metavars.py

#!/usr/bin/env python

"""
Pandoc filter to allow interpolation of metadata fields
into a document.  %{fields} will be replaced by the field's
value, assuming it is of the type MetaInlines or MetaString.
"""

import sys
from pandocfilters import toJSONFilter, attributes, Span, Str, Table
import re

pattern = re.compile('([^%]*)%\{(.*)\}([^%]*)')

def metavars(key, value, format, meta):
    if key == 'Str':
        m = pattern.match(value)
        if m:
            pre = m.group(1)
            field = m.group(2)
            post = m.group(3)

            result = meta.get(field, {})
            if result:
                if 'MetaInlines' in result['t']:
                    return Span(attributes({'class': 'interpolated',
                                            'field': field}),
                                [Str(pre)] + result['c'] + [Str(post)])
                elif 'MetaString' in result['t']:
                    return Str(result['c'])
                elif 'MetaBlocks' in result['t']:
                    res = result['c'][0]['c']
                    # res = Table( tab[0], tab[1], tab[2], tab[3], tab[4])
                    sys.stderr.write("\n{0} -> {1}\n\n".format(field, repr(res)))
                    return res

            else:
                sys.stderr.write("\n\nError: Variable %{{{0}}} used but not declared in document.\n\n".format(field))
                exit(-1)

if __name__ == "__main__":
    toJSONFilter(metavars)