gskinnerteam/flutter-hatcha-app/genui-a2a

User Input
 │
 ▼
Conversation
 │  submit(ChatMessage)
 ▼
A2uiTransportAdapter (wraps A2uiAgentConnector as Transport)
 │  delegates to connector
 ▼
A2uiAgentConnector
 │  converts ChatMessage → A2A Message
 │  manages taskId / contextId
 ▼
A2AClient
 │  JSON-RPC 2.0 over Transport (SSE or HTTP)
 ▼
A2A Server
 │
 │  streams back A2AStreamEvents
 ▼
A2uiAgentConnector
 │  extracts A2UI messages from DataParts
 │  emits Stream<A2uiMessage>
 ▼
SurfaceController
 │  handles A2uiMessage → SurfaceUpdate
 ▼
Surface renders dynamic UI

A2uiAgentConnector({
  Uri? url,                 // Server URL — provide exactly one of url or client
  A2AClient? client,        // Pre-configured client — provide exactly one
  String? contextId,
})

{
  "actionName": "submit",
  "sourceComponentId": "btn_1",
  "timestamp": "2026-04-14T...",
  "resolvedContext": { ... }
}

A2uiTransportAdapter({
  required A2uiAgentConnector connector,
})

A2AClient({
  required String url,
  Transport? transport,  // Defaults to SseTransport
  Logger? log,
})

static Future<A2AClient> fromAgentCardUrl(String agentCardUrl, {Logger? log})

abstract class Transport {
  Map<String, String> get authHeaders;
  Future<Map<String, Object?>> get(String path, {Map<String, String> headers});
  Future<Map<String, Object?>> send(Map<String, Object?> request, {String path, Map<String, String> headers});
  Stream<Map<String, Object?>> sendStream(Map<String, Object?> request, {Map<String, String> headers});
  void close();
}

sealed class Event {
  factory Event.statusUpdate({taskId, contextId, status, final_})
  factory Event.taskStatusUpdate({taskId, contextId, status, final_})
  factory Event.artifactUpdate({taskId, contextId, artifact, append, lastChunk})
}

Message({
  required Role role,
  required List<Part> parts,
  Map<String, Object?>? metadata,
  List<String>? extensions,
  List<String>? referenceTaskIds,
  required String messageId,
  String? taskId,
  String? contextId,
})

enum TaskState {
  submitted, working, inputRequired, completed, canceled, failed, rejected, authRequired, unknown
}

// 1. Create the connector
final connector = A2uiAgentConnector(url: Uri.parse('http://localhost:8080'));
 
// 2. Create a SurfaceController
final controller = SurfaceController(catalogs: [BasicCatalog.asCatalog()]);
 
// 3. Wire connector stream to controller
connector.stream.listen(controller.handleMessage);
 
// 4. Create Conversation with transport adapter
final conversation = Conversation(
  transport: A2uiTransportAdapter(connector: connector),
  surfaceController: controller,
);
 
// 5. Render surfaces
Surface(host: controller, surfaceId: 'main');