#!/usr/bin/env python3

import argparse
import sys
import re


def get_opts():

    parser = argparse.ArgumentParser(
        description="TOC for markdown.",
        epilog="""Automatic TOC guide:
Add these hidden comments in the markdown:
[TOCSTART]: #
[TOCEND]: #

Then, use this command to generate TOC: (make a backup first...)
    sed -i -n \\
        -e '1,/^\[TOCSTART\]: #/p;/^\[TOCEND\]: #/,$p' \\
        -e '/^\[TOCSTART\]: #/r '<( md-toc document.md ) \\
        document.md
""",
        formatter_class=argparse.RawTextHelpFormatter,
    )
    parser.add_argument("-n", help="Number TOC", action="store_true")
    parser.add_argument("-l", help="TOC as links", action="store_true")
    parser.add_argument(
        "markdown",
        help="Filename to read. - for stdin",
        action="store",
        default="-",
        nargs="?",
    )
    args = parser.parse_args()
    return args


def main():
    opts = get_opts()
    if opts.markdown == "-":
        fp = sys.stdin
    else:
        fp = open(opts.markdown, "rt")

    bullet = "-"
    counters = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
    lastlev = 0
    re_anchor = re.compile("[^0-9a-z-]")
    for row in fp:
        if row.startswith("#"):
            headers, title = row.strip().split(" ", 1)
            if opts.l:
                anchor = re_anchor.sub("", title.lower().replace(" ", "-"))
                title = "[{}](#{})".format(title, anchor)
            pad = headers.count("#") - 1
            if pad < lastlev:
                counters = [x if i <= pad else 0 for i, x in enumerate(counters)]
            counters[pad] += 1
            lastlev = pad
            if opts.n:
                bullet = "{:d}.".format(counters[pad])

            print("{}{} {}".format(pad * "    ", bullet, title))
    print("")


if __name__ == "__main__":
    main()