#!/usr/bin/python3
"""Generate CSV from some Markdown with RFC-822 headers in it.

I wrote a file for a survey of parsers, and this script puts its
regular part into CSV form.

"""
import csv
import sys


def parse(infile):
    prev_line = None
    items = []
    seeking_headers = False
    canonical_header_names = {}
    current_header_name = None
    
    for raw_line in infile:
        line = raw_line.strip()
        if len(line) > 3 and all(c == '-' for c in line):
            items.append((prev_line, {}))
            seeking_headers = True
        elif seeking_headers and ': ' in line:
            name, value = line.split(': ', 1)
            if ' ' in name:
                seeking_headers = False
                current_header_name = None
            else:
                if name.lower() not in canonical_header_names:
                    canonical_header_names[name.lower()] = name
                current_header_name = canonical_header_names[name.lower()]
                items[-1][1][current_header_name] = value.strip()
        elif (seeking_headers and raw_line[0] in ' \t'
              and current_header_name is not None):
            items[-1][1][current_header_name] += ' ' + line
        elif line:
            seeking_headers = False
            current_header_name = None

        prev_line = line

    return items

def dump(items, outfile):
    w = csv.writer(outfile)
    headings = tuple(sorted(set().union(*(set(fields.keys())
                                          for title, fields in items))))
    w.writerow(('Name',) + headings)
    for title, fields in items:
        w.writerow((title,) + tuple(fields.get(field, '') for field in headings))

def main(infilename):
    dump(parse(open(infilename)), sys.stdout)

if __name__ == '__main__':
    main(sys.argv[1])