from fastapi import FastAPI, HTTPException
from pydantic import BaseModel

app = FastAPI()

class Item(BaseModel):
    name: str
    price: float

@app.get("/items/{item_id}")
async def read_item(item_id: int):
    if item_id not in item_db:
        # 關(guān)鍵在這里：拋出帶狀態(tài)碼和詳情的異常
        raise HTTPException(
            status_code=404,
            detail="Item not found",
            headers={"X-Error": "ItemID-Missing"}
        )
    return {"item": item_db[item_id]}

from fastapi import FastAPI, Request
from fastapi.responses import JSONResponse
import traceback

app = FastAPI()

# 1. 先定義一個(gè)標(biāo)準(zhǔn)的錯(cuò)誤響應(yīng)模型
class ErrorResponse(BaseModel):
    code: int
    message: str
    detail: Optional[str] = None
    request_id: Optional[str] = None # 用于鏈路追蹤

# 2. 捕獲所有未處理異常的“總閘”
@app.exception_handler(Exception)
async def universal_exception_handler(request: Request, exc: Exception):
    # 獲取請(qǐng)求ID，便于追蹤（假設(shè)從中間件或header傳入）
    request_id = request.headers.get("X-Request-ID", "unknown")
    
    # 這里可以根據(jù)exc的類(lèi)型進(jìn)行更精細(xì)的分類(lèi)
    error_code = 500 # 默認(rèn)內(nèi)部錯(cuò)誤
    message = "Internal Server Error"
    
    if isinstance(exc, ValueError):
        error_code = 400
        message = "Invalid input value"
    # ... 可以添加更多類(lèi)型判斷
    
    # 在生產(chǎn)環(huán)境，detail可能不返回具體堆棧，開(kāi)發(fā)環(huán)境可以返回
    import os
    detail = traceback.format_exc() if os.getenv("ENV") == "development" else None
    
    return JSONResponse(
        status_code=error_code,
        content=ErrorResponse(
            code=error_code,
            message=message,
            detail=detail,
            request_id=request_id
        ).dict()
    )

# 3. 專(zhuān)門(mén)處理HTTPException，覆蓋FastAPI默認(rèn)行為
@app.exception_handler(HTTPException)
async def http_exception_handler(request: Request, exc: HTTPException):
    return JSONResponse(
        status_code=exc.status_code,
        content=ErrorResponse(
            code=exc.status_code,
            message=exc.detail,
            request_id=request.headers.get("X-Request-ID", "unknown")
        ).dict(),
        headers=exc.headers
    )

# 定義自己的業(yè)務(wù)異常類(lèi)
class BusinessError(Exception):
    def __init__(self, code: int, message: str, extra_data: dict = None):
        self.code = code # 業(yè)務(wù)錯(cuò)誤碼，如 1001
        self.message = message
        self.extra_data = extra_data or {}

# 定義幾個(gè)具體的業(yè)務(wù)異常
class InsufficientBalanceError(BusinessError):
    def __init__(self, current_balance: float, required_amount: float):
        super().__init__(
            code=1001,
            message="Insufficient balance",
            extra_data={
                "current_balance": current_balance,
                "required_amount": required_amount
            }
        )

class ActivityExpiredError(BusinessError):
    def __init__(self, activity_id: str, expire_time: str):
        super().__init__(
            code=1002,
            message="Activity has expired",
            extra_data={"activity_id": activity_id, "expire_time": expire_time}
        )

# 為自定義業(yè)務(wù)異常注冊(cè)處理器
@app.exception_handler(BusinessError)
async def business_exception_handler(request: Request, exc: BusinessError):
    return JSONResponse(
        status_code=422, # 或用200，但body里表明錯(cuò)誤，看前端約定
        content={
            "success": False,
            "error": {
                "code": exc.code,
                "message": exc.message,
                **exc.extra_data # 展開(kāi)額外數(shù)據(jù)，前端可以直接用
            }
        }
    )

# 在路由中使用
@app.post("/purchase")
async def make_purchase(user_id: int, amount: float):
    user_balance = get_balance(user_id)
    if user_balance < amount:
        # 拋出業(yè)務(wù)異常，而不是簡(jiǎn)單的HTTP 400
        raise InsufficientBalanceError(
            current_balance=user_balance,
            required_amount=amount
        )
    # ... 購(gòu)買(mǎi)邏輯

from fastapi import WebSocket, WebSocketException

@app.websocket("/ws")
async def websocket_endpoint(websocket: WebSocket):
    await websocket.accept()
    try:
        while True:
            data = await websocket.receive_json()
            # 一些業(yè)務(wù)驗(yàn)證
            if data.get("type") not in VALID_TYPES:
                # 拋出WebSocketException，指定關(guān)閉碼和原因
                raise WebSocketException(
                    code=1008, # 1008表示政策違規(guī)
                    reason="Invalid message type received"
                )
            # ... 處理消息
    except WebSocketException as e:
        # 這里其實(shí)raise之后，F(xiàn)astAPI會(huì)幫你關(guān)閉連接
        raise
    except Exception as e:
        # 其他未知異常，也以WebSocketException形式關(guān)閉
        raise WebSocketException(code=1011, reason=f"Internal error: {str(e)}")