social-app/backend/src/app.py

from __future__ import annotations

from fastapi import FastAPI, HTTPException, Request
from fastapi.exceptions import RequestValidationError
from fastapi.middleware.cors import CORSMiddleware
from fastapi.responses import JSONResponse
from starlette.exceptions import HTTPException as StarletteHTTPException

from core.config.settings import config
from core.http.models import HealthResponse
from core.http.response import build_problem_details
from core.logging import configure_logging, get_logger
from v1.router import router as mobile_router


configure_logging(config)

app = FastAPI()
app.add_middleware(
    CORSMiddleware,
    allow_origins=config.cors.allow_origins,
    allow_credentials=config.cors.allow_credentials,
    allow_methods=config.cors.allow_methods,
    allow_headers=config.cors.allow_headers,
)
app.include_router(mobile_router)
logger = get_logger("api.app")


@app.get("/health", response_model=HealthResponse)
async def health() -> HealthResponse:
    return HealthResponse(status="ok")


def _build_http_error_response(
    request: Request,
    exc: Exception,
    status_code: int,
    detail: object,
) -> JSONResponse:
    instance = request.url.path
    detail_text = detail if isinstance(detail, str) else "Request failed"
    logger.warning(
        "HTTP error",
        status_code=status_code,
        detail=detail_text,
        detail_extra=detail,
        path=request.url.path,
        method=request.method,
    )
    problem = build_problem_details(
        status_code=status_code,
        detail=detail_text,
        instance=instance,
    )
    return JSONResponse(
        status_code=status_code,
        content=problem.model_dump(),
        media_type="application/problem+json",
    )


@app.exception_handler(HTTPException)
async def http_exception_handler(
    request: Request,
    exc: HTTPException,
) -> JSONResponse:
    return _build_http_error_response(
        request=request,
        exc=exc,
        status_code=exc.status_code,
        detail=exc.detail,
    )


@app.exception_handler(StarletteHTTPException)
async def starlette_http_exception_handler(
    request: Request,
    exc: StarletteHTTPException,
) -> JSONResponse:
    return _build_http_error_response(
        request=request,
        exc=exc,
        status_code=exc.status_code,
        detail=exc.detail,
    )


@app.exception_handler(RequestValidationError)
async def validation_exception_handler(
    request: Request,
    exc: RequestValidationError,
) -> JSONResponse:
    instance = request.url.path
    logger.warning(
        "Request validation error",
        path=request.url.path,
        method=request.method,
        errors=exc.errors(),
    )
    problem = build_problem_details(
        status_code=422,
        detail="Invalid request",
        instance=instance,
    )
    return JSONResponse(
        status_code=422,
        content=problem.model_dump(),
        media_type="application/problem+json",
    )


@app.exception_handler(Exception)
async def unhandled_exception_handler(
    request: Request,
    exc: Exception,
) -> JSONResponse:
    instance = request.url.path
    logger.exception(
        "Unhandled error",
        path=request.url.path,
        method=request.method,
    )
    problem = build_problem_details(
        status_code=500,
        detail="Internal Server Error",
        instance=instance,
    )
    return JSONResponse(
        status_code=500,
        content=problem.model_dump(),
        media_type="application/problem+json",
    )