# -*- coding: utf-8 -*-
from copy import deepcopy
import re

from django.utils.encoding import force_str
from lxml import etree
from catalogue.constants import TRIM_BEGIN, TRIM_END, MASTERS

RE_TRIM_BEGIN = re.compile("^<!--%s-->$" % TRIM_BEGIN, re.M)
RE_TRIM_END = re.compile("^<!--%s-->$" % TRIM_END, re.M)


class ParseError(BaseException):
    pass


def _trim(text, trim_begin=True, trim_end=True):
    """
        Cut off everything before RE_TRIM_BEGIN and after RE_TRIM_END, so
        that eg. one big XML file can be compiled from many small XML files.
    """
    if trim_begin:
        text = RE_TRIM_BEGIN.split(text, maxsplit=1)[-1]
    if trim_end:
        text = RE_TRIM_END.split(text, maxsplit=1)[0]
    return text


def compile_text(parts):
    """
        Compiles full text from an iterable of parts,
        trimming where applicable.
    """
    texts = []
    trim_begin = False
    text = ''
    for next_text in parts:
        if not next_text:
            continue
        if text:
            # trim the end, because there's more non-empty text
            # don't trim beginning, if `text' is the first non-empty part
            texts.append(_trim(text, trim_begin=trim_begin))
            trim_begin = True
        text = next_text
    # don't trim the end, because there's no more text coming after `text'
    # only trim beginning if it's not still the first non-empty
    texts.append(_trim(text, trim_begin=trim_begin, trim_end=False))
    return "".join(texts)


def add_trim_begin(text):
    trim_tag = etree.Comment(TRIM_BEGIN)
    e = etree.fromstring(text)
    for master in e[::-1]:
        if master.tag in MASTERS:
            break
    if master.tag not in MASTERS:
        raise ParseError('No master tag found!')

    master.insert(0, trim_tag)
    trim_tag.tail = '\n\n\n' + (master.text or '')
    master.text = '\n'
    return unicode(etree.tostring(e, encoding="utf-8"), 'utf-8')


def add_trim_end(text):
    trim_tag = etree.Comment(TRIM_END)
    e = etree.fromstring(text)
    for master in e[::-1]:
        if master.tag in MASTERS:
            break
    if master.tag not in MASTERS:
        raise ParseError('No master tag found!')

    master.append(trim_tag)
    trim_tag.tail = '\n'
    prev = trim_tag.getprevious()
    if prev is not None:
        prev.tail = (prev.tail or '') + '\n\n\n'
    else:
        master.text = (master.text or '') + '\n\n\n'
    return unicode(etree.tostring(e, encoding="utf-8"), 'utf-8')


def split_xml(text):
    """Splits text into chapters.

    All this stuff really must go somewhere else.

    """
    src = etree.fromstring(text)
    chunks = []

    splitter = u'naglowek_rozdzial'
    parts = src.findall('.//naglowek_rozdzial')
    while parts:
        # copy the document
        copied = deepcopy(src)

        element = parts[-1]

        # find the chapter's title
        name_elem = deepcopy(element)
        for tag in 'extra', 'motyw', 'pa', 'pe', 'pr', 'pt', 'uwaga':
            for a in name_elem.findall('.//' + tag):
                a.text = ''
                del a[:]
        name = etree.tostring(name_elem, method='text', encoding='utf-8').strip()

        # in the original, remove everything from the start of the last chapter
        parent = element.getparent()
        del parent[parent.index(element):]
        element, parent = parent, parent.getparent()
        while parent is not None:
            del parent[parent.index(element) + 1:]
            element, parent = parent, parent.getparent()

        # in the copy, remove everything before the last chapter
        element = copied.findall('.//naglowek_rozdzial')[-1]
        parent = element.getparent()
        while parent is not None:
            parent.text = None
            while parent[0] is not element:
                del parent[0]
            element, parent = parent, parent.getparent()
        chunks[:0] = [[name, unicode(etree.tostring(copied, encoding='utf-8'), 'utf-8')]]

        parts = src.findall('.//naglowek_rozdzial')

    chunks[:0] = [[u'początek', unicode(etree.tostring(src, encoding='utf-8'), 'utf-8')]]

    for ch in chunks[1:]:
        ch[1] = add_trim_begin(ch[1])
    for ch in chunks[:-1]:
        ch[1] = add_trim_end(ch[1])

    return chunks


def wl2_to_wl1(wl2_xml, slug):
    from lxml import etree
    import re
    from StringIO import StringIO
    from urllib import unquote
    import os.path
    from django.conf import settings
    from fnpdjango.utils.text.slughifi import slughifi
    from librarian import ParseError, DCNS

    def _register_function(f):
        """ Register extension function with lxml """
        ns = etree.FunctionNamespace('http://wolnelektury.pl/functions')
        ns[f.__name__] = f
        return f

    @_register_function
    def slugify(context, text):
        """Remove unneeded whitespace from beginning and end"""
        if isinstance(text, list):
            text = ''.join(text)
        return slughifi(text)

    @_register_function
    def rmext(context, text):
        if isinstance(text, list):
            text = ''.join(text)
        text = unquote(text)
        if '.' in text:
            name, ext = text.rsplit('.', 1)
            if ext.lower() in ('doc', 'docx', 'odt', 'pdf', 'jpg', 'jpeg'):
                text = name
        return text

    t = etree.parse(os.path.join(settings.PROJECT_ROOT, 'xslt/wl2to1.xslt'))
    ft = wl2_xml.replace('&nbsp;', ' ')
    f2 = StringIO(ft)
    i1 = etree.parse(f2)

    for sect in i1.findall('//section'):
        if sect[0].text and sect[0].text.strip() == u'Przebieg zajęć':
            # Prostujemy.
            first = sect.find('section')
            subs = first.findall('.//section')
            for sub in subs:
                sect.append(sub)
            break
    else:
        dc_type = i1.findall('//dc:type', namespaces={'dc': DCNS.uri})
        if dc_type and dc_type[0] in ('course', 'synthetic'):
            raise ParseError('Brak przebiegu')

    i1.getroot().attrib['redslug'] = slug
    i1.getroot().attrib['wlslug'] = slug  # THIS!
    w1t = i1.xslt(t)
    for h in w1t.findall('//aktywnosc/opis'):
        if len(h) == 0:
            raise ParseError('Pusty element aktywnosc/opis')
        # FIXME assumption that every lesson has at most 9 parts
        if not h[0].text or not re.match(r'\d\.\s', h[0].text):
            raise ParseError('Niepoprawny nagłówek (aktywnosc/opis): %s' % repr(h[0].text))
        h[0].text = h[0].text[3:]
    return etree.tostring(w1t, encoding='utf-8')


EXCEPTIONS = [
    ('div', 'img'),
    ('div', 'video'),
    ('div', 'table.cell'),
]


def remove_element(element):
    parent = element.getparent()
    tail = element.tail
    if tail:
        prev = element.getprevious()
        if prev is not None:
            prev.tail = (prev.tail or '') + tail
        else:
            parent.text = (parent.text or '') + tail
    parent.remove(element)


def remove_empty_elements(xml):
    try:
        tree = etree.fromstring(force_str(xml.replace('&nbsp;', u'\xa0')))
    except SyntaxError:
        return None
    changed = False
    another_loop = True
    while another_loop:
        another_loop = False
        for element in tree.findall('.//*'):
            if (not element.text or not element.text.strip()) and len(element) == 0:
                if (element.tag, element.attrib.get('class')) not in EXCEPTIONS:
                    remove_element(element)
                    changed = True
                    another_loop = True
    return etree.tostring(tree, encoding=unicode) if changed else None