"""Point d'entree de l'application FastAPI.

Ce fichier se limite a l'assemblage : configuration, middlewares, gestion des
erreurs, montage des routeurs et du frontend statique.
"""

from __future__ import annotations

import logging
from contextlib import asynccontextmanager

from fastapi import FastAPI, Request
from fastapi.exceptions import RequestValidationError
from fastapi.middleware.cors import CORSMiddleware
from fastapi.responses import JSONResponse

from app.api import api_router
from app.config import get_settings
from app.db.init_db import init_db
from app.logging_config import configure_logging
from app.middleware import MaxBodySizeMiddleware, SecurityHeadersMiddleware
from app.services.errors import ShareError
from app.web import mount_frontend

logger = logging.getLogger(__name__)


@asynccontextmanager
async def lifespan(app: FastAPI):  # type: ignore[no-untyped-def]
    settings = get_settings()
    configure_logging(settings.log_level)
    init_db()
    logger.info(
        "%s demarre (max_nodes=%s, max_map_size_mb=%s)",
        settings.app_name,
        settings.max_nodes,
        settings.max_map_size_mb,
    )
    yield
    logger.info("Arret de %s", settings.app_name)


def create_app() -> FastAPI:
    settings = get_settings()
    configure_logging(settings.log_level)

    app = FastAPI(
        title=f"{settings.app_name} API",
        version="1.0.0",
        description="API de partage de cartes. Les cartes privees restent dans le navigateur.",
        lifespan=lifespan,
        docs_url="/api/docs",
        openapi_url="/api/openapi.json",
        redoc_url=None,
    )

    app.add_middleware(SecurityHeadersMiddleware)
    app.add_middleware(MaxBodySizeMiddleware, max_body_size=settings.max_map_size_bytes)

    # CORS restrictif : par defaut aucune origine externe, l'app etant servie
    # par ce meme serveur (meme origine).
    origins = settings.cors_origin_list
    if origins:
        app.add_middleware(
            CORSMiddleware,
            allow_origins=origins,
            allow_credentials=False,
            allow_methods=["GET", "POST", "PUT", "DELETE", "OPTIONS"],
            allow_headers=["Content-Type", "X-Management-Token"],
        )

    register_exception_handlers(app)
    app.include_router(api_router)
    mount_frontend(app, settings.static_dir)
    return app


def register_exception_handlers(app: FastAPI) -> None:
    """Aucune erreur brute ne doit remonter au client."""

    @app.exception_handler(ShareError)
    async def _share_error(_request: Request, exc: ShareError) -> JSONResponse:
        return JSONResponse(status_code=exc.status_code, content={"detail": exc.message})

    @app.exception_handler(RequestValidationError)
    async def _validation_error(_request: Request, exc: RequestValidationError) -> JSONResponse:
        # On expose un message lisible, pas la structure interne de validation.
        first = exc.errors()[0] if exc.errors() else None
        detail = "Les donnees envoyees ne forment pas une carte valide."
        if first and first.get("msg"):
            reason = str(first["msg"]).replace("Value error, ", "")
            detail = f"{detail} ({reason})"
        return JSONResponse(status_code=422, content={"detail": detail})

    @app.exception_handler(Exception)
    async def _unhandled(request: Request, exc: Exception) -> JSONResponse:
        # La traceback complete reste cote serveur.
        logger.exception("Erreur non geree sur %s %s", request.method, request.url.path)
        return JSONResponse(
            status_code=500,
            content={"detail": "Une erreur interne est survenue. Reessayez plus tard."},
        )


app = create_app()