#!/usr/bin/env python3
"""Compare a fresh snapshot against the committed baseline.

Usage:
    python scripts/diff_golden.py \
      [--baseline tests/golden/snapshot.json] \
      [--base-url http://localhost:8001] \
      [--allow-timing-pct 25]

Exit code 0 if fingerprints match. Non-zero if any query's ordered result
fingerprint changed or if elapsed_ms regressed by more than the allowed
percentage.
"""

from __future__ import annotations

import argparse
import json
import sys
import time
from pathlib import Path

REPO_ROOT = Path(__file__).resolve().parent.parent
sys.path.insert(0, str(REPO_ROOT / "scripts"))

from golden_queries import GOLDEN_QUERIES  # noqa: E402
from snapshot_golden import _fetch  # noqa: E402


def main() -> int:
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("--baseline", default=str(REPO_ROOT / "tests" / "golden" / "snapshot.json"))
    parser.add_argument("--base-url", default="http://localhost:8001")
    parser.add_argument("--timeout", type=float, default=30.0)
    parser.add_argument("--allow-timing-pct", type=float, default=25.0)
    args = parser.parse_args()

    baseline_path = Path(args.baseline)
    if not baseline_path.exists():
        print(f"Baseline {baseline_path} does not exist. Run snapshot_golden.py first.")
        return 2

    baseline = json.loads(baseline_path.read_text())
    baseline_by_id = {q["id"]: q for q in baseline["queries"]}

    drift = []
    timing_regressions = []
    missing_in_baseline = []

    for query in GOLDEN_QUERIES:
        fresh = _fetch(args.base_url, query, args.timeout)
        bid = query["id"]
        prior = baseline_by_id.get(bid)

        if prior is None:
            missing_in_baseline.append(bid)
            continue

        if not fresh.get("ok"):
            drift.append((bid, "fresh fetch failed", fresh.get("error")))
            continue
        if not prior.get("ok"):
            drift.append((bid, "baseline was a failure, now ok", None))
            continue

        if fresh["fingerprint"] != prior["fingerprint"]:
            drift.append((bid, "fingerprint changed", None))
            continue

        prior_ms = prior.get("elapsed_ms") or 1
        fresh_ms = fresh.get("elapsed_ms") or 1
        if prior_ms >= 50:  # only flag timing on queries that take meaningful time
            growth_pct = (fresh_ms - prior_ms) / prior_ms * 100
            if growth_pct > args.allow_timing_pct:
                timing_regressions.append((bid, prior_ms, fresh_ms, growth_pct))

    print(f"\nBaseline captured: {baseline.get('captured_at')}")
    print(f"Fresh capture:     {time.strftime('%Y-%m-%dT%H:%M:%S')}")
    print(f"Queries checked:   {len(GOLDEN_QUERIES)}")

    if drift:
        print(f"\n{len(drift)} query(ies) drifted:")
        for bid, kind, extra in drift:
            print(f"  - {bid}: {kind}" + (f" ({extra})" if extra else ""))

    if timing_regressions:
        print(f"\n{len(timing_regressions)} query(ies) regressed in timing:")
        for bid, prior_ms, fresh_ms, growth_pct in timing_regressions:
            print(f"  - {bid}: {prior_ms}ms -> {fresh_ms}ms (+{growth_pct:.1f}%)")

    if missing_in_baseline:
        print(f"\n{len(missing_in_baseline)} query(ies) not in baseline (run snapshot_golden.py to add):")
        for bid in missing_in_baseline:
            print(f"  - {bid}")

    if not drift and not timing_regressions:
        print("\nAll golden queries match baseline.")
        return 0

    return 1


if __name__ == "__main__":
    raise SystemExit(main())