"""Gitea container-registry garbage collection.

Lists tagged versions of one container package and deletes old ones.
Always preserves:

  - the `latest` tag (Watchtower's auto-deploy target)
  - the `--keep-latest` most-recent date-tagged versions (YYYY.MM.DD)
  - the `--keep-latest` most-recent short-SHA tags (rollback pins)
  - anything pushed within `--keep-days` days

OCI blob-level versions (`sha256:...`) are never touched directly — those
are managed by Gitea's internal package GC cron when their last tag
goes away.

Usage:

    GITEA_TOKEN=... python scripts/registry_gc.py \\
        --owner justin \\
        --package hvm-docs \\
        --keep-days 90 \\
        --keep-latest 5

The Gitea endpoint shape (confirmed 2026-05-22 against git.jpaul.io):

    GET    /api/v1/packages/{owner}/container/{package}
           -> [{id, version, created_at, ...}, ...]
    DELETE /api/v1/packages/{owner}/container/{package}/{version}
"""
from __future__ import annotations

import argparse
import json
import os
import re
import sys
from datetime import datetime, timedelta, timezone
from urllib.error import HTTPError
from urllib.parse import quote
from urllib.request import Request, urlopen

GITEA_HOST = os.environ.get("GITEA_HOST", "https://git.jpaul.io")
DATE_TAG = re.compile(r"^\d{4}\.\d{2}\.\d{2}$")
SHA_TAG = re.compile(r"^[0-9a-f]{7,40}$")  # short or full git SHA
BLOB_VER = re.compile(r"^sha256:")          # OCI blob versions — skip


def api(token: str, method: str, path: str) -> object:
    # Explicit User-Agent: git.jpaul.io is behind Cloudflare, whose default
    # Bot Fight Mode 403s `Python-urllib/X.Y` with error 1010. Any
    # recognizable browser/curl-style UA passes.
    req = Request(f"{GITEA_HOST}{path}",
                  headers={
                      "Authorization": f"token {token}",
                      "User-Agent": "hvm-docs-registry-gc/1.0",
                  },
                  method=method)
    try:
        with urlopen(req, timeout=30) as r:
            body = r.read()
            return json.loads(body) if body else None
    except HTTPError as e:
        if e.code == 404:
            return None
        raise


def main() -> int:
    p = argparse.ArgumentParser()
    p.add_argument("--owner", required=True)
    p.add_argument("--package", required=True)
    p.add_argument("--keep-days", type=int, default=90)
    p.add_argument("--keep-latest", type=int, default=5)
    p.add_argument("--dry-run", action="store_true")
    args = p.parse_args()

    token = os.environ.get("GITEA_TOKEN")
    if not token:
        print("GITEA_TOKEN not set", file=sys.stderr)
        return 1

    versions = api(token, "GET",
                   f"/api/v1/packages/{args.owner}/container/{args.package}") or []
    if not versions:
        print(f"no versions found for {args.owner}/container/{args.package}")
        return 0

    cutoff = datetime.now(timezone.utc) - timedelta(days=args.keep_days)
    print(f"  {len(versions)} version(s); cutoff={cutoff.isoformat()}  "
          f"keep_days={args.keep_days}  keep_latest={args.keep_latest}")

    # Sort newest first by created_at.
    def parsed_ts(v: dict) -> datetime:
        try:
            return datetime.fromisoformat(v["created_at"].replace("Z", "+00:00"))
        except (KeyError, ValueError):
            return datetime.min.replace(tzinfo=timezone.utc)

    versions.sort(key=parsed_ts, reverse=True)

    # Compute the keep-set: top-N date tags + top-N sha tags + always latest.
    keep_dates: list[str] = []
    keep_shas: list[str] = []
    for v in versions:
        ver = v.get("version") or ""
        if DATE_TAG.match(ver) and len(keep_dates) < args.keep_latest:
            keep_dates.append(ver)
        elif SHA_TAG.match(ver) and len(keep_shas) < args.keep_latest:
            keep_shas.append(ver)
    keep = {"latest", *keep_dates, *keep_shas}
    print(f"  keep tags: {sorted(keep)}")

    deleted = skipped_blob = skipped_age = skipped_keep = 0
    for v in versions:
        ver = v.get("version") or ""
        ts = parsed_ts(v)
        if BLOB_VER.match(ver):
            skipped_blob += 1
            continue
        if ver in keep:
            skipped_keep += 1
            continue
        if ts >= cutoff:
            skipped_age += 1
            continue
        print(f"  deleting {ver!r}  id={v.get('id')}  created={v.get('created_at')}")
        if not args.dry_run:
            api(token, "DELETE",
                f"/api/v1/packages/{args.owner}/container/{args.package}/{quote(ver, safe='')}")
            deleted += 1

    print(f"done: deleted={deleted}  kept_named={skipped_keep}  "
          f"kept_recent={skipped_age}  skipped_blobs={skipped_blob}")
    return 0


if __name__ == "__main__":
    sys.exit(main())