import 'dart:typed_data';

import 'package:abawo_bt_app/model/firmware_file_selection.dart';
import 'package:abawo_bt_app/model/shifter_types.dart';
import 'package:abawo_bt_app/service/dfu_protocol.dart';
import 'package:abawo_bt_app/service/firmware_file_selection_service.dart';
import 'package:flutter_test/flutter_test.dart';

void main() {
  group('FirmwareFileSelectionService', () {
    test('prepares bootloader metadata for selected .bin firmware', () async {
      final image = _validBootloaderImage();
      final service = FirmwareFileSelectionService(
        filePicker: _FakeFirmwareFilePicker(
          selection: FirmwarePickerSelection(
            fileName: 'firmware.BIN',
            filePath: '/tmp/firmware.BIN',
            fileBytes: image,
          ),
        ),
        sessionIdGenerator: () => 0x1AB,
      );

      final result = await service.selectAndPrepareBootloaderDfu();
      expect(result.isSuccess, isTrue);

      final firmware = result.firmware!;
      expect(firmware.fileName, 'firmware.BIN');
      expect(firmware.filePath, '/tmp/firmware.BIN');
      expect(firmware.fileBytes, image);
      expect(firmware.metadata.totalLength, image.length);
      expect(firmware.metadata.crc32, BootloaderDfuProtocol.crc32(image));
      expect(firmware.metadata.appStart, universalShifterDfuAppStart);
      expect(firmware.metadata.imageVersion, 0);
      expect(firmware.metadata.sessionId, 0xAB);
      expect(firmware.metadata.flags, universalShifterDfuFlagNone);
      expect(firmware.metadata.vectorStackPointer, 0x20001000);
      expect(firmware.metadata.vectorReset, 0x00030009);
    });

    test('returns canceled result when user dismisses picker', () async {
      final service = FirmwareFileSelectionService(
        filePicker: _FakeFirmwareFilePicker(selection: null),
      );

      final result = await service.selectAndPrepareBootloaderDfu();

      expect(result.isSuccess, isFalse);
      expect(result.isCanceled, isTrue);
      expect(result.failure?.reason, FirmwareSelectionFailureReason.canceled);
    });

    test('rejects unsupported extension', () async {
      final service = FirmwareFileSelectionService(
        filePicker: _FakeFirmwareFilePicker(
          selection: FirmwarePickerSelection(
            fileName: 'firmware.hex',
            fileBytes: _validBootloaderImage(),
          ),
        ),
      );

      final result = await service.selectAndPrepareBootloaderDfu();

      expect(result.isSuccess, isFalse);
      expect(result.failure?.reason,
          FirmwareSelectionFailureReason.unsupportedExtension);
    });

    test('rejects empty payload', () async {
      final service = FirmwareFileSelectionService(
        filePicker: _FakeFirmwareFilePicker(
          selection: FirmwarePickerSelection(
            fileName: 'firmware.bin',
            fileBytes: Uint8List(0),
          ),
        ),
      );

      final result = await service.selectAndPrepareBootloaderDfu();

      expect(result.isSuccess, isFalse);
      expect(result.failure?.reason, FirmwareSelectionFailureReason.emptyFile);
    });

    test('rejects images that are too small for a vector table', () async {
      final service = FirmwareFileSelectionService(
        filePicker: _FakeFirmwareFilePicker(
          selection: FirmwarePickerSelection(
            fileName: 'firmware.bin',
            fileBytes: Uint8List.fromList(<int>[1, 2, 3, 4]),
          ),
        ),
      );

      final result = await service.selectAndPrepareBootloaderDfu();

      expect(result.isSuccess, isFalse);
      expect(
          result.failure?.reason, FirmwareSelectionFailureReason.imageTooSmall);
    });

    test('rejects images larger than the application slot', () async {
      final image = Uint8List(universalShifterDfuAppSlotSizeBytes + 1);
      _writeLeU32(image, 0, 0x20001000);
      _writeLeU32(image, 4, 0x00030009);
      final service = FirmwareFileSelectionService(
        filePicker: _FakeFirmwareFilePicker(
          selection: FirmwarePickerSelection(
            fileName: 'firmware.bin',
            fileBytes: image,
          ),
        ),
      );

      final result = await service.selectAndPrepareBootloaderDfu();

      expect(result.isSuccess, isFalse);
      expect(
          result.failure?.reason, FirmwareSelectionFailureReason.imageTooLarge);
    });

    test('rejects images with invalid vector table', () async {
      final image = _validBootloaderImage();
      _writeLeU32(image, 0, 0x10001000);
      final service = FirmwareFileSelectionService(
        filePicker: _FakeFirmwareFilePicker(
          selection: FirmwarePickerSelection(
            fileName: 'firmware.bin',
            fileBytes: image,
          ),
        ),
      );

      final result = await service.selectAndPrepareBootloaderDfu();

      expect(result.isSuccess, isFalse);
      expect(result.failure?.reason,
          FirmwareSelectionFailureReason.invalidVectorTable);
    });

    test('generates session id per run', () async {
      var nextSession = 9;
      final service = FirmwareFileSelectionService(
        filePicker: _FakeFirmwareFilePicker(
          selection: FirmwarePickerSelection(
            fileName: 'firmware.bin',
            fileBytes: _validBootloaderImage(),
          ),
        ),
        sessionIdGenerator: () => nextSession++,
      );

      final first = await service.selectAndPrepareBootloaderDfu();
      final second = await service.selectAndPrepareBootloaderDfu();

      expect(first.firmware?.metadata.sessionId, 9);
      expect(second.firmware?.metadata.sessionId, 10);
    });

    test('maps picker read failure to explicit validation error', () async {
      final service = FirmwareFileSelectionService(
        filePicker: _FakeFirmwareFilePicker(
          selection: null,
          error: const FormatException('broken pick payload'),
        ),
      );

      final result = await service.selectAndPrepareBootloaderDfu();

      expect(result.isSuccess, isFalse);
      expect(result.failure?.reason, FirmwareSelectionFailureReason.readFailed);
      expect(result.failure?.message, contains('broken pick payload'));
    });
  });
}

Uint8List _validBootloaderImage() {
  final image = Uint8List(16);
  _writeLeU32(image, 0, 0x20001000);
  _writeLeU32(image, 4, 0x00030009);
  return image;
}

void _writeLeU32(Uint8List bytes, int offset, int value) {
  final data = ByteData.sublistView(bytes);
  data.setUint32(offset, value, Endian.little);
}

class _FakeFirmwareFilePicker implements FirmwareFilePicker {
  _FakeFirmwareFilePicker({
    required this.selection,
    this.error,
  });

  final FirmwarePickerSelection? selection;
  final Object? error;

  @override
  Future<FirmwarePickerSelection?> pickFirmwareFile() async {
    if (error != null) {
      throw error!;
    }
    return selection;
  }
}