import axios, { AxiosInstance } from "axios";

let apiClient: AxiosInstance | null = null;
let _onUnauthorized: (() => void) | undefined;

function serializeParams(params: Record<string, any>): string {
  const searchParams = new URLSearchParams();
  for (const [key, value] of Object.entries(params ?? {})) {
    if (value === undefined || value === null) continue;
    if (Array.isArray(value)) {
      for (const item of value) searchParams.append(key, String(item));
    } else if (typeof value === "object") {
      for (const [nestedKey, nestedValue] of Object.entries(value)) {
        if (nestedValue === undefined || nestedValue === null) continue;
        searchParams.append(`${key}[${nestedKey}]`, String(nestedValue));
      }
    } else {
      searchParams.append(key, String(value));
    }
  }
  return searchParams.toString();
}

export function initApi(baseUrl: string, getToken?: () => string | null, onUnauthorized?: () => void): AxiosInstance {
  if (apiClient && apiClient.defaults.baseURL === baseUrl) {
    _onUnauthorized = onUnauthorized;
    return apiClient;
  }

  _onUnauthorized = onUnauthorized;

  apiClient = axios.create({
    baseURL: baseUrl,
    headers: { "Content-Type": "application/json" },
    paramsSerializer: serializeParams,
  });

  apiClient.interceptors.request.use((config) => {
    const token = getToken?.();
    if (token) {
      config.headers.Authorization = `Bearer ${token}`;
    }
    return config;
  });

  apiClient.interceptors.response.use(
    (res) => res,
    (error) => {
      if (error.response?.status === 401) {
        console.log("[useApi] 401 from %s %s - dispatching auth:unauthorized", error.config?.method, error.config?.url);
        window.dispatchEvent(new CustomEvent("auth:unauthorized"));
        _onUnauthorized?.();
      } else {
        console.log("[useApi] non-401 error %s from %s %s", error.response?.status, error.config?.method, error.config?.url);
      }
      return Promise.reject(error);
    }
  );

  return apiClient;
}

export function getApi(): AxiosInstance {
  if (!apiClient) {
    throw new Error("API client not initialized. Make sure AppProvider is mounted.");
  }
  return apiClient;
}