telegram.ts

const Q = {
  telegramContainer: "//main//section[@class='tgme_channel_history js-message_history']",
  postId: "string(./div[@data-post]/@data-post)",
  linkExternal: "string(.//a[@class='tgme_widget_message_link_preview' and @href]/@href)",
};

export class TelegramBehavior {
  static id = "Telegram";

  static isMatch() {
    return !!window.location.href.match(/https:\/\/t.me\/s\/\w[\w]+/);
  }

  static init() {
    return {
      state: { messages: 0 }
    };
  }

  async waitForPrev(ctx, child) {
    if (!child) {
      return null;
    }

    await ctx.Lib.sleep(ctx.Lib.waitUnit * 5);

    if (!child.previousElementSibling) {
      return null;
    }

    return child.previousElementSibling;
  }

  async* run(ctx) {
    const { getState, scrollIntoView, sleep, waitUnit, xpathNode, xpathString } = ctx.Lib;
    let root = xpathNode(Q.telegramContainer);

    if (!root) {
      return;
    }

    let child = root.lastElementChild;

    while (child) {
      scrollIntoView(child);

      const postId = xpathString(Q.postId, child) || "unknown";

      const linkUrl = xpathString(Q.linkExternal, child);

      if (linkUrl && linkUrl.endsWith(".jpg") || linkUrl.endsWith(".png")) {
        yield getState(ctx, "Loading External Image: " + linkUrl);
        const image = new Image();
        image.src = linkUrl;
        document.body.appendChild(image);
        await sleep(waitUnit * 2.5);
        document.body.removeChild(image);
      }

      yield getState(ctx, "Loading Message: " + postId, "messages");

      child = await this.waitForPrev(ctx, child);
    }
  }
}