/**
 * Error thrown by every C2 API request (server-26#286).
 *
 * `message` is a sentence a user can read — FastAPI's `detail` when the
 * server sent one, otherwise a plain mapping of the status. The raw status
 * and body stay on the error for callers that need the structured parts
 * (the Discord parsers read `invite`/`code` out of `body`).
 */
export class C2ApiError extends Error {
  readonly status: number;
  readonly body: string;

  constructor(status: number, body: string) {
    super(humanMessage(status, body));
    this.name = "C2ApiError";
    this.status = status;
    this.body = body;
  }

  // Call sites render String(e); without this it reads "C2ApiError: …".
  toString(): string {
    return this.message;
  }
}

function detailOf(body: string): string | null {
  try {
    const parsed = JSON.parse(body);
    const d = parsed?.detail;
    if (typeof d === "string" && d.trim()) return d;
    // pydantic validation errors: [{loc, msg, type}, ...]
    if (Array.isArray(d)) {
      const msgs = d.map((x: { msg?: unknown }) => (typeof x?.msg === "string" ? x.msg : null)).filter(Boolean);
      if (msgs.length) return msgs.join("; ");
    }
  } catch {
    /* not JSON */
  }
  return null;
}

function humanMessage(status: number, body: string): string {
  const detail = detailOf(body);
  if (status === 401) return "Your session has expired. Sign in again.";
  if (status === 403) return detail ? `Not allowed: ${detail}` : "You don't have permission to do that.";
  if (detail) return detail;
  if (status === 404) return "Not found. It may have been deleted.";
  if (status === 429) return "Too many requests. Wait a moment and try again.";
  if (status >= 500) return "The server hit an error. Try again in a moment.";
  return `Request failed (${status}).`;
}

/** Message for any caught value — use in catch blocks instead of String(e). */
export function errorMessage(e: unknown): string {
  if (e instanceof Error) return e.message;
  return String(e);
}

/** Rebuilds the legacy `C2 API error <status>: <body>` string for the
 *  Discord parsers, which predate C2ApiError and match on that shape. */
export function legacyErrorText(err: unknown): string {
  if (err instanceof C2ApiError) return `C2 API error ${err.status}: ${err.body}`;
  return err instanceof Error ? err.message : String(err);
}