import re

from django.shortcuts import get_object_or_404
from django import template
from django.utils.text import re_tag
from django.core.urlresolvers import reverse

from boards.mdx_neboard import LINE_BREAK_HTML
from boards import settings


IMG_ACTION_URL = '[<a href="{}">{}</a>]'
REGEX_NEWLINE = re.compile(LINE_BREAK_HTML)
TRUNCATOR = '...'
HTML4_SINGLETS =(
    'br', 'col', 'link', 'base', 'img', 'param', 'area', 'hr', 'input'
)


register = template.Library()


@register.simple_tag(name='post_url')
def post_url(*args, **kwargs):
    post_id = args[0]

    post = get_object_or_404('Post', id=post_id)

    return post.get_absolute_url()


@register.inclusion_tag('boards/post.html', name='post_view', takes_context=True)
def post_view(context, post, *args, **kwargs):
    kwargs['perms'] = context['perms']
    return post.get_view_params(*args, **kwargs)


@register.simple_tag(name='page_url')
def page_url(paginator, page_number, *args, **kwargs):
    if paginator.supports_urls():
        return paginator.get_page_url(page_number)


@register.filter(name='truncatenewlines_html')
def truncatenewlines_html(value, arg):
    end_pos = 0
    start_pos = 0
    match_count = 0

    # Collect places for truncation
    while match_count <= arg:
        m = REGEX_NEWLINE.search(value, end_pos)
        if m is None:
            break
        else:
            match_count += 1
            end_pos = m.end()
            start_pos = m.start()

    # Find and close open tags
    if match_count > arg:
        truncate_pos = start_pos

        open_tags = []
        text = value[:truncate_pos]
        current_pos = 0
        while True:
            tag = re_tag.search(text, current_pos)
            if tag is None:
                break
            else:
                closing_tag, tagname, self_closing = tag.groups()
                tagname = tagname.lower()
                if self_closing or tagname in HTML4_SINGLETS:
                    pass
                elif closing_tag:
                    # Check for match in open tags list
                    try:
                        i = open_tags.index(tagname)
                    except ValueError:
                        pass
                    else:
                        # SGML: An end tag closes, back to the matching start tag,
                        # all unclosed intervening start tags with omitted end tags
                        open_tags = open_tags[i + 1:]
                else:
                    # Add it to the start of the open tags list
                    open_tags.insert(0, tagname)

                current_pos = tag.end()

        if not text.endswith(TRUNCATOR):
            text += TRUNCATOR
        for tag in open_tags:
            text += '</{}>'.format(tag)
    else:
        text = value

    return text