"""
A reader for corpora whose documents are in MTE format.
"""
import os
import re
from functools import reduce

from six import string_types

from nltk.corpus.reader import concat, TaggedCorpusReader
from nltk.corpus.reader.xmldocs import XMLCorpusView


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, 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.")
