#!/usr/bin/python3
#
# This lists all new release tags, which need to be built. The list of
# previously known tags is kept in a file given as the argument to this script.
# If the file doesn't exist, all existing release tags are saved there, and
# nothing is printed: this is so that on the first run, nothing is new and
# nothing needs to be built.
#
# A release tag MUST match "vX.Y.Z", where X, Y, and Z are integers.

import os
import re
import subprocess
import sys


TAG_PATTERN = re.compile(r"^[a-zA-Z0-9-]*(\d+)?.(\d+)\.(\d+)$")


def release_tags():
    p = subprocess.run(["git", "tag", "-l"], check=True, capture_output=True)
    lines = p.stdout.decode().splitlines()
    return [line for line in lines if tag_sort_key(line) is not None]


def sorted_tags(tags):
    return list(sorted(tags, key=tag_sort_key))


def tag_sort_key(tag):
    m = TAG_PATTERN.match(tag)
    if not m:
        return None
    return (m.group(1), m.group(2), m.group(3))


def built_tags(filename):
    if os.path.exists(filename):
        return list(line.strip() for line in open(filename).readlines())
    return []


def save_built_tags(filename, tags):
    msg(f"saving tags to {filename}: {built}")
    return open(filename, "w").write("".join(f"{tag}\n" for tag in tags))


def msg(s):
    sys.stderr.write(f"{s}\n")
    sys.stderr.flush()


tags_filename = sys.argv[1]

tags = sorted_tags(release_tags())
msg(f"found tags: {tags}")

if os.path.exists(tags_filename):
    built = built_tags(tags_filename)
    msg(f"previously built tags: {built}")
    new = [tag for tag in tags if tag not in built]
    if new:
        for tag in new:
            msg(f"build tag {tag}")
            print(tag)
            built.append(tag)
    else:
        msg("no new tags, not building anything")
else:
    msg("no list of old tags, not building anything")
    built = tags

save_built_tags(tags_filename, built)