export type ApiError = { code: string; message: string };
export type ApiResult<T> = { data: T } | { error: ApiError };

export async function fetchJson<T>(input: RequestInfo, init?: RequestInit): Promise<ApiResult<T>> {
    const res = await fetch(input, {
        ...init,
        credentials: "include",
        headers: {
            "Content-Type": "application/json",
            ...(init?.headers || {})
        }
    });

    const payload = await res.json().catch(() => ({}));
    if (!res.ok) {
        const errorPayload = payload?.error;
        let code = String(res.status);
        let message = res.statusText || "Request failed";

        if (typeof errorPayload === "string") {
            message = errorPayload;
        } else if (errorPayload && typeof errorPayload === "object") {
            if (typeof errorPayload.code === "string") code = errorPayload.code;
            if (typeof errorPayload.message === "string") message = errorPayload.message;
        } else if (typeof payload?.message === "string") {
            message = payload.message;
        }

        return { error: { code, message } };
    }
    return { data: payload as T };
}