1

backend/app/routers/chat.py

@@ -0,0 +1,125 @@
+import json
+import logging
+import uuid
+from typing import AsyncGenerator
+
+import httpx
+from fastapi import APIRouter, HTTPException
+from fastapi.responses import StreamingResponse
+from pydantic import BaseModel
+
+from app.config import settings
+
+logger = logging.getLogger(__name__)
+
+router = APIRouter(prefix="/chat", tags=["chat"])
+
+TENCENT_SSE_URL = "https://wss.lke.cloud.tencent.com/v1/qbot/chat/sse"
+
+
+class ChatRequest(BaseModel):
+    session_id: str
+    content: str
+    visitor_biz_id: str = "default_visitor"
+
+
+async def forward_events(
+    response: httpx.Response, request_id: str
+) -> AsyncGenerator[bytes, None]:
+    """Read the upstream SSE stream and forward it as-is."""
+    async for line in response.aiter_lines():
+        stripped = line.strip()
+        if not stripped:
+            yield b"\n"
+            continue
+
+        logger.info("[%s] Forwarding: %s", request_id, stripped[:200])
+        yield (stripped + "\n").encode("utf-8")
+
+
+def build_error_event(message: str, request_id: str, code: int = 500) -> bytes:
+    event = {
+        "type": "error",
+        "request_id": request_id,
+        "error": {
+            "code": code,
+            "message": message,
+        },
+    }
+    return (
+        f"event: error\n"
+        f"data: {json.dumps(event, ensure_ascii=False)}\n\n"
+    ).encode("utf-8")
+
+
+@router.post("")
+async def chat(payload: ChatRequest):
+    request_id = str(uuid.uuid4())[:8]
+    logger.info(
+        "[%s] Chat request received: session_id=%s, content=%s",
+        request_id,
+        payload.session_id,
+        payload.content[:50],
+    )
+
+    if not settings.bot_app_key:
+        logger.error("[%s] BOT_APP_KEY is not configured", request_id)
+        raise HTTPException(
+            status_code=500,
+            detail="BOT_APP_KEY is not configured",
+        )
+
+    request_body = {
+        "request_id": request_id,
+        "content": payload.content,
+        "bot_app_key": settings.bot_app_key,
+        "visitor_biz_id": payload.visitor_biz_id,
+        "session_id": payload.session_id,
+        "stream": "enable",
+    }
+
+    logger.info("[%s] Sending to Tencent: %s", request_id, TENCENT_SSE_URL)
+
+    async def stream_generator() -> AsyncGenerator[bytes, None]:
+        async with httpx.AsyncClient(timeout=120.0) as client:
+            try:
+                async with client.stream(
+                    "POST",
+                    TENCENT_SSE_URL,
+                    json=request_body,
+                    headers={"Accept": "text/event-stream"},
+                ) as response:
+                    logger.info(
+                        "[%s] Tencent response status: %s",
+                        request_id,
+                        response.status_code,
+                    )
+
+                    if response.status_code != 200:
+                        body = await response.aread()
+                        error_msg = body.decode("utf-8", errors="replace")
+                        logger.error("[%s] Tencent error: %s", request_id, error_msg)
+                        yield build_error_event(
+                            error_msg,
+                            request_id,
+                            response.status_code,
+                        )
+                        return
+
+                    logger.info("[%s] Starting to forward events", request_id)
+                    async for chunk in forward_events(response, request_id):
+                        yield chunk
+
+                    logger.info("[%s] Stream completed", request_id)
+            except httpx.RequestError as exc:
+                logger.exception("[%s] Request to Tencent failed: %s", request_id, exc)
+                yield build_error_event(str(exc), request_id)
+
+    return StreamingResponse(
+        stream_generator(),
+        media_type="text/event-stream",
+        headers={
+            "Cache-Control": "no-cache",
+            "X-Accel-Buffering": "no",
+        },
+    )