worker.js

import { shortcutURL, supportedVersions } from './modules/global-variables';
import twitterAPIClient from './modules/twitter-api-client';
import landingPage from './modules/landing-page';

// return Response with its corresponding Content-Type
const jsonResponseBuilder = (body, options = {}) => {
  return new Response(JSON.stringify(body), {
    headers: {
      'Content-Type': 'application/json; charset=UTF-8'
    },
    ...options
  });
};

// Check params
const objectValidator = (object) => {
  // Check if installed version is a supported one
  if (!object.version || !supportedVersions.includes(object.version)) {
    object.message = `Your current version is outdated. Please download the latest one on ${shortcutURL}.`;
    return object;
  }
  // Check for valid URL
  if (!object.url) {
    object.message = 'The URL field is required and cannot be left blank.';
    return object;
  }
  // Check for valid tweet ID
  if (!(/^https:\/\/(twitter|x)\.com\/[^/]+\/status\/\d{18,}/.test(object.url))) {
    object.message = `The provided URL (${object.url}) is not valid.`;
    return object;
  }
  // Save the id on params object
  [object.id] = object.url.match(/\d{18,}/);
  // Rewrite selector key to save the boolean from the dictionary, or accept a string selector like "true"
  try {
    const parsedSelector = JSON.parse(object.selector);
    object.selector = Object.hasOwn(parsedSelector, 'selector') ? parsedSelector.selector : parsedSelector;
  } catch (error) {
    object.selector = false;
  }
  return object;
};

// Iterate through the form data and return an object
const formToObject = async (request) => {
  try {
    const objectForm = Object.fromEntries(await request.formData());
    return objectValidator(objectForm);
  } catch (error) {
    return { message: 'There was an error processing the form data.' };
  }
};

// Handle POST request
const handlePostRequest = async (request, env) => {
  if (env.MAINTENANCE === 'true') {
    return jsonResponseBuilder(
      { error: 'DTwitter is under maintenance. Find more at @heismauri on Twitter/X.' },
      { status: 503 }
    );
  }
  const params = await formToObject(request);
  if (params.message) {
    return jsonResponseBuilder({ error: params.message }, { status: 400 });
  }
  const twitterJSON = await twitterAPIClient(params, env);
  // Check if the API gave any errors
  if (twitterJSON.error) {
    switch (twitterJSON.error.message) {
      case 'NotFound':
        return jsonResponseBuilder(
          { error: 'Sorry, the tweet you were looking for could not be found.' },
          { status: 404 }
        );
      case 'Protected':
        return jsonResponseBuilder(
          { error: 'Sorry, the tweet you are trying to access is private and cannot be viewed or downloaded.' },
          { status: 403 }
        );
      case 'NsfwLoggedOut':
        return jsonResponseBuilder(
          { error: 'Sorry, the download has failed due to the presence of NSFW content in the tweet.' },
          { status: 403 }
        );
      case 'Suspended':
      case 'TweetUnavailable':
        return jsonResponseBuilder(
          { error: 'Sorry, the tweet you are trying to access is unavailable.' },
          { status: 410 }
        );
      case 'NoMedia':
        return jsonResponseBuilder(
          { error: 'Sorry, no media could be found for the provided URL.' },
          { status: 422 }
        );
      default:
        return jsonResponseBuilder(
          {
            error: "Twitter's API does not seem to be working right now. Please try again later. "
                   + 'Contact @heismauri on Twitter/X if the problem persists.'
          },
          { status: 503 }
        );
    }
  }
  // Success
  return jsonResponseBuilder(twitterJSON);
};

export default {
  fetch(request, env) {
    if (request.method === 'POST') {
      return handlePostRequest(request, env);
    }
    return new Response(landingPage(), {
      headers: {
        'Content-Type': 'text/html; charset=UTF-8'
      }
    });
  }
};