#!/usr/bin/env python3
"""Compute the next monotonic Android versionCode for an application id.

Implements the rule from fdroid-repo-ci#6 -- read that issue for the reasoning
behind each part; this is only the arithmetic and the index read.

    candidate  = whole minutes since 2026-01-01T00:00:00Z
    published  = highest versionCode already in the index for this app id
    result     = max(candidate, published + 1)

Minutes, not seconds or raw Unix time: versionCode is a signed 32-bit int,
and minutes-since-2026 does not exhaust it for 4,082 years. The clamp against
`published` is not optional -- two builds inside the same minute would
otherwise compute the same candidate, and it also covers a clock stepping
backwards or an old commit being rebuilt, both of which would otherwise emit
a number lower than one a device has already seen.

Reads `packages.<applicationId>.versions.*.manifest.versionCode`, the shape
fdroidserver's own index.py actually writes (`packages` keyed by
applicationId/packageName; `versions` a dict keyed by each APK's sha256, not
a list; the versionCode nested under that version's `manifest`) -- verified
against fdroidserver's source, not assumed from an older v1-shaped example.

An application id absent from the index entirely is not an error: it is the
first-ever publish for a channel, and "published" is then simply nobody, so
the bare candidate is correct. An unreadable or unparseable index IS an
error -- guessing a number when the published state is unknown is exactly
how a duplicate or a decrease gets published.

Standard library only, deliberately -- no third-party dependency for a script
that reads a signed index. `urllib.request` handles the http(s) case; a local
path is read directly, which is what makes the offline test suite possible
(fixture index-v2.json files, no server, no network).
"""
import argparse
import datetime
import json
import os
import sys
import urllib.request

EPOCH = datetime.datetime(2026, 1, 1, 0, 0, 0, tzinfo=datetime.timezone.utc)


def minutes_since_epoch(now=None):
    now = now if now is not None else datetime.datetime.now(datetime.timezone.utc)
    return int((now - EPOCH).total_seconds() // 60)


def load_index(source, timeout=30):
    """source is an http(s) URL or a local file path to index-v2.json."""
    if source.startswith("http://") or source.startswith("https://"):
        with urllib.request.urlopen(source, timeout=timeout) as resp:
            data = resp.read()
    else:
        with open(source, "rb") as f:
            data = f.read()
    return json.loads(data)


def highest_published_version_code(index, application_id):
    """The highest versionCode already published for application_id, or None
    if the index has no entry for it at all (a normal state: the first
    publish for this channel)."""
    packages = index.get("packages") or {}
    package = packages.get(application_id)
    if not package:
        return None
    versions = package.get("versions") or {}
    codes = [
        manifest["versionCode"]
        for version in versions.values()
        if isinstance((manifest := (version or {}).get("manifest")), dict)
        and isinstance(manifest.get("versionCode"), int)
    ]
    return max(codes) if codes else None


def next_version_code(source, application_id, now=None):
    index = load_index(source)
    candidate = minutes_since_epoch(now)
    published = highest_published_version_code(index, application_id)
    if published is None:
        return candidate
    return max(candidate, published + 1)


def main(argv):
    parser = argparse.ArgumentParser(
        description="Print the next monotonic versionCode for an application id."
    )
    parser.add_argument("index_source", help="index-v2.json URL or local path")
    parser.add_argument("application_id")
    args = parser.parse_args(argv)

    # Testing seam only, deliberately undocumented in the usage banner: lets
    # the offline suite pin "now" so `candidate` is a fixed, known number
    # instead of whatever minute the test happens to run in. Unset in every
    # real invocation, so production behaviour is untouched.
    now = None
    now_override = os.environ.get("NEXT_VERSION_CODE_NOW")
    if now_override:
        now = datetime.datetime.fromisoformat(now_override)
        if now.tzinfo is None:
            now = now.replace(tzinfo=datetime.timezone.utc)

    try:
        result = next_version_code(args.index_source, args.application_id, now=now)
    except (OSError, ValueError) as e:
        # OSError covers both a local file that can't be read and a network
        # failure (urllib.error.URLError is a subclass); ValueError covers
        # malformed JSON. Fail loudly on stderr, print nothing on stdout --
        # a caller doing `versionCode=$(next-version-code.sh ...)` must never
        # capture a number that was actually an error message.
        print(f"next-version-code.py: could not read the index at "
              f"{args.index_source!r}: {e}", file=sys.stderr)
        return 1

    print(result)
    return 0


if __name__ == "__main__":
    sys.exit(main(sys.argv[1:]))