"""Gitea container-registry garbage collection.

Prunes old container tags from a Gitea registry package. Always
preserves:

  - The ``latest`` tag (Watchtower auto-pull target)
  - Any ``corpus-*`` tag (production pins; Drawbar may have them locked)
  - The ``--keep-latest`` most-recent OTHER tags (typically commit-sha pins)
  - Anything pushed within ``--keep-days`` days

The actual disk reclaim happens on Gitea's next package GC cron
(admin site settings). This script marks versions for deletion.

Why this script doesn't use the Docker Registry v2 API: that API has
tag listing + manifest delete by digest, but no per-tag created-at
timestamp without an extra blob-fetch round-trip. Gitea's packages
API gives us {tag, created_at} in one call, which is what the keep
policy needs.

The endpoint shape that actually works (matches Gitea 1.21+):

  GET    /api/v1/packages/{owner}?type=container&q={name}
         → JSON array, ONE entry per tag, each with id + version=tag + created_at
  DELETE /api/v1/packages/{owner}/container/{name}/{tag}
         → 204 on success, 404 if already gone

Auth: GITEA_TOKEN env var (PAT with delete:packages scope; the
push-only PAT we use as REGISTRY_TOKEN may not be enough — if you
see 403s, mint a separate PAT and pass it as GITEA_TOKEN here).

Usage:

    python scripts/registry_gc.py \\
        --owner justin \\
        --package crop-chem-docs \\
        --keep-days 180 \\
        --keep-latest 6
        [--dry-run]
"""
from __future__ import annotations

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


GITEA_HOST = os.environ.get("GITEA_HOST", "https://git.jpaul.io")


def api(token: str, method: str, path: str) -> object:
    # User-Agent matters: Cloudflare in front of git.jpaul.io returns
    # 403 to the default `Python-urllib/3.x` UA. Any non-Python UA
    # passes. Curl works, requests works, we just need to not look
    # like a vanilla urllib script.
    req = Request(
        f"{GITEA_HOST}{path}",
        headers={
            "Authorization": f"token {token}",
            "User-Agent": "crop-chem-docs-registry-gc/0.1",
        },
        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 _parse_created(version: dict) -> datetime:
    """Gitea returns RFC3339 with offset like '2026-05-24T16:07:50-04:00'.
    Python 3.11+ handles this directly via fromisoformat."""
    return datetime.fromisoformat(version["created_at"])


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=180)
    p.add_argument("--keep-latest", type=int, default=6,
                   help="Keep this many most-recent commit-sha (etc.) "
                        "tags BEFORE applying --keep-days. corpus-* and "
                        ":latest are kept regardless.")
    p.add_argument("--dry-run", action="store_true",
                   help="Show what would be deleted without calling DELETE.")
    args = p.parse_args()

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

    # Gitea's q= is a substring match; filter to exact name so we don't
    # accidentally GC a sibling package that shares the prefix.
    versions = api(
        token, "GET",
        f"/api/v1/packages/{args.owner}?type=container&q={args.package}",
    ) or []
    versions = [v for v in versions if v.get("name") == args.package]

    if not versions:
        print(f"no versions found for {args.owner}/{args.package} — nothing to GC")
        return 0

    cutoff = datetime.now(timezone.utc) - timedelta(days=args.keep_days)
    versions.sort(key=_parse_created, reverse=True)  # newest first

    keep: list[tuple[str, str]] = []     # (tag, reason)
    delete: list[dict] = []
    other_kept = 0

    for v in versions:
        tag = v.get("version", "")
        created = _parse_created(v)
        if tag == "latest":
            keep.append((tag, "always-keep (:latest)"))
            continue
        if tag.startswith("corpus-"):
            keep.append((tag, "production pin (corpus-*)"))
            continue
        if other_kept < args.keep_latest:
            other_kept += 1
            keep.append((tag, f"keep-latest #{other_kept}/{args.keep_latest}"))
            continue
        if created >= cutoff:
            keep.append((tag, f"within --keep-days ({args.keep_days})"))
            continue
        delete.append(v)

    print(f"=== {args.owner}/{args.package}: {len(versions)} total tag(s) ===")
    for tag, reason in keep:
        print(f"  KEEP  {tag:<28}  {reason}")
    for v in delete:
        print(f"  DEL   {v['version']:<28}  created={v['created_at']}")

    if not delete:
        print("nothing to delete")
        return 0
    if args.dry_run:
        print(f"--dry-run; would delete {len(delete)} tag(s)")
        return 0

    failed = 0
    for v in delete:
        tag = v["version"]
        try:
            api(token, "DELETE",
                f"/api/v1/packages/{args.owner}/container/{args.package}/{tag}")
            print(f"  ✓ deleted {tag}")
        except HTTPError as e:
            print(f"  ✗ failed {tag}: HTTP {e.code} {e.reason}", file=sys.stderr)
            failed += 1

    print(f"done: deleted {len(delete) - failed} / {len(delete)} tag(s)")
    return 0 if failed == 0 else 1


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