Make SubFox production-ready with parallel translation and UI controls

.venv/lib/python3.10/site-packages/fastapi/sse.py

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+from typing import Annotated, Any
+
+from annotated_doc import Doc
+from pydantic import AfterValidator, BaseModel, Field, model_validator
+from starlette.responses import StreamingResponse
+
+# Canonical SSE event schema matching the OpenAPI 3.2 spec
+# (Section 4.14.4 "Special Considerations for Server-Sent Events")
+_SSE_EVENT_SCHEMA: dict[str, Any] = {
+    "type": "object",
+    "properties": {
+        "data": {"type": "string"},
+        "event": {"type": "string"},
+        "id": {"type": "string"},
+        "retry": {"type": "integer", "minimum": 0},
+    },
+}
+
+
+class EventSourceResponse(StreamingResponse):
+    """Streaming response with `text/event-stream` media type.
+
+    Use as `response_class=EventSourceResponse` on a *path operation* that uses `yield`
+    to enable Server Sent Events (SSE) responses.
+
+    Works with **any HTTP method** (`GET`, `POST`, etc.), which makes it compatible
+    with protocols like MCP that stream SSE over `POST`.
+
+    The actual encoding logic lives in the FastAPI routing layer. This class
+    serves mainly as a marker and sets the correct `Content-Type`.
+    """
+
+    media_type = "text/event-stream"
+
+
+def _check_id_no_null(v: str | None) -> str | None:
+    if v is not None and "\0" in v:
+        raise ValueError("SSE 'id' must not contain null characters")
+    return v
+
+
+class ServerSentEvent(BaseModel):
+    """Represents a single Server-Sent Event.
+
+    When `yield`ed from a *path operation function* that uses
+    `response_class=EventSourceResponse`, each `ServerSentEvent` is encoded
+    into the [SSE wire format](https://html.spec.whatwg.org/multipage/server-sent-events.html#parsing-an-event-stream)
+    (`text/event-stream`).
+
+    If you yield a plain object (dict, Pydantic model, etc.) instead, it is
+    automatically JSON-encoded and sent as the `data:` field.
+
+    All `data` values **including plain strings** are JSON-serialized.
+
+    For example, `data="hello"` produces `data: "hello"` on the wire (with
+    quotes).
+    """
+
+    data: Annotated[
+        Any,
+        Doc(
+            """
+            The event payload.
+
+            Can be any JSON-serializable value: a Pydantic model, dict, list,
+            string, number, etc. It is **always** serialized to JSON: strings
+            are quoted (`"hello"` becomes `data: "hello"` on the wire).
+
+            Mutually exclusive with `raw_data`.
+            """
+        ),
+    ] = None
+    raw_data: Annotated[
+        str | None,
+        Doc(
+            """
+            Raw string to send as the `data:` field **without** JSON encoding.
+
+            Use this when you need to send pre-formatted text, HTML fragments,
+            CSV lines, or any non-JSON payload. The string is placed directly
+            into the `data:` field as-is.
+
+            Mutually exclusive with `data`.
+            """
+        ),
+    ] = None
+    event: Annotated[
+        str | None,
+        Doc(
+            """
+            Optional event type name.
+
+            Maps to `addEventListener(event, ...)` on the browser. When omitted,
+            the browser dispatches on the generic `message` event.
+            """
+        ),
+    ] = None
+    id: Annotated[
+        str | None,
+        AfterValidator(_check_id_no_null),
+        Doc(
+            """
+            Optional event ID.
+
+            The browser sends this value back as the `Last-Event-ID` header on
+            automatic reconnection. **Must not contain null (`\\0`) characters.**
+            """
+        ),
+    ] = None
+    retry: Annotated[
+        int | None,
+        Field(ge=0),
+        Doc(
+            """
+            Optional reconnection time in **milliseconds**.
+
+            Tells the browser how long to wait before reconnecting after the
+            connection is lost. Must be a non-negative integer.
+            """
+        ),
+    ] = None
+    comment: Annotated[
+        str | None,
+        Doc(
+            """
+            Optional comment line(s).
+
+            Comment lines start with `:` in the SSE wire format and are ignored by
+            `EventSource` clients. Useful for keep-alive pings to prevent
+            proxy/load-balancer timeouts.
+            """
+        ),
+    ] = None
+
+    @model_validator(mode="after")
+    def _check_data_exclusive(self) -> "ServerSentEvent":
+        if self.data is not None and self.raw_data is not None:
+            raise ValueError(
+                "Cannot set both 'data' and 'raw_data' on the same "
+                "ServerSentEvent. Use 'data' for JSON-serialized payloads "
+                "or 'raw_data' for pre-formatted strings."
+            )
+        return self
+
+
+def format_sse_event(
+    *,
+    data_str: Annotated[
+        str | None,
+        Doc(
+            """
+            Pre-serialized data string to use as the `data:` field.
+            """
+        ),
+    ] = None,
+    event: Annotated[
+        str | None,
+        Doc(
+            """
+            Optional event type name (`event:` field).
+            """
+        ),
+    ] = None,
+    id: Annotated[
+        str | None,
+        Doc(
+            """
+            Optional event ID (`id:` field).
+            """
+        ),
+    ] = None,
+    retry: Annotated[
+        int | None,
+        Doc(
+            """
+            Optional reconnection time in milliseconds (`retry:` field).
+            """
+        ),
+    ] = None,
+    comment: Annotated[
+        str | None,
+        Doc(
+            """
+            Optional comment line(s) (`:` prefix).
+            """
+        ),
+    ] = None,
+) -> bytes:
+    """Build SSE wire-format bytes from **pre-serialized** data.
+
+    The result always ends with `\n\n` (the event terminator).
+    """
+    lines: list[str] = []
+
+    if comment is not None:
+        for line in comment.splitlines():
+            lines.append(f": {line}")
+
+    if event is not None:
+        lines.append(f"event: {event}")
+
+    if data_str is not None:
+        for line in data_str.splitlines():
+            lines.append(f"data: {line}")
+
+    if id is not None:
+        lines.append(f"id: {id}")
+
+    if retry is not None:
+        lines.append(f"retry: {retry}")
+
+    lines.append("")
+    lines.append("")
+    return "\n".join(lines).encode("utf-8")
+
+
+# Keep-alive comment, per the SSE spec recommendation
+KEEPALIVE_COMMENT = b": ping\n\n"
+
+# Seconds between keep-alive pings when a generator is idle.
+# Private but importable so tests can monkeypatch it.
+_PING_INTERVAL: float = 15.0