#!/usr/bin/env python3
"""Package release data directories into per-community tar.zst archives."""

from __future__ import annotations

import argparse
import hashlib
import json
import shutil
import subprocess
from datetime import datetime, timezone
from pathlib import Path


HF_DIR = Path(__file__).resolve().parents[1]
DATA_DIR = HF_DIR / "data"
ARCHIVES_DIR = HF_DIR / "archives"
ARCHIVES_MANIFEST = HF_DIR / "archives_manifest.json"
RELEASE_MANIFEST = HF_DIR / "release_manifest.json"


def community_key(path: Path) -> int:
    return int(path.name.rsplit("_", 1)[1])


def sha256_file(path: Path, chunk_size: int = 1024 * 1024 * 16) -> str:
    digest = hashlib.sha256()
    with path.open("rb") as handle:
        for chunk in iter(lambda: handle.read(chunk_size), b""):
            digest.update(chunk)
    return digest.hexdigest()


def load_json(path: Path) -> dict:
    if not path.exists():
        return {}
    return json.loads(path.read_text(encoding="utf-8"))


def write_json(path: Path, data: object) -> None:
    path.write_text(
        json.dumps(data, ensure_ascii=False, indent=2) + "\n",
        encoding="utf-8",
    )


def archive_is_current(record: dict | None, archive_path: Path) -> bool:
    return (
        bool(record)
        and archive_path.exists()
        and record.get("size_bytes") == archive_path.stat().st_size
        and bool(record.get("sha256"))
    )


def build_archive(community_dir: Path, archive_path: Path, compression_level: int) -> None:
    archive_path.parent.mkdir(parents=True, exist_ok=True)
    tmp_path = archive_path.with_suffix(archive_path.suffix + ".tmp")
    if tmp_path.exists():
        tmp_path.unlink()

    compressor = f"zstd -T0 -{compression_level}"
    cmd = [
        "tar",
        "--use-compress-program",
        compressor,
        "-cf",
        str(tmp_path.relative_to(HF_DIR)),
        str(community_dir.relative_to(HF_DIR)),
    ]
    subprocess.run(cmd, cwd=HF_DIR, check=True)
    tmp_path.replace(archive_path)


def main() -> None:
    parser = argparse.ArgumentParser()
    parser.add_argument("--level", type=int, default=6, help="zstd compression level")
    parser.add_argument("--force", action="store_true", help="rebuild existing archives")
    args = parser.parse_args()

    if not shutil.which("zstd"):
        raise SystemExit("zstd is required but was not found on PATH")

    community_dirs = sorted(
        (path for path in DATA_DIR.glob("community_*") if path.is_dir()),
        key=community_key,
    )
    existing_manifest = load_json(ARCHIVES_MANIFEST)
    existing_records = {
        record["community_id"]: record
        for record in existing_manifest.get("archives", [])
        if "community_id" in record
    }

    records = []
    for index, community_dir in enumerate(community_dirs, start=1):
        community_id = community_dir.name
        archive_path = ARCHIVES_DIR / f"{community_id}.tar.zst"
        existing_record = existing_records.get(community_id)

        print(f"[{index}/{len(community_dirs)}] {community_id}", flush=True)
        if args.force or not archive_is_current(existing_record, archive_path):
            build_archive(community_dir, archive_path, args.level)

        size_bytes = archive_path.stat().st_size
        digest = (
            existing_record["sha256"]
            if archive_is_current(existing_record, archive_path)
            else sha256_file(archive_path)
        )
        records.append(
            {
                "community_id": community_id,
                "archive_path": f"archives/{archive_path.name}",
                "extracts_to": f"data/{community_id}",
                "size_bytes": size_bytes,
                "sha256": digest,
            }
        )

    manifest = {
        "created_at": datetime.now(timezone.utc).isoformat(),
        "compression": {
            "format": "tar.zst",
            "zstd_level": args.level,
            "command_template": "tar --use-compress-program 'zstd -T0 -LEVEL' -cf archives/community_N.tar.zst data/community_N",
        },
        "num_archives": len(records),
        "total_size_bytes": sum(record["size_bytes"] for record in records),
        "archives": records,
    }
    write_json(ARCHIVES_MANIFEST, manifest)

    release_manifest = load_json(RELEASE_MANIFEST)
    if release_manifest:
        release_manifest["archives_manifest"] = "archives_manifest.json"
        release_manifest["archive_policy"] = (
            "Data is published as one tar.zst archive per release community. "
            "Each archive extracts to the data_path referenced by the question JSON."
        )
        write_json(RELEASE_MANIFEST, release_manifest)

    print(json.dumps(manifest, ensure_ascii=False, indent=2), flush=True)


if __name__ == "__main__":
    main()