// On the server (SSR / route handlers / RSC) prefer INTERNAL_API_URL — Docker compose service name.
// In the browser, NEXT_PUBLIC_API_URL is baked in at build time and points at the host.
const rawBaseUrl =
  typeof window === "undefined"
    ? process.env.INTERNAL_API_URL ?? process.env.NEXT_PUBLIC_API_URL
    : process.env.NEXT_PUBLIC_API_URL;
const baseUrl = (rawBaseUrl ?? "http://localhost:8000").replace(/\/$/, "");

export class ApiError extends Error {
  constructor(public status: number, message: string, public body?: unknown) {
    super(message);
    this.name = "ApiError";
  }
}

type FetchInit = RequestInit & { token?: string; locale?: string };

async function request<T>(path: string, init: FetchInit = {}): Promise<T> {
  const { token, locale, headers, ...rest } = init;
  const res = await fetch(`${baseUrl}${path.startsWith("/") ? path : `/${path}`}`, {
    ...rest,
    headers: {
      "Content-Type": "application/json",
      ...(locale ? { "Accept-Language": locale } : {}),
      ...(token ? { Authorization: `Bearer ${token}` } : {}),
      ...headers,
    },
  });

  if (!res.ok) {
    let body: unknown;
    try {
      body = await res.json();
    } catch {
      body = await res.text().catch(() => undefined);
    }
    throw new ApiError(res.status, `${res.status} ${res.statusText}`, body);
  }

  if (res.status === 204) return undefined as T;
  return res.json() as Promise<T>;
}

export const api = {
  baseUrl,
  get: <T>(path: string, init?: FetchInit) => request<T>(path, { ...init, method: "GET" }),
  post: <T>(path: string, body?: unknown, init?: FetchInit) =>
    request<T>(path, { ...init, method: "POST", body: body ? JSON.stringify(body) : undefined }),
  patch: <T>(path: string, body?: unknown, init?: FetchInit) =>
    request<T>(path, { ...init, method: "PATCH", body: body ? JSON.stringify(body) : undefined }),
  delete: <T>(path: string, init?: FetchInit) => request<T>(path, { ...init, method: "DELETE" }),
};