import logging
from contextlib import asynccontextmanager
from fastapi import FastAPI, Request
from fastapi.middleware.cors import CORSMiddleware
from fastapi.responses import JSONResponse
from app.core.config import settings
from app.core.health import router as health_router
from app.core.logging import request_id_var, setup_logging
from app.core.middleware import RequestContextMiddleware
from app.api.v1.router import api_router

# 日志必须在任何模块开始产日志之前配置好，故放模块顶层而非 lifespan 内
setup_logging(level=settings.LOG_LEVEL, json_output=settings.LOG_JSON)

logger = logging.getLogger("track.main")


def _init_error_tracking() -> None:
    """可选错误追踪：未配置 DSN，或未安装 sentry-sdk 时静默跳过"""
    if not settings.SENTRY_DSN:
        return
    try:
        import sentry_sdk
    except ImportError:
        logger.warning(
            "已配置 SENTRY_DSN 但未安装 sentry-sdk，错误追踪未启用；"
            "需要时执行 pip install sentry-sdk"
        )
        return
    sentry_sdk.init(
        dsn=settings.SENTRY_DSN,
        traces_sample_rate=settings.SENTRY_TRACES_SAMPLE_RATE,
        environment="production" if not settings.DEBUG else "development",
        release=settings.APP_VERSION,
    )
    logger.info("错误追踪已启用 (Sentry)")


@asynccontextmanager
async def lifespan(app: FastAPI):
    """应用生命周期：启动时初始化连接，关闭时释放资源"""
    _init_error_tracking()
    logger.info(
        "服务启动",
        extra={
            "extra_fields": {
                "version": settings.APP_VERSION,
                "debug": settings.DEBUG,
                "cors_origins": settings.CORS_ORIGINS_LIST,
            }
        },
    )
    yield
    logger.info("服务关闭")


app = FastAPI(
    title="Track Production API",
    description="工厂生产流转管理系统 API",
    version=settings.APP_VERSION,
    lifespan=lifespan,
)

# ---- CORS 跨域配置（从环境变量读取白名单） ----
app.add_middleware(
    CORSMiddleware,
    allow_origins=settings.CORS_ORIGINS_LIST,
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
    # 暴露给浏览器 JS 读取：前端报错时才能把 request_id 一起带上便于对账
    expose_headers=["X-Request-ID"],
)

# Starlette 的 add_middleware 是「后添加者在外层」，故 RequestContextMiddleware
# 最后注册 → 最先进入请求，才能覆盖包括 CORS 预检在内的全部请求并回写 X-Request-ID
app.add_middleware(RequestContextMiddleware)


@app.exception_handler(Exception)
async def unhandled_exception_handler(request: Request, exc: Exception) -> JSONResponse:
    """兜底异常处理。

    完整堆栈只进日志；响应体仅返回 request_id —— 既不把内部实现泄露给客户端，
    又让用户报障时能凭这个 ID 在日志里精确定位到本次失败。
    """
    # 优先取 request.state（见 RequestContextMiddleware 的说明）：
    # 本处理器由 ServerErrorMiddleware 调用，此时 contextvar 已被重置
    request_id = getattr(request.state, "request_id", None) or request_id_var.get()
    logger.exception(
        "未处理异常: %s %s",
        request.method,
        request.url.path,
        extra={"extra_fields": {"method": request.method, "path": request.url.path}},
    )
    return JSONResponse(
        status_code=500,
        content={"detail": "服务器内部错误", "request_id": request_id},
    )


# ---- 注册路由 ----
app.include_router(api_router, prefix="/api/v1")
# 健康检查挂在根路径（/health*），运维探针不经过 /api/v1
app.include_router(health_router)