"""Verify the downloaded bundle, then restore images and original JSONL files."""
import argparse
import hashlib
import json
import os
from pathlib import Path, PurePosixPath
import shutil
import tarfile


def main():
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument('--bundle', type=Path, default=Path(__file__).resolve().parent)
    parser.add_argument('--destination', type=Path)
    parser.add_argument('--verify-only', action='store_true')
    args = parser.parse_args()
    root = args.bundle.resolve()
    if not args.verify_only and args.destination is None:
        parser.error('--destination is required for extraction')
    for line in (root / 'SHA256SUMS').read_text().splitlines():
        expected, rel = line.split('  ', 1)
        p = PurePosixPath(rel)
        assert not p.is_absolute() and '..' not in p.parts
        h = hashlib.sha256()
        with (root / rel).open('rb') as file:
            for block in iter(lambda: file.read(8 * 1024 * 1024), b''):
                h.update(block)
        if h.hexdigest() != expected:
            raise RuntimeError(f'SHA-256 mismatch: {rel}')
        print(f'Verified {rel}', flush=True)
    if args.verify_only:
        return
    dest = args.destination.resolve()
    dest.mkdir(parents=True, exist_ok=True)
    for name in ('images', 'annotations'):
        if (dest / name).exists():
            raise RuntimeError(f'Refusing to overwrite {dest / name}; select an empty destination')
    expected_images = json.loads((root / 'manifests/package_summary.json').read_text())['image_count']
    count = 0
    for shard in json.loads((root / 'manifests/shards.json').read_text())['shards']:
        shard_count = 0
        with tarfile.open(root / shard['path'], mode='r|') as archive:
            for member in archive:
                p = PurePosixPath(member.name)
                if not member.isfile() or p.is_absolute() or '..' in p.parts or p.parts[0] != 'images':
                    raise RuntimeError(f'Unsafe archive member: {member.name}')
                target = dest / member.name
                target.parent.mkdir(parents=True, exist_ok=True)
                with archive.extractfile(member) as source, target.open('xb') as out:
                    shutil.copyfileobj(source, out)
                if target.stat().st_size != member.size:
                    raise RuntimeError(f'Incomplete image: {target}')
                shard_count += 1
        if shard_count != shard['image_count']:
            raise RuntimeError(f'Image count mismatch: {shard["path"]}')
        count += shard_count
        print(f'Extracted {shard["path"]}: {count:,} images', flush=True)
    if count != expected_images:
        raise RuntimeError('Total image count mismatch')
    shutil.copytree(root / 'annotations', dest / 'annotations')
    shutil.copyfile(root / 'source_roots.yaml', dest / 'source_roots.yaml')
    print(f'Complete: {count:,} images and three annotation files in {dest}', flush=True)


if __name__ == '__main__':
    main()