#!/usr/bin/env python3
"""
Download and unpack experiment data from archives.

Downloads per-experiment .tar.gz archives into data/archives/, extracts them
into data/{experiment}/, and verifies file integrity against manifest.json checksums.

Usage:
    python data/unpack.py                              # unpack all from data/archives/
    python data/unpack.py card lottery                 # unpack specific experiments
    python data/unpack.py --source /path/to/archives   # unpack from local directory
    python data/unpack.py --source https://...         # download from URL
    python data/unpack.py --verify                     # verify existing files only
"""
import argparse
import hashlib
import json
import shutil
import tarfile
import urllib.request
from pathlib import Path
from typing import Dict, Optional

EXPERIMENTS = ['card', 'cardd', 'cards', 'rv', 'rvq', 'location', 'lottery', 'users']
DATA_DIR = Path(__file__).parent
ARCHIVES_DIR = DATA_DIR / 'archives'


def md5_file(path: Path) -> str:
    h = hashlib.md5()
    with open(path, 'rb') as f:
        for chunk in iter(lambda: f.read(8192), b''):
            h.update(chunk)
    return h.hexdigest()


def verify_experiment(experiment_dir: Path) -> Dict:
    """
    Verify files on disk against manifest.json checksums.

    Returns dict with: verified, missing, corrupt counts.
    """
    manifest_path = experiment_dir / 'manifest.json'
    if not manifest_path.exists():
        return {'verified': 0, 'missing': 0, 'corrupt': 0, 'error': 'no manifest'}

    manifest = json.loads(manifest_path.read_text())
    verified = missing = corrupt = 0

    for entry in manifest.get('files', []):
        file_path = experiment_dir / entry['filename']
        if not file_path.exists():
            missing += 1
        elif md5_file(file_path) != entry['md5_hash']:
            corrupt += 1
        else:
            verified += 1

    return {'verified': verified, 'missing': missing, 'corrupt': corrupt}


def _fetch_archive(url_or_path: str, dest: Path) -> Path:
    """Download or copy archive to dest. Returns path to local archive."""
    if url_or_path.startswith(('http://', 'https://')):
        print(f"    Downloading {url_or_path}...")
        urllib.request.urlretrieve(url_or_path, dest)
    else:
        src = Path(url_or_path)
        if src != dest:
            shutil.copy2(src, dest)
    return dest


def unpack_experiment(
    experiment_dir: Path,
    source: Optional[str] = None,
) -> Dict:
    """
    Extract and verify one experiment from its archive.

    Archives are stored in data/archives/ and extracted into data/{experiment}/.

    Args:
        experiment_dir: Path to experiment directory (e.g. data/card/)
        source: Base URL or local directory containing archives.
                If None, uses data/archives/ then falls back to download_url in manifest.

    Returns:
        Dict with status ('ok' or 'error'), message, and counts.
    """
    manifest_path = experiment_dir / 'manifest.json'
    if not manifest_path.exists():
        return {'status': 'error', 'message': f"No manifest.json in {experiment_dir}"}

    manifest = json.loads(manifest_path.read_text())
    dataset = manifest['dataset']
    exp_name = experiment_dir.name

    # Archive lives in <data>/archives/ (sibling of the experiment dir)
    archives_dir = experiment_dir.parent / 'archives'
    archives_dir.mkdir(exist_ok=True)
    archive_dest = archives_dir / f"{exp_name}.tar.gz"
    expected_md5 = manifest.get('archive_md5')

    # Fetch only if the archive isn't already on disk. A present-but-md5-mismatched
    # archive is NOT rejected here: archive_md5 goes stale whenever the archive is
    # re-packed (gzip embeds an mtime), so per-file md5 verification after extraction
    # (verify_experiment) is the authoritative integrity check.
    if not archive_dest.exists():
        if source:
            source_path = source.rstrip('/')
            if source_path.startswith(('http://', 'https://')):
                archive_url = f"{source_path}/{exp_name}.tar.gz"
            else:
                archive_url = str(Path(source_path) / f"{exp_name}.tar.gz")
        elif manifest.get('download_url'):
            archive_url = manifest['download_url']
        else:
            return {
                'status': 'error',
                'message': f"No archive in {archives_dir}/ and no download source for {dataset} — "
                           f"place {exp_name}.tar.gz in {archives_dir}/ or provide --source"
            }

        try:
            _fetch_archive(archive_url, archive_dest)
        except Exception as e:
            return {'status': 'error', 'message': f"Download failed: {e}"}

    if expected_md5 and md5_file(archive_dest) != expected_md5:
        print(f"    WARNING: archive_md5 mismatch for {exp_name} "
              f"(manifest may be stale) — relying on per-file verification")
    else:
        print(f"    Archive present in {archives_dir}/, extracting...")

    # Extract into the data dir (archives stay put)
    experiment_dir.mkdir(parents=True, exist_ok=True)
    try:
        with tarfile.open(archive_dest, 'r:gz') as tf:
            tf.extractall(experiment_dir.parent)
    except Exception as e:
        return {'status': 'error',
                'message': f"Extract failed for {exp_name} (archive may be corrupt): {e}"}

    # Per-file md5 verification is authoritative
    result = verify_experiment(experiment_dir)
    result['status'] = 'ok' if result['missing'] == 0 and result['corrupt'] == 0 else 'error'
    return result


def main():
    parser = argparse.ArgumentParser(description='Download and unpack experiment data')
    parser.add_argument('experiments', nargs='*', help='Experiments to unpack (default: all)')
    parser.add_argument('--source', help='Base URL or local path to archives')
    parser.add_argument('--verify', action='store_true', help='Verify existing files only')
    parser.add_argument('--data-dir', default=str(DATA_DIR),
                        help='Path to data directory (default: data/)')
    args = parser.parse_args()

    experiments = args.experiments or EXPERIMENTS
    data_dir = Path(args.data_dir)

    failed = []
    for exp in experiments:
        exp_dir = data_dir / exp
        if not (exp_dir / 'manifest.json').exists():
            print(f"  {exp}: no manifest.json, skipping")
            continue

        manifest = json.loads((exp_dir / 'manifest.json').read_text())
        print(f"  {exp} ({manifest['file_count']} files):")

        if args.verify:
            result = verify_experiment(exp_dir)
            status = "OK" if result['missing'] == 0 and result['corrupt'] == 0 else "ISSUES"
            print(f"    {status} — verified={result['verified']}, "
                  f"missing={result['missing']}, corrupt={result['corrupt']}")
            if result['missing'] or result['corrupt']:
                failed.append(exp)
        else:
            result = unpack_experiment(exp_dir, source=args.source)
            if result['status'] == 'ok':
                print(f"    OK — verified={result['verified']} files")
            else:
                print(f"    ERROR — {result.get('message', 'unknown')}")
                failed.append(exp)

    if failed:
        print(f"\nFailed: {', '.join(failed)}")
        return 1
    print("\nDone.")
    return 0


if __name__ == '__main__':
    exit(main())