#!/usr/bin/env python
# -*- coding: utf-8 -*-



"""Primitive sentence splitting using Sampo Pyysalo's GeniaSS sentence split
refiner. Also a primitive Japanese sentence splitter without refinement.

Author:     Pontus Stenetorp <pontus stenetorp se>
Version:    2011-05-09
"""

from re import compile as re_compile
from re import DOTALL, VERBOSE

# Constants
# Reasonably well-behaved sentence end regular expression
SENTENCE_END_REGEX = re_compile(r'''
        # Require a leading non-whitespace character for the sentence
        \S
        # Then, anything goes, but don't be greedy
        .*?
        # Anchor the sentence at...
        (:?
            # One (or multiple) terminal character(s)
            #   followed by one (or multiple) whitespace
            (:?(\.|!|\?|。|！|？)+(?=\s+))
        | # Or...
            # Newlines, to respect file formatting
            (:?(?=\n+))
        | # Or...
            # End-of-file, excluding whitespaces before it
            (:?(?=\s*$))
        )
    ''', DOTALL | VERBOSE)
# Only newlines can end a sentence to preserve pre-processed formatting
SENTENCE_END_NEWLINE_REGEX = re_compile(r'''
        # Require a leading non-whitespace character for the sentence
        \S
        # Then, anything goes, but don't be greedy
        .*?
        # Anchor the sentence at...
        (:?
            # One (or multiple) newlines
            (:?(?=\n+))
        | # Or...
            # End-of-file, excluding whitespaces before it
            (:?(?=\s*$))
        )
    ''', DOTALL | VERBOSE)
###


def _refine_split(offsets, original_text):
    # Postprocessor expects newlines, so add. Also, replace
    # sentence-internal newlines with spaces not to confuse it.
    new_text = '\n'.join((original_text[o[0]:o[1]].replace('\n', ' ')
                          for o in offsets))

    from sspostproc import refine_split
    output = refine_split(new_text)

    # Align the texts and see where our offsets don't match
    old_offsets = offsets[::-1]
    # Protect against edge case of single-line docs missing
    #   sentence-terminal newline
    if len(old_offsets) == 0:
        old_offsets.append((0, len(original_text), ))
    new_offsets = []
    for refined_sentence in output.split('\n'):
        new_offset = old_offsets.pop()
        # Merge the offsets if we have received a corrected split
        while new_offset[1] - new_offset[0] < len(refined_sentence) - 1:
            _, next_end = old_offsets.pop()
            new_offset = (new_offset[0], next_end)
        new_offsets.append(new_offset)

    # Protect against missing document-final newline causing the last
    #   sentence to fall out of offset scope
    if len(new_offsets) != 0 and new_offsets[-1][1] != len(original_text) - 1:
        start = new_offsets[-1][1] + 1
        while start < len(original_text) and original_text[start].isspace():
            start += 1
        if start < len(original_text) - 1:
            new_offsets.append((start, len(original_text) - 1))

    # Finally, inject new-lines from the original document as to respect the
    #   original formatting where it is made explicit.
    last_newline = -1
    while True:
        try:
            orig_newline = original_text.index('\n', last_newline + 1)
        except ValueError:
            # No more newlines
            break

        for o_start, o_end in new_offsets:
            if o_start <= orig_newline < o_end:
                # We need to split the existing offsets in two
                new_offsets.remove((o_start, o_end))
                new_offsets.extend(((o_start, orig_newline, ),
                                    (orig_newline + 1, o_end), ))
                break
            elif o_end == orig_newline:
                # We have already respected this newline
                break
        else:
            # Stand-alone "null" sentence, just insert it
            new_offsets.append((orig_newline, orig_newline, ))

        last_newline = orig_newline

    new_offsets.sort()
    return new_offsets


def _sentence_boundary_gen(text, regex):
    for match in regex.finditer(text):
        yield match.span()


def regex_sentence_boundary_gen(text):
    for o in _refine_split([_o for _o in _sentence_boundary_gen(
            text, SENTENCE_END_REGEX)], text):
        yield o


def newline_sentence_boundary_gen(text):
    for o in _sentence_boundary_gen(text, SENTENCE_END_NEWLINE_REGEX):
        yield o


if __name__ == '__main__':
    from sys import argv

    from annotation import open_textfile

    def _text_by_offsets_gen(text, offsets):
        for start, end in offsets:
            yield text[start:end]

    if len(argv) > 1:
        try:
            for txt_file_path in argv[1:]:
                print()
                print('### Splitting:', txt_file_path)
                with open_textfile(txt_file_path, 'r') as txt_file:
                    text = txt_file.read()
                print('# Original text:')
                print(text.replace('\n', '\\n'))
                offsets = [o for o in newline_sentence_boundary_gen(text)]
                print('# Offsets:')
                print(offsets)
                print('# Sentences:')
                for sentence in _text_by_offsets_gen(text, offsets):
                    # These should only be allowed when coming from original
                    #   explicit newlines.
                    #assert sentence, 'blank sentences disallowed'
                    # assert not sentence[0].isspace(), (
                    #        'sentence may not start with white-space "%s"' % sentence)
                    print('"%s"' % sentence.replace('\n', '\\n'))
        except IOError:
            pass  # Most likely a broken pipe
    else:
        sentence = 'This is a short sentence.\nthis is another one.'
        print('Sentence:', sentence)
        print('Len sentence:', len(sentence))

        ret = [o for o in en_sentence_boundary_gen(sentence)]
        last_end = 0
        for start, end in ret:
            if last_end != start:
                print('DROPPED: "%s"' % sentence[last_end:start])
            print('SENTENCE: "%s"' % sentence[start:end])
            last_end = end
        print(ret)

        sentence = '　変しん！　両になった。うそ！　かも　'
        print('Sentence:', sentence)
        print('Len sentence:', len(sentence))

        ret = [o for o in jp_sentence_boundary_gen(sentence)]
        ans = [(1, 5), (6, 12), (12, 15), (16, 18)]
        assert ret == ans, '%s != %s' % (ret, ans)
        print('Successful!')

        sentence = ' One of these days Jimmy, one of these days. Boom! Kaboom '
        print('Sentence:', sentence)
        print('Len sentence:', len(sentence))

        ret = [o for o in en_sentence_boundary_gen(sentence)]
        ans = [(1, 44), (45, 50), (51, 57)]
        assert ret == ans, '%s != %s' % (ret, ans)
        print('Successful!')