# cython: language_level=3str
# cython: auto_pickle=False
"""
Python Lexical Analyser

Scanning an input stream
"""
from __future__ import absolute_import

import cython

cython.declare(BOL=object, EOL=object, EOF=object, NOT_FOUND=object)  # noqa:E402

from . import Errors
from .Regexps import BOL, EOL, EOF

NOT_FOUND = object()


class Scanner(object):
    """
    A Scanner is used to read tokens from a stream of characters
    using the token set specified by a Plex.Lexicon.

    Constructor:

      Scanner(lexicon, stream, name = '')

        See the docstring of the __init__ method for details.

    Methods:

      See the docstrings of the individual methods for more
      information.

      read() --> (value, text)
        Reads the next lexical token from the stream.

      position() --> (name, line, col)
        Returns the position of the last token read using the
        read() method.

      begin(state_name)
        Causes scanner to change state.

      produce(value [, text])
        Causes return of a token value to the caller of the
        Scanner.

    """

    #  lexicon = None        # Lexicon
    #  stream = None         # file-like object
    #  name = ''
    #  buffer = ''
    #
    #  These positions are used by the scanner to track its internal state:
    #  buf_start_pos = 0     # position in input of start of buffer
    #  next_pos = 0          # position in input of next char to read
    #  cur_pos = 0           # position in input of current char
    #  cur_line = 1          # line number of current char
    #  cur_line_start = 0    # position in input of start of current line
    #  start_pos = 0         # position in input of start of token
    #  current_scanner_position_tuple = ("", 0, 0)
    #        tuple of filename, line number and position in line, really mainly for error reporting
    #
    #  These positions are used to track what was read from the queue
    #   (which may differ from the internal state when tokens are replaced onto the queue)
    #  last_token_position_tuple = ("", 0, 0)  # tuple of filename, line number and position in line

    #  text = None           # text of last token read
    #  initial_state = None  # Node
    #  state_name = ''       # Name of initial state
    #  queue = None          # list of tokens and positions to be returned
    #  trace = 0

    def __init__(self, lexicon, stream, name='', initial_pos=None):
        """
        Scanner(lexicon, stream, name = '')

          |lexicon| is a Plex.Lexicon instance specifying the lexical tokens
          to be recognised.

          |stream| can be a file object or anything which implements a
          compatible read() method.

          |name| is optional, and may be the name of the file being
          scanned or any other identifying string.
        """
        self.trace = 0

        self.buffer = u''
        self.buf_start_pos = 0
        self.next_pos = 0
        self.cur_pos = 0
        self.cur_line = 1
        self.start_pos = 0
        self.current_scanner_position_tuple = ("", 0, 0)
        self.last_token_position_tuple = ("", 0, 0)
        self.text = None
        self.state_name = None

        self.lexicon = lexicon
        self.stream = stream
        self.name = name
        self.queue = []
        self.initial_state = None
        self.begin('')
        self.next_pos = 0
        self.cur_pos = 0
        self.cur_line_start = 0
        self.cur_char = BOL
        self.input_state = 1
        if initial_pos is not None:
            self.cur_line, self.cur_line_start = initial_pos[1], -initial_pos[2]

    def read(self):
        """
        Read the next lexical token from the stream and return a
        tuple (value, text), where |value| is the value associated with
        the token as specified by the Lexicon, and |text| is the actual
        string read from the stream. Returns (None, '') on end of file.
        """
        queue = self.queue
        while not queue:
            self.text, action = self.scan_a_token()
            if action is None:
                self.produce(None)
                self.eof()
            else:
                value = action.perform(self, self.text)
                if value is not None:
                    self.produce(value)
        result, self.last_token_position_tuple = queue[0]
        del queue[0]
        return result

    def unread(self, token, value, position):
        self.queue.insert(0, ((token, value), position))

    def get_current_scan_pos(self):
        # distinct from the position of the last token due to the queue
        return self.current_scanner_position_tuple

    def scan_a_token(self):
        """
        Read the next input sequence recognised by the machine
        and return (text, action). Returns ('', None) on end of
        file.
        """
        self.start_pos = self.cur_pos
        self.current_scanner_position_tuple = (
            self.name, self.cur_line, self.cur_pos - self.cur_line_start
        )
        action = self.run_machine_inlined()
        if action is not None:
            if self.trace:
                print("Scanner: read: Performing %s %d:%d" % (
                    action, self.start_pos, self.cur_pos))
            text = self.buffer[
                self.start_pos - self.buf_start_pos:
                self.cur_pos - self.buf_start_pos]
            return (text, action)
        else:
            if self.cur_pos == self.start_pos:
                if self.cur_char is EOL:
                    self.next_char()
                if self.cur_char is None or self.cur_char is EOF:
                    return (u'', None)
            raise Errors.UnrecognizedInput(self, self.state_name)

    def run_machine_inlined(self):
        """
        Inlined version of run_machine for speed.
        """
        state = self.initial_state
        cur_pos = self.cur_pos
        cur_line = self.cur_line
        cur_line_start = self.cur_line_start
        cur_char = self.cur_char
        input_state = self.input_state
        next_pos = self.next_pos
        buffer = self.buffer
        buf_start_pos = self.buf_start_pos
        buf_len = len(buffer)
        b_action, b_cur_pos, b_cur_line, b_cur_line_start, b_cur_char, b_input_state, b_next_pos = \
            None, 0, 0, 0, u'', 0, 0

        trace = self.trace
        while 1:
            if trace:
                print("State %d, %d/%d:%s -->" % (
                    state['number'], input_state, cur_pos, repr(cur_char)))

            # Begin inlined self.save_for_backup()
            action = state['action']
            if action is not None:
                b_action, b_cur_pos, b_cur_line, b_cur_line_start, b_cur_char, b_input_state, b_next_pos = \
                    action, cur_pos, cur_line, cur_line_start, cur_char, input_state, next_pos
            # End inlined self.save_for_backup()

            c = cur_char
            new_state = state.get(c, NOT_FOUND)
            if new_state is NOT_FOUND:
                new_state = c and state.get('else')

            if new_state:
                if trace:
                    print("State %d" % new_state['number'])
                state = new_state
                # Begin inlined: self.next_char()
                if input_state == 1:
                    cur_pos = next_pos
                    # Begin inlined: c = self.read_char()
                    buf_index = next_pos - buf_start_pos
                    if buf_index < buf_len:
                        c = buffer[buf_index]
                        next_pos += 1
                    else:
                        discard = self.start_pos - buf_start_pos
                        data = self.stream.read(0x1000)
                        buffer = self.buffer[discard:] + data
                        self.buffer = buffer
                        buf_start_pos += discard
                        self.buf_start_pos = buf_start_pos
                        buf_len = len(buffer)
                        buf_index -= discard
                        if data:
                            c = buffer[buf_index]
                            next_pos += 1
                        else:
                            c = u''
                    # End inlined: c = self.read_char()
                    if c == u'\n':
                        cur_char = EOL
                        input_state = 2
                    elif not c:
                        cur_char = EOL
                        input_state = 4
                    else:
                        cur_char = c
                elif input_state == 2:  # after EoL (1) -> BoL (3)
                    cur_char = u'\n'
                    input_state = 3
                elif input_state == 3:  # start new code line
                    cur_line += 1
                    cur_line_start = cur_pos = next_pos
                    cur_char = BOL
                    input_state = 1
                elif input_state == 4:  # after final line (1) -> EoF (5)
                    cur_char = EOF
                    input_state = 5
                else:  # input_state == 5  (EoF)
                    cur_char = u''
                    # End inlined self.next_char()
            else:  # not new_state
                if trace:
                    print("blocked")
                # Begin inlined: action = self.back_up()
                if b_action is not None:
                    (action, cur_pos, cur_line, cur_line_start,
                     cur_char, input_state, next_pos) = \
                        (b_action, b_cur_pos, b_cur_line, b_cur_line_start,
                         b_cur_char, b_input_state, b_next_pos)
                else:
                    action = None
                break  # while 1
                # End inlined: action = self.back_up()

        self.cur_pos = cur_pos
        self.cur_line = cur_line
        self.cur_line_start = cur_line_start
        self.cur_char = cur_char
        self.input_state = input_state
        self.next_pos = next_pos
        if trace:
            if action is not None:
                print("Doing %s" % action)
        return action

    def next_char(self):
        input_state = self.input_state
        if self.trace:
            print("Scanner: next: %s [%d] %d" % (" " * 20, input_state, self.cur_pos))
        if input_state == 1:
            self.cur_pos = self.next_pos
            c = self.read_char()
            if c == u'\n':
                self.cur_char = EOL
                self.input_state = 2
            elif not c:
                self.cur_char = EOL
                self.input_state = 4
            else:
                self.cur_char = c
        elif input_state == 2:
            self.cur_char = u'\n'
            self.input_state = 3
        elif input_state == 3:
            self.cur_line += 1
            self.cur_line_start = self.cur_pos = self.next_pos
            self.cur_char = BOL
            self.input_state = 1
        elif input_state == 4:
            self.cur_char = EOF
            self.input_state = 5
        else:  # input_state = 5
            self.cur_char = u''
        if self.trace:
            print("--> [%d] %d %r" % (input_state, self.cur_pos, self.cur_char))

    def position(self):
        """
        Return a tuple (name, line, col) representing the location of
        the last token read using the read() method. |name| is the
        name that was provided to the Scanner constructor; |line|
        is the line number in the stream (1-based); |col| is the
        position within the line of the first character of the token
        (0-based).
        """
        return self.last_token_position_tuple

    def get_position(self):
        """
        Python accessible wrapper around position(), only for error reporting.
        """
        return self.position()

    def begin(self, state_name):
        """Set the current state of the scanner to the named state."""
        self.initial_state = (
            self.lexicon.get_initial_state(state_name))
        self.state_name = state_name

    def produce(self, value, text=None):
        """
        Called from an action procedure, causes |value| to be returned
        as the token value from read(). If |text| is supplied, it is
        returned in place of the scanned text.

        produce() can be called more than once during a single call to an action
        procedure, in which case the tokens are queued up and returned one
        at a time by subsequent calls to read(), until the queue is empty,
        whereupon scanning resumes.
        """
        if text is None:
            text = self.text
        self.queue.append(((value, text), self.current_scanner_position_tuple))

    def eof(self):
        """
        Override this method if you want something to be done at
        end of file.
        """
        pass

    @property
    def start_line(self):
        return self.last_token_position_tuple[1]
