src/app/main.py

"""FastAPI application factory: middleware, routers, lifespan, error handling."""

from __future__ import annotations

from contextlib import asynccontextmanager

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

from app.api.v1 import api_router
from app.core.config import settings
from app.core.exceptions import register_exception_handlers
from app.core.logging import configure_logging, get_logger
from app.schemas.common import HealthResponse

configure_logging()
logger = get_logger(__name__)


@asynccontextmanager
async def lifespan(app: FastAPI):
    logger.info(
        "startup",
        app=settings.app_name,
        env=settings.environment,
        ai_enabled=settings.ai_enabled,
    )
    yield
    logger.info("shutdown")


def create_app() -> FastAPI:
    app = FastAPI(
        title=settings.app_name,
        version="1.0.0",
        description="Production-grade predictive maintenance API.",
        lifespan=lifespan,
        docs_url="/docs",
        redoc_url="/redoc",
    )

    app.add_middleware(
        CORSMiddleware,
        allow_origins=["*"],  # tighten for production deployments
        allow_credentials=True,
        allow_methods=["*"],
        allow_headers=["*"],
    )

    register_exception_handlers(app)
    app.include_router(api_router, prefix=settings.api_v1_prefix)

    @app.get("/health", response_model=HealthResponse, tags=["system"])
    async def health() -> HealthResponse:
        return HealthResponse(
            status="ok",
            environment=settings.environment,
            ai_enabled=settings.ai_enabled,
        )

    @app.get("/", tags=["system"])
    async def root() -> dict[str, str]:
        return {
            "name": settings.app_name,
            "docs": "/docs",
            "health": "/health",
        }

    return app


app = create_app()