initial commit

backend/app/routers/chat.py

@@ -0,0 +1,48 @@
+"""FluentGerman.ai — Chat router with SSE streaming."""
+
+import json
+import logging
+
+from fastapi import APIRouter, Depends
+from fastapi.responses import StreamingResponse
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.auth import get_current_user
+from app.database import get_db
+from app.models import User
+from app.schemas import ChatRequest
+from app.services.instruction_service import get_system_prompt
+from app.services.llm_service import chat_stream
+
+logger = logging.getLogger("fluentgerman.chat")
+
+router = APIRouter(prefix="/api/chat", tags=["chat"])
+
+
+@router.post("/")
+async def chat(
+    body: ChatRequest,
+    user: User = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    """Send a message and receive a streamed SSE response."""
+    logger.info("Chat request from user=%s message_len=%d history=%d",
+                user.username, len(body.message), len(body.history))
+
+    system_prompt = await get_system_prompt(db, user.id)
+
+    messages = [{"role": "system", "content": system_prompt}]
+    for msg in body.history:
+        messages.append({"role": msg.role, "content": msg.content})
+    messages.append({"role": "user", "content": body.message})
+
+    async def event_generator():
+        try:
+            async for token in chat_stream(messages):
+                yield f"data: {json.dumps({'token': token})}\n\n"
+            yield "data: [DONE]\n\n"
+        except Exception as e:
+            logger.error("LLM streaming error: %s", e, exc_info=True)
+            yield f"data: {json.dumps({'error': str(e)})}\n\n"
+
+    return StreamingResponse(event_generator(), media_type="text/event-stream")