import asyncio
import json
import logging
import time
from uuid import uuid4
from contextlib import suppress
from fastapi import FastAPI, HTTPException, Request
from fastapi.exceptions import RequestValidationError
from fastapi.middleware.cors import CORSMiddleware
from fastapi.responses import JSONResponse
from starlette.responses import Response
from sqlalchemy import text
from sqlalchemy.exc import IntegrityError
from backend.app.core.config import settings
from backend.app.core.response import build_envelope
from backend.app.db.session import engine, SessionLocal
from backend.app.db.base import Base
from backend.app import models  # noqa: F401
from backend.app.services.seed import seed_data
from backend.app.services.center_sync import run_center_sync_loop
from backend.app.routers import auth, users, roles, campuses, departments, shifts, schedule, duty, statistics, adjust_logs, sync, ws


app = FastAPI(title=settings.app_name)
app.add_middleware(
    CORSMiddleware,
    allow_origins=[
        "http://localhost:5173",
        "http://127.0.0.1:5173"
    ],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

logger = logging.getLogger("uvicorn.error")
sync_stop_event = asyncio.Event()
sync_task: asyncio.Task | None = None


def _clone_headers(response, trace_id: str) -> dict:
    headers = dict(response.headers)
    headers.pop("content-length", None)
    headers["X-Trace-Id"] = trace_id
    return headers


@app.middleware("http")
async def add_trace_and_wrap(request: Request, call_next):
    trace_id = request.headers.get("x-trace-id") or request.headers.get("traceId") or uuid4().hex
    request.state.trace_id = trace_id
    response = await call_next(request)

    content_type = response.headers.get("content-type", "")
    if response.status_code >= 400 or "application/json" not in content_type:
        response.headers["X-Trace-Id"] = trace_id
        return response

    body = b""
    async for chunk in response.body_iterator:
        body += chunk

    headers = _clone_headers(response, trace_id)

    if not body:
        return JSONResponse(build_envelope(None, trace_id), status_code=response.status_code, headers=headers)

    try:
        data = json.loads(body)
    except json.JSONDecodeError:
        return Response(
            content=body,
            status_code=response.status_code,
            headers=headers,
            media_type=response.media_type,
        )

    if isinstance(data, dict) and {"code", "message", "data"}.issubset(data.keys()):
        data.setdefault("traceId", trace_id)
        data.setdefault("ts", int(time.time() * 1000))
        return JSONResponse(data, status_code=response.status_code, headers=headers)

    return JSONResponse(build_envelope(data, trace_id), status_code=response.status_code, headers=headers)


def get_trace_id(request: Request) -> str:
    trace_id = getattr(request.state, "trace_id", None)
    return trace_id or uuid4().hex


@app.exception_handler(RequestValidationError)
async def validation_exception_handler(request: Request, exc: RequestValidationError):
    field_errors = []
    for err in exc.errors():
        loc = [str(item) for item in err.get("loc", []) if item not in ("body", "query", "path")]
        field = ".".join(loc) if loc else ".".join([str(item) for item in err.get("loc", [])])
        field_errors.append({"field": field, "reason": err.get("msg")})
    trace_id = get_trace_id(request)
    payload = build_envelope(
        None,
        trace_id,
        code="VALIDATION_ERROR",
        message="参数校验失败",
        details={"fieldErrors": field_errors},
    )
    return JSONResponse(payload, status_code=400)


@app.exception_handler(HTTPException)
async def http_exception_handler(request: Request, exc: HTTPException):
    code_map = {
        400: "VALIDATION_ERROR",
        401: "UNAUTHORIZED",
        403: "FORBIDDEN",
        404: "NOT_FOUND",
        409: "CONFLICT",
        429: "RATE_LIMITED",
    }
    trace_id = get_trace_id(request)
    code = code_map.get(exc.status_code, "INTERNAL_ERROR")
    message = exc.detail if isinstance(exc.detail, str) else "请求失败"
    payload = build_envelope(None, trace_id, code=code, message=message)
    return JSONResponse(payload, status_code=exc.status_code)


@app.exception_handler(IntegrityError)
async def integrity_exception_handler(request: Request, exc: IntegrityError):
    trace_id = get_trace_id(request)
    logger.exception("IntegrityError traceId=%s", trace_id)
    payload = build_envelope(None, trace_id, code="CONFLICT", message="数据冲突")
    return JSONResponse(payload, status_code=409)


@app.exception_handler(Exception)
async def general_exception_handler(request: Request, exc: Exception):
    trace_id = get_trace_id(request)
    logger.exception("Unhandled error traceId=%s", trace_id)
    payload = build_envelope(None, trace_id, code="INTERNAL_ERROR", message="系统异常，请稍后再试")
    return JSONResponse(payload, status_code=500)


@app.on_event("startup")
async def on_startup():
    global sync_task
    async with engine.begin() as conn:
        # 依赖 pgcrypto 扩展提供 gen_random_uuid()
        # 若数据库账号无权限创建扩展，会在这里直接失败并提示，避免后续插入时报错更隐蔽
        await conn.execute(text('CREATE EXTENSION IF NOT EXISTS "pgcrypto";'))
        await conn.run_sync(Base.metadata.create_all)
    async with SessionLocal() as session:
        await seed_data(session)
    sync_task = asyncio.create_task(run_center_sync_loop(sync_stop_event))


@app.on_event("shutdown")
async def on_shutdown():
    sync_stop_event.set()
    if sync_task:
        sync_task.cancel()
        with suppress(asyncio.CancelledError):
            await sync_task


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


app.include_router(auth.router)
app.include_router(users.router)
app.include_router(roles.router)
app.include_router(campuses.router)
app.include_router(departments.router)
app.include_router(shifts.router)
app.include_router(schedule.router)
app.include_router(duty.router)
app.include_router(statistics.router)
app.include_router(adjust_logs.router)
app.include_router(sync.router)
app.include_router(ws.router)