"""AI Knowledge Link — FastAPI 应用工厂。

Phase 1 只包含：配置校验、日志、异常处理器、健康检查、lifespan 资源管理。
后续 Phase 逐步挂载：auth、knowledge-bases、documents、public /k/ 路由。
"""

from contextlib import asynccontextmanager
from pathlib import Path

from fastapi import FastAPI
from fastapi.middleware.cors import CORSMiddleware

from app.api.health import router as health_router
from app.core.config import get_settings
from app.core.db import dispose_engine
from app.core.errors import register_exception_handlers
from app.core.logging import get_logger, setup_logging

logger = get_logger(__name__)


@asynccontextmanager
async def lifespan(app: FastAPI):
    settings = get_settings()
    setup_logging()

    # 确保 data 目录存在
    data_dir = settings.storage_root_path
    data_dir.mkdir(parents=True, exist_ok=True)
    logger.info("Starting backend (env=%s, data=%s)", settings.environment, data_dir)

    yield

    dispose_engine()
    logger.info("Backend shutdown complete")


def create_app() -> FastAPI:
    settings = get_settings()
    app = FastAPI(
        title="AI Knowledge Link",
        version="0.1.0",
        lifespan=lifespan,
        docs_url="/api/docs" if not settings.is_production else None,
        openapi_url="/api/openapi.json" if not settings.is_production else None,
    )

    # CORS（开发期允许 Vite dev server）
    app.add_middleware(
        CORSMiddleware,
        allow_origins=[settings.frontend_origin],
        allow_credentials=True,
        allow_methods=["GET", "POST", "PUT", "PATCH", "DELETE", "OPTIONS"],
        allow_headers=["Content-Type", "X-Requested-With"],
    )

    register_exception_handlers(app)

    # 路由挂载
    app.include_router(health_router, prefix="/api", tags=["health"])
    # Phase 3+: app.include_router(auth_router, prefix="/api/auth", tags=["auth"])
    # Phase 4+: app.include_router(kb_router, prefix="/api/knowledge-bases", tags=["knowledge-bases"])
    # Phase 10+: app.include_router(public_router, tags=["public"])

    return app


app = create_app()