# minke.corpus
# Corpus reader and parser object for accessing data on disk.
#
# Author:   Benjamin Bengfort <bbengfort@districtdatalabs.com>
# Created:  Tue Apr 19 12:39:13 2016 -0400
#
# Copyright (C) 2016 District Data Labs
# For license information, see LICENSE.txt
#
# ID: corpus.py [0753dd0] benjamin@bengfort.com $

"""
Corpus reader and parser object for accessing data on disk.
"""

##########################################################################
## Imports
##########################################################################

import os
import bs4
import time
import json
import nltk
import codecs
import pickle
import nltk.data

from six import string_types

from nltk.tokenize import WordPunctTokenizer
from nltk.corpus.reader.api import CorpusReader
from nltk.corpus.reader.api import CategorizedCorpusReader
from readability.readability import Document as Paper
from readability.readability import Unparseable

##########################################################################
## Module Constants
##########################################################################

DOC_PATTERN = r'(?!\.)[a-z_\s]+/[a-f0-9]+\.json'
PKL_PATTERN = r'(?!\.)[a-z_\s]+/[a-f0-9]+\.pickle'
CAT_PATTERN = r'([a-z_\s]+)/.*'


##########################################################################
## BaleenCorpusReader
##########################################################################

class BaleenCorpusReader(CategorizedCorpusReader, CorpusReader):
    """
    A corpus reader for the raw JSON Baleen documents that have not been
    preprocessed and have the complete feed information exported from Mongo.
    """

    # Tags to extract as paragraphs from the HTML text
    TAGS = [
        'h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'h7', 'p', 'li'
    ]

    def __init__(self, root, fileids=DOC_PATTERN, tags=None,
                 word_tokenizer=WordPunctTokenizer(),
                 sent_tokenizer=nltk.data.LazyLoader(
                    'tokenizers/punkt/english.pickle'),
                 encoding='utf8', **kwargs):
        """
        Initialize the corpus reader.  Categorization arguments
        (``cat_pattern``, ``cat_map``, and ``cat_file``) are passed to
        the ``CategorizedCorpusReader`` constructor.  The remaining arguments
        are passed to the ``CorpusReader`` constructor.
        """
        # Add the default category pattern if not passed into the class.
        if not any(key.startswith('cat_') for key in kwargs.keys()):
            kwargs['cat_pattern'] = CAT_PATTERN

        CategorizedCorpusReader.__init__(self, kwargs)
        CorpusReader.__init__(self, root, fileids, encoding)

        self._word_tokenizer = word_tokenizer
        self._sent_tokenizer = sent_tokenizer
        self._good_tags = tags or self.TAGS

    def feeds(self):
        """
        Opens and returns the collection of feeds associated with the corpus.
        """
        data = self.open('feeds.json')
        return json.load(data)

    def _resolve(self, fileids, categories):
        """
        Returns a list of fileids or categories depending on what is passed
        to each internal corpus reader function. This primarily bubbles up to
        the high level ``docs`` method, but is implemented here similar to
        the nltk ``CategorizedPlaintextCorpusReader``.
        """
        if fileids is not None and categories is not None:
            raise ValueError("Specify fileids or categories, not both")

        if categories is not None:
            return self.fileids(categories)
        return fileids

    def docs(self, fileids=None, categories=None):
        """
        Returns the complete JSON document for every file in the corpus.
        Note that I attempted to use the nltk ``CorpusView`` and ``concat``
        methods here, but was not getting memory safe iteration. Instead the
        simple Python generator by far did a better job of ensuring that file
        handles got closed and that not all data was loaded into memory at a
        time. In the future, I will try to re-implement the corpus view.
        """
        # Resolve the fileids and the categories
        fileids = self._resolve(fileids, categories)

        # Create a generator, loading one document into memory at a time.
        for path, enc, fileid in self.abspaths(fileids, True, True):
            with codecs.open(path, 'r', encoding=enc) as f:
                yield json.load(f)

    def fields(self, fields, fileids=None, categories=None):
        """
        Helper function to extract particular fields from the json documents.
        Fields can be a string or an iterable of fields. If just one field is
        passed in, then the values are returned, otherwise dictionaries of
        the requsted fields are returned.

        This method doesn't raise KeyErrors nor does it yield None values if
        the document doesn't contain a particular field.

        For example to get title and pubdate from the documents:

            corpus.fields(['title', 'pubdate'])

        Or to simply get all of the summaries:

            corpus.fields('summary')

        Note: there is not yet support for nested fields.
        """
        if isinstance(fields, string_types):
            fields = [fields,]

        if len(fields) == 1:
            for doc in self.docs(fileids, categories):
                if fields[0] in doc:
                    yield doc[fields[0]]

        else:
            for doc in self.docs(fileids, categories):
                yield {
                    key: doc.get(key, None)
                    for key in fields
                }

    def html(self, fileids=None, categories=None, readability=True):
        """
        Returns the HTML content from each JSON document for every file in
        the corpus, ensuring that it exists. Note, this simply returns the
        HTML strings, it doesn't perform any parsing of the HTML.

        If readability is True, clean HTML is returned.
        """
        ## Returns a generator of documents.
        html = self.fields('content', fileids, categories)
        if readability:
            for doc in html:
                try:
                    yield Paper(doc).summary()
                except Unparseable as e:
                    print("Could not parse HTML: {}".format(e))
        else:
            for doc in html:
                yield doc

    def paras(self, fileids=None, categories=None):
        """
        Uses BeautifulSoup to parse the paragraphs from the HTML.
        Currently, this just sends raw text, it does not do any segmentation
        or tokenization as the standard NLTK CorpusReader objects do.
        """
        for html in self.html(fileids, categories):
            soup = bs4.BeautifulSoup(html, 'lxml')
            for element in soup.find_all(self._good_tags):
                yield element.text

    def sents(self, fileids=None, categories=None):
        """
        Uses the built in sentence tokenizer to extract sentences from the
        paragraphs. Note that this method uses BeautifulSoup to parse HTML.
        """
        for paragraph in self.paras(fileids, categories):
            for sentence in self._sent_tokenizer.tokenize(paragraph):
                yield sentence

    def words(self, fileids=None, categories=None):
        """
        Uses the built in word tokenizer to extract tokens from sentences.
        Note that this method uses BeautifulSoup to parse HTML content.
        """
        for sentence in self.sents(fileids, categories):
            for token in self._word_tokenizer.tokenize(sentence):
                yield token

    def sizes(self, fileids=None, categories=None):
        """
        Returns a list of tuples, the fileid and the size on disk of the file.
        This function is used to detect oddly large files in the corpus.
        """
        # Resolve the fileids and the categories
        fileids = self._resolve(fileids, categories)

        # Create a generator, getting every path and computing filesize
        for path, enc, fileid in self.abspaths(fileids, True, True):
            yield os.path.getsize(path)

    def describe(self, fileids=None, categories=None):
        """
        Performs a single pass of the corpus and returns a dictionary with a
        variety of metrics concerning the state of the corpus.
        """
        # Structures to perform counting.
        counts  = nltk.FreqDist()
        tokens  = nltk.FreqDist()
        started = time.time()

        # Perform single pass over paragraphs, tokenize and count
        for para in self.paras(fileids, categories):
            counts['paras'] += 1

            for sent in self._sent_tokenizer.tokenize(para):
                counts['sents'] += 1

                for word in self._word_tokenizer.tokenize(sent):
                    counts['words'] += 1
                    tokens[word] += 1

        # Compute the number of files and categories in the corpus
        n_fileids = len(self._resolve(fileids, categories) or self.fileids())
        n_topics  = len(self.categories(self._resolve(fileids, categories)))

        # Return data structure with information
        return {
            'files':  n_fileids,
            'topics': n_topics,
            'paras':  counts['paras'],
            'sents':  counts['sents'],
            'words':  counts['words'],
            'vocab':  len(tokens),
            'lexdiv': float(counts['words']) / float(len(tokens)),
            'ppdoc':  float(counts['paras']) / float(n_fileids),
            'sppar':  float(counts['sents']) / float(counts['paras']),
            'secs':   time.time() - started,
        }

    def describes(self, fileids=None, categories=None):
        """
        Returns a string representation of the describe command.
        """
        return (
            "Baleen corpus contains {files} files in {topics} categories.\n"
            "Structured as:\n"
            "    {paras} paragraphs ({ppdoc:0.3f} mean paragraphs per file)\n"
            "    {sents} sentences ({sppar:0.3f} mean sentences per paragraph).\n"
            "Word count of {words} with a vocabulary of {vocab} "
            "({lexdiv:0.3f} lexical diversity).\n"
            "Corpus scan took {secs:0.3f} seconds."
        ).format(**self.describe(fileids, categories))


##########################################################################
## BaleenCorpusReader
##########################################################################

class BaleenPickledCorpusReader(BaleenCorpusReader):
    """
    A corpus reader for the preprocessed pickled documents created by the
    `Preprocessor` module. This reader contains all the functionality of the
    BaleenCorpusReader but may contain less data and fields, but hopefully
    should be much faster reading and parsing data from disk.
    """

    def __init__(self, root, fileids=PKL_PATTERN, **kwargs):
        """
        Initialize the corpus reader.  Categorization arguments
        (``cat_pattern``, ``cat_map``, and ``cat_file``) are passed to
        the ``CategorizedCorpusReader`` constructor.  The remaining arguments
        are passed to the ``CorpusReader`` constructor.
        """
        # Add the default category pattern if not passed into the class.
        if not any(key.startswith('cat_') for key in kwargs.keys()):
            kwargs['cat_pattern'] = CAT_PATTERN

        CategorizedCorpusReader.__init__(self, kwargs)
        CorpusReader.__init__(self, root, fileids)

    def docs(self, fileids=None, categories=None):
        """
        Returns the document loaded from a pickled object for every file in
        the corpus. Similar to the BaleenCorpusReader, this uses a generator
        to acheive memory safe iteration.
        """
        # Resolve the fileids and the categories
        fileids = self._resolve(fileids, categories)

        # Create a generator, loading one document into memory at a time.
        for path, enc, fileid in self.abspaths(fileids, True, True):
            with open(path, 'rb') as f:
                yield pickle.load(f)

    def fields(self, fields, fileids=None, categories=None):
        """
        The preprocessed pickles do not contain raw JSON to extract fields.
        """
        raise TypeError(
            "Preprocessed corpus does not contain JSON fields."
        )

    def html(self, fileids=None, categories=None):
        """
        The preprocessed pickles do not contain HTML data.
        """
        raise TypeError(
            "Preprocessed corpus does not contain HTML data."
        )

    def paras(self, fileids=None, categories=None):
        """
        Returns a generator of paragraphs where each paragraph is a list of
        sentences, which is in turn a list of (token, tag) tuples.
        """
        for doc in self.docs(fileids, categories):
            for paragraph in doc:
                yield paragraph

    def sents(self, fileids=None, categories=None):
        """
        Returns a generator of sentences where each sentence is a list of
        (token, tag) tuples.
        """
        for paragraph in self.paras(fileids, categories):
            for sentence in paragraph:
                yield sentence

    def words(self, fileids=None, categories=None):
        """
        Returns a generator of (token, tag) tuples.
        """
        for sentence in self.sents(fileids, categories):
            for token in sentence:
                yield token

    def describe(self, fileids=None, categories=None):
        """
        Performs a single pass of the corpus and returns a dictionary with a
        variety of metrics concerning the state of the corpus.
        """
        # Structures to perform counting.
        counts  = nltk.FreqDist()
        tokens  = nltk.FreqDist()
        started = time.time()

        # Perform single pass over paragraphs, tokenize and count
        for para in self.paras(fileids, categories):
            counts['paras'] += 1

            for sent in para:
                counts['sents'] += 1

                for word, tag in sent:
                    counts['words'] += 1
                    tokens[word] += 1

        # Compute the number of files and categories in the corpus
        n_fileids = len(self._resolve(fileids, categories) or self.fileids())
        n_topics  = len(self.categories(self._resolve(fileids, categories)))

        # Return data structure with information
        return {
            'files':  n_fileids,
            'topics': n_topics,
            'paras':  counts['paras'],
            'sents':  counts['sents'],
            'words':  counts['words'],
            'vocab':  len(tokens),
            'lexdiv': float(counts['words']) / float(len(tokens)),
            'ppdoc':  float(counts['paras']) / float(n_fileids),
            'sppar':  float(counts['sents']) / float(counts['paras']),
            'secs':   time.time() - started,
        }


if __name__ == '__main__':

    PROJECT = os.path.join(os.path.dirname(__file__), "..")
    # RCORPUS = os.path.join(PROJECT, "fixtures", "corpus")
    PCORPUS = os.path.join(PROJECT, "fixtures", "tagged")
    SCORPUS = os.path.join(PROJECT, "fixtures", "sample")

    # rcorpus = BaleenCorpusReader(RCORPUS)
    pcorpus = BaleenPickledCorpusReader(PCORPUS)
    # scorpus = BaleenCorpusReader(SCORPUS)

    print(pcorpus.describes())
