YTOAuthClient

YouTube OAuth2 client library for Tampermonkey
This script should not be not be installed directly. It is a library for other scripts to include with the meta directive // @require https://update.greasyfork.org/scripts/575889/1811329/YTOAuthClient.js
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// ==UserScript==
// @name         YTOAuthClient
// @namespace    https://greasyfork.org/
// @version      1.0.0
// @description  YouTube OAuth2 client library for Tampermonkey
// @author       yourname
// @match        *://*/*
// @grant        GM_xmlhttpRequest
// @grant        GM_setValue
// @grant        GM_getValue
// @connect      accounts.google.com
// @connect      www.googleapis.com
// ==/UserScript==

(function () {
  'use strict';

  class YTOAuthClient {
    constructor({ clientId, redirectUri = 'https://localhost' } = {}) {
      if (!clientId) throw new Error('clientId is required');
      this._clientId = clientId;
      this._redirectUri = redirectUri;
      this._scope = 'https://www.googleapis.com/auth/youtube.readonly';
      this._tokenKey = `yt_oauth_token_${clientId}`;
    }

    // ─── トークン管理 ──────────────────────────────────

    getToken() {
      const raw = GM_getValue(this._tokenKey, null);
      if (!raw) return null;
      const token = JSON.parse(raw);
      // 有効期限チェック
      if (Date.now() > token.expiresAt) {
        this.clearToken();
        return null;
      }
      return token.accessToken;
    }

    saveToken(accessToken, expiresIn) {
      GM_setValue(this._tokenKey, JSON.stringify({
        accessToken,
        expiresAt: Date.now() + expiresIn * 1000,
      }));
    }

    clearToken() {
      GM_setValue(this._tokenKey, null);
    }

    isAuthenticated() {
      return this.getToken() !== null;
    }

    // ─── 認証フロー ────────────────────────────────────

    startAuth() {
      const params = new URLSearchParams({
        client_id: this._clientId,
        redirect_uri: this._redirectUri,
        response_type: 'token',
        scope: this._scope,
      });
      window.open(
        `https://accounts.google.com/o/oauth2/v2/auth?${params}`,
        '_blank'
      );
    }

    // リダイレクト先ページで呼ぶ（@match に redirectUri を追加した上で）
    handleRedirect() {
      if (!location.href.startsWith(this._redirectUri)) return false;
      const hash = new URLSearchParams(location.hash.slice(1));
      const accessToken = hash.get('access_token');
      const expiresIn = Number(hash.get('expires_in') ?? 3600);
      if (!accessToken) return false;
      this.saveToken(accessToken, expiresIn);
      return true;
    }

    // ─── API リクエスト ────────────────────────────────

    request({ url, method = 'GET', data } = {}) {
      return new Promise((resolve, reject) => {
        const token = this.getToken();
        if (!token) return reject(new Error('Not authenticated'));

        GM_xmlhttpRequest({
          method,
          url,
          headers: {
            Authorization: `Bearer ${token}`,
            'Content-Type': 'application/json',
          },
          data: data ? JSON.stringify(data) : undefined,
          onload: (res) => {
            const json = JSON.parse(res.responseText);
            if (res.status === 401) {
              this.clearToken();
              return reject(new Error('Token expired'));
            }
            if (json.error) return reject(json.error);
            resolve(json);
          },
          onerror: (e) => reject(new Error(`Network error: ${e.status}`)),
        });
      });
    }

    // ─── YouTube API ───────────────────────────────────

    async getLiveId() {
      const data = await this.request({
        url: 'https://www.googleapis.com/youtube/v3/liveBroadcasts'
          + '?part=snippet,id&broadcastStatus=active&broadcastType=all',
      });
      const item = data.items?.[0];
      if (!item) return null;
      return {
        liveId: item.id,
        liveChatId: item.snippet.liveChatId,
      };
    }
  }

  window.YTOAuthClient = YTOAuthClient;
})();