import asyncio
import itertools
from typing import Dict

import httpx
from fastapi import FastAPI, Request, WebSocket
from fastapi.responses import StreamingResponse, Response
import uvicorn

# ===================== 配置区 =====================

WORKERS = [
    "http://127.0.0.1:6001",
    "http://127.0.0.1:6002",
    "http://127.0.0.1:6003",
    "http://127.0.0.1:6004",

]

REQUEST_TIMEOUT = None  # Streaming / SSE 必须是 None

# ===================== 核心状态 =====================

worker_cycle = itertools.cycle(WORKERS)

def next_worker() -> str:
    """轮询获取下一个 worker"""
    return next(worker_cycle)

# ===================== FastAPI =====================

app = FastAPI()

client = httpx.AsyncClient(
    timeout=REQUEST_TIMEOUT,
    limits=httpx.Limits(max_connections=1000)
)

# ===================== HTTP 转发 =====================

@app.api_route("/{path:path}", methods=["GET", "POST", "PUT", "DELETE"])
async def proxy_http(request: Request, path: str):
    """
    普通 HTTP / SSE 请求转发
    """
    backend = next_worker()
    url = f"{backend}/{path}"

    headers = dict(request.headers)
    headers.pop("host", None)

    body = await request.body()

    # Streaming / SSE
    if request.headers.get("accept") == "text/event-stream":
        async def stream():
            async with client.stream(
                method=request.method,
                url=url,
                headers=headers,
                content=body,
                params=request.query_params,
            ) as resp:
                async for chunk in resp.aiter_raw():
                    yield chunk

        return StreamingResponse(
            stream(),
            media_type="text/event-stream",
        )

    # 普通请求
    resp = await client.request(
        method=request.method,
        url=url,
        headers=headers,
        content=body,
        params=request.query_params,
    )

    return Response(
        content=resp.content,
        status_code=resp.status_code,
        headers=dict(resp.headers),
        media_type=resp.headers.get("content-type"),
    )

# ===================== WebSocket 转发 =====================

@app.websocket("/{path:path}")
async def proxy_ws(ws: WebSocket, path: str):
    """
    WebSocket 直通转发
    """
    await ws.accept()
    backend = next_worker()
    backend_ws = backend.replace("http", "ws") + f"/{path}"

    async with httpx.AsyncClient() as session:
        async with session.ws_connect(backend_ws) as backend_socket:
            async def client_to_backend():
                while True:
                    msg = await ws.receive_text()
                    await backend_socket.send_text(msg)

            async def backend_to_client():
                while True:
                    msg = await backend_socket.receive_text()
                    await ws.send_text(msg)

            await asyncio.gather(
                client_to_backend(),
                backend_to_client(),
            )

# ===================== 健康检查 =====================

@app.get("/health")
async def health():
    return {
        "status": "ok",
        "workers": WORKERS,
    }

# ===================== 启动 =====================

if __name__ == "__main__":
    uvicorn.run(
        app,
        host="0.0.0.0",
        port=6000,
        log_level="info",
    )