pandoc filter for packetdiag

pandoc-packetdiag-filter.py

#!/usr/bin/env python

"""
Pandoc filter to process code blocks with class "packetdiag" into
packetdiag-generated images.
"""

import os
import sys
import subprocess

from pandocfilters import toJSONFilter, Para, Image
from pandocfilters import get_filename4code, get_caption, get_extension

import cairosvg

PACKETDIAG_BIN = os.environ.get('PACKETDIAG_BIN', 'packetdiag')

def packetdiag(key, value, format_, _):
    if key == 'CodeBlock':
        [[ident, classes, keyvals], code] = value

        if "packetdiag" in classes:
            caption, typef, keyvals = get_caption(keyvals)

            filename = get_filename4code("packetdiag", code)
            filetype = get_extension(format_, "png", html="svg", latex="png")

            src = filename + '.diag'
            med = filename + '.svg'
            dest = filename + '.' + filetype

            if not os.path.isfile(dest):
                txt = code.encode(sys.getfilesystemencoding())
                with open(src, "wb") as f:
                    f.write(txt)

                subprocess.check_call(PACKETDIAG_BIN.split() + ["-T", "svg", src, "-o", med])
                sys.stderr.write('Created image ' + dest + '\n')

                if filetype == 'png':
                    cairosvg.svg2png(url=med, write_to=dest)

            return Para([Image([ident, [], keyvals], caption, [dest, typef])])

def main():
    toJSONFilter(packetdiag)

if __name__ == "__main__":
    main()