|
| 1 | +from collections.abc import AsyncIterator |
| 2 | + |
| 3 | +from a2a.client.client import ( |
| 4 | + Client, |
| 5 | + ClientCallContext, |
| 6 | + ClientConfig, |
| 7 | + ClientEvent, |
| 8 | + Consumer, |
| 9 | +) |
| 10 | +from a2a.client.client_task_manager import ClientTaskManager |
| 11 | +from a2a.client.errors import A2AClientInvalidStateError |
| 12 | +from a2a.client.middleware import ClientCallInterceptor |
| 13 | +from a2a.client.transports.base import ClientTransport |
| 14 | +from a2a.types import ( |
| 15 | + AgentCard, |
| 16 | + GetTaskPushNotificationConfigParams, |
| 17 | + Message, |
| 18 | + MessageSendConfiguration, |
| 19 | + MessageSendParams, |
| 20 | + Task, |
| 21 | + TaskArtifactUpdateEvent, |
| 22 | + TaskIdParams, |
| 23 | + TaskPushNotificationConfig, |
| 24 | + TaskQueryParams, |
| 25 | + TaskStatusUpdateEvent, |
| 26 | +) |
| 27 | + |
| 28 | + |
| 29 | +class BaseClient(Client): |
| 30 | + """Base implementation of the A2A client, containing transport-independent logic.""" |
| 31 | + |
| 32 | + def __init__( |
| 33 | + self, |
| 34 | + card: AgentCard, |
| 35 | + config: ClientConfig, |
| 36 | + transport: ClientTransport, |
| 37 | + consumers: list[Consumer], |
| 38 | + middleware: list[ClientCallInterceptor], |
| 39 | + ): |
| 40 | + super().__init__(consumers, middleware) |
| 41 | + self._card = card |
| 42 | + self._config = config |
| 43 | + self._transport = transport |
| 44 | + |
| 45 | + async def send_message( |
| 46 | + self, |
| 47 | + request: Message, |
| 48 | + *, |
| 49 | + context: ClientCallContext | None = None, |
| 50 | + ) -> AsyncIterator[ClientEvent | Message]: |
| 51 | + """Sends a message to the agent. |
| 52 | +
|
| 53 | + This method handles both streaming and non-streaming (polling) interactions |
| 54 | + based on the client configuration and agent capabilities. It will yield |
| 55 | + events as they are received from the agent. |
| 56 | +
|
| 57 | + Args: |
| 58 | + request: The message to send to the agent. |
| 59 | + context: The client call context. |
| 60 | +
|
| 61 | + Yields: |
| 62 | + An async iterator of `ClientEvent` or a final `Message` response. |
| 63 | + """ |
| 64 | + config = MessageSendConfiguration( |
| 65 | + accepted_output_modes=self._config.accepted_output_modes, |
| 66 | + blocking=not self._config.polling, |
| 67 | + push_notification_config=( |
| 68 | + self._config.push_notification_configs[0] |
| 69 | + if self._config.push_notification_configs |
| 70 | + else None |
| 71 | + ), |
| 72 | + ) |
| 73 | + params = MessageSendParams(message=request, configuration=config) |
| 74 | + |
| 75 | + if not self._config.streaming or not self._card.capabilities.streaming: |
| 76 | + response = await self._transport.send_message( |
| 77 | + params, context=context |
| 78 | + ) |
| 79 | + result = ( |
| 80 | + (response, None) if isinstance(response, Task) else response |
| 81 | + ) |
| 82 | + await self.consume(result, self._card) |
| 83 | + yield result |
| 84 | + return |
| 85 | + |
| 86 | + tracker = ClientTaskManager() |
| 87 | + stream = self._transport.send_message_streaming(params, context=context) |
| 88 | + |
| 89 | + first_event = await anext(stream) |
| 90 | + # The response from a server may be either exactly one Message or a |
| 91 | + # series of Task updates. Separate out the first message for special |
| 92 | + # case handling, which allows us to simplify further stream processing. |
| 93 | + if isinstance(first_event, Message): |
| 94 | + await self.consume(first_event, self._card) |
| 95 | + yield first_event |
| 96 | + return |
| 97 | + |
| 98 | + yield await self._process_response(tracker, first_event) |
| 99 | + |
| 100 | + async for event in stream: |
| 101 | + yield await self._process_response(tracker, event) |
| 102 | + |
| 103 | + async def _process_response( |
| 104 | + self, |
| 105 | + tracker: ClientTaskManager, |
| 106 | + event: Task | Message | TaskStatusUpdateEvent | TaskArtifactUpdateEvent, |
| 107 | + ) -> ClientEvent: |
| 108 | + if isinstance(event, Message): |
| 109 | + raise A2AClientInvalidStateError( |
| 110 | + 'received a streamed Message from server after first response; this is not supported' |
| 111 | + ) |
| 112 | + await tracker.process(event) |
| 113 | + task = tracker.get_task_or_raise() |
| 114 | + update = None if isinstance(event, Task) else event |
| 115 | + client_event = (task, update) |
| 116 | + await self.consume(client_event, self._card) |
| 117 | + return client_event |
| 118 | + |
| 119 | + async def get_task( |
| 120 | + self, |
| 121 | + request: TaskQueryParams, |
| 122 | + *, |
| 123 | + context: ClientCallContext | None = None, |
| 124 | + ) -> Task: |
| 125 | + """Retrieves the current state and history of a specific task. |
| 126 | +
|
| 127 | + Args: |
| 128 | + request: The `TaskQueryParams` object specifying the task ID. |
| 129 | + context: The client call context. |
| 130 | +
|
| 131 | + Returns: |
| 132 | + A `Task` object representing the current state of the task. |
| 133 | + """ |
| 134 | + return await self._transport.get_task(request, context=context) |
| 135 | + |
| 136 | + async def cancel_task( |
| 137 | + self, |
| 138 | + request: TaskIdParams, |
| 139 | + *, |
| 140 | + context: ClientCallContext | None = None, |
| 141 | + ) -> Task: |
| 142 | + """Requests the agent to cancel a specific task. |
| 143 | +
|
| 144 | + Args: |
| 145 | + request: The `TaskIdParams` object specifying the task ID. |
| 146 | + context: The client call context. |
| 147 | +
|
| 148 | + Returns: |
| 149 | + A `Task` object containing the updated task status. |
| 150 | + """ |
| 151 | + return await self._transport.cancel_task(request, context=context) |
| 152 | + |
| 153 | + async def set_task_callback( |
| 154 | + self, |
| 155 | + request: TaskPushNotificationConfig, |
| 156 | + *, |
| 157 | + context: ClientCallContext | None = None, |
| 158 | + ) -> TaskPushNotificationConfig: |
| 159 | + """Sets or updates the push notification configuration for a specific task. |
| 160 | +
|
| 161 | + Args: |
| 162 | + request: The `TaskPushNotificationConfig` object with the new configuration. |
| 163 | + context: The client call context. |
| 164 | +
|
| 165 | + Returns: |
| 166 | + The created or updated `TaskPushNotificationConfig` object. |
| 167 | + """ |
| 168 | + return await self._transport.set_task_callback(request, context=context) |
| 169 | + |
| 170 | + async def get_task_callback( |
| 171 | + self, |
| 172 | + request: GetTaskPushNotificationConfigParams, |
| 173 | + *, |
| 174 | + context: ClientCallContext | None = None, |
| 175 | + ) -> TaskPushNotificationConfig: |
| 176 | + """Retrieves the push notification configuration for a specific task. |
| 177 | +
|
| 178 | + Args: |
| 179 | + request: The `GetTaskPushNotificationConfigParams` object specifying the task. |
| 180 | + context: The client call context. |
| 181 | +
|
| 182 | + Returns: |
| 183 | + A `TaskPushNotificationConfig` object containing the configuration. |
| 184 | + """ |
| 185 | + return await self._transport.get_task_callback(request, context=context) |
| 186 | + |
| 187 | + async def resubscribe( |
| 188 | + self, |
| 189 | + request: TaskIdParams, |
| 190 | + *, |
| 191 | + context: ClientCallContext | None = None, |
| 192 | + ) -> AsyncIterator[ClientEvent]: |
| 193 | + """Resubscribes to a task's event stream. |
| 194 | +
|
| 195 | + This is only available if both the client and server support streaming. |
| 196 | +
|
| 197 | + Args: |
| 198 | + request: Parameters to identify the task to resubscribe to. |
| 199 | + context: The client call context. |
| 200 | +
|
| 201 | + Yields: |
| 202 | + An async iterator of `ClientEvent` objects. |
| 203 | +
|
| 204 | + Raises: |
| 205 | + NotImplementedError: If streaming is not supported by the client or server. |
| 206 | + """ |
| 207 | + if not self._config.streaming or not self._card.capabilities.streaming: |
| 208 | + raise NotImplementedError( |
| 209 | + 'client and/or server do not support resubscription.' |
| 210 | + ) |
| 211 | + |
| 212 | + tracker = ClientTaskManager() |
| 213 | + # Note: resubscribe can only be called on an existing task. As such, |
| 214 | + # we should never see Message updates, despite the typing of the service |
| 215 | + # definition indicating it may be possible. |
| 216 | + async for event in self._transport.resubscribe( |
| 217 | + request, context=context |
| 218 | + ): |
| 219 | + yield await self._process_response(tracker, event) |
| 220 | + |
| 221 | + async def get_card( |
| 222 | + self, *, context: ClientCallContext | None = None |
| 223 | + ) -> AgentCard: |
| 224 | + """Retrieves the agent's card. |
| 225 | +
|
| 226 | + This will fetch the authenticated card if necessary and update the |
| 227 | + client's internal state with the new card. |
| 228 | +
|
| 229 | + Args: |
| 230 | + context: The client call context. |
| 231 | +
|
| 232 | + Returns: |
| 233 | + The `AgentCard` for the agent. |
| 234 | + """ |
| 235 | + card = await self._transport.get_card(context=context) |
| 236 | + self._card = card |
| 237 | + return card |
| 238 | + |
| 239 | + async def close(self) -> None: |
| 240 | + """Closes the underlying transport.""" |
| 241 | + await self._transport.close() |
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