app_factory.py

import os.path
import tomllib
from contextlib import asynccontextmanager
from typing import Awaitable, Callable

from common import project_root
from common.exception import CommonException
from fastapi import FastAPI, Request
from fastapi.middleware.cors import CORSMiddleware
from fastapi.responses import JSONResponse, Response


async def exception_handler(_: Request, e: Exception) -> Response:
    if isinstance(e, CommonException):
        return JSONResponse(
            status_code=e.code, content={"code": e.code, "error": e.error}
        )
    return JSONResponse(
        status_code=500,
        content={"code": 500, "error": CommonException.parse_exception(e)},
    )


def app_factory(
    startup_funcs: list[Callable[..., Awaitable]] | None = None,
    shutdown_funcs: list[Callable[..., Awaitable]] | None = None,
    version: str | None = None,
    patch_funcs: list[Callable[[FastAPI], None]] | None = None,
) -> FastAPI:
    @asynccontextmanager
    async def lifespan(fastapi: FastAPI):
        for startup_func in startup_funcs or []:
            await startup_func(fastapi)
        yield
        for shutdown_func in shutdown_funcs or []:
            await shutdown_func(fastapi)

    project_file: str = "pyproject.toml"
    if version is None and os.path.exists(project_root.path(project_file)):
        with project_root.open(project_file, "rb") as f:
            version = tomllib.load(f)["project"]["version"]

    app = FastAPI(lifespan=lifespan, version=version)

    for patch_func in patch_funcs or []:
        patch_func(app)

    app.add_middleware(
        CORSMiddleware,  # noqa
        allow_origins=["*"],
        allow_credentials=True,
        allow_methods=["*"],
        allow_headers=["*"],
    )

    app.add_exception_handler(Exception, exception_handler)

    return app