"""Latex filters.

Module of useful filters for processing Latex within Jinja latex templates.
"""
#-----------------------------------------------------------------------------
# Copyright (c) 2013, the IPython Development Team.
#
# Distributed under the terms of the Modified BSD License.
#
# The full license is in the file COPYING.txt, distributed with this software.
#-----------------------------------------------------------------------------

#-----------------------------------------------------------------------------
# Imports
#-----------------------------------------------------------------------------
import re

#-----------------------------------------------------------------------------
# Globals and constants
#-----------------------------------------------------------------------------

MARKDOWN_IMAGE_RE = re.compile(r'!\[(?P<caption>.*?)\]\(/?files/(?P<location>.*?)\)')

LATEX_RE_SUBS = (
    (re.compile(r'\.\.\.+'), r'\\ldots'),
)

# Latex substitutions for escaping latex.
# see: http://stackoverflow.com/questions/16259923/how-can-i-escape-latex-special-characters-inside-django-templates

LATEX_SUBS = {
    '&':  r'\&',
    '%':  r'\%',
    '$':  r'\$',
    '#':  r'\#',
    '_':  r'\_',
    '{':  r'\{',
    '}':  r'\}',
    '~':  r'\textasciitilde{}',
    '^':  r'\^{}',
    '\\': r'\textbackslash{}',
}


#-----------------------------------------------------------------------------
# Functions
#-----------------------------------------------------------------------------

__all__ = ['escape_latex', 
           'strip_url_static_file_prefix']

def escape_latex(text):
    """
    Escape characters that may conflict with latex.

    Parameters
    ----------
    text : str
        Text containing characters that may conflict with Latex
    """
    text = ''.join(LATEX_SUBS.get(c, c) for c in text)
    for pattern, replacement in LATEX_RE_SUBS:
        text = pattern.sub(replacement, text)

    return text


def strip_url_static_file_prefix(text):
    text = MARKDOWN_IMAGE_RE.sub(r'![\1](\2)', text)
    return text