"""Verify and extract an individual FlyControl figure archive."""
import argparse, hashlib, json, tarfile
from pathlib import Path

def sha(path):
    h=hashlib.sha256()
    with Path(path).open('rb') as f:
        for block in iter(lambda:f.read(8*1024*1024),b''):h.update(block)
    return h.hexdigest()

def extract(figure, root, output):
    root,output=Path(root).resolve(),Path(output).resolve()
    index=json.loads((root/'archive_index.json').read_text())['archives']
    item=next(x for x in index if x['paper_item']==figure)
    archive=root/item['path']
    assert archive.stat().st_size==item['bytes'] and sha(archive)==item['sha256'], 'Archive integrity failure'
    manifest={x['path']:x for x in map(json.loads,(root/'manifests'/f'{figure}.jsonl').open())}
    assert len(manifest)==item['members']
    output.mkdir(parents=True,exist_ok=True)
    seen=set()
    with tarfile.open(archive,'r|gz') as tar:
        for member in tar:
            if not member.isfile() or member.name not in manifest or member.name in seen:
                raise ValueError('Unexpected archive member: '+member.name)
            dest=(output/member.name).resolve()
            if not dest.is_relative_to(output):raise ValueError('Unsafe member path')
            expected=manifest[member.name]
            assert member.size==expected['bytes']
            dest.parent.mkdir(parents=True,exist_ok=True)
            if dest.exists():
                assert dest.stat().st_size==expected['bytes'] and sha(dest)==expected['sha256'], str(dest)
            else:
                stream=tar.extractfile(member)
                hasher=hashlib.sha256()
                try:
                    with dest.open('xb') as f:
                        for block in iter(lambda:stream.read(8*1024*1024),b''):
                            f.write(block);hasher.update(block)
                    assert hasher.hexdigest()==expected['sha256'], str(dest)
                except BaseException:
                    dest.unlink(missing_ok=True)
                    raise
            seen.add(member.name)
    assert seen==set(manifest)
    print(json.dumps(dict(figure=figure,members=len(seen),verified=True,output=str(output))))

if __name__=='__main__':
    p=argparse.ArgumentParser(description=__doc__)
    p.add_argument('--figure',required=True)
    p.add_argument('--dataset-dir',default=str(Path(__file__).parent))
    p.add_argument('--output',required=True)
    a=p.parse_args();extract(a.figure,a.dataset_dir,a.output)