import 'dart:math';
import 'dart:typed_data';

import 'package:bip340/bip340.dart' as bip340;
import 'package:block2_spike/block2_spike.dart';
import 'package:commons_core/commons_core.dart';
import 'package:test/test.dart';

/// Q1 — Identity derivation: a deterministic, one-way secp256k1 (Nostr) key from
/// the Duniter/Ğ1-style root seed, so the user still backs up ONE thing.
void main() {
  group('NostrKey.deriveFromSeed', () {
    // A fixed seed so expectations are reproducible across runs/machines.
    final seed = Uint8List.fromList(List.generate(32, (i) => i));

    test('is reproducible: same seed → identical key', () {
      final a = NostrKey.deriveFromSeed(seed);
      final b = NostrKey.deriveFromSeed(seed);
      expect(a.privateKeyHex, b.privateKeyHex);
      expect(a.publicKeyHex, b.publicKeyHex);
      expect(a.npub, b.npub);
    });

    test('produces a well-formed x-only key and npub/nsec', () {
      final key = NostrKey.deriveFromSeed(seed);
      expect(key.privateKeyHex, matches(RegExp(r'^[0-9a-f]{64}$')));
      expect(key.publicKeyHex, matches(RegExp(r'^[0-9a-f]{64}$')));
      // Cross-check: bip340 derives the same pubkey from our private hex.
      expect(bip340.getPublicKey(key.privateKeyHex), key.publicKeyHex);
      expect(key.npub, startsWith('npub1'));
      expect(key.nsec, startsWith('nsec1'));
    });

    test('the derived key actually signs & verifies (BIP340)', () {
      final key = NostrKey.deriveFromSeed(seed);
      final message = 'a' * 64; // 32-byte hex message
      final sig = bip340.sign(key.privateKeyHex, message, 'b' * 64);
      expect(bip340.verify(key.publicKeyHex, message, sig), isTrue);
    });

    test('different seeds → different keys (avalanche on a 1-bit flip)', () {
      final flipped = Uint8List.fromList(seed)..[0] ^= 0x01;
      final a = NostrKey.deriveFromSeed(seed);
      final b = NostrKey.deriveFromSeed(flipped);
      expect(a.privateKeyHex, isNot(b.privateKeyHex));
      expect(a.publicKeyHex, isNot(b.publicKeyHex));
    });

    test('one-wayness: neither key contains the seed, and HKDF is not '
        'invertible', () {
      final key = NostrKey.deriveFromSeed(seed);
      final seedHex = seed
          .map((b) => b.toRadixString(16).padLeft(2, '0'))
          .join();
      // The seed does not appear verbatim in the derived material.
      expect(key.privateKeyHex, isNot(contains(seedHex)));
      expect(key.publicKeyHex, isNot(contains(seedHex)));
      // Structural argument (documented in findings §1): recovery of the seed
      // would require inverting HMAC-SHA256. We assert the property we CAN test:
      // two unrelated seeds never collide to the same key.
      final other = NostrKey.deriveFromSeed(
        Uint8List.fromList(List.generate(32, (i) => 255 - i)),
      );
      expect(key.privateKeyHex, isNot(other.privateKeyHex));
    });

    test('integrates with the real IdentityService seed length', () {
      final rootSeed = IdentityService(
        random: Random(42),
      ).generateRootSeed();
      expect(rootSeed.length, IdentityService.rootSeedLengthBytes);
      final key = NostrKey.deriveFromSeed(rootSeed);
      expect(key.publicKeyHex, matches(RegExp(r'^[0-9a-f]{64}$')));
    });
  });
}