feat: MeshCore SAR - Flutter BLE mesh radio companion app

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/utils/drawing_message_parser.dart

@@ -0,0 +1,161 @@
+import 'dart:convert';
+import '../models/map_drawing.dart';
+
+/// Parser for drawing messages transmitted over mesh network
+class DrawingMessageParser {
+  /// Drawing message prefix
+  static const String prefix = 'D:';
+
+  /// Check if message is a drawing message
+  static bool isDrawingMessage(String text) {
+    return text.startsWith(prefix);
+  }
+
+  /// Parse drawing message text into MapDrawing object
+  /// senderName and messageId should be extracted from packet metadata
+  /// Returns null if parsing fails
+  static MapDrawing? parseDrawingMessage(
+    String text, {
+    String? senderName,
+    String? messageId,
+  }) {
+    if (!isDrawingMessage(text)) {
+      return null;
+    }
+
+    try {
+      // Remove prefix
+      final jsonStr = text.substring(prefix.length);
+
+      // Parse JSON
+      final json = jsonDecode(jsonStr) as Map<String, dynamic>;
+
+      // Use ultra-compact network format parser
+      // Sender name and message ID come from packet metadata, not JSON
+      return MapDrawing.fromNetworkJson(
+        json,
+        senderName: senderName,
+        messageId: messageId,
+      );
+    } catch (e) {
+      return null;
+    }
+  }
+
+  /// Create drawing message text from MapDrawing object
+  /// Sender will be determined from packet metadata on receiving end
+  static String createDrawingMessage(MapDrawing drawing) {
+    final json = drawing.toNetworkJson();
+    final jsonStr = jsonEncode(json).toString();
+    return '$prefix$jsonStr';
+  }
+
+  /// Get drawing type display name from drawing message text
+  /// Returns "Line" or "Rectangle", or null if parsing fails
+  static String? getDrawingTypeDisplay(String text) {
+    if (!isDrawingMessage(text)) return null;
+
+    try {
+      final jsonStr = text.substring(prefix.length);
+      final json = jsonDecode(jsonStr) as Map<String, dynamic>;
+      final typeNum = json['t'] as int?;
+
+      if (typeNum == null) return null;
+
+      switch (typeNum) {
+        case 0:
+          return 'Line';
+        case 1:
+          return 'Rectangle';
+        default:
+          return null;
+      }
+    } catch (e) {
+      return null;
+    }
+  }
+
+  /// Get color name from drawing message text
+  /// Returns color name like "Red", "Blue", etc., or null if parsing fails
+  static String? getColorName(String text) {
+    if (!isDrawingMessage(text)) return null;
+
+    try {
+      final jsonStr = text.substring(prefix.length);
+      final json = jsonDecode(jsonStr) as Map<String, dynamic>;
+      final colorIndex = json['c'] as int?;
+
+      if (colorIndex == null) return null;
+
+      // Color mapping from DrawingColor enum
+      const colorNames = [
+        'Red',    // 0
+        'Blue',   // 1
+        'Green',  // 2
+        'Yellow', // 3
+        'Orange', // 4
+        'Purple', // 5
+        'Pink',   // 6
+        'Cyan',   // 7
+      ];
+
+      if (colorIndex >= 0 && colorIndex < colorNames.length) {
+        return colorNames[colorIndex];
+      }
+
+      return null;
+    } catch (e) {
+      return null;
+    }
+  }
+
+  /// Get drawing metadata for display in message bubbles
+  /// Returns map with type, color, and pointCount, or null if parsing fails
+  static Map<String, dynamic>? getDrawingMetadata(String text) {
+    if (!isDrawingMessage(text)) return null;
+
+    try {
+      final jsonStr = text.substring(prefix.length);
+      final json = jsonDecode(jsonStr) as Map<String, dynamic>;
+
+      final typeNum = json['t'] as int?;
+      final colorIndex = json['c'] as int?;
+
+      if (typeNum == null || colorIndex == null) return null;
+
+      // Get type display name
+      String type;
+      int? pointCount;
+
+      switch (typeNum) {
+        case 0: // Line
+          type = 'Line';
+          final points = json['p'] as List?;
+          pointCount = points != null ? points.length ~/ 2 : null;
+          break;
+        case 1: // Rectangle
+          type = 'Rectangle';
+          pointCount = 4; // Rectangles always have 4 corners
+          break;
+        default:
+          return null;
+      }
+
+      // Get color name
+      const colorNames = [
+        'Red', 'Blue', 'Green', 'Yellow', 'Orange', 'Purple', 'Pink', 'Cyan',
+      ];
+      final color = colorIndex >= 0 && colorIndex < colorNames.length
+          ? colorNames[colorIndex]
+          : 'Unknown';
+
+      return {
+        'type': type,
+        'color': color,
+        'pointCount': pointCount,
+      };
+    } catch (e) {
+      return null;
+    }
+  }
+}