/** 全局认证 fetch 客户端 */

let tokenGetter: () => string | null = () => null;
const inflightGetRequests = new Map<string, Promise<unknown>>();

export class ApiRequestError extends Error {
  readonly status: number;
  readonly code: string | null;
  readonly retryable: boolean;

  constructor(message: string, status: number, code: string | null, retryable: boolean) {
    super(message);
    this.name = 'ApiRequestError';
    this.status = status;
    this.code = code;
    this.retryable = retryable;
  }
}

interface ApiErrorPayload {
  error?: unknown;
  message?: unknown;
  code?: unknown;
  retryable?: unknown;
}

export function setTokenGetter(fn: () => string | null) {
  tokenGetter = fn;
}

async function executeJsonRequest<T>(url: string, options: RequestInit | undefined, token: string | null): Promise<T> {
  const res = await fetch(url, {
    ...options,
    headers: {
      ...options?.headers,
      ...(token ? { Authorization: `Bearer ${token}` } : {}),
    },
  });
  if (res.status === 401) {
    window.dispatchEvent(new CustomEvent('auth:unauthorized'));
    throw new Error('Unauthorized');
  }
  if (!res.ok) {
    let payload: ApiErrorPayload = {};
    try {
      const parsed: unknown = await res.json();
      if (typeof parsed === 'object' && parsed !== null) payload = parsed as ApiErrorPayload;
    } catch {
      payload = {};
    }
    const message = typeof payload?.error === 'string'
      ? payload.error
      : typeof payload?.message === 'string'
        ? payload.message
        : `请求失败（${res.status}）`;
    const code = typeof payload?.code === 'string' ? payload.code : null;
    const retryable = typeof payload?.retryable === 'boolean' ? payload.retryable : res.status >= 500;
    throw new ApiRequestError(message, res.status, code, retryable);
  }
  return res.json();
}

export async function fetchJson<T>(url: string, options?: RequestInit): Promise<T> {
  const token = tokenGetter();
  const method = (options?.method || 'GET').toUpperCase();
  const canDedupe = method === 'GET' && options?.body == null && options?.signal == null;
  if (!canDedupe) return executeJsonRequest<T>(url, options, token);

  const key = `${token || 'anonymous'}:${url}`;
  const existing = inflightGetRequests.get(key) as Promise<T> | undefined;
  if (existing) return existing;

  const request = executeJsonRequest<T>(url, options, token)
    .finally(() => {
      if (inflightGetRequests.get(key) === request) inflightGetRequests.delete(key);
    });
  inflightGetRequests.set(key, request);
  return request;
}

export function _clearApiClientInflightForTests(): void {
  inflightGetRequests.clear();
}