Safe message sending script in Telegram with just 49 lines of code

deno-telegram-mailer.ts

import fetchify from "https://deno.land/x/fetchify@0.2.8/mod.ts";

export class TelegramMailer {
  private tgApi;
  private queue: Deno.Kv = undefined as unknown as Deno.Kv;

  constructor(token: string) {
    this.tgApi = fetchify.create({
      baseURL: `https://api.telegram.org/bot${token}/`,
      limiter: {
        rps: 28,
        "429": (res) =>
          res.headers.get("retry_after") as unknown as number *
            1000 || 1000,
      },
      headers: {
        "Content-Type": "application/json",
      },
    });
  }

  async start() {
    this.queue = await Deno.openKv();
    this.queue.listenQueue(async (msg) => {
      // @ts-expect-error
      const { chat_id, text } = msg;

      try {
        const res = await this.tgApi.post("sendMessage", {
          timeout: 10000,
          body: JSON.stringify({ chat_id, text }),
        });

        console.log(
          `message delivered to ${chat_id}; ${res.status} ${res.statusText}`,
        );
      } catch (e) {
        console.log(`the message was not delivered to ${chat_id}`);
        console.log(e);
      }
    });
  }

  async notify(chat_id: number, text: string, delay?: number) {
    await this.queue.enqueue({ text, chat_id }, {
      delay,
    });
  }
}

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