import axios from "axios";

function messagesFromValue(value: unknown): string[] {
  if (value == null) return [];
  if (typeof value === "string") return [value];
  if (Array.isArray(value)) return value.flatMap(messagesFromValue);
  if (typeof value === "object") {
    const record = value as Record<string, unknown>;
    if ("detail" in record) {
      const fromDetail = messagesFromValue(record.detail);
      if (fromDetail.length > 0) return fromDetail;
    }
    const messages: string[] = [];
    for (const [key, nested] of Object.entries(record)) {
      if (key === "detail") continue;
      for (const part of messagesFromValue(nested)) {
        messages.push(key === "non_field_errors" ? part : `${key}: ${part}`);
      }
    }
    return messages;
  }
  return [];
}

/** Extract human-readable message(s) from a Django REST Framework / axios error response. */
export function getApiErrorMessage(err: unknown, fallback = "Something went wrong"): string {
  if (axios.isAxiosError(err)) {
    const data = err.response?.data;
    if (data !== undefined) {
      const messages = messagesFromValue(data);
      if (messages.length > 0) return messages.join(". ");
    }
    if (err.response?.status && err.message.startsWith("Request failed")) {
      return fallback;
    }
    return err.message || fallback;
  }
  if (err instanceof Error) return err.message;
  return fallback;
}