import {
  getHostRuntime,
  navigateHostNativePage,
} from './host-bridge/hostBridge';

const SUBSCRIBE_RESULT_HASH_KEY = 'wx_subscribe_result';
const MINI_PROGRAM_SUBSCRIBE_MESSAGE_PAGE_URL = '/pages/subscribe-message/index';
const SUBSCRIBE_RESULT_TIMEOUT_MS = 2_500;
const SUBSCRIBE_RESULT_RETURN_FALLBACK_MS = 800;

function clearSubscribeResultHash() {
  const rawHash = window.location.hash.replace(/^#/, '');
  if (!rawHash.includes(`${SUBSCRIBE_RESULT_HASH_KEY}=`)) {
    return;
  }

  const params = new URLSearchParams(rawHash);
  params.delete(SUBSCRIBE_RESULT_HASH_KEY);
  const nextHash = params.toString();
  window.history.replaceState(
    null,
    '',
    `${window.location.pathname}${window.location.search}${nextHash ? `#${nextHash}` : ''}`,
  );
}

function readSubscribeResultFromHash() {
  const value = new URLSearchParams(window.location.hash.replace(/^#/, '')).get(
    SUBSCRIBE_RESULT_HASH_KEY,
  );
  if (!value) {
    return null;
  }
  clearSubscribeResultHash();
  return value;
}

function waitSubscribeResultFromHash(timeoutMs = SUBSCRIBE_RESULT_TIMEOUT_MS) {
  const immediateResult = readSubscribeResultFromHash();
  if (immediateResult) {
    return Promise.resolve(immediateResult);
  }

  return new Promise<string | null>((resolve) => {
    let timer: number | null = null;
    let resumeFallbackTimer: number | null = null;
    const cleanup = () => {
      window.removeEventListener('hashchange', handleHashChange);
      window.removeEventListener('focus', handleResume);
      window.removeEventListener('pageshow', handleResume);
      document.removeEventListener('visibilitychange', handleResume);
      if (timer !== null) {
        window.clearTimeout(timer);
      }
      if (resumeFallbackTimer !== null) {
        window.clearTimeout(resumeFallbackTimer);
      }
    };
    const finish = (result: string | null) => {
      cleanup();
      resolve(result);
    };
    const consume = () => {
      const result = readSubscribeResultFromHash();
      if (result) {
        finish(result);
        return true;
      }
      return false;
    };
    const handleHashChange = () => {
      consume();
    };
    const handleResume = () => {
      if (
        typeof document !== 'undefined' &&
        document.visibilityState === 'hidden'
      ) {
        return;
      }
      if (consume()) {
        return;
      }
      // 中文注释：订阅授权只影响后续通知，不应阻断生成；原生页返回但没有 hash
      // 回灌时，按已返回处理，让原本的生成提交流程继续执行。
      if (resumeFallbackTimer === null) {
        resumeFallbackTimer = window.setTimeout(
          () => finish('returned'),
          SUBSCRIBE_RESULT_RETURN_FALLBACK_MS,
        );
      }
    };

    window.addEventListener('hashchange', handleHashChange);
    window.addEventListener('focus', handleResume);
    window.addEventListener('pageshow', handleResume);
    document.addEventListener('visibilitychange', handleResume);
    timer = window.setTimeout(() => finish(null), timeoutMs);
  });
}

export async function requestGenerationResultSubscribePermission() {
  if (
    getHostRuntime().kind !== 'wechat_mini_program' ||
    typeof window === 'undefined'
  ) {
    return false;
  }

  const requestId = `subscribe_generation_result_${Date.now()}`;
  let resultPromise: Promise<string | null> | null = null;
  try {
    const navigated = await navigateHostNativePage(
      `${MINI_PROGRAM_SUBSCRIBE_MESSAGE_PAGE_URL}?requestId=${encodeURIComponent(requestId)}&scene=generation-result`,
      {
        errorMessage: 'wechat_js_sdk_unavailable',
        beforeNavigate() {
          resultPromise = waitSubscribeResultFromHash();
        },
      },
    );
    if (!navigated) {
      return false;
    }
  } catch {
    return false;
  }

  const result = await (resultPromise ?? Promise.resolve(null));
  return Boolean(result);
}