"""Verify the complete release and safely extract its data into the code tree."""
import argparse, hashlib, json, os, tarfile
from pathlib import Path, PurePosixPath

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

def safe_target(root, name):
    p=PurePosixPath(name)
    if p.is_absolute() or '..' in p.parts or not p.parts or p.parts[0] not in ('datasets','metadata'):
        raise ValueError('Unsafe archive path: '+name)
    target=root.joinpath(*p.parts)
    if not target.resolve().is_relative_to(root.resolve()): raise ValueError('Path escapes destination')
    for parent in [target]+list(target.parents):
        if parent==root:break
        if parent.is_symlink():raise ValueError('Refusing destination symlink')
    return target

def extract(repo, destination):
    manifest=json.loads((repo/'metadata/archives.json').read_text())
    files_path=repo/'metadata/files.jsonl'
    if digest(files_path)!=manifest['files_manifest_sha256']:raise ValueError('File manifest checksum mismatch')
    rows=[json.loads(s) for s in files_path.read_text().splitlines() if s.strip()]
    expected={r['path']:r for r in rows}
    if len(expected)!=len(rows) or len(rows)!=manifest['file_count']:raise ValueError('Invalid manifest counts')
    seen=set(); destination.mkdir(parents=True,exist_ok=True)
    for archive in manifest['archives']:
        ap=PurePosixPath(archive['path'])
        if ap.is_absolute() or '..' in ap.parts or ap.parts[0]!='archives':raise ValueError('Invalid archive path')
        path=repo.joinpath(*ap.parts)
        if path.stat().st_size!=archive['size'] or digest(path)!=archive['sha256']:raise ValueError('Archive checksum mismatch: '+archive['path'])
        count=0
        with tarfile.open(path,'r:gz') as tar:
            for m in tar:
                if not m.isfile():raise ValueError('Only regular files are permitted')
                if m.name.startswith('__shards__/'):continue
                if m.name not in expected or m.name in seen:raise ValueError('Unexpected or repeated member')
                row=expected[m.name]
                if row['archive']!=archive['path'] or row['size']!=m.size:raise ValueError('Manifest member mismatch')
                dest=safe_target(destination,m.name)
                if dest.exists():
                    if not dest.is_file() or digest(dest)!=row['sha256']:raise ValueError('Existing file differs: '+m.name)
                else:
                    dest.parent.mkdir(parents=True,exist_ok=True)
                    temp=dest.with_name(dest.name+'.extract-partial')
                    # Exclusive creation avoids overwriting any existing user file.
                    with temp.open('xb') as out, tar.extractfile(m) as inp:
                        for b in iter(lambda:inp.read(1024*1024),b''):out.write(b)
                    if digest(temp)!=row['sha256']:raise ValueError('Extracted file checksum mismatch')
                    temp.replace(dest)
                seen.add(m.name);count+=1
        if count!=archive['file_count']:raise ValueError('Archive member count mismatch')
        print('Verified',archive['path'],count,'files',flush=True)
    if seen!=set(expected):raise ValueError('Incomplete extraction')
    print('Complete:',len(seen),'verified files')

if __name__=='__main__':
    p=argparse.ArgumentParser();p.add_argument('--destination',type=Path,default=Path('code'));args=p.parse_args()
    extract(Path(__file__).resolve().parents[1],args.destination.resolve())