from django import template
register = template.Library()

# Pygments: http://pygments.org -- a generic syntax highlighter.
from pygments import highlight
from pygments.formatters import HtmlFormatter
from pygments.lexers import get_lexer_by_name, guess_lexer

# Python Markdown
from markdown import markdown

# Need to unescape HTML Entities
from HTMLParser import HTMLParser

# BeautifulSoup4: http://www.crummy.com/software/BeautifulSoup/
from bs4 import BeautifulSoup, Tag 

@register.filter(is_safe=True)
def render(content, safe="unsafe"):
    """Render this content for display."""

    # First, pull out all the code blocks, to keep them away
    # from Markdown (and preserve whitespace).
    soup = BeautifulSoup(unicode(content), 'html.parser' )
    code_blocks = soup.findAll('code')
    for block in code_blocks:
        tag = Tag(name='removed')
        block.replaceWith(tag)

    # Run the post through markdown.
    if safe == "unsafe":
        safe_mode = False
    else:
        safe_mode = True
    markeddown = markdown(unicode(soup), safe_mode=safe_mode)
    # Replace the pulled code blocks with syntax-highlighted versions.
    soup = BeautifulSoup(markeddown, 'html.parser')
    empty_code_blocks, index = soup.findAll('removed'), 0
    formatter = HtmlFormatter(cssclass='source')
    for block in code_blocks:
        if block.has_attr('class'):
            # class="python"
            language = block['class'][0]
        else:
            # plain text, whitespace-preserved
            language = 'text'
        try:
            lexer = get_lexer_by_name(language, stripnl=True, encoding='UTF-8')
        except ValueError, e:
            try:
                # Guess a lexer by the contents of the block.
                lexer = guess_lexer(block.renderContents())
            except ValueError, e:
                # Just make it plain text.
                lexer = get_lexer_by_name('text', stripnl=True, encoding='UTF-8')
        tag = Tag(name='code')
        tag['class'] = language
        unescaped_content = HTMLParser().unescape(block.renderContents())
        tag.insert(0, BeautifulSoup(highlight(unescaped_content, lexer, formatter), 'html.parser'))
        empty_code_blocks[index].replaceWith(tag)
        index = index + 1

    return str(soup)