import 'dart:convert';

/// 信令消息模型，对应 Android 端的 SignalMessage。
///
/// 字段含义：
/// - [type]        消息类型：REGISTER / OFFER / ANSWER / ICE_CANDIDATE
/// - [fromDeviceId] 发送方设备 ID
/// - [toDeviceId]   接收方设备 ID
/// - [deviceType]   设备类型：CONTROLLER / CONTROLLED
/// - [payload]      JSON 字符串形式的负载（SDP / ICE 候选等）
/// - [authType]     鉴权类型：CODE（动态验证码）/ PASSWORD（固定密码）
/// - [authValue]    鉴权值：动态验证码或固定密码
class SignalMessage {
  final String? type;
  final String? fromDeviceId;
  final String? toDeviceId;
  final String? deviceType;
  final String? payload;
  final String? authType;
  final String? authValue;

  const SignalMessage({
    this.type,
    this.fromDeviceId,
    this.toDeviceId,
    this.deviceType,
    this.payload,
    this.authType,
    this.authValue,
  });

  factory SignalMessage.fromJson(Map<String, dynamic> json) => SignalMessage(
        type: json['type'] as String?,
        fromDeviceId: json['fromDeviceId'] as String?,
        toDeviceId: json['toDeviceId'] as String?,
        deviceType: json['deviceType'] as String?,
        payload: json['payload'] as String?,
        authType: json['authType'] as String?,
        authValue: json['authValue'] as String?,
      );

  Map<String, dynamic> toJson() => {
        if (type != null) 'type': type,
        if (fromDeviceId != null) 'fromDeviceId': fromDeviceId,
        if (toDeviceId != null) 'toDeviceId': toDeviceId,
        if (deviceType != null) 'deviceType': deviceType,
        if (payload != null) 'payload': payload,
        if (authType != null) 'authType': authType,
        if (authValue != null) 'authValue': authValue,
      };

  /// 便捷构造方法：payload 为任意 Map，会自动序列化为 JSON 字符串。
  factory SignalMessage.withPayload({
    required String type,
    required String fromDeviceId,
    required String toDeviceId,
    required String deviceType,
    required Map<String, dynamic> payload,
    String? authType,
    String? authValue,
  }) {
    return SignalMessage(
      type: type,
      fromDeviceId: fromDeviceId,
      toDeviceId: toDeviceId,
      deviceType: deviceType,
      payload: jsonEncode(payload),
      authType: authType,
      authValue: authValue,
    );
  }

  @override
  String toString() => jsonEncode(toJson());
}