"""
A reader for corpora whose documents are in MTE format.
"""
import os
from functools import reduce
from nltk import compat
from nltk.corpus.reader import concat, TaggedCorpusReader
from nltk.corpus.reader.xmldocs import XMLCorpusView

import xml.etree.ElementTree as etree
import re

def xpath(root, path, ns):
    return root.findall(path, ns)

class MTECorpusView(XMLCorpusView):
    """
    Class for lazy viewing the MTE Corpus.
    """

    def __init__(self, fileid, tagspec, elt_handler=None):
        XMLCorpusView.__init__(self, fileid, tagspec, elt_handler)

    def read_block(self, stream, tagspec=None, elt_handler=None):
        return list(filter(lambda x: x is not None, XMLCorpusView.read_block(self, stream, tagspec, elt_handler)))

class MTEFileReader:
    """
    Class for loading the content of the multext-east corpus. It
    parses the xml files and does some tag-filtering depending on the
    given method parameters.
    """
    ns = {'tei': 'http://www.tei-c.org/ns/1.0',
          'xml': 'http://www.w3.org/XML/1998/namespace'}
    tag_ns = '{http://www.tei-c.org/ns/1.0}'
    xml_ns = '{http://www.w3.org/XML/1998/namespace}'
    word_path = "TEI/text/body/div/div/p/s/(w|c)"
    sent_path = "TEI/text/body/div/div/p/s"
    para_path = "TEI/text/body/div/div/p"


    def __init__(self, file_path):
        self.__file_path = file_path

    @classmethod
    def _word_elt(self, elt, context):
        return elt.text

    @classmethod
    def _sent_elt(self, elt, context):
        return [self._word_elt(w, None) for w in xpath(elt, '*', self.ns)]

    @classmethod
    def _para_elt(self, elt, context):
        return [self._sent_elt(s, None) for s in xpath(elt, '*', self.ns)]

    @classmethod
    def _tagged_word_elt(self, elt, context):
        if ('ana' not in elt.attrib):
            return (elt.text, '')

        if self.__tags == "" and self.__tagset == "msd":
            return (elt.text, elt.attrib['ana'])
        elif self.__tags == "" and self.__tagset == "universal":
            return (elt.text, MTETagConverter.msd_to_universal(elt.attrib['ana']))
        else:
            tags = re.compile('^' + re.sub("-", ".", self.__tags) + '.*$')
            if (tags.match(elt.attrib['ana'])):
                if self.__tagset == "msd":
                    return (elt.text, elt.attrib['ana'])
                else:
                    return (elt.text, MTETagConverter.msd_to_universal(elt.attrib['ana']))
            else:
                return None

    @classmethod
    def _tagged_sent_elt(self, elt, context):
        return list(filter(lambda x: x is not None, [self._tagged_word_elt(w, None) for w in xpath(elt, '*', self.ns)]))

    @classmethod
    def _tagged_para_elt(self, elt, context):
        return list(filter(lambda x: x is not None, [self._tagged_sent_elt(s, None) for s in xpath(elt, '*', self.ns)]))

    @classmethod
    def _lemma_word_elt(self, elt, context):
        if ('lemma' not in elt.attrib):
            return (elt.text, '')
        else:
            return (elt.text, elt.attrib['lemma'])

    @classmethod
    def _lemma_sent_elt(self, elt, context):
        return [self._lemma_word_elt(w, None) for w in xpath(elt, '*', self.ns)]

    @classmethod
    def _lemma_para_elt(self, elt, context):
        return [self._lemma_sent_elt(s, None) for s in xpath(elt, '*', self.ns)]

    def words(self):
        return MTECorpusView(self.__file_path, MTEFileReader.word_path, MTEFileReader._word_elt)

    def sents(self):
        return MTECorpusView(self.__file_path, MTEFileReader.sent_path, MTEFileReader._sent_elt)

    def paras(self):
        return MTECorpusView(self.__file_path, MTEFileReader.para_path, MTEFileReader._para_elt)

    def lemma_words(self):
        return MTECorpusView(self.__file_path, MTEFileReader.word_path, MTEFileReader._lemma_word_elt)

    def tagged_words(self, tagset, tags):
        MTEFileReader.__tagset = tagset
        MTEFileReader.__tags = tags
        return MTECorpusView(self.__file_path, MTEFileReader.word_path, MTEFileReader._tagged_word_elt)

    def lemma_sents(self):
        return MTECorpusView(self.__file_path, MTEFileReader.sent_path, MTEFileReader._lemma_sent_elt)

    def tagged_sents(self, tagset, tags):
        MTEFileReader.__tagset = tagset
        MTEFileReader.__tags = tags
        return MTECorpusView(self.__file_path, MTEFileReader.sent_path, MTEFileReader._tagged_sent_elt)

    def lemma_paras(self):
        return MTECorpusView(self.__file_path, MTEFileReader.para_path, MTEFileReader._lemma_para_elt)

    def tagged_paras(self, tagset, tags):
        MTEFileReader.__tagset = tagset
        MTEFileReader.__tags = tags
        return MTECorpusView(self.__file_path, MTEFileReader.para_path, MTEFileReader._tagged_para_elt)


class MTETagConverter:
    """
    Class for converting msd tags to universal tags, more conversion
    options are currently not implemented.
    """

    mapping_msd_universal = {
        'A': 'ADJ', 'S': 'ADP', 'R': 'ADV', 'C': 'CONJ',
        'D': 'DET', 'N': 'NOUN', 'M': 'NUM', 'Q': 'PRT',
        'P': 'PRON', 'V': 'VERB', '.': '.', '-': 'X'}

    @staticmethod
    def msd_to_universal(tag):
        """
        This function converts the annotation from the Multex-East to the universal tagset
        as described in Chapter 5 of the NLTK-Book

        Unknown Tags will be mapped to X. Punctuation marks are not supported in MSD tags, so
        """
        indicator = tag[0] if not tag[0] == "#" else tag[1]

        if not indicator in MTETagConverter.mapping_msd_universal:
            indicator = '-'

        return MTETagConverter.mapping_msd_universal[indicator]

class MTECorpusReader(TaggedCorpusReader):
    """
    Reader for corpora following the TEI-p5 xml scheme, such as MULTEXT-East.
    MULTEXT-East contains part-of-speech-tagged words with a quite precise tagging
    scheme. These tags can be converted to the Universal tagset
    """

    def __init__(self, root=None, fileids=None, encoding='utf8'):
        """
        Construct a new MTECorpusreader for a set of documents
        located at the given root directory.  Example usage:

            >>> root = '/...path to corpus.../'
            >>> reader = MTECorpusReader(root, 'oana-*.xml', 'utf8') # doctest: +SKIP

        :param root: The root directory for this corpus. (default points to location in multext config file)
        :param fileids: A list or regexp specifying the fileids in this corpus. (default is oana-en.xml)
        :param enconding: The encoding of the given files (default is utf8)
        """
        TaggedCorpusReader.__init__(self, root, fileids, encoding)

    def __fileids(self, fileids):
        if fileids is None: fileids = self._fileids
        elif isinstance(fileids, compat.string_types): fileids = [fileids]
        # filter wrong userinput
        fileids = filter(lambda x : x in self._fileids, fileids)
        # filter multext-east sourcefiles that are not compatible to the teip5 specification
        fileids = filter(lambda x : x not in ["oana-bg.xml", "oana-mk.xml"], fileids)
        if not fileids:
            print("No valid multext-east file specified")
        return fileids

    def readme(self):
        """
        Prints some information about this corpus.
        :return: the content of the attached README file
        :rtype: str
        """
        return self.open("00README.txt").read()

    def raw(self, fileids=None):
        """
	    :param fileids: A list specifying the fileids that should be used.
        :return: the given file(s) as a single string.
        :rtype: str
        """
        return reduce([self.open(f).read() for f in self.__fileids(fileids)], [])

    def words(self, fileids=None):
        """
	    :param fileids: A list specifying the fileids that should be used.
        :return: the given file(s) as a list of words and punctuation symbols.
        :rtype: list(str)
        """
        return  concat([MTEFileReader(os.path.join(self._root, f)).words() for f in self.__fileids(fileids)])

    def sents(self, fileids=None):
        """
	    :param fileids: A list specifying the fileids that should be used.
        :return: the given file(s) as a list of sentences or utterances,
                 each encoded as a list of word strings
        :rtype: list(list(str))
        """
        return  concat([MTEFileReader(os.path.join(self._root, f)).sents() for f in self.__fileids(fileids)])

    def paras(self, fileids=None):
        """
	    :param fileids: A list specifying the fileids that should be used.
        :return: the given file(s) as a list of paragraphs, each encoded as a list
                 of sentences, which are in turn encoded as lists of word string
        :rtype: list(list(list(str)))
        """
        return  concat([MTEFileReader(os.path.join(self._root, f)).paras() for f in self.__fileids(fileids)])

    def lemma_words(self, fileids=None):
        """
	    :param fileids: A list specifying the fileids that should be used.
        :return: the given file(s) as a list of words, the corresponding lemmas
                 and punctuation symbols, encoded as tuples (word, lemma)
        :rtype: list(tuple(str,str))
        """
        return  concat([MTEFileReader(os.path.join(self._root, f)).lemma_words() for f in self.__fileids(fileids)])

    def tagged_words(self, fileids=None, tagset="msd", tags=""):
        """
	    :param fileids: A list specifying the fileids that should be used.
        :param tagset: The tagset that should be used in the returned object,
                       either "universal" or "msd", "msd" is the default
        :param tags: An MSD Tag that is used to filter all parts of the used corpus
                     that are not more precise or at least equal to the given tag
        :return: the given file(s) as a list of tagged words and punctuation symbols
                 encoded as tuples (word, tag)
        :rtype: list(tuple(str, str))
        """
        if tagset == "universal" or tagset == "msd":
            return concat([MTEFileReader(os.path.join(self._root, f)).tagged_words(tagset, tags) for f in self.__fileids(fileids)])
        else:
            print("Unknown tagset specified.")

    def lemma_sents(self, fileids=None):
        """
	    :param fileids: A list specifying the fileids that should be used.
        :return: the given file(s) as a list of sentences or utterances, each
                 encoded as a list of tuples of the word and the corresponding
                 lemma (word, lemma)
        :rtype: list(list(tuple(str, str)))
        """
        return  concat([MTEFileReader(os.path.join(self._root, f)).lemma_sents() for f in self.__fileids(fileids)])


    def tagged_sents(self, fileids=None, tagset="msd", tags=""):
        """
	    :param fileids: A list specifying the fileids that should be used.
        :param tagset: The tagset that should be used in the returned object,
                       either "universal" or "msd", "msd" is the default
        :param tags: An MSD Tag that is used to filter all parts of the used corpus
                     that are not more precise or at least equal to the given tag
        :return: the given file(s) as a list of sentences or utterances, each
                 each encoded as a list of (word,tag) tuples
        :rtype: list(list(tuple(str, str)))
        """
        if tagset == "universal" or tagset == "msd":
            return concat([MTEFileReader(os.path.join(self._root, f)).tagged_sents(tagset, tags) for f in self.__fileids(fileids)])
        else:
            print("Unknown tagset specified.")

    def lemma_paras(self, fileids=None):
        """
	    :param fileids: A list specifying the fileids that should be used.
        :return: the given file(s) as a list of paragraphs, each encoded as a
                 list of sentences, which are in turn encoded as a list of
                 tuples of the word and the corresponding lemma (word, lemma)
        :rtype: list(List(List(tuple(str, str))))
        """
        return concat([MTEFileReader(os.path.join(self._root, f)).lemma_paras() for f in self.__fileids(fileids)])

    def tagged_paras(self, fileids=None, tagset="msd", tags=""):
        """
	    :param fileids: A list specifying the fileids that should be used.
        :param tagset: The tagset that should be used in the returned object,
                       either "universal" or "msd", "msd" is the default
        :param tags: An MSD Tag that is used to filter all parts of the used corpus
                     that are not more precise or at least equal to the given tag
        :return: the given file(s) as a list of paragraphs, each encoded as a
                 list of sentences, which are in turn encoded as a list
                 of (word,tag) tuples
        :rtype: list(list(list(tuple(str, str))))
        """
        if tagset == "universal" or tagset == "msd":
            return concat([MTEFileReader(os.path.join(self._root, f)).tagged_paras(tagset, tags) for f in self.__fileids(fileids)])
        else:
            print("Unknown tagset specified.")
