from fastapi import FastAPI, Request
from fastapi.exceptions import RequestValidationError
from fastapi.middleware.cors import CORSMiddleware
from fastapi.responses import JSONResponse

from app.api.controllers.admin import router as admin_router
from app.api.controllers.agent_runs import router as agent_runs_router
from app.api.controllers.auth import router as auth_router
from app.api.controllers.conversations import router as conversations_router
from app.api.controllers.health import router as health_router
from app.api.controllers.knowledge import router as knowledge_router
from app.api.controllers.knowledge_management import router as knowledge_management_router
from app.api.controllers.offsite_fund import operation_router as offsite_operation_router
from app.api.controllers.offsite_fund import router as offsite_fund_router
from app.api.controllers.promotion_material import router as promotion_material_router
from app.api.controllers.public_platform import router as public_platform_router
from app.api.controllers.rbac import router as rbac_router
from app.api.controllers.risk import router as risk_router
from app.api.middleware import attach_trace_id
from app.core.config import get_settings
from app.core.errors import AgentError


def _trace_id(request: Request) -> str:
    """取本次请求的追踪标识：请求上下文 → state → 客户端 `X-Trace-ID` → 空串。

    没有就返回空字符串，绝不凭空生成——凭空生成会让客户端拿到的 trace_id 与服务端日志
    里的不是同一个，反而失去定位价值。
    """
    context = getattr(request.state, "request_context", None)
    return str(
        getattr(context, "trace_id", None)
        or getattr(request.state, "trace_id", None)
        or request.headers.get("X-Trace-ID")
        or ""
    )


def create_app() -> FastAPI:
    settings = get_settings()
    application = FastAPI(title=settings.app_name, version="0.1.0")
    # 接口文档承诺的 X-Trace-ID 此前完全没实现；中间件对成功与错误响应都生效。
    application.middleware("http")(attach_trace_id)
    application.add_middleware(
        CORSMiddleware,
        allow_origins=[
            origin.strip()
            for origin in settings.cors_allowed_origins.split(",")
            if origin.strip()
        ],
        allow_credentials=False,
        allow_methods=["*"],
        allow_headers=["*"],
    )

    @application.exception_handler(AgentError)
    async def agent_error_handler(request: Request, exc: AgentError) -> JSONResponse:
        context = getattr(request.state, "request_context", None)
        # 认证失败时请求上下文尚未建立（`build_request_context` 不会写 request_context），
        # 按文档 §3.4 优先复用请求头里客户端带来的 `X-Trace-ID`；都没有就是空字符串，
        # 绝不凭空生成 id——会让排障时把两个请求认成同一个。
        trace_id = (getattr(context, "trace_id", None)
                    or getattr(request.state, "trace_id", None)
                    or request.headers.get("X-Trace-ID") or "")
        # retryable 按文档 §3.6 逐码标注，不再简单按 5xx 推导
        # （例如 RESOURCE_VERSION_CONFLICT 是 409 但文档标注可重试）。
        headers: dict[str, str] = {}
        retry_after = getattr(exc, "retry_after_seconds", None)
        if isinstance(retry_after, int):
            # 文档 §3.6 把 RATE_LIMITED 标注为可重试：只给 retryable=true 而不给
            # Retry-After，客户端只能自己猜退避时长（或立刻重试再被拒）。
            headers["Retry-After"] = str(retry_after)
        return JSONResponse(status_code=exc.status_code, content={
            "error": {"code": exc.code, "message": exc.message,
                      "retryable": exc.is_retryable, "field_errors": []},
            "meta": {"trace_id": trace_id},
        }, headers=headers or None)
    @application.exception_handler(RequestValidationError)
    async def request_validation_error_handler(
        request: Request, exc: RequestValidationError
    ) -> JSONResponse:
        """请求校验失败也必须走统一错误信封（文档 §3.4 / §3.6 `AGENT_INPUT_INVALID`）。

        不加这个处理器时，FastAPI 会返回自己的 `{"detail": [...]}` 结构（422），客户端
        必须为"参数错误"单独兼容一套解析逻辑；同一套接口因此出现两种错误体形态。
        这里保留 422 状态码（文档 §3.5：已解析请求不满足字段或业务输入约束），
        把字段级原因放进 `error.field_errors`，与业务异常的信封完全一致。
        """
        field_errors = [
            {
                "field": ".".join(str(part) for part in error.get("loc", ())),
                "message": str(error.get("msg", "")),
            }
            for error in exc.errors()
        ]
        return JSONResponse(status_code=422, content={
            "error": {
                "code": "AGENT_INPUT_INVALID",
                "message": "请求参数不满足接口约束",
                "retryable": False,
                "field_errors": field_errors,
            },
            "meta": {"trace_id": _trace_id(request)},
        })
    application.include_router(auth_router)
    application.include_router(agent_runs_router)
    application.include_router(conversations_router)
    application.include_router(public_platform_router)
    application.include_router(rbac_router)
    application.include_router(risk_router)
    application.include_router(offsite_fund_router)
    application.include_router(offsite_operation_router)
    application.include_router(promotion_material_router)
    application.include_router(knowledge_router)
    application.include_router(knowledge_management_router)
    application.include_router(health_router)
    application.include_router(admin_router)
    return application


app = create_app()