#!/usr/bin/env python3
"""Build compact CVE SQLite plus optionally incremental row-level delta (CVE slice)."""
import argparse
import base64
import datetime as dt
import hashlib
import json
import sqlite3
import zlib
from pathlib import Path
import subprocess

SCHEMA = '''CREATE TABLE cve (
    cve_id TEXT PRIMARY KEY,
    state TEXT NOT NULL,
    date_updated TEXT,
    affected BLOB NOT NULL,
    row_hash TEXT NOT NULL
) WITHOUT ROWID;
CREATE INDEX idx_cve_state ON cve(state);'''

def encode_record(doc):
    meta = doc['cveMetadata']
    cna = doc.get('containers', {}).get('cna', {})
    # Preserve entire CNA affected array as structured JSON. Do NOT infer ranges.
    affected = json.dumps(cna.get('affected', []), sort_keys=True, separators=(',', ':'), ensure_ascii=False).encode('utf-8')
    blob = zlib.compress(affected, level=9)
    row = (meta['cveId'], meta.get('state', 'UNKNOWN'), meta.get('dateUpdated'), blob)
    digest = hashlib.sha256(json.dumps([row[0], row[1], row[2]], separators=(',', ':')).encode() + blob).hexdigest()
    return (*row, digest)

def fingerprint(conn):
    h = hashlib.sha256()
    for cve_id, row_hash in conn.execute('SELECT cve_id,row_hash FROM cve ORDER BY cve_id'):
        h.update(cve_id.encode() + b'\x00' + row_hash.encode() + b'\n')
    return h.hexdigest()

def export_zstd(path, output):
    with output.open('wb') as dst:
        subprocess.run(['zstd', '-q', '-12', '-c', str(path)], stdout=dst, check=True)

def main():
    ap = argparse.ArgumentParser()
    ap.add_argument('--source', type=Path, required=True, help='vuln-cve/data')
    ap.add_argument('--output', type=Path, default=Path('dist'))
    ap.add_argument('--previous', type=Path, help='previous SQLite master.db')
    ap.add_argument('--source-revision', default='unknown')
    args = ap.parse_args()
    args.output.mkdir(parents=True, exist_ok=True)
    db = args.output / 'master.db'
    db.unlink(missing_ok=True)
    current = sqlite3.connect(db)
    current.executescript(SCHEMA)
    count = 0
    for path in sorted(args.source.rglob('CVE-*.json')):
        with path.open(encoding='utf-8') as fh:
            doc = json.load(fh)
        if doc.get('cveMetadata', {}).get('cveId') != path.stem:
            raise ValueError(f'CVE metadata mismatch at {path}')
        current.execute('INSERT INTO cve VALUES (?,?,?,?,?)', encode_record(doc))
        count += 1
        if count % 5000 == 0:
            current.commit()
    if count == 0:
        raise RuntimeError('No CVE records, refusing empty release')
    current.commit()
    current.execute('VACUUM')
    current.commit()
    current_hash = fingerprint(current)
    previous_hash = None
    changed = removed = 0
    if args.previous:
        prev = sqlite3.connect(f'file:{args.previous.resolve()}?mode=ro', uri=True)
        previous_hash = fingerprint(prev)
        old = {row[0]: row[1] for row in prev.execute('SELECT cve_id,row_hash FROM cve')}
        delta_file = args.output / 'delta.jsonl.zst'
        plain_delta = args.output / 'delta.jsonl'
        with plain_delta.open('w', encoding='utf-8') as out:
            header = {'type': 'header', 'format': 1, 'base': previous_hash, 'target': current_hash}
            out.write(json.dumps(header) + '\n')
            for id, state, date, blob, row_hash in current.execute('SELECT * FROM cve ORDER BY cve_id'):
                old_hash = old.pop(id, None)
                if old_hash != row_hash:
                    change = {'type': 'upsert', 'id': id, 'state': state, 'updated': date, 'affected_b64': base64.b64encode(blob).decode(), 'hash': row_hash}
                    out.write(json.dumps(change, separators=(',', ':')) + '\n')
                    changed += 1
            for id in sorted(old):
                out.write(json.dumps({'type': 'delete', 'id': id}) + '\n')
                removed += 1
        export_zstd(plain_delta, delta_file)
        plain_delta.unlink()
        prev.close()
    export_zstd(db, args.output / 'master.db.zst')
    manifest = {
        'format': 1,
        'schema': 'cve-index-v1',
        'built_at': dt.datetime.now(dt.timezone.utc).isoformat(),
        'sources': {'cve': args.source_revision},
        'records': count,
        'content_sha256': current_hash,
        'previous_content_sha256': previous_hash,
        'upserts': changed,
        'deletions': removed,
        'artifacts': {},
    }
    for f in sorted(args.output.glob('*.zst')):
        manifest['artifacts'][f.name] = {'sha256': hashlib.sha256(f.read_bytes()).hexdigest(), 'bytes': f.stat().st_size}
    (args.output / 'manifest.json').write_text(json.dumps(manifest, indent=2) + '\n')
    print(json.dumps(manifest, indent=2))
    current.close()

if __name__ == '__main__':
    main()