Download course script

dl.js

const https = require("https");

// For using in browser, remove `require` and `fetch` mockup
function fetch(url) {
  return new Promise((resolve, reject) => {
    https
      .get(url, (res) => {
        res.setEncoding("utf8");
        let response = "";
        res.on("data", (data) => {
          response += data;
        });
        res.on("end", () =>
          resolve({
            text: () => response,
            json: () => JSON.parse(response),
          })
        );
      })
      .on("error", reject);
  });
}

class TokenFetch {
  // Class constants
  HTML_PARSE_REGEX = /\/s\/([a-z0-9]+)\/(.*)\/(.*)\.mp4/;
  FREE_COURSE_URL = "https://coursehunter.net/course/rubyonrails";

  constructor(cronTimer = 3000) {
    this.token = null;
    this.taskTimer = null;
    this.CRON_TIMER = cronTimer;

    return this;
  }
  // Fetch request and expect response as HTML Response
  fetch = async () => {
    return fetch(this.FREE_COURSE_URL).then((res) => res.text());
  };
  // Parse `token` from HTML
  parse = (html) => {
    const [_, token] = html.match(this.HTML_PARSE_REGEX);

    return token;
  };

  // Fetch and parse, expects response as Token (type:String)
  get = () => {
    return this.fetch().then(this.parse);
  };
  // Set tokens to class property to cache and re-use later
  set = (token) => {
    this.token = token;

    return token;
  };
  // Asks token, does `get` and `set` token together
  ask = () => {
    return this.get().then(this.set);
  };
  cachedAsk = () => {
    if (this.token) {
      return this.token;
    }
    return this.ask();
  };

  // Creates cron task (fake cron with `setInterval`) and returns timer
  cronTask = () => {
    return setInterval(this.ask, this.CRON_TIMER);
  };
  // Creates and attachs task into class property
  registerTask = () => {
    this.taskTimer = this.cronTask();

    return () => {
      clearInterval(this.taskTimer);
      this.taskTimer = null;
    };
  };

  // Initialize all logics
  init = async () => {
    await this.ask();

    return this.registerTask();
  };
}

class DownloadCourse {
  URL_MATCH_REGEX = /\/s\/([a-z0-9]+)\//;
  constructor(link) {
    this.link = link;
    this.tokenClass = new TokenFetch();
  }
  setToken = (token) => {
    this.tokenClass.set(token);

    return this;
  };
  parseUrl = async (url) => {
    const userToken = await this.tokenClass.cachedAsk();

    return url.replace(this.URL_MATCH_REGEX, `/s/${userToken}/`);
  };
}

class ArgsParse {
  constructor() {
    this.args = {};

    for (let i = 0, len = process.argv.length; i < len; i += 2) {
      const key = process.argv[i];
      const value = process.argv[i + 1];

      if (key.startsWith("--")) {
        this.args[key.substr(2)] = value || null;
      }
    }

    return this;
  }
  list = () => {
    return this.args;
  };
  get = (key) => {
    return this.args[key];
  };
  set = (key, value) => {
    this.args[key] = value;

    return this;
  };
}

async function main() {
  const args = new ArgsParse();
  const dl = new DownloadCourse();

  const token = args.get("token");
  const url = args.get("url");
  const help = args.get("help");

  if (help !== undefined) {
    console.log("coursehunter.net - Token normalizer script");
    console.log("Made by @dalisoft with love for community");
    console.log("(c) 2020 @dalisoft");
    console.log("Licensed under MIT-License", "\n");

    console.log("Commands:");
    console.log("url [Required] - Download URL of course");
    console.log(
      "Example: --url https://dls1.coursehunter.net/s/8f0f260a050519d80207882a14121419/udemy-sg-docker-kubernetes.zip"
    );
    console.log(
      "Returns: New URL for download course with modified token",
      "\n"
    );

    console.log("token [Optional] - Set your token");
    console.log("Example: --token 8f0f260a050519d80207882a14121419");
    console.log("`url` and `token` commands should be used together", "\n");

    return;
  }

  if (token) {
    dl.setToken(token);
  }

  try {
    if (url) {
      const changedUrl = await dl.parseUrl(url);

      console.log(changedUrl);
    }
  } catch (err) {
    console.log(err);
    console.log("Failed to get url");
  }
}
main();