"""FastAPI application factory (架构文档 §3.1 L3 API 层).

The API layer only orchestrates: auth, validation, idempotency, quota,
unified response, OpenAPI. Business rules live in ``packages/<domain>``.
"""

from __future__ import annotations

from collections.abc import AsyncIterator
from contextlib import asynccontextmanager

from fastapi import FastAPI

from apps.api.deps import build_llm_gateway
from apps.api.routers import (
    agent,
    auth,
    auth_sms,
    events,
    health,
    kb,
    quota,
    reports,
    reservations,
    tasks,
    uploads,
)
from packages.shared.config import Settings, get_settings
from packages.shared.db import dispose_engine
from packages.shared.handlers import install_exception_handlers
from packages.shared.logging import configure_logging, get_logger
from packages.shared.middleware import RequestContextMiddleware, install_version_alias
from packages.shared.observability import setup_tracing
from packages.shared.redis_client import close_redis

logger = get_logger(__name__)


@asynccontextmanager
async def lifespan(app: FastAPI) -> AsyncIterator[None]:
    settings: Settings = get_settings()
    app.state.llm_gateway = build_llm_gateway(settings)
    logger.info(
        "api_started",
        env=settings.app_env,
        api_prefix=settings.api_prefix,
        llm_primary=settings.llm_primary_provider,
        llm_model=settings.deepseek_model,
    )
    try:
        yield
    finally:
        await app.state.llm_gateway.aclose()
        await close_redis()
        await dispose_engine()
        logger.info("api_stopped")


def create_app(settings: Settings | None = None) -> FastAPI:
    cfg = settings or get_settings()
    configure_logging(
        level=cfg.log_level, json_output=cfg.log_json, extra_redact_keys=cfg.extra_redact_keys
    )

    app = FastAPI(
        title="美搭 backend",
        version="0.1.0",
        description=(
            "AI 穿搭美学助手服务端。统一响应见架构文档 §9.2；"
            "所有业务接口在 " + cfg.api_prefix + " 之下（/v1 为等价别名）。"
        ),
        openapi_url=f"{cfg.api_prefix}/openapi.json",
        docs_url=f"{cfg.api_prefix}/docs" if cfg.is_local else None,
        redoc_url=None,
        lifespan=lifespan,
    )

    install_version_alias(app, cfg.api_prefix)
    app.add_middleware(RequestContextMiddleware)
    install_exception_handlers(app)
    setup_tracing(app, cfg)

    app.include_router(health.router)
    routers = (
        auth.router,
        auth_sms.router,
        agent.router,
        quota.router,
        tasks.router,
        events.router,
        uploads.router,
        kb.router,
        reports.router,
        reservations.router,
    )
    for router in routers:
        app.include_router(router, prefix=cfg.api_prefix)

    return app


app = create_app()