Pandoc filter to wrap Span/Div in LaTeX based on classes

pandoc-expand-simple.py

#!/usr/bin/env python

"""
Pandoc filter to wrap Span/Div in LaTeX based on classes
"""

import pandocfilters as pf
import re

begin_command = None
end_command = None
want_latex = None
cmd_env_re = re.compile(r'(?u)^(\w+)-(cmd|env)$')
constructor_for = { 'Span': None, 'Div': None }

latex_for = {
    'Span': {
        'cmd': {
            'begin': lambda c, n: pf.RawInline('tex', '\\' + n),
            'end': lambda c, n: None,
        },
        'env': {
            'begin': lambda c, n: pf.RawInline('tex', r'\%s{%s} ' % (c, n)),
            'end': lambda c, n: pf.RawInline('tex', r'\%s{%s}' % (c, n)),
        },
    },
    'Div': {
        'cmd': {
            'begin': lambda c, n: pf.RawBlock('tex', r'\%s{' % n),
            'end': lambda c, n: pf.RawBlock('tex', r'}'),
        },
        'env': {
            'begin': lambda c, n: pf.RawBlock('tex', r'\%s{%s}' % (c, n)),
            'end': lambda c, n: pf.RawBlock('tex', r'\%s{%s}' % (c, n)),
        },
    }
}

def expand(key, val, format, meta):
    global begin_command, end_command, want_latex
    if want_latex == None:
        want_latex = format == 'latex' or meta.get('expand_latex', False)
    if not want_latex or not key in ['Span', 'Div']:
        return None
    else:
        cmd_env = dict([(c, m) for c in val[0][1]   # classes
                        for m in [cmd_env_re.search(c)] if m])
        if not len(cmd_env):
            return None
        if begin_command == None:
            begin_command = pf.stringify([meta.get('expand_begin')]) or 'begin'
        if end_command == None:
            end_command = pf.stringify([meta.get('expand_end')]) or 'end'
        if constructor_for[key] == None:
            constructor_for[key] = getattr(pf, key)
        constructor = constructor_for[key]
        val = list(val)     # why is it a tuple?
        val[0][1] = [c for c in val[0][1] if not c in cmd_env]
        ret = []
        for (cls, match) in cmd_env.items():
            (name, cmd_or_env) = match.groups()
            begin = latex_for[key][cmd_or_env]['begin'](begin_command, name)
            end = latex_for[key][cmd_or_env]['end'](end_command, name)
            if len(ret):
                elem = constructor(["",[cls],[]], ret)
            else:
                val[0][1].append(cls)
                elem = constructor(*val)
            ret = [e for e in [begin, elem, end] if isinstance(e, dict) and 't' in e]
        return ret

if __name__ == "__main__":
    pf.toJSONFilter(expand)