export class ApiRequestError extends Error {
  readonly log?: string;

  constructor(message: string, log?: string) {
    super(message);
    this.name = "ApiRequestError";
    this.log = log;
  }
}

async function errorOf(res: Response, fallback: string): Promise<ApiRequestError> {
  let message = fallback;
  let log: string | undefined;
  try {
    const data: unknown = await res.json();
    if (data && typeof data === "object") {
      if ("error" in data && typeof data.error === "string") message = data.error;
      if ("log" in data && typeof data.log === "string") log = data.log;
    }
  } catch {
    /* non-JSON error body */
  }
  return new ApiRequestError(message, log);
}

export async function post<T>(path: string, body: unknown): Promise<T> {
  const res = await fetch(path, {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify(body),
  });
  if (!res.ok) throw await errorOf(res, `${path} failed (${res.status})`);
  return res.json() as Promise<T>;
}

/**
 * Compile LaTeX to a PDF blob.
 * Dev: the Vite middleware at /local/compile runs the machine's real pdflatex.
 * Deployed: that route 404s and we fall back to the Worker's remote compile proxy.
 */
export async function compilePdf(latex: string): Promise<Blob> {
  const local = await fetch("/local/compile", {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({ latex }),
  });
  if (local.ok) return local.blob();
  if (local.status === 422) throw await errorOf(local, "pdflatex failed");

  const remote = await fetch("/api/pdf", {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({ latex }),
  });
  if (remote.ok) return remote.blob();
  throw await errorOf(remote, `PDF compile failed (${remote.status})`);
}