feat(dfu): add protocol constants and progress models

lib/model/shifter_types.dart

@@ -10,14 +10,103 @@ const String universalShifterCommandCharacteristicUuid =
     '0993826f-0ee4-4b37-9614-d13ecba40005';
 const String universalShifterGearRatiosCharacteristicUuid =
     '0993826f-0ee4-4b37-9614-d13ecba40006';
+const String universalShifterDfuControlCharacteristicUuid =
+    '0993826f-0ee4-4b37-9614-d13ecba40008';
+const String universalShifterDfuDataCharacteristicUuid =
+    '0993826f-0ee4-4b37-9614-d13ecba40009';
+const String universalShifterDfuAckCharacteristicUuid =
+    '0993826f-0ee4-4b37-9614-d13ecba4000a';
 const String ftmsServiceUuid = '00001826-0000-1000-8000-00805f9b34fb';
 
+const int universalShifterDfuOpcodeStart = 0x01;
+const int universalShifterDfuOpcodeFinish = 0x02;
+const int universalShifterDfuOpcodeAbort = 0x03;
+
+const int universalShifterDfuFrameSizeBytes = 64;
+const int universalShifterDfuFramePayloadSizeBytes = 63;
+
+const int universalShifterDfuFlagEncrypted = 0x01;
+const int universalShifterDfuFlagSigned = 0x02;
+
 const int errorSequence = 1;
 const int errorFtmsMissing = 2;
 const int errorPairingAuth = 3;
 const int errorPairingEncrypt = 4;
 const int errorFtmsRequiredCharMissing = 5;
 
+enum DfuUpdateState {
+  idle,
+  starting,
+  waitingForAck,
+  transferring,
+  finishing,
+  completed,
+  aborted,
+  failed,
+}
+
+class DfuUpdateFlags {
+  const DfuUpdateFlags({
+    this.encrypted = false,
+    this.signed = false,
+  });
+
+  final bool encrypted;
+  final bool signed;
+
+  int get rawValue {
+    var value = 0;
+    if (encrypted) {
+      value |= universalShifterDfuFlagEncrypted;
+    }
+    if (signed) {
+      value |= universalShifterDfuFlagSigned;
+    }
+    return value;
+  }
+
+  static DfuUpdateFlags fromRaw(int rawValue) {
+    return DfuUpdateFlags(
+      encrypted: (rawValue & universalShifterDfuFlagEncrypted) != 0,
+      signed: (rawValue & universalShifterDfuFlagSigned) != 0,
+    );
+  }
+}
+
+class DfuUpdateProgress {
+  const DfuUpdateProgress({
+    required this.state,
+    required this.totalBytes,
+    required this.sentBytes,
+    required this.lastAckedSequence,
+    required this.sessionId,
+    required this.flags,
+    this.errorMessage,
+  });
+
+  final DfuUpdateState state;
+  final int totalBytes;
+  final int sentBytes;
+  final int lastAckedSequence;
+  final int sessionId;
+  final DfuUpdateFlags flags;
+  final String? errorMessage;
+
+  double get fractionComplete {
+    if (totalBytes <= 0) {
+      return 0;
+    }
+    return sentBytes.clamp(0, totalBytes) / totalBytes;
+  }
+
+  int get percentComplete => (fractionComplete * 100).round();
+
+  bool get isTerminal =>
+      state == DfuUpdateState.completed ||
+      state == DfuUpdateState.aborted ||
+      state == DfuUpdateState.failed;
+}
+
 class ShifterErrorInfo {
   const ShifterErrorInfo({
     required this.code,