#!/usr/bin/env python

## Copyright (C) 2014 Gary Benson <gbenson@redhat.com>
##
## This program is free software; you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 2 of the License, or
## (at your option) any later version.
##
## This program is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
## GNU General Public License for more details.

# GIT prepare-commit-msg hook for projects that want ChangeLog
# entries included in the commit message.

import copy
import os
import re
import sys

cl_hdr_re = re.compile(r"/ChangeLog:$")
cl_old_re = re.compile(r"^\d{4}-\d{2}-\d{2}\s+.*?\s+<[^@]+@[^@]+>$")
cl_mod_re = re.compile(r"^modified:\s+(.*/ChangeLog)$")

msgfile = sys.argv[1]

def cleanup_head():
    global head
    if head and head[-1] and head[-1][-1] == "/":
        head.pop()
    while head and not head[-1]:
        head.pop()
    head.append("")

in_foot = in_changelog = False
changelogs, head, foot = [], [], []
for line in open(msgfile).xreadlines():
    line = line.rstrip()
    bits = line.split("#", 1)
    if len(bits) == 2:
        comment = bits.pop().lstrip()
        if not in_foot:
            if comment.startswith("Please enter the commit message "):
                in_foot = True
        if in_foot:
            match = cl_mod_re.search(comment)
            if match is not None:
                changelogs.append(match.group(1))
        if in_changelog:
            cleanup_head()
            in_changelog = False
    if not in_foot and not in_changelog:
        for ex in cl_hdr_re, cl_old_re:
            if ex.search(line) is not None:
                in_changelog = True
                break
    if in_foot:
        foot.append(line)
    elif not in_changelog:
        head.append(line)
cleanup_head()

def read_changelog(path):
    STARTUP, SKIP_HDR, READ_BODY = 1, 2, 3
    lines, state = [path + ":"], STARTUP
    for line in open(path).xreadlines():
        line = line.rstrip()
        if line and not line[0].isspace():
            if state == STARTUP:
                state = SKIP_HDR
                continue
            assert state == READ_BODY
            break
        if state == SKIP_HDR:
            if line:
                continue
            state = READ_BODY
        assert state == READ_BODY
        lines.append(line)
    return lines

lines = copy.copy(head)
for changelog in changelogs:
    lines.extend(read_changelog(changelog))
lines.extend(foot)

print >>open(msgfile, "w"), "\n".join(lines)