import 'dart:typed_data';

import 'package:flutter_test/flutter_test.dart';
import 'package:uto_manager/domain/entities/authorized_rank.dart';
import 'package:uto_manager/domain/entities/doctrinal_branch.dart';
import 'package:uto_manager/domain/entities/echelon.dart';
import 'package:uto_manager/domain/entities/personnel_record.dart';
import 'package:uto_manager/domain/entities/position_slot.dart';
import 'package:uto_manager/domain/entities/unit_node.dart';
import 'package:uto_manager/domain/value_objects/duty_mos.dart';
import 'package:uto_manager/infrastructure/codecs/protobuf_codec.dart';
import 'package:uto_manager/infrastructure/codecs/unit_tree_codec.dart';

void main() {
  const codec = ProtobufCodec();

  // ---------------------------------------------------------------------------
  // Helpers
  // ---------------------------------------------------------------------------

  UnitNode makeUnit(String id, {String? parentId}) => UnitNode(
        unitId: id,
        echelon: Echelon.platoon,
        branch: DoctrinalBranch.infantry,
        parentUnitId: parentId,
        name: 'Unit $id',
        isKeyLeader: false,
      );

  PositionSlot makeSlot(String id, String unitId) => PositionSlot(
        slotId: id,
        unitId: unitId,
        positionTitle: 'Rifleman',
        dutyMos: DutyMos.unvalidated('11B'),
        authorizedRank: AuthorizedRank.e3,
        isKeyLeader: false,
      );

  PersonnelRecord makeSoldier(String id) => PersonnelRecord(
        soldierId: id,
        name: 'SGT Test',
        primaryMos: DutyMos.unvalidated('11B'),
        payGrade: AuthorizedRank.e5,
        readinessState: ReadinessState.fullyMissionCapable,
      );

  // ---------------------------------------------------------------------------
  // Encode / Decode
  // ---------------------------------------------------------------------------

  group('ProtobufCodec — encode/decode', () {
    test('encodes to non-empty Uint8List', () {
      final units = [makeUnit('u1')];
      final bytes = codec.encode(units: units, slots: const [], personnel: const []);
      expect(bytes, isA<Uint8List>());
      expect(bytes.length, greaterThan(12));
    });

    test('header contains correct magic bytes "UTOB"', () {
      final bytes = codec.encode(units: [makeUnit('u1')], slots: const [], personnel: const []);
      // Magic: 0x55544F42
      expect(bytes[0], 0x55);
      expect(bytes[1], 0x54);
      expect(bytes[2], 0x4F);
      expect(bytes[3], 0x42);
    });

    test('header contains version 1', () {
      final bytes = codec.encode(units: [makeUnit('u1')], slots: const [], personnel: const []);
      // Version at bytes 4–7
      expect(bytes[4], 0x00);
      expect(bytes[5], 0x00);
      expect(bytes[6], 0x00);
      expect(bytes[7], 0x01);
    });

    test('round-trip preserves units', () {
      final units = [makeUnit('u1'), makeUnit('u2', parentId: 'u1')];
      final bytes = codec.encode(units: units, slots: const [], personnel: const []);
      final snapshot = codec.decode(bytes);

      expect(snapshot.units.length, 2);
      expect(snapshot.units.map((u) => u.unitId), containsAll(['u1', 'u2']));
      expect(snapshot.units.firstWhere((u) => u.unitId == 'u2').parentUnitId, 'u1');
    });

    test('round-trip preserves slots', () {
      final units = [makeUnit('u1')];
      final slots = [makeSlot('sl1', 'u1'), makeSlot('sl2', 'u1')];
      final bytes = codec.encode(units: units, slots: slots, personnel: const []);
      final snapshot = codec.decode(bytes);

      expect(snapshot.slots.length, 2);
      expect(snapshot.slots.map((s) => s.slotId), containsAll(['sl1', 'sl2']));
    });

    test('round-trip preserves personnel', () {
      final units = [makeUnit('u1')];
      final personnel = [makeSoldier('s1'), makeSoldier('s2')];
      final bytes = codec.encode(units: units, slots: const [], personnel: personnel);
      final snapshot = codec.decode(bytes);

      expect(snapshot.personnel.length, 2);
      expect(snapshot.personnel.map((p) => p.soldierId), containsAll(['s1', 's2']));
    });

    test('empty tree encodes and decodes correctly', () {
      final bytes = codec.encode(units: const [], slots: const [], personnel: const []);
      final snapshot = codec.decode(bytes);
      expect(snapshot.units, isEmpty);
      expect(snapshot.slots, isEmpty);
      expect(snapshot.personnel, isEmpty);
    });

    test('binary output is smaller than JSON for non-trivial tree', () {
      final units = List.generate(
        20,
        (i) => makeUnit('u$i', parentId: i > 0 ? 'u${i - 1}' : null),
      );
      final slots = List.generate(40, (i) => makeSlot('sl$i', 'u${i % 20}'));

      final binaryBytes = codec.encode(units: units, slots: slots, personnel: const []);
      final jsonLen =
          const UnitTreeCodec().encode(units: units, slots: slots, personnel: const []).length;

      expect(binaryBytes.length, lessThan(jsonLen));
    });
  });

  // ---------------------------------------------------------------------------
  // Error handling
  // ---------------------------------------------------------------------------

  group('ProtobufCodec — error handling', () {
    test('decode throws FormatException for data shorter than 12 bytes', () {
      expect(
        () => codec.decode(Uint8List.fromList([0x55, 0x54, 0x4F])),
        throwsA(isA<FormatException>()),
      );
    });

    test('decode throws FormatException for wrong magic bytes', () {
      final bad = Uint8List(16);
      bad[0] = 0xDE;
      bad[1] = 0xAD;
      bad[2] = 0xBE;
      bad[3] = 0xEF;
      expect(() => codec.decode(bad), throwsA(isA<FormatException>()));
    });

    test('decode throws FormatException for wrong version', () {
      // Build a valid header but with version = 99.
      final bytes = codec.encode(units: [makeUnit('u1')], slots: const [], personnel: const []);
      final tampered = Uint8List.fromList(bytes);
      tampered[7] = 99; // version byte (big-endian, LSB)
      expect(() => codec.decode(tampered), throwsA(isA<FormatException>()));
    });

    test('decode throws FormatException for truncated payload', () {
      final bytes = codec.encode(units: [makeUnit('u1')], slots: const [], personnel: const []);
      // Truncate to just the header.
      final truncated = bytes.sublist(0, 12);
      expect(() => codec.decode(truncated), throwsA(isA<FormatException>()));
    });
  });

  // ---------------------------------------------------------------------------
  // compressionRatio
  // ---------------------------------------------------------------------------

  group('ProtobufCodec.compressionRatio', () {
    test('returns 1.0 when jsonBytes is 0', () {
      expect(ProtobufCodec.compressionRatio(100, 0), 1.0);
    });

    test('returns correct ratio', () {
      expect(ProtobufCodec.compressionRatio(50, 100), closeTo(0.5, 0.001));
    });

    test('ratio < 1.0 for compressed data', () {
      final units = List.generate(10, (i) => makeUnit('u$i'));
      final bytes = codec.encode(units: units, slots: const [], personnel: const []);
      final jsonLen =
          const UnitTreeCodec().encode(units: units, slots: const [], personnel: const []).length;
      final ratio = ProtobufCodec.compressionRatio(bytes.length, jsonLen);
      expect(ratio, lessThan(1.0));
    });
  });
}