# -*- coding: utf-8 -*-
# Licensed under a 3-clause BSD style license - see LICENSE.rst

# Note that  files generated by lex/yacc not always fully py 2/3 compatible.
# Hence, the ``clean_parse_tables.py`` tool in the astropy-tools
# (https://github.com/astropy/astropy-tools) repository should be used to fix
# this when/if lextab/parsetab files are re-generated.

"""
This module contains utility functions that are for internal use in
astropy.coordinates.angles. Mainly they are conversions from one format
of data to another.
"""
from __future__ import (absolute_import, division, print_function,
                        unicode_literals)

import os
from warnings import warn

import numpy as np

from .errors import (IllegalHourWarning, IllegalHourError,
                     IllegalMinuteWarning, IllegalMinuteError,
                     IllegalSecondWarning, IllegalSecondError)
from ..utils import format_exception
from .. import units as u


class _AngleParser(object):
    """
    Parses the various angle formats including:

       * 01:02:30.43 degrees
       * 1 2 0 hours
       * 1°2′3″
       * 1d2m3s
       * -1h2m3s

    This class should not be used directly.  Use `parse_angle`
    instead.
    """
    def __init__(self):
        # TODO: in principle, the parser should be invalidated if we change unit
        # system (from CDS to FITS, say).  Might want to keep a link to the
        # unit_registry used, and regenerate the parser/lexer if it changes.
        # Alternatively, perhaps one should not worry at all and just pre-
        # generate the parser for each release (as done for unit formats).
        # For some discussion of this problem, see
        # https://github.com/astropy/astropy/issues/5350#issuecomment-248770151
        if '_parser' not in _AngleParser.__dict__:
            _AngleParser._parser, _AngleParser._lexer = self._make_parser()

    @classmethod
    def _get_simple_unit_names(cls):
        simple_units = set(
            u.radian.find_equivalent_units(include_prefix_units=True))
        simple_unit_names = set()
        # We filter out degree and hourangle, since those are treated
        # separately.
        for unit in simple_units:
            if unit != u.deg and unit != u.hourangle:
                simple_unit_names.update(unit.names)
        return list(simple_unit_names)

    @classmethod
    def _make_parser(cls):
        from ..extern.ply import lex, yacc

        # List of token names.
        tokens = (
            'SIGN',
            'UINT',
            'UFLOAT',
            'COLON',
            'DEGREE',
            'HOUR',
            'MINUTE',
            'SECOND',
            'SIMPLE_UNIT'
        )

        # NOTE THE ORDERING OF THESE RULES IS IMPORTANT!!
        # Regular expression rules for simple tokens
        def t_UFLOAT(t):
            r'((\d+\.\d*)|(\.\d+))([eE][+-−]?\d+)?'
            # The above includes Unicode "MINUS SIGN" \u2212.  It is
            # important to include the hyphen last, or the regex will
            # treat this as a range.
            t.value = float(t.value.replace('−', '-'))
            return t

        def t_UINT(t):
            r'\d+'
            t.value = int(t.value)
            return t

        def t_SIGN(t):
            r'[+−-]'
            # The above include Unicode "MINUS SIGN" \u2212.  It is
            # important to include the hyphen last, or the regex will
            # treat this as a range.
            if t.value == '+':
                t.value = 1.0
            else:
                t.value = -1.0
            return t

        def t_SIMPLE_UNIT(t):
            t.value = u.Unit(t.value)
            return t
        t_SIMPLE_UNIT.__doc__ = '|'.join(
            '(?:{0})'.format(x) for x in cls._get_simple_unit_names())

        t_COLON = ':'
        t_DEGREE = r'd(eg(ree(s)?)?)?|°'
        t_HOUR = r'hour(s)?|h(r)?|ʰ'
        t_MINUTE = r'm(in(ute(s)?)?)?|′|\'|ᵐ'
        t_SECOND = r's(ec(ond(s)?)?)?|″|\"|ˢ'

        # A string containing ignored characters (spaces)
        t_ignore = ' '

        # Error handling rule
        def t_error(t):
            raise ValueError(
                "Invalid character at col {0}".format(t.lexpos))

        # Build the lexer
        # PY2: need str() to ensure we do not pass on a unicode object.
        lexer = lex.lex(optimize=True, lextab=str('angle_lextab'),
                        outputdir=os.path.dirname(__file__))

        def p_angle(p):
            '''
            angle : hms
                  | dms
                  | arcsecond
                  | arcminute
                  | simple
            '''
            p[0] = p[1]

        def p_sign(p):
            '''
            sign : SIGN
                 |
            '''
            if len(p) == 2:
                p[0] = p[1]
            else:
                p[0] = 1.0

        def p_ufloat(p):
            '''
            ufloat : UFLOAT
                   | UINT
            '''
            p[0] = float(p[1])

        def p_colon(p):
            '''
            colon : sign UINT COLON ufloat
                  | sign UINT COLON UINT COLON ufloat
            '''
            if len(p) == 5:
                p[0] = (p[1] * p[2], p[4])
            elif len(p) == 7:
                p[0] = (p[1] * p[2], p[4], p[6])

        def p_spaced(p):
            '''
            spaced : sign UINT ufloat
                   | sign UINT UINT ufloat
            '''
            if len(p) == 4:
                p[0] = (p[1] * p[2], p[3])
            elif len(p) == 5:
                p[0] = (p[1] * p[2], p[3], p[4])

        def p_generic(p):
            '''
            generic : colon
                    | spaced
                    | sign UFLOAT
                    | sign UINT
            '''
            if len(p) == 2:
                p[0] = p[1]
            else:
                p[0] = p[1] * p[2]

        def p_hms(p):
            '''
            hms : sign UINT HOUR
                | sign UINT HOUR ufloat
                | sign UINT HOUR UINT MINUTE
                | sign UINT HOUR UFLOAT MINUTE
                | sign UINT HOUR UINT MINUTE ufloat
                | sign UINT HOUR UINT MINUTE ufloat SECOND
                | generic HOUR
            '''
            if len(p) == 3:
                p[0] = (p[1], u.hourangle)
            elif len(p) == 4:
                p[0] = (p[1] * p[2], u.hourangle)
            elif len(p) in (5, 6):
                p[0] = ((p[1] * p[2], p[4]), u.hourangle)
            elif len(p) in (7, 8):
                p[0] = ((p[1] * p[2], p[4], p[6]), u.hourangle)

        def p_dms(p):
            '''
            dms : sign UINT DEGREE
                | sign UINT DEGREE ufloat
                | sign UINT DEGREE UINT MINUTE
                | sign UINT DEGREE UFLOAT MINUTE
                | sign UINT DEGREE UINT MINUTE ufloat
                | sign UINT DEGREE UINT MINUTE ufloat SECOND
                | generic DEGREE
            '''
            if len(p) == 3:
                p[0] = (p[1], u.degree)
            elif len(p) == 4:
                p[0] = (p[1] * p[2], u.degree)
            elif len(p) in (5, 6):
                p[0] = ((p[1] * p[2], p[4]), u.degree)
            elif len(p) in (7, 8):
                p[0] = ((p[1] * p[2], p[4], p[6]), u.degree)

        def p_simple(p):
            '''
            simple : generic
                   | generic SIMPLE_UNIT
            '''
            if len(p) == 2:
                p[0] = (p[1], None)
            else:
                p[0] = (p[1], p[2])

        def p_arcsecond(p):
            '''
            arcsecond : generic SECOND
            '''
            p[0] = (p[1], u.arcsecond)

        def p_arcminute(p):
            '''
            arcminute : generic MINUTE
            '''
            p[0] = (p[1], u.arcminute)

        def p_error(p):
            raise ValueError

        # PY2: need str() to ensure we do not pass on a unicode object.
        parser = yacc.yacc(debug=False, tabmodule=str('angle_parsetab'),
                           outputdir=os.path.dirname(__file__),
                           write_tables=True)

        return parser, lexer

    def parse(self, angle, unit, debug=False):
        try:
            found_angle, found_unit = self._parser.parse(
                angle, lexer=self._lexer, debug=debug)
        except ValueError as e:
            if str(e):
                raise ValueError("{0} in angle {1!r}".format(
                    str(e), angle))
            else:
                raise ValueError(
                    "Syntax error parsing angle {0!r}".format(angle))

        if unit is None and found_unit is None:
            raise u.UnitsError("No unit specified")

        return found_angle, found_unit


def _check_hour_range(hrs):
    """
    Checks that the given value is in the range (-24, 24).
    """
    if np.any(np.abs(hrs) == 24.):
        warn(IllegalHourWarning(hrs, 'Treating as 24 hr'))
    elif np.any(hrs < -24.) or np.any(hrs > 24.):
        raise IllegalHourError(hrs)


def _check_minute_range(m):
    """
    Checks that the given value is in the range [0,60].  If the value
    is equal to 60, then a warning is raised.
    """
    if np.any(m == 60.):
        warn(IllegalMinuteWarning(m, 'Treating as 0 min, +1 hr/deg'))
    elif np.any(m < -60.) or np.any(m > 60.):
        # "Error: minutes not in range [-60,60) ({0}).".format(min))
        raise IllegalMinuteError(m)


def _check_second_range(sec):
    """
    Checks that the given value is in the range [0,60].  If the value
    is equal to 60, then a warning is raised.
    """
    if np.any(sec == 60.):
        warn(IllegalSecondWarning(sec, 'Treating as 0 sec, +1 min'))
    elif sec is None:
        pass
    elif np.any(sec < -60.) or np.any(sec > 60.):
        # "Error: seconds not in range [-60,60) ({0}).".format(sec))
        raise IllegalSecondError(sec)


def check_hms_ranges(h, m, s):
    """
    Checks that the given hour, minute and second are all within
    reasonable range.
    """
    _check_hour_range(h)
    _check_minute_range(m)
    _check_second_range(s)
    return None


def parse_angle(angle, unit=None, debug=False):
    """
    Parses an input string value into an angle value.

    Parameters
    ----------
    angle : str
        A string representing the angle.  May be in one of the following forms:

            * 01:02:30.43 degrees
            * 1 2 0 hours
            * 1°2′3″
            * 1d2m3s
            * -1h2m3s

    unit : `~astropy.units.UnitBase` instance, optional
        The unit used to interpret the string.  If ``unit`` is not
        provided, the unit must be explicitly represented in the
        string, either at the end or as number separators.

    debug : bool, optional
        If `True`, print debugging information from the parser.

    Returns
    -------
    value, unit : tuple
        ``value`` is the value as a floating point number or three-part
        tuple, and ``unit`` is a `Unit` instance which is either the
        unit passed in or the one explicitly mentioned in the input
        string.
    """
    return _AngleParser().parse(angle, unit, debug=debug)


def degrees_to_dms(d):
    """
    Convert a floating-point degree value into a ``(degree, arcminute,
    arcsecond)`` tuple.
    """
    sign = np.copysign(1.0, d)

    (df, d) = np.modf(np.abs(d))  # (degree fraction, degree)
    (mf, m) = np.modf(df * 60.)  # (minute fraction, minute)
    s = mf * 60.

    return np.floor(sign * d), sign * np.floor(m), sign * s


def dms_to_degrees(d, m, s=None):
    """
    Convert degrees, arcminute, arcsecond to a float degrees value.
    """

    _check_minute_range(m)
    _check_second_range(s)

    # determine sign
    sign = np.copysign(1.0, d)

    try:
        d = np.floor(np.abs(d))
        if s is None:
            m = np.abs(m)
            s = 0
        else:
            m = np.floor(np.abs(m))
            s = np.abs(s)
    except ValueError:
        raise ValueError(format_exception(
            "{func}: dms values ({1[0]},{2[1]},{3[2]}) could not be "
            "converted to numbers.", d, m, s))

    return sign * (d + m / 60. + s / 3600.)


def hms_to_hours(h, m, s=None):
    """
    Convert hour, minute, second to a float hour value.
    """

    check_hms_ranges(h, m, s)

    # determine sign
    sign = np.copysign(1.0, h)

    try:
        h = np.floor(np.abs(h))
        if s is None:
            m = np.abs(m)
            s = 0
        else:
            m = np.floor(np.abs(m))
            s = np.abs(s)
    except ValueError:
        raise ValueError(format_exception(
            "{func}: HMS values ({1[0]},{2[1]},{3[2]}) could not be "
            "converted to numbers.", h, m, s))

    return sign * (h + m / 60. + s / 3600.)


def hms_to_degrees(h, m, s):
    """
    Convert hour, minute, second to a float degrees value.
    """

    return hms_to_hours(h, m, s) * 15.


def hms_to_radians(h, m, s):
    """
    Convert hour, minute, second to a float radians value.
    """

    return u.degree.to(u.radian, hms_to_degrees(h, m, s))


def hms_to_dms(h, m, s):
    """
    Convert degrees, arcminutes, arcseconds to an ``(hour, minute, second)``
    tuple.
    """

    return degrees_to_dms(hms_to_degrees(h, m, s))


def hours_to_decimal(h):
    """
    Convert any parseable hour value into a float value.
    """
    from . import angles
    return angles.Angle(h, unit=u.hourangle).hour


def hours_to_radians(h):
    """
    Convert an angle in Hours to Radians.
    """

    return u.hourangle.to(u.radian, h)


def hours_to_hms(h):
    """
    Convert an floating-point hour value into an ``(hour, minute,
    second)`` tuple.
    """

    sign = np.copysign(1.0, h)

    (hf, h) = np.modf(np.abs(h))  # (degree fraction, degree)
    (mf, m) = np.modf(hf * 60.0)  # (minute fraction, minute)
    s = mf * 60.0

    return (np.floor(sign * h), sign * np.floor(m), sign * s)


def radians_to_degrees(r):
    """
    Convert an angle in Radians to Degrees.
    """
    return u.radian.to(u.degree, r)


def radians_to_hours(r):
    """
    Convert an angle in Radians to Hours.
    """
    return u.radian.to(u.hourangle, r)


def radians_to_hms(r):
    """
    Convert an angle in Radians to an ``(hour, minute, second)`` tuple.
    """

    hours = radians_to_hours(r)
    return hours_to_hms(hours)


def radians_to_dms(r):
    """
    Convert an angle in Radians to an ``(degree, arcminute,
    arcsecond)`` tuple.
    """

    degrees = u.radian.to(u.degree, r)
    return degrees_to_dms(degrees)


def sexagesimal_to_string(values, precision=None, pad=False, sep=(':',),
                          fields=3):
    """
    Given an already separated tuple of sexagesimal values, returns
    a string.

    See `hours_to_string` and `degrees_to_string` for a higher-level
    interface to this functionality.
    """

    # If the coordinates are negative, we need to take the absolute value of
    # the (arc)minutes and (arc)seconds. We need to use np.abs because abs(-0)
    # is -0.
    values = (values[0], np.abs(values[1]), np.abs(values[2]))

    if pad:
        # Check to see if values[0] is negative, using np.copysign to handle -0
        if np.copysign(1.0, values[0]) == -1:
            pad = 3
        else:
            pad = 2
    else:
        pad = 0

    if not isinstance(sep, tuple):
        sep = tuple(sep)

    if fields < 1 or fields > 3:
        raise ValueError(
            "fields must be 1, 2, or 3")

    if not sep:  # empty string, False, or None, etc.
        sep = ('', '', '')
    elif len(sep) == 1:
        if fields == 3:
            sep = sep + (sep[0], '')
        elif fields == 2:
            sep = sep + ('', '')
        else:
            sep = ('', '', '')
    elif len(sep) == 2:
        sep = sep + ('',)
    elif len(sep) != 3:
        raise ValueError(
            "Invalid separator specification for converting angle to string.")

    # Simplify the expression based on the requested precision.  For
    # example, if the seconds will round up to 60, we should convert
    # it to 0 and carry upwards.  If the field is hidden (by the
    # fields kwarg) we round up around the middle, 30.0.
    if precision is None:
        rounding_thresh = 60.0 - (10.0 ** -4)
    else:
        rounding_thresh = 60.0 - (10.0 ** -precision)

    values = list(values)
    if fields == 3 and values[2] >= rounding_thresh:
        values[2] = 0.0
        values[1] += 1.0
    elif fields < 3 and values[2] >= 30.0:
        values[1] += 1.0

    if fields >= 2 and int(values[1]) >= 60.0:
        values[1] = 0.0
        values[0] += 1.0
    elif fields < 2 and int(values[1]) >= 30.0:
        values[0] += 1.0

    literal = []
    last_value = ''
    literal.append('{0:0{pad}.0f}{sep[0]}')
    if fields >= 2:
        literal.append('{1:02d}{sep[1]}')
    if fields == 3:
        if precision is None:
            last_value = '{0:.4f}'.format(abs(values[2]))
            last_value = last_value.rstrip('0').rstrip('.')
        else:
            last_value = '{0:.{precision}f}'.format(
                abs(values[2]), precision=precision)
        if len(last_value) == 1 or last_value[1] == '.':
            last_value = '0' + last_value
        literal.append('{last_value}{sep[2]}')
    literal = ''.join(literal)
    return literal.format(values[0], int(abs(values[1])), abs(values[2]),
                          sep=sep, pad=pad,
                          last_value=last_value)


def hours_to_string(h, precision=5, pad=False, sep=('h', 'm', 's'),
                    fields=3):
    """
    Takes a decimal hour value and returns a string formatted as hms with
    separator specified by the 'sep' parameter.

    ``h`` must be a scalar.
    """
    h, m, s = hours_to_hms(h)
    return sexagesimal_to_string((h, m, s), precision=precision, pad=pad,
                                 sep=sep, fields=fields)


def degrees_to_string(d, precision=5, pad=False, sep=':', fields=3):
    """
    Takes a decimal hour value and returns a string formatted as dms with
    separator specified by the 'sep' parameter.

    ``d`` must be a scalar.
    """
    d, m, s = degrees_to_dms(d)
    return sexagesimal_to_string((d, m, s), precision=precision, pad=pad,
                                 sep=sep, fields=fields)


def angular_separation(lon1, lat1, lon2, lat2):
    """
    Angular separation between two points on a sphere.

    Parameters
    ----------
    lon1, lat1, lon2, lat2 : `Angle`, `~astropy.units.Quantity` or float
        Longitude and latitude of the two points. Quantities should be in
        angular units; floats in radians.

    Returns
    -------
    angular separation : `~astropy.units.Quantity` or float
        Type depends on input; `Quantity` in angular units, or float in
        radians.

    Notes
    -----
    The angular separation is calculated using the Vincenty formula [1]_,
    which is slightly more complex and computationally expensive than
    some alternatives, but is stable at at all distances, including the
    poles and antipodes.

    .. [1] http://en.wikipedia.org/wiki/Great-circle_distance
    """

    sdlon = np.sin(lon2 - lon1)
    cdlon = np.cos(lon2 - lon1)
    slat1 = np.sin(lat1)
    slat2 = np.sin(lat2)
    clat1 = np.cos(lat1)
    clat2 = np.cos(lat2)

    num1 = clat2 * sdlon
    num2 = clat1 * slat2 - slat1 * clat2 * cdlon
    denominator = slat1 * slat2 + clat1 * clat2 * cdlon

    return np.arctan2(np.hypot(num1, num2), denominator)


def position_angle(lon1, lat1, lon2, lat2):
    """
    Position Angle (East of North) between two points on a sphere.

    Parameters
    ----------
    lon1, lat1, lon2, lat2 : `Angle`, `~astropy.units.Quantity` or float
        Longitude and latitude of the two points. Quantities should be in
        angular units; floats in radians.

    Returns
    -------
    pa : `~astropy.coordinates.Angle`
        The (positive) position angle of the vector pointing from position 1 to
        position 2.  If any of the angles are arrays, this will contain an array
        following the appropriate `numpy` broadcasting rules.

    """
    from .angles import Angle

    deltalon = lon2 - lon1
    colat = np.cos(lat2)

    x = np.sin(lat2) * np.cos(lat1) - colat * np.sin(lat1) * np.cos(deltalon)
    y = np.sin(deltalon) * colat

    return Angle(np.arctan2(y, x), u.radian).wrap_at(360*u.deg)
