refactor!: Push notification changes [DO NOT MERGE] (#212)

```
Release-As: 0.2.11
```

* Removes push_notifier interface from the SDK and introduces
push_notification_config_store and push_notification_sender for
supporting push notifications. Following is an example for the changes
required with new version:

Previously:
```py
from a2a.server.tasks import InMemoryPushNotifier
...
...
httpx_client = httpx.AsyncClient()
request_handler = DefaultRequestHandler(
    agent_executor=CurrencyAgentExecutor(),
    task_store=InMemoryTaskStore(),
    push_notifier=InMemoryPushNotifier(httpx_client),
)
...
...
```

Now:
```py
from a2a.server.tasks import InMemoryPushNotificationConfigStore, BasePushNotificationSender
...
...
httpx_client = httpx.AsyncClient()
push_notification_config_store = InMemoryPushNotificationConfigStore()
push_notification_sender = BasePushNotificationSender(httpx_client,
                        config_store=push_notification_config_store)
        
request_handler = DefaultRequestHandler(
    agent_executor=CurrencyAgentExecutor(),
    task_store=InMemoryTaskStore(),
    push_config_store=push_notification_config_store,
    push_sender=push_notification_sender
)
...
...
```
* Adds support for more than one push_notification_config per task.
* Adds support for List and Delete push notification configurations

---------

Co-authored-by: Holt Skinner <13262395+holtskinner@users.noreply.github.com>

Author: kthota-g

src/a2a/server/apps/jsonrpc/jsonrpc_app.py

@@ -25,6 +25,7 @@
     A2ARequest,
     AgentCard,
     CancelTaskRequest,
+    DeleteTaskPushNotificationConfigRequest,
     GetTaskPushNotificationConfigRequest,
     GetTaskRequest,
     InternalError,
@@ -33,6 +34,7 @@
     JSONRPCError,
     JSONRPCErrorResponse,
     JSONRPCResponse,
+    ListTaskPushNotificationConfigRequest,
     SendMessageRequest,
     SendStreamingMessageRequest,
     SendStreamingMessageResponse,
@@ -297,12 +299,22 @@ async def _process_non_streaming_request(
                     request_obj, context
                 )
             case SetTaskPushNotificationConfigRequest():
-                handler_result = await self.handler.set_push_notification(
+                handler_result = await self.handler.set_push_notification_config(
                     request_obj,
                     context,
                 )
             case GetTaskPushNotificationConfigRequest():
-                handler_result = await self.handler.get_push_notification(
+                handler_result = await self.handler.get_push_notification_config(
+                    request_obj,
+                    context,
+                )
+            case ListTaskPushNotificationConfigRequest():
+                handler_result = await self.handler.list_push_notification_config(
+                    request_obj,
+                    context,
+                )
+            case DeleteTaskPushNotificationConfigRequest():
+                handler_result = await self.handler.delete_push_notification_config(
                     request_obj,
                     context,
                 )

src/a2a/server/request_handlers/default_request_handler.py

@@ -1,6 +1,5 @@
 import asyncio
 import logging
-import uuid
 
 from collections.abc import AsyncGenerator
 from typing import cast
@@ -21,15 +20,18 @@
 )
 from a2a.server.request_handlers.request_handler import RequestHandler
 from a2a.server.tasks import (
-    PushNotifier,
+    PushNotificationConfigStore,
+    PushNotificationSender,
     ResultAggregator,
     TaskManager,
     TaskStore,
 )
 from a2a.types import (
+    DeleteTaskPushNotificationConfigParams,
     GetTaskPushNotificationConfigParams,
     InternalError,
     InvalidParamsError,
+    ListTaskPushNotificationConfigParams,
     Message,
     MessageSendConfiguration,
     MessageSendParams,
@@ -67,12 +69,13 @@ class DefaultRequestHandler(RequestHandler):
 
     _running_agents: dict[str, asyncio.Task]
 
-    def __init__(
+    def __init__(  # noqa: PLR0913
         self,
         agent_executor: AgentExecutor,
         task_store: TaskStore,
         queue_manager: QueueManager | None = None,
-        push_notifier: PushNotifier | None = None,
+        push_config_store: PushNotificationConfigStore | None = None,
+        push_sender: PushNotificationSender | None = None,
         request_context_builder: RequestContextBuilder | None = None,
     ) -> None:
         """Initializes the DefaultRequestHandler.
@@ -81,14 +84,16 @@ def __init__(
             agent_executor: The `AgentExecutor` instance to run agent logic.
             task_store: The `TaskStore` instance to manage task persistence.
             queue_manager: The `QueueManager` instance to manage event queues. Defaults to `InMemoryQueueManager`.
-            push_notifier: The `PushNotifier` instance for sending push notifications. Defaults to None.
+            push_config_store: The `PushNotificationConfigStore` instance for managing push notification configurations. Defaults to None.
+            push_sender: The `PushNotificationSender` instance for sending push notifications. Defaults to None.
             request_context_builder: The `RequestContextBuilder` instance used
               to build request contexts. Defaults to `SimpleRequestContextBuilder`.
         """
         self.agent_executor = agent_executor
         self.task_store = task_store
         self._queue_manager = queue_manager or InMemoryQueueManager()
-        self._push_notifier = push_notifier
+        self._push_config_store = push_config_store
+        self._push_sender = push_sender
         self._request_context_builder = (
             request_context_builder
             or SimpleRequestContextBuilder(
@@ -198,15 +203,15 @@ async def _setup_message_execution(
 
             task = task_manager.update_with_message(params.message, task)
             if self.should_add_push_info(params):
-                assert isinstance(self._push_notifier, PushNotifier)
+                assert self._push_config_store is not None
                 assert isinstance(
                     params.configuration, MessageSendConfiguration
                 )
                 assert isinstance(
                     params.configuration.pushNotificationConfig,
                     PushNotificationConfig,
                 )
-                await self._push_notifier.set_info(
+                await self._push_config_store.set_info(
                     task.id, params.configuration.pushNotificationConfig
                 )
 
@@ -247,10 +252,10 @@ async def _send_push_notification_if_needed(
         self, task_id: str, result_aggregator: ResultAggregator
     ) -> None:
         """Sends push notification if configured and task is available."""
-        if self._push_notifier and task_id:
+        if self._push_sender and task_id:
             latest_task = await result_aggregator.current_result
             if isinstance(latest_task, Task):
-                await self._push_notifier.send_notification(latest_task)
+                await self._push_sender.send_notification(latest_task)
 
     async def on_message_send(
         self,
@@ -329,11 +334,11 @@ async def on_message_send_stream(
                     self._validate_task_id_match(task_id, event.id)
 
                 if (
-                    self._push_notifier
+                    self._push_config_store
                     and params.configuration
                     and params.configuration.pushNotificationConfig
                 ):
-                    await self._push_notifier.set_info(
+                    await self._push_config_store.set_info(
                         task_id,
                         params.configuration.pushNotificationConfig,
                     )
@@ -372,16 +377,14 @@ async def on_set_task_push_notification_config(
 
         Requires a `PushNotifier` to be configured.
         """
-        if not self._push_notifier:
+        if not self._push_config_store:
             raise ServerError(error=UnsupportedOperationError())
 
         task: Task | None = await self.task_store.get(params.taskId)
         if not task:
             raise ServerError(error=TaskNotFoundError())
 
-        # Generate a unique id for the notification
-        params.pushNotificationConfig.id = str(uuid.uuid4())
-        await self._push_notifier.set_info(
+        await self._push_config_store.set_info(
             params.taskId,
             params.pushNotificationConfig,
         )
@@ -395,21 +398,27 @@ async def on_get_task_push_notification_config(
     ) -> TaskPushNotificationConfig:
         """Default handler for 'tasks/pushNotificationConfig/get'.
 
-        Requires a `PushNotifier` to be configured.
+        Requires a `PushConfigStore` to be configured.
         """
-        if not self._push_notifier:
+        if not self._push_config_store:
             raise ServerError(error=UnsupportedOperationError())
 
         task: Task | None = await self.task_store.get(params.id)
         if not task:
             raise ServerError(error=TaskNotFoundError())
 
-        push_notification_config = await self._push_notifier.get_info(params.id)
-        if not push_notification_config:
-            raise ServerError(error=InternalError())
+        push_notification_config = await self._push_config_store.get_info(
+            params.id
+        )
+        if not push_notification_config or not push_notification_config[0]:
+            raise ServerError(
+                error=InternalError(
+                    message='Push notification config not found'
+                )
+            )
 
         return TaskPushNotificationConfig(
-            taskId=params.id, pushNotificationConfig=push_notification_config
+            taskId=params.id, pushNotificationConfig=push_notification_config[0]
         )
 
     async def on_resubscribe_to_task(
@@ -450,10 +459,61 @@ async def on_resubscribe_to_task(
         async for event in result_aggregator.consume_and_emit(consumer):
             yield event
 
+    async def on_list_task_push_notification_config(
+        self,
+        params: ListTaskPushNotificationConfigParams,
+        context: ServerCallContext | None = None,
+    ) -> list[TaskPushNotificationConfig]:
+        """Default handler for 'tasks/pushNotificationConfig/list'.
+
+        Requires a `PushConfigStore` to be configured.
+        """
+        if not self._push_config_store:
+            raise ServerError(error=UnsupportedOperationError())
+
+        task: Task | None = await self.task_store.get(params.id)
+        if not task:
+            raise ServerError(error=TaskNotFoundError())
+
+        push_notification_config_list = await self._push_config_store.get_info(
+            params.id
+        )
+
+        task_push_notification_config = []
+        if push_notification_config_list:
+            for config in push_notification_config_list:
+                task_push_notification_config.append(
+                    TaskPushNotificationConfig(
+                        taskId=params.id, pushNotificationConfig=config
+                    )
+                )
+
+        return task_push_notification_config
+
+    async def on_delete_task_push_notification_config(
+        self,
+        params: DeleteTaskPushNotificationConfigParams,
+        context: ServerCallContext | None = None,
+    ) -> None:
+        """Default handler for 'tasks/pushNotificationConfig/delete'.
+
+        Requires a `PushConfigStore` to be configured.
+        """
+        if not self._push_config_store:
+            raise ServerError(error=UnsupportedOperationError())
+
+        task: Task | None = await self.task_store.get(params.id)
+        if not task:
+            raise ServerError(error=TaskNotFoundError())
+
+        await self._push_config_store.delete_info(
+            params.id, params.pushNotificationConfigId
+        )
+
     def should_add_push_info(self, params: MessageSendParams) -> bool:
         """Determines if push notification info should be set for a task."""
         return bool(
-            self._push_notifier
+            self._push_config_store
             and params.configuration
             and params.configuration.pushNotificationConfig
         )

src/a2a/server/request_handlers/jsonrpc_handler.py

@@ -10,6 +10,9 @@
     CancelTaskRequest,
     CancelTaskResponse,
     CancelTaskSuccessResponse,
+    DeleteTaskPushNotificationConfigRequest,
+    DeleteTaskPushNotificationConfigResponse,
+    DeleteTaskPushNotificationConfigSuccessResponse,
     GetTaskPushNotificationConfigRequest,
     GetTaskPushNotificationConfigResponse,
     GetTaskPushNotificationConfigSuccessResponse,
@@ -18,6 +21,9 @@
     GetTaskSuccessResponse,
     InternalError,
     JSONRPCErrorResponse,
+    ListTaskPushNotificationConfigRequest,
+    ListTaskPushNotificationConfigResponse,
+    ListTaskPushNotificationConfigSuccessResponse,
     Message,
     SendMessageRequest,
     SendMessageResponse,
@@ -214,7 +220,7 @@ async def on_resubscribe_to_task(
                 )
             )
 
-    async def get_push_notification(
+    async def get_push_notification_config(
         self,
         request: GetTaskPushNotificationConfigRequest,
         context: ServerCallContext | None = None,
@@ -252,7 +258,7 @@ async def get_push_notification(
         lambda self: self.agent_card.capabilities.pushNotifications,
         'Push notifications are not supported by the agent',
     )
-    async def set_push_notification(
+    async def set_push_notification_config(
         self,
         request: SetTaskPushNotificationConfigRequest,
         context: ServerCallContext | None = None,
@@ -325,3 +331,69 @@ async def on_get_task(
                     id=request.id, error=e.error if e.error else InternalError()
                 )
             )
+
+    async def list_push_notification_config(
+        self,
+        request: ListTaskPushNotificationConfigRequest,
+        context: ServerCallContext | None = None,
+    ) -> ListTaskPushNotificationConfigResponse:
+        """Handles the 'tasks/pushNotificationConfig/list' JSON-RPC method.
+
+        Args:
+            request: The incoming `ListTaskPushNotificationConfigRequest` object.
+            context: Context provided by the server.
+
+        Returns:
+            A `ListTaskPushNotificationConfigResponse` object containing the config or a JSON-RPC error.
+        """
+        try:
+            config = (
+                await self.request_handler.on_list_task_push_notification_config(
+                    request.params, context
+                )
+            )
+            return prepare_response_object(
+                request.id,
+                config,
+                (list,),
+                ListTaskPushNotificationConfigSuccessResponse,
+                ListTaskPushNotificationConfigResponse,
+            )
+        except ServerError as e:
+            return ListTaskPushNotificationConfigResponse(
+                root=JSONRPCErrorResponse(
+                    id=request.id, error=e.error if e.error else InternalError()
+                )
+            )
+
+    async def delete_push_notification_config(
+        self,
+        request: DeleteTaskPushNotificationConfigRequest,
+        context: ServerCallContext | None = None,
+    ) -> DeleteTaskPushNotificationConfigResponse:
+        """Handles the 'tasks/pushNotificationConfig/list' JSON-RPC method.
+
+        Args:
+            request: The incoming `DeleteTaskPushNotificationConfigRequest` object.
+            context: Context provided by the server.
+
+        Returns:
+            A `DeleteTaskPushNotificationConfigResponse` object containing the config or a JSON-RPC error.
+        """
+        try:
+            (
+                await self.request_handler.on_delete_task_push_notification_config(
+                    request.params, context
+                )
+            )
+            return DeleteTaskPushNotificationConfigResponse(
+                root=DeleteTaskPushNotificationConfigSuccessResponse(
+                    id=request.id, result=None
+                )
+            )
+        except ServerError as e:
+            return DeleteTaskPushNotificationConfigResponse(
+                root=JSONRPCErrorResponse(
+                    id=request.id, error=e.error if e.error else InternalError()
+                )
+            )