"""RFC 7807 problem+json errors for every failure the API returns."""

from __future__ import annotations

from collections.abc import Mapping
from typing import Any

from fastapi import FastAPI, Request, status
from fastapi.exceptions import HTTPException, RequestValidationError
from fastapi.responses import JSONResponse

PROBLEM_TYPE = "application/problem+json"


class Problem(Exception):
    def __init__(
        self,
        status_code: int,
        title: str,
        detail: str | None = None,
        *,
        extra: dict[str, Any] | None = None,
        headers: Mapping[str, str] | None = None,
    ) -> None:
        self.status_code = status_code
        self.title = title
        self.detail = detail
        self.extra = extra or {}
        self.headers = headers


def _response(
    status_code: int,
    title: str,
    detail: str | None = None,
    extra: dict[str, Any] | None = None,
    headers: Mapping[str, str] | None = None,
) -> JSONResponse:
    body: dict[str, Any] = {"status": status_code, "title": title}
    if detail:
        body["detail"] = detail
    if extra:
        body.update(extra)
    return JSONResponse(body, status_code=status_code, media_type=PROBLEM_TYPE, headers=headers)


def install_error_handlers(app: FastAPI) -> None:
    @app.exception_handler(Problem)
    async def _problem(_: Request, exc: Problem) -> JSONResponse:
        return _response(exc.status_code, exc.title, exc.detail, exc.extra, exc.headers)

    @app.exception_handler(HTTPException)
    async def _http(_: Request, exc: HTTPException) -> JSONResponse:
        detail = exc.detail if isinstance(exc.detail, str) else None
        return _response(exc.status_code, _title_for(exc.status_code), detail, headers=exc.headers)

    @app.exception_handler(RequestValidationError)
    async def _validation(_: Request, exc: RequestValidationError) -> JSONResponse:
        return _response(
            status.HTTP_422_UNPROCESSABLE_ENTITY,
            "Validation error",
            extra={"errors": exc.errors()},
        )


def _title_for(code: int) -> str:
    return {
        400: "Bad request",
        401: "Unauthorized",
        403: "Forbidden",
        404: "Not found",
        409: "Conflict",
        429: "Too many requests",
    }.get(code, "Error")