#!/usr/bin/env python3

import re
import os
import sys

def version_cmp(a, b):
    a = re.split(r"[\.-]+", a)
    b = re.split(r"[\.-]+", b)
    i = 0
    while True:
        if len(a) <= i:
            if len(b) <= i:
                return 0
            return -1
        if len(b) <= i:
            return 1
        if int(a[i]) < int(b[i]):
            return -1
        if int(a[i]) > int(b[i]):
            return 1
        i += 1

if len(sys.argv) == 4:
    sys.argv.append("debian.master/changelog")

if len(sys.argv) == 5:
    changelog, end, start, source_changelog = sys.argv[1:]
else:
    print("Usage: insert-ubuntu-changes <changelog> <stop at> <start at> [<source changelog>]")
    sys.exit(1)

changes = []
output = False
with open(source_changelog) as fh:
    for line in fh:
        m = re.match(r"^\S+\s+\((.*)\)", line)
        if m:
            if version_cmp(m.group(1), end) <= 0:
                break
            if m.group(1) == start:
                output = True
            if output:
                changes.append("\n")
                changes.append("  [ Ubuntu: {} ]\n".format(m.group(1)))
                changes.append("\n")
                continue

        if output and re.match(r"^(  * |    |      )\S", line):
            changes.append(line)

printed = 3
with open(changelog + ".new", "w") as fh_new:
    with open(changelog) as fh:
        for line in fh:
            if line.startswith("  CHANGELOG: "):
                printed -= 1
                fh_new.write(line)
                if printed == 0:
                    fh_new.write("".join(changes))
                continue
            fh_new.write(line)

os.rename(changelog + ".new", changelog)