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9792ea7 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 | # -*- coding: utf-8 -*-
"""Protocol middleware base class for converting AgentEvent stream to
various protocols."""
import json
from abc import ABC, abstractmethod
from typing import AsyncGenerator, Callable
from fastapi import Request, Response
from fastapi.responses import StreamingResponse
from starlette.middleware.base import BaseHTTPMiddleware
from starlette.types import ASGIApp
from agentscope.event import AgentEvent
class ProtocolMiddlewareBase(BaseHTTPMiddleware, ABC):
"""Base middleware for converting AgentEvent stream to protocol format.
This middleware intercepts ``text/event-stream`` responses, deserializes
AgentEvent objects from SSE ``data:`` frames, and converts them to a
specific protocol format.
Subclasses should implement the `_convert_to_protocol` method to define
the conversion logic for their specific protocol (e.g., AGUI, A2A).
Example:
```python
class AGUIMiddleware(ProtocolMiddlewareBase):
def _convert_to_protocol(self, event: AgentEvent) -> dict:
# Implement AGUI-specific conversion logic
return {...}
app = FastAPI()
app.add_middleware(AGUIMiddleware)
```
"""
def __init__(self, app: ASGIApp) -> None:
"""Initialize the protocol middleware.
Args:
app: The ASGI application to wrap.
"""
super().__init__(app)
async def dispatch(
self,
request: Request,
call_next: Callable,
) -> Response:
"""Process the request and convert AgentEvent stream to protocol
format.
Args:
request: The incoming HTTP request.
call_next: The next middleware or endpoint handler.
Returns:
The response, potentially with converted stream content.
"""
# Call the next middleware or endpoint
response = await call_next(request)
content_type = response.headers.get("content-type", "")
body_iterator = getattr(response, "body_iterator", None)
if (
content_type.startswith("text/event-stream")
and body_iterator is not None
):
# Wrap the original stream with our conversion logic
converted_stream = self._convert_stream(body_iterator)
# Create a new StreamingResponse with the converted stream
return StreamingResponse(
content=converted_stream,
status_code=response.status_code,
headers=dict(response.headers),
media_type=response.media_type,
)
return response
async def _convert_stream(
self,
original_stream: AsyncGenerator,
) -> AsyncGenerator[bytes, None]:
"""Convert AgentEvent stream to protocol format.
Args:
original_stream: The original stream yielding serialized
AgentEvent objects.
Yields:
Bytes in protocol format.
"""
async for chunk in original_stream:
if isinstance(chunk, bytes):
chunk_str = chunk.decode("utf-8")
else:
chunk_str = chunk
converted = self._convert_sse_frame(chunk_str)
if converted is not None:
yield converted
continue
# Fallback for subclasses that may override dispatch() to handle
# non-SSE streams while still reusing this converter.
converted = self._convert_event_json(chunk_str)
if converted is not None:
yield converted
continue
if isinstance(chunk, bytes):
yield chunk
else:
yield chunk.encode("utf-8")
def _convert_sse_frame(self, frame: str) -> bytes | None:
"""Convert AgentEvent payloads inside an SSE frame.
Note:
This method targets the AgentScope service's SSE stream shape:
each ``data:`` line contains a complete JSON payload, and each
input ``frame`` contains one or more complete SSE frames. SSE
multi-line ``data:`` concatenation and cross-chunk frame
reassembly are intentionally out of scope here.
Args:
frame: A server-sent event frame.
Returns:
Converted frame bytes if at least one ``data:`` payload was
converted, otherwise ``None``.
"""
lines = frame.splitlines(keepends=True)
converted_lines: list[str] = []
converted_any = False
for line in lines:
if not line.startswith("data:"):
converted_lines.append(line)
continue
line_content, line_ending = self._split_line_ending(line)
payload = line_content.removeprefix("data:")
if payload.startswith(" "):
payload = payload[1:]
converted = self._convert_event_json(payload)
if converted is None:
converted_lines.append(line)
continue
converted_json = converted.decode("utf-8").rstrip("\n")
converted_lines.append(f"data: {converted_json}{line_ending}")
converted_any = True
if not converted_any:
return None
return "".join(converted_lines).encode("utf-8")
@staticmethod
def _split_line_ending(line: str) -> tuple[str, str]:
"""Split a line into content and its original line ending."""
if line.endswith("\r\n"):
return line[:-2], "\r\n"
if line.endswith("\n"):
return line[:-1], "\n"
if line.endswith("\r"):
return line[:-1], "\r"
return line, ""
def _convert_event_json(self, chunk_str: str) -> bytes | None:
"""Convert a serialized AgentEvent JSON string.
Args:
chunk_str: Serialized AgentEvent JSON.
Returns:
Converted protocol JSON bytes with trailing newline, or ``None``
when ``chunk_str`` is not a valid AgentEvent payload.
"""
try:
event_dict = json.loads(chunk_str)
agent_event = self._deserialize_event(event_dict)
protocol_data = self._convert_to_protocol(agent_event)
return (
json.dumps(protocol_data, ensure_ascii=False).encode(
"utf-8",
)
+ b"\n"
)
except (json.JSONDecodeError, KeyError, TypeError, ValueError):
return None
def _deserialize_event(self, event_dict: dict) -> AgentEvent:
"""Deserialize event dictionary to AgentEvent object.
Args:
event_dict: Dictionary containing event data with 'type' field.
Returns:
Deserialized AgentEvent object.
Raises:
ValueError: If event type is unknown or deserialization fails.
"""
from pydantic import Field, TypeAdapter
from typing import Annotated
# Use Pydantic's discriminated union to automatically deserialize
# based on the 'type' field
adapter = TypeAdapter(
Annotated[AgentEvent, Field(discriminator="type")],
)
return adapter.validate_python(event_dict)
@abstractmethod
def _convert_to_protocol(self, event: AgentEvent) -> dict:
"""Convert AgentEvent to protocol format.
This is an abstract method that must be implemented by subclasses
to define the conversion logic for their specific protocol.
Args:
event: The AgentEvent object to convert.
Returns:
Dictionary in the target protocol format.
Example:
```python
class AGUIMiddleware(ProtocolMiddlewareBase):
def _convert_to_protocol(self, event: AgentEvent) -> dict:
# Convert to AGUI format
agui_data = event.model_dump()
agui_data["agui_version"] = "1.0"
return agui_data
```
"""
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