#!/usr/bin/env python

# Creates a man page from a C file.

# Comments beginning with `/**` are treated as Groff man.

# Non-blank lines immediately following a man page comment are treated
# as function signatures or examples and parsed into .Ft, .Fo, .Fa, .Fc. The
# immediately preceding man documentation chunk is printed after the example
# as a comment on it.

# That's about it!

import sys, re, os
from datetime import date

comment_start_re = re.compile('^\/\*\* ?')
comment_delim_re = re.compile('^[/ ]\** ?')
comment_end_re = re.compile('^ \**\/')
function_re = re.compile('^ *(?:CMARK_EXPORT\s+)?(?P<type>(?:const\s+)?\w+(?:\s*[*])?)\s*(?P<name>\w+)\s*\((?P<args>[^)]*)\)')
blank_re = re.compile('^\s*$')
macro_re = re.compile('CMARK_EXPORT *')
typedef_start_re = re.compile('typedef.*{$')
typedef_end_re = re.compile('}')

typedef = False
mdlines = []
chunk = []
sig = []

if len(sys.argv) > 1:
    sourcefile = sys.argv[1]
else:
    print("Usage:  make_man_page.py sourcefile")
    exit(1)

with open(sourcefile, 'r') as cmarkh:
    state = 'default'
    for line in cmarkh:
        # state transition
        oldstate = state
        if comment_start_re.match(line):
            state = 'man'
        elif comment_end_re.match(line) and state == 'man':
            continue
        elif comment_delim_re.match(line) and state == 'man':
            state = 'man'
        elif not typedef and blank_re.match(line):
            state = 'default'
        elif typedef and typedef_end_re.match(line):
            typedef = False
        elif state == 'man':
            state = 'signature'
            typedef = typedef_start_re.match(line)

        # handle line
        if state == 'man':
            chunk.append(re.sub(comment_delim_re, '', line))
        elif state == 'signature':
            ln = re.sub(macro_re, '', line)
            if typedef or not re.match(blank_re, ln):
                sig.append(ln)
        elif oldstate == 'signature' and state != 'signature':
            if len(mdlines) > 0 and mdlines[-1] != '\n':
                mdlines.append('\n')
            rawsig = ''.join(sig)
            m = function_re.match(rawsig)
            if m:
                mdlines.append('.Ft ' + m.group('type') + '\n')
                mdlines.append('.Fo ' + m.group('name') + '\n')
                for argument in re.split('/s*,/s*', m.group('args')):
                    mdlines.append('.Fa ' + argument + '\n')
                mdlines.append('.Fc\n')
            else:
                mdlines.append('.Bd -literal\n')
                mdlines += sig
                mdlines.append('.Ed\n')
            if len(mdlines) > 0 and mdlines[-1] != '\n':
                mdlines.append('\n')
            mdlines += chunk
            chunk = []
            sig = []
        elif oldstate == 'man' and state != 'signature':
            if len(mdlines) > 0 and mdlines[-1] != '\n':
                mdlines.append('\n')
            mdlines += chunk # add man chunk
            chunk = []
            mdlines.append('\n')

sys.stdout.write('.Dd ' + date.today().strftime('%B %d, %Y') + '\n')
sys.stdout.write('.Dt ' + os.path.basename(sourcefile).replace('.h','') + ' 3\n')
sys.stdout.write(''.join(mdlines))