox = [min(zbox[0],self._zbox[0]), max(zbox[1],self._zbox[1])]
        else:
            # first time zbox is being set
            self._zbox = zbox
        return zbox

    def __mbox(self, s):
        mpos = 3 if s.shapeType in (11,13,15,18,31) else 2
        m = []
        for p in s.points:
            try:
                if p[mpos] is not None:
                    # mbox should only be calculated on valid m values
                    m.append(p[mpos])
            except IndexError:
                # point did not have m value so is missing
                # mbox should only be calculated on valid m values
                pass
        if not m:
            # only if none of the shapes had m values, should mbox be set to missing m values
            m.append(NODATA)
        mbox = [min(m), max(m)]
        # update global
        if self._mbox:
            # compare with existing
            self._mbox = [min(mbox[0],self._mbox[0]), max(mbox[1],self._mbox[1])]
        else:
            # first time mbox is being set
            self._mbox = mbox
        return mbox

    @property
    def shapeTypeName(self):
        return SHAPETYPE_LOOKUP[self.shapeType]

    def bbox(self):
        """Returns the current bounding box for the shapefile which is
        the lower-left and upper-right corners. It does not contain the
        elevation or measure extremes."""
        return self._bbox

    def zbox(self):
        """Returns the current z extremes for the shapefile."""
        return self._zbox

    def mbox(self):
        """Returns the current m extremes for the shapefile."""
        return self._mbox

    def __shapefileHeader(self, fileObj, headerType='shp'):
        """Writes the specified header type to the specified file-like object.
        Several of the shapefile formats are so similar that a single generic
        method to read or write them is warranted."""
        f = self.__getFileObj(fileObj)
        f.seek(0)
        # File code, Unused bytes
        f.write(pack(">6i", 9994,0,0,0,0,0))
        # File length (Bytes / 2 = 16-bit words)
        if headerType == 'shp':
            f.write(pack(">i", self.__shpFileLength()))
        elif headerType == 'shx':
            f.write(pack('>i', ((100 + (self.shpNum * 8)) // 2)))
        # Version, Shape type
        if self.shapeType is None:
            self.shapeType = NULL
        f.write(pack("<2i", 1000, self.shapeType))
        # The shapefile's bounding box (lower left, upper right)
        if self.shapeType != 0:
            try:
                bbox = self.bbox()
                if bbox is None:
                    # The bbox is initialized with None, so this would mean the shapefile contains no valid geometries.
                    # In such cases of empty shapefiles, ESRI spec says the bbox values are 'unspecified'.
                    # Not sure what that means, so for now just setting to 0s, which is the same behavior as in previous versions.
                    # This would also make sense since the Z and M bounds are similarly set to 0 for non-Z/M type shapefiles.
                    bbox = [0,0,0,0] 
                f.write(pack("<4d", *bbox))
            except error:
                raise ShapefileException("Failed to write shapefile bounding box. Floats required.")
        else:
            f.write(pack("<4d", 0,0,0,0))
        # Elevation
        if self.shapeType in (11,13,15,18):
            # Z values are present in Z type
            zbox = self.zbox()
            if zbox is None:
                # means we have empty shapefile/only null geoms (see commentary on bbox above)
                zbox = [0,0]
        else:
            # As per the ESRI shapefile spec, the zbox for non-Z type shapefiles are set to 0s
            zbox = [0,0]
        # Measure
        if self.shapeType in (11,13,15,18,21,23,25,28,31):
            # M values are present in M or Z type
            mbox = self.mbox()
            if mbox is None:
                # means we have empty shapefile/only null geoms (see commentary on bbox above)
                mbox = [0,0]
        else:
            # As per the ESRI shapefile spec, the mbox for non-M type shapefiles are set to 0s
            mbox = [0,0]
        # Try writing
        try:
            f.write(pack("<4d", zbox[0], zbox[1], mbox[0], mbox[1]))
        except error:
            raise ShapefileException("Failed to write shapefile elevation and measure values. Floats required.")

    def __dbfHeader(self):
        """Writes the dbf header and field descriptors."""
        f = self.__getFileObj(self.dbf)
        f.seek(0)
        version = 3
        year, month, day = time.localtime()[:3]
        year -= 1900
        # Get all fields, ignoring DeletionFlag if specified
        fields = [field for field in self.fields if field[0] != 'DeletionFlag']
        # Ensure has at least one field
        if not fields:
            raise ShapefileException("Shapefile dbf file must contain at least one field.")
        numRecs = self.recNum
        numFields = len(fields)
        headerLength = numFields * 32 + 33
        if headerLength >= 65535:
            raise ShapefileException(
                    "Shapefile dbf header length exceeds maximum length.")
        recordLength = sum([int(field[2]) for field in fields]) + 1
        header = pack('<BBBBLHH20x', version, year, month, day, numRecs,
                headerLength, recordLength)
        f.write(header)
        # Field descriptors
        for field in fields:
            name, fieldType, size, decimal = field
            name = b(name, self.encoding, self.encodingErrors)
            name = name.replace(b' ', b'_')
            name = name[:10].ljust(11).replace(b' ', b'\x00')
            fieldType = b(fieldType, 'ascii')
            size = int(size)
            fld = pack('<11sc4xBB14x', name, fieldType, size, decimal)
            f.write(fld)
        # Terminator
        f.write(b'\r')

    def shape(self, s):
        # Balance if already not balanced
        if self.autoBalance and self.recNum < self.shpNum:
            self.balance()
        # Check is shape or import from geojson
        if not isinstance(s, Shape):
            if hasattr(s, "__geo_interface__"):
                s = s.__geo_interface__
            if isinstance(s, dict):
                s = Shape._from_geojson(s)
            else:
                raise Exception("Can only write Shape objects, GeoJSON dictionaries, "
                                "or objects with the __geo_interface__, "
                                "not: %r" % s)
        # Write to file
        offset,length = self.__shpRecord(s)
        self.__shxRecord(offset, length)

    def __shpRecord(self, s):
        f = self.__getFileObj(self.shp)
        offset = f.tell()
        # Record number, Content length place holder
        self.shpNum += 1
        f.write(pack(">2i", self.shpNum, 0))
        start = f.tell()
        # Shape Type
        if self.shapeType is None and s.shapeType != NULL:
            self.shapeType = s.shapeType
        if s.shapeType != NULL and s.shapeType != self.shapeType:
            raise Exception("The shape's type (%s) must match the type of the shapefile (%s)." % (s.shapeType, self.shapeType))
        f.write(pack("<i", s.shapeType))

        # For point just update bbox of the whole shapefile
        if s.shapeType in (1,11,21):
            self.__bbox(s)
        # All shape types capable of having a bounding box
        if s.shapeType in (3,5,8,13,15,18,23,25,28,31):
            try:
                f.write(pack("<4d", *self.__bbox(s)))
            except error:
                raise ShapefileException("Failed to write bounding box for record %s. Expected floats." % self.shpNum)
        # Shape types with parts
        if s.shapeType in (3,5,13,15,23,25,31):
            # Number of parts
            f.write(pack("<i", len(s.parts)))
        # Shape types with multiple points per record
        if s.shapeType in (3,5,8,13,15,18,23,25,28,31):
            # Number of points
            f.write(pack("<i", len(s.points)))
        # Write part indexes
        if s.shapeType in (3,5,13,15,23,25,31):
            for p in s.parts:
                f.write(pack("<i", p))
        # Part types for Multipatch (31)
        if s.shapeType == 31:
            for pt in s.partTypes:
                f.write(pack("<i", pt))
        # Write points for multiple-point records
        if s.shapeType in (3,5,8,13,15,18,23,25,28,31):
            try:
                [f.write(pack("<2d", *p[:2])) for p in s.points]
            except error:
                raise ShapefileException("Failed to write points for record %s. Expected floats." % self.shpNum)
        # Write z extremes and values
        # Note: missing z values are autoset to 0, but not sure if this is ideal.
        if s.shapeType in (13,15,18,31):
            try:
                f.write(pack("<2d", *self.__zbox(s)))
            except error:
                raise ShapefileException("Failed to write elevation extremes for record %s. Expected floats." % self.shpNum)
            try:
                if hasattr(s,"z"):
                    # if z values are stored in attribute
                    f.write(pack("<%sd" % len(s.z), *s.z))
                else:
                    # if z values are stored as 3rd dimension
                    [f.write(pack("<d", p[2] if len(p) > 2 else 0)) for p in s.points]  
            except error:
                raise ShapefileException("Failed to write elevation values for record %s. Expected floats." % self.shpNum)
        # Write m extremes and values
        # When reading a file, pyshp converts NODATA m values to None, so here we make sure to convert them back to NODATA
        # Note: missing m values are autoset to NODATA.
        if s.shapeType in (13,15,18,23,25,28,31):
            try:
                f.write(pack("<2d", *self.__mbox(s)))
            except error:
                raise ShapefileException("Failed to write measure extremes for record %s. Expected floats" % self.shpNum)
            try:
                if hasattr(s,"m"): 
                    # if m values are stored in attribute
                    f.write(pack("<%sd" % len(s.m), *[m if m is not None else NODATA for m in s.m]))
                else:
                    # if m values are stored as 3rd/4th dimension
                    # 0-index position of m value is 3 if z type (x,y,z,m), or 2 if m type (x,y,m)
                    mpos = 3 if s.shapeType in (13,15,18,31) else 2
                    [f.write(pack("<d", p[mpos] if len(p) > mpos and p[mpos] is not None else NODATA)) for p in s.points]
            except error:
                raise ShapefileException("Failed to write measure values for record %s. Expected floats" % self.shpNum)
        # Write a single point
        if s.shapeType in (1,11,21):
            try:
                f.write(pack("<2d", s.points[0][0], s.points[0][1]))
            except error:
                raise ShapefileException("Failed to write point for record %s. Expected floats." % self.shpNum)
        # Write a single Z value
        # Note: missing z values are autoset to 0, but not sure if this is ideal.
        if s.shapeType == 11:
            # update the global z box
            self.__zbox(s)
            # then write value
            if hasattr(s, "z"):
                # if z values are stored in attribute
                try:
                    if not s.z:
                        s.z = (0,)
                    f.write(pack("<d", s.z[0]))
                except error:
                    raise ShapefileException("Failed to write elevation value for record %s. Expected floats." % self.shpNum)
            else:
                # if z values are stored as 3rd dimension
                try:
                    if len(s.points[0]) < 3:
                        s.points[0].append(0)
                    f.write(pack("<d", s.points[0][2]))
                except error:
                    raise ShapefileException("Failed to write elevation value for record %s. Expected floats." % self.shpNum)
        # Write a single M value
        # Note: missing m values are autoset to NODATA.
        if s.shapeType in (11,21):
            # update the global m box
            self.__mbox(s)
            # then write value
            if hasattr(s, "m"):
                # if m values are stored in attribute
                try:
                    if not s.m or s.m[0] is None:
                        s.m = (NODATA,) 
                    f.write(pack("<1d", s.m[0]))
                except error:
                    raise ShapefileException("Failed to write measure value for record %s. Expected floats." % self.shpNum)
            else:
                # if m values are stored as 3rd/4th dimension
                # 0-index position of m value is 3 if z type (x,y,z,m), or 2 if m type (x,y,m)
                try:
                    mpos = 3 if s.shapeType == 11 else 2
                    if len(s.points[0]) < mpos+1:
                        s.points[0].append(NODATA)
                    elif s.points[0][mpos] is None:
                        s.points[0][mpos] = NODATA
                    f.write(pack("<1d", s.points[0][mpos]))
                except error:
                    raise ShapefileException("Failed to write measure value for record %s. Expected floats." % self.shpNum)
        # Finalize record length as 16-bit words
        finish = f.tell()
        length = (finish - start) // 2
        # start - 4 bytes is the content length field
        f.seek(start-4)
        f.write(pack(">i", length))
        f.seek(finish)
        return offset,length

    def __shxRecord(self, offset, length):
         """Writes the shx records."""
         f = self.__getFileObj(self.shx)
         try:
             f.write(pack(">i", offset // 2))
         except error:
             raise ShapefileException('The .shp file has reached its file size limit > 4294967294 bytes (4.29 GB). To fix this, break up your file into multiple smaller ones.')
         f.write(pack(">i", length))

    def record(self, *recordList, **recordDict):
        """Creates a dbf attribute record. You can submit either a sequence of
        field values or keyword arguments of field names and values. Before
        adding records you must add fields for the record values using the
        field() method. If the record values exceed the number of fields the
        extra ones won't be added. In the case of using keyword arguments to specify
        field/value pairs only fields matching the already registered fields
        will be added."""
        # Balance if already not balanced
        if self.autoBalance and self.recNum > self.shpNum:
            self.balance()
            
        fieldCount = sum((1 for field in self.fields if field[0] != 'DeletionFlag'))
        if recordList:
            record = list(recordList)
            while len(record) < fieldCount:
                record.append("")
        elif recordDict:
            record = []
            for field in self.fields:
                if field[0] == 'DeletionFlag':
                    continue # ignore deletionflag field in case it was specified
                if field[0] in recordDict:
                    val = recordDict[field[0]]
                    if val is None:
                        record.append("")
                    else:
                        record.append(val)
                else:
                    record.append("") # need empty value for missing dict entries
        else:
            # Blank fields for empty record
            record = ["" for _ in range(fieldCount)]
        self.__dbfRecord(record)

    def __dbfRecord(self, record):
        """Writes the dbf records."""
        f = self.__getFileObj(self.dbf)
        if self.recNum == 0:
            # first records, so all fields should be set
            # allowing us to write the dbf header
            # cannot change the fields after this point
            self.__dbfHeader()
        # first byte of the record is deletion flag, always disabled
        f.write(b' ')
        # begin
        self.recNum += 1
        fields = (field for field in self.fields if field[0] != 'DeletionFlag') # ignore deletionflag field in case it was specified
        for (fieldName, fieldType, size, deci), value in zip(fields, record):
            # write 
            fieldType = fieldType.upper()
            size = int(size)
            if fieldType in ("N","F"):
                # numeric or float: number stored as a string, right justified, and padded with blanks to the width of the field.
                if value in MISSING:
                    value = b"*"*size # QGIS NULL
                elif not deci:
                    # force to int
                    try:
                        # first try to force directly to int.
                        # forcing a large int to float and back to int
                        # will lose information and result in wrong nr.
                        value = int(value) 
                    except ValueError:
                        # forcing directly to int failed, so was probably a float.
                        value = int(float(value))
                    value = format(value, "d")[:size].rjust(size) # caps the size if exceeds the field size
                else:
                    value = float(value)
                    value = format(value, ".%sf"%deci)[:size].rjust(size) # caps the size if exceeds the field size
            elif fieldType == "D":
                # date: 8 bytes - date stored as a string in the format YYYYMMDD.
                if isinstance(value, date):
                    value = '{:04d}{:02d}{:02d}'.format(value.year, value.month, value.day)
                elif isinstance(value, list) and len(value) == 3:
                    value = '{:04d}{:02d}{:02d}'.format(*value)
                elif value in MISSING:
                    value = b'0' * 8 # QGIS NULL for date type
                elif is_string(value) and len(value) == 8:
                    pass # value is already a date string
                else:
                    raise ShapefileException("Date values must be either a datetime.date object, a list, a YYYYMMDD string, or a missing value.")
            elif fieldType == 'L':
                # logical: 1 byte - initialized to 0x20 (space) otherwise T or F.
                if value in MISSING:
                    value = b' ' # missing is set to space
                elif value in [True,1]:
                    value = b'T'
                elif value in [False,0]:
                    value = b'F'
                else:
                    value = b' ' # unknown is set to space
            else:
                # anything else is forced to string, truncated to the length of the field
                value = b(value, self.encoding, self.encodingErrors)[:size].ljust(size)
            if not isinstance(value, bytes):
                # just in case some of the numeric format() and date strftime() results are still in unicode (Python 3 only)
                value = b(value, 'ascii', self.encodingErrors) # should be default ascii encoding
            if len(value) != size:
                raise ShapefileException(
                    "Shapefile Writer unable to pack incorrect sized value"
                    " (size %d) into field '%s' (size %d)." % (len(value), fieldName, size))
            f.write(value)

    def balance(self):
        """Adds corresponding empty attributes or null geometry records depending
        on which type of record was created to make sure all three files
        are in synch."""
        while self.recNum > self.shpNum:
            self.null()
        while self.recNum < self.shpNum:
            self.record()


    def null(self):
        """Creates a null shape."""
        self.shape(Shape(NULL))


    def point(self, x, y):
        """Creates a POINT shape."""
        shapeType = POINT
        pointShape = Shape(shapeType)
        pointShape.points.append([x, y])
        self.shape(pointShape)

    def pointm(self, x, y, m=None):
        """Creates a POINTM shape.
        If the m (measure) value is not set, it defaults to NoData."""
        shapeType = POINTM
        pointShape = Shape(shapeType)
        pointShape.points.append([x, y, m])
        self.shape(pointShape)

    def pointz(self, x, y, z=0, m=None):
        """Creates a POINTZ shape.
        If the z (elevation) value is not set, it defaults to 0.
        If the m (measure) value is not set, it defaults to NoData."""
        shapeType = POINTZ
        pointShape = Shape(shapeType)
        pointShape.points.append([x, y, z, m])
        self.shape(pointShape)
        

    def multipoint(self, points):
        """Creates a MULTIPOINT shape.
        Points is a list of xy values."""
        shapeType = MULTIPOINT
        points = [points] # nest the points inside a list to be compatible with the generic shapeparts method
        self._shapeparts(parts=points, shapeType=shapeType)

    def multipointm(self, points):
        """Creates a MULTIPOINTM shape.
        Points is a list of xym values.
        If the m (measure) value is not included, it defaults to None (NoData)."""
        shapeType = MULTIPOINTM
        points = [points] # nest the points inside a list to be compatible with the generic shapeparts method
        self._shapeparts(parts=points, shapeType=shapeType)

    def multipointz(self, points):
        """Creates a MULTIPOINTZ shape.
        Points is a list of xyzm values.
        If the z (elevation) value is not included, it defaults to 0.
        If the m (measure) value is not included, it defaults to None (NoData)."""
        shapeType = MULTIPOINTZ
        points = [points] # nest the points inside a list to be compatible with the generic shapeparts method
        self._shapeparts(parts=points, shapeType=shapeType)


    def line(self, lines):
        """Creates a POLYLINE shape.
        Lines is a collection of lines, each made up of a list of xy values."""
        shapeType = POLYLINE
        self._shapeparts(parts=lines, shapeType=shapeType)

    def linem(self, lines):
        """Creates a POLYLINEM shape.
        Lines is a collection of lines, each made up of a list of xym values.
        If the m (measure) value is not included, it defaults to None (NoData)."""
        shapeType = POLYLINEM
        self._shapeparts(parts=lines, shapeType=shapeType)

    def linez(self, lines):
        """Creates a POLYLINEZ shape.
        Lines is a collection of lines, each made up of a list of xyzm values.
        If the z (elevation) value is not included, it defaults to 0.
        If the m (measure) value is not included, it defaults to None (NoData)."""
        shapeType = POLYLINEZ
        self._shapeparts(parts=lines, shapeType=shapeType)


    def poly(self, polys):
        """Creates a POLYGON shape.
        Polys is a collection of polygons, each made up of a list of xy values.
        Note that for ordinary polygons the coordinates must run in a clockwise direction.
        If some of the polygons are holes, these must run in a counterclockwise direction."""
        shapeType = POLYGON
        self._shapeparts(parts=polys, shapeType=shapeType)

    def polym(self, polys):
        """Creates a POLYGONM shape.
        Polys is a collection of polygons, each made up of a list of xym values.
        Note that for ordinary polygons the coordinates must run in a clockwise direction.
        If some of the polygons are holes, these must run in a counterclockwise direction.
        If the m (measure) value is not included, it defaults to None (NoData)."""
        shapeType = POLYGONM
        self._shapeparts(parts=polys, shapeType=shapeType)

    def polyz(self, polys):
        """Creates a POLYGONZ shape.
        Polys is a collection of polygons, each made up of a list of xyzm values.
        Note that for ordinary polygons the coordinates must run in a clockwise direction.
        If some of the polygons are holes, these must run in a counterclockwise direction.
        If the z (elevation) value is not included, it defaults to 0.
        If the m (measure) value is not included, it defaults to None (NoData)."""
        shapeType = POLYGONZ
        self._shapeparts(parts=polys, shapeType=shapeType)


    def multipatch(self, parts, partTypes):
        """Creates a MULTIPATCH shape.
        Parts is a collection of 3D surface patches, each made up of a list of xyzm values.
        PartTypes is a list of types that define each of the surface patches.
        The types can be any of the following module constants: TRIANGLE_STRIP,
        TRIANGLE_FAN, OUTER_RING, INNER_RING, FIRST_RING, or RING.
        If the z (elevation) value is not included, it defaults to 0.
        If the m (measure) value is not included, it defaults to None (NoData)."""
        shapeType = MULTIPATCH
        polyShape = Shape(shapeType)
        polyShape.parts = []
        polyShape.points = []
        for part in parts:
            # set part index position
            polyShape.parts.append(len(polyShape.points))
            # add points
            for point in part:
                # Ensure point is list
                if not isinstance(point, list):
                    point = list(point)
                polyShape.points.append(point)
        polyShape.partTypes = partTypes
        # write the shape
        self.shape(polyShape)


    def _shapeparts(self, parts, shapeType):
        """Internal method for adding a shape that has multiple collections of points (parts):
        lines, polygons, and multipoint shapes.
        """
        polyShape = Shape(shapeType)
        polyShape.parts = []
        polyShape.points = []
        # Make sure polygon rings (parts) are closed
        if shapeType in (5,15,25,31):
            for part in parts:
                if part[0] != part[-1]:
                    part.append(part[0])
        # Add points and part indexes
        for part in parts:
            # set part index position
            polyShape.parts.append(len(polyShape.points))
            # add points
            for point in part:
                # Ensure point is list
                if not isinstance(point, list):
                    point = list(point)
                polyShape.points.append(point)
        # write the shape
        self.shape(polyShape)

    def field(self, name, fieldType="C", size="50", decimal=0):
        """Adds a dbf field descriptor to the shapefile."""
        if fieldType == "D":
            size = "8"
            decimal = 0
        elif fieldType == "L":
            size = "1"
            decimal = 0
        if len(self.fields) >= 2046:
            raise ShapefileException(
                "Shapefile Writer reached maximum number of fields: 2046.")
        self.fields.append((name, fieldType, size, decimal))

##    def saveShp(self, target):
##        """Save an shp file."""
##        if not hasattr(target, "write"):
##            target = os.path.splitext(target)[0] + '.shp'
##        self.shp = self.__getFileObj(target)
##        self.__shapefileHeader(self.shp, headerType='shp')
##        self.shp.seek(100)
##        self._shp.seek(0)
##        chunk = True
##        while chunk:
##            chunk = self._shp.read(self.bufsize)
##            self.shp.write(chunk)
##
##    def saveShx(self, target):
##        """Save an shx file."""
##        if not hasattr(target, "write"):
##            target = os.path.splitext(target)[0] + '.shx'
##        self.shx = self.__getFileObj(target)
##        self.__shapefileHeader(self.shx, headerType='shx')
##        self.shx.seek(100)
##        self._shx.seek(0)
##        chunk = True
##        while chunk:
##            chunk = self._shx.read(self.bufsize)
##            self.shx.write(chunk)
##
##    def saveDbf(self, target):
##        """Save a dbf file."""
##        if not hasattr(target, "write"):
##            target = os.path.splitext(target)[0] + '.dbf'
##        self.dbf = self.__getFileObj(target)
##        self.__dbfHeader() # writes to .dbf
##        self._dbf.seek(0)
##        chunk = True
##        while chunk:
##            chunk = self._dbf.read(self.bufsize)
##            self.dbf.write(chunk)

##    def save(self, target=None, shp=None, shx=None, dbf=None):
##        """Save the shapefile data to three files or
##        three file-like objects. SHP and DBF files can also
##        be written exclusively using saveShp, saveShx, and saveDbf respectively.
##        If target is specified but not shp, shx, or dbf then the target path and
##        file name are used.  If no options or specified, a unique base file name
##        is generated to save the files and the base file name is returned as a 
##        string. 
##        """
##        # Balance if already not balanced
##        if shp and dbf:
##            if self.autoBalance:
##                self.balance()
##            if self.recNum != self.shpNum:
##                raise ShapefileException("When saving both the dbf and shp file, "
##                                         "the number of records (%s) must correspond "
##                                         "with the number of shapes (%s)" % (self.recNum, self.shpNum))
##        # Save
##        if shp:
##            self.saveShp(shp)
##        if shx:
##            self.saveShx(shx)
##        if dbf:
##            self.saveDbf(dbf)
##        # Create a unique file name if one is not defined
##        if not shp and not shx and not dbf:
##            generated = False
##            if not target:
##                temp = tempfile.NamedTemporaryFile(prefix="shapefile_",dir=os.getcwd())
##                target = temp.name
##                generated = True         
##            self.saveShp(target)
##            self.shp.close()
##            self.saveShx(target)
##            self.shx.close()
##            self.saveDbf(target)
##            self.dbf.close()
##            if generated:
##                return target

# Begin Testing
def test(**kwargs):
    import doctest
    doctest.NORMALIZE_WHITESPACE = 1
    verbosity = kwargs.get('verbose', 0)
    if verbosity == 0:
        print('Running doctests...')

    # ignore py2-3 unicode differences
    import re
    class Py23DocChecker(doctest.OutputChecker):
        def check_output(self, want, got, optionflags):
            if sys.version_info[0] == 2:
                got = re.sub("u'(.*?)'", "'\\1'", got)
                got = re.sub('u"(.*?)"', '"\\1"', got)
            res = doctest.OutputChecker.check_output(self, want, got, optionflags)
            return res
        def summarize(self):
            doctest.OutputChecker.summarize(True)

    # run tests
    runner = doctest.DocTestRunner(checker=Py23DocChecker(), verbose=verbosity)
    with open("README.md","rb") as fobj:
        test = doctest.DocTestParser().get_doctest(string=fobj.read().decode("utf8").replace('\r\n','\n'), globs={}, name="README", filename="README.md", lineno=0)
    failure_count, test_count = runner.run(test)

    # print results
    if verbosity:
        runner.summarize(True)
    else:
        if failure_count == 0:
            print('All test passed successfully')
        elif failure_count > 0:
            runner.summarize(verbosity)

    return failure_count
    
if __name__ == "__main__":
    """
    Doctests are contained in the file 'README.md', and are tested using the built-in
    testing libraries. 
    """
    failure_count = test()
    sys.exit(failure_count)
