# encoding: utf-8
# Natural Language Toolkit: Senna POS Tagger
#
# Copyright (C) 2001-2016 NLTK Project
# Author: Rami Al-Rfou' <ralrfou@cs.stonybrook.edu>
# URL: <http://nltk.org/>
# For license information, see LICENSE.TXT

"""
Senna POS tagger, NER Tagger, Chunk Tagger

The input is:
- path to the directory that contains SENNA executables. If the path is incorrect, 
   SennaTagger will automatically search for executable file specified in SENNA environment variable 
- (optionally) the encoding of the input data (default:utf-8)

    >>> from nltk.tag import SennaTagger
    >>> tagger = SennaTagger('/usr/share/senna-v2.0')
    >>> tagger.tag('What is the airspeed of an unladen swallow ?'.split())
    [('What', 'WP'), ('is', 'VBZ'), ('the', 'DT'), ('airspeed', 'NN'),
    ('of', 'IN'), ('an', 'DT'), ('unladen', 'NN'), ('swallow', 'NN'), ('?', '.')]

    >>> from nltk.tag import SennaChunkTagger
    >>> chktagger = SennaChunkTagger('/usr/share/senna-v2.0')
    >>> chktagger.tag('What is the airspeed of an unladen swallow ?'.split())
    [('What', 'B-NP'), ('is', 'B-VP'), ('the', 'B-NP'), ('airspeed', 'I-NP'),
    ('of', 'B-PP'), ('an', 'B-NP'), ('unladen', 'I-NP'), ('swallow', 'I-NP'),
    ('?', 'O')]

    >>> from nltk.tag import SennaNERTagger
    >>> nertagger = SennaNERTagger('/usr/share/senna-v2.0')
    >>> nertagger.tag('Shakespeare theatre was in London .'.split())
    [('Shakespeare', 'B-PER'), ('theatre', 'O'), ('was', 'O'), ('in', 'O'),
    ('London', 'B-LOC'), ('.', 'O')]
    >>> nertagger.tag('UN headquarters are in NY , USA .'.split())
    [('UN', 'B-ORG'), ('headquarters', 'O'), ('are', 'O'), ('in', 'O'),
    ('NY', 'B-LOC'), (',', 'O'), ('USA', 'B-LOC'), ('.', 'O')]
"""

from nltk.compat import python_2_unicode_compatible
from nltk.classify import Senna

@python_2_unicode_compatible
class SennaTagger(Senna):
    def __init__(self, path, encoding='utf-8'):
        super(SennaTagger, self).__init__(path, ['pos'], encoding)

    def tag_sents(self, sentences):
        """
        Applies the tag method over a list of sentences. This method will return
        for each sentence a list of tuples of (word, tag).
        """
        tagged_sents = super(SennaTagger, self).tag_sents(sentences)
        for i in range(len(tagged_sents)):
            for j in range(len(tagged_sents[i])):
                annotations = tagged_sents[i][j]
                tagged_sents[i][j] = (annotations['word'], annotations['pos'])
        return tagged_sents

@python_2_unicode_compatible
class SennaChunkTagger(Senna):
    def __init__(self, path, encoding='utf-8'):
        super(SennaChunkTagger, self).__init__(path, ['chk'], encoding)

    def tag_sents(self, sentences):
        """
        Applies the tag method over a list of sentences. This method will return
        for each sentence a list of tuples of (word, tag).
        """
        tagged_sents = super(SennaChunkTagger, self).tag_sents(sentences)
        for i in range(len(tagged_sents)):
            for j in range(len(tagged_sents[i])):
                annotations = tagged_sents[i][j]
                tagged_sents[i][j] = (annotations['word'], annotations['chk'])
        return tagged_sents
        
    def bio_to_chunks(self, tagged_sent, chunk_type):
        """
        Extracts the chunks in a BIO chunk-tagged sentence.
        
        >>> from nltk.tag import SennaChunkTagger
        >>> chktagger = SennaChunkTagger('/usr/share/senna-v2.0')
        >>> sent = 'What is the airspeed of an unladen swallow ?'.split()
        >>> tagged_sent = chktagger.tag(sent)
        >>> tagged_sent
        [('What', 'B-NP'), ('is', 'B-VP'), ('the', 'B-NP'), ('airspeed', 'I-NP'),
        ('of', 'B-PP'), ('an', 'B-NP'), ('unladen', 'I-NP'), ('swallow', 'I-NP'),
        ('?', 'O')]
        >>> list(chktagger.bio_to_chunks(tagged_sent, chunk_type='NP'))
        [('What', '0'), ('the airspeed', '2-3'), ('an unladen swallow', '5-6-7')]
        
        :param tagged_sent: A list of tuples of word and BIO chunk tag.
        :type tagged_sent: list(tuple)
        :param tagged_sent: The chunk tag that users want to extract, e.g. 'NP' or 'VP'
        :type tagged_sent: str
        
        :return: An iterable of tuples of chunks that users want to extract
          and their corresponding indices. 
        :rtype: iter(tuple(str))
        """
        current_chunk = []
        current_chunk_position = []
        for idx, word_pos in enumerate(tagged_sent):
            word, pos = word_pos
            if '-'+chunk_type in pos: # Append the word to the current_chunk.
                current_chunk.append((word))
                current_chunk_position.append((idx))
            else:
                if current_chunk: # Flush the full chunk when out of an NP.
                    _chunk_str = ' '.join(current_chunk) 
                    _chunk_pos_str = '-'.join(map(str, current_chunk_position))
                    yield _chunk_str, _chunk_pos_str 
                    current_chunk = []
                    current_chunk_position = []
        if current_chunk: # Flush the last chunk.
            yield ' '.join(current_chunk), '-'.join(map(str, current_chunk_position))
    

@python_2_unicode_compatible
class SennaNERTagger(Senna):
    def __init__(self, path, encoding='utf-8'):
        super(SennaNERTagger, self).__init__(path, ['ner'], encoding)

    def tag_sents(self, sentences):
        """
        Applies the tag method over a list of sentences. This method will return
        for each sentence a list of tuples of (word, tag).
        """
        tagged_sents = super(SennaNERTagger, self).tag_sents(sentences)
        for i in range(len(tagged_sents)):
            for j in range(len(tagged_sents[i])):
                annotations = tagged_sents[i][j]
                tagged_sents[i][j] = (annotations['word'], annotations['ner'])
        return tagged_sents



# skip doctests if Senna is not installed
def setup_module(module):
    from nose import SkipTest
    try:
        tagger = Senna('/usr/share/senna-v2.0', ['pos', 'chk', 'ner'])
    except OSError:
        raise SkipTest("Senna executable not found")

