archive.social/app/server.js

/**
 * archive.social
 * @module server.js
 * @author The Harvard Library Innovation Lab
 * @license MIT
 */
import assert from "assert";

import nunjucks from "nunjucks";

import { AccessKeys, SuccessLog, TwitterCapture } from "./utils/index.js";
import {
  TEMPLATES_PATH,
  STATIC_PATH,
  MAX_PARALLEL_CAPTURES_TOTAL,
  MAX_PARALLEL_CAPTURES_PER_ACCESS_KEY,
} from "./const.js";

/**
 * @type {SuccessLog}
 */
const successLog = new SuccessLog();

/**
 * @type {AccessKeys}
 */
const accessKeys = new AccessKeys();

/**
 * Keeps track of how many capture processes are currently running. 
 * May be used to redirect users if over capacity. 
 * 
 * [!] Only good for early prototyping. 
 * 
 * @type {{
 *  currentTotal: number, 
 *  maxTotal: number, 
 *  currentByAccessKey: object.<string, number>, 
 *  maxPerAccessKey: number
 * }}
 */
const CAPTURES_WATCH = {
  currentTotal: 0,
  maxTotal: MAX_PARALLEL_CAPTURES_TOTAL,
  currentByAccessKey: {},
  maxPerAccessKey: MAX_PARALLEL_CAPTURES_PER_ACCESS_KEY,
}


/**
 * [GET] / 
 * Shows the landing page / form.
 * Assumes `fastify` is in scope.
 * 
 * @param {fastify.FastifyRequest} request
 * @param {fastify.FastifyReply} reply 
 * @returns {Promise<fastify.FastifyReply>}
 */
async function index(request, reply) {
  const html = nunjucks.render(`${TEMPLATES_PATH}index.njk`);

  return reply
    .code(200)
    .header('Content-Type', 'text/html; charset=utf-8')
    .send(html);
}

/**
 * [POST] `/`
 * Processes a request to capture a `twitter.com` url. 
 * Serves PDF bytes directly if operation is successful.
 * Returns to form with specific error code, passed as `errorReason`, otherwise.
 * Assumes `fastify` is in scope.
 * 
 * @param {fastify.FastifyRequest} request
 * @param {fastify.FastifyReply} reply 
 * @returns {Promise<fastify.FastifyReply>}
 */
async function capture(request, reply) {
  const data = request.body;
  const accessKey = data["access-key"];
  
  request.log.info(`Capture capacity: ${CAPTURES_WATCH.currentTotal} / ${CAPTURES_WATCH.maxTotal}.`);
  
  //
  // Check access key
  //
  if (!accessKeys.check(accessKey)) {
    const html = nunjucks.render(`${TEMPLATES_PATH}index.njk`, {
      error: true,
      errorReason: "ACCESS-KEY"
    });

    return reply
      .code(401)
      .header('Content-Type', 'text/html; charset=utf-8')
      .send(html);
  }

  //
  // Check url
  //
  try {
    const url = new URL(data.url);
    assert(url.origin === "https://twitter.com");
  }
  catch(err) {
    const html = nunjucks.render(`${TEMPLATES_PATH}index.njk`, {
      error: true,
      errorReason: "URL"
    });

    return reply
      .code(400)
      .header('Content-Type', 'text/html; charset=utf-8')
      .send(html);
  }

  //
  // Check that there is still capture capacity (total)
  //
  if (CAPTURES_WATCH.currentTotal >= CAPTURES_WATCH.maxTotal) {
    const html = nunjucks.render(`${TEMPLATES_PATH}index.njk`, {
      error: true,
      errorReason: "TOO-MANY-CAPTURES-TOTAL"
    });

    return reply
      .code(503)
      .header('Content-Type', 'text/html; charset=utf-8')
      .send(html);
  }

  //
  // Check that there is still capture capacity (for this access key)
  //
  if (CAPTURES_WATCH.currentByAccessKey[accessKey] >= CAPTURES_WATCH.maxPerAccessKey) {
    const html = nunjucks.render(`${TEMPLATES_PATH}index.njk`, {
      error: true,
      errorReason: "TOO-MANY-CAPTURES-USER"
    });

    return reply
      .code(429)
      .header('Content-Type', 'text/html; charset=utf-8')
      .send(html);
  }

  //
  // Process capture request
  //
  try {
    CAPTURES_WATCH.currentTotal += 1;

    if (accessKey in CAPTURES_WATCH.currentByAccessKey) {
      CAPTURES_WATCH.currentByAccessKey[accessKey] += 1;
    }
    else {
      CAPTURES_WATCH.currentByAccessKey[accessKey] = 1;
    }

    const tweets = new TwitterCapture(data.url, {runBrowserBehaviors: "auto-scroll" in data});
    const pdf = await tweets.capture();

    successLog.add(accessKey, pdf);

    return reply
      .code(200)
      .header('Content-Type', 'application/pdf')
      .header('Content-Disposition', 'attachment; filename="capture.pdf"')
      .send(pdf);
  }
  catch(err) {
    request.log.error(`Capture failed. ${err}`);

    const html = nunjucks.render(`${TEMPLATES_PATH}index.njk`, {
      error: true,
      errorReason: "CAPTURE-ISSUE"
    });

    return reply
      .code(500)
      .header('Content-Type', 'text/html; charset=utf-8')
      .send(html);
  }
  // In any case: we need to decrease CAPTURES_WATCH counts.
  finally {
    CAPTURES_WATCH.currentTotal -= 1;

    if (accessKey && accessKey in CAPTURES_WATCH.currentByAccessKey) {
      CAPTURES_WATCH.currentByAccessKey[data["access-key"]] -= 1;
    }
  }

}

/**
 * [GET] `/api/v1/hashes/check/<sha512-hash>`. 
 * Checks if a given SHA512 hash is in the "success" logs, meaning this app created it. 
 * Hash is passed as the last parameter, url encoded. 
 * Assumes `fastify` is in scope. 
 * 
 * Returns HTTP 200 if found, HTTP 404 if not. 
 * 
 * @param {fastify.FastifyRequest} request
 * @param {fastify.FastifyReply} reply 
 * @returns {Promise<fastify.FastifyReply>}
 */
async function checkHash(request, reply) {
  let found = false;
  const { hash } = request.params;

  if (hash.length === 95 || hash.length === 88) {
    found = successLog.findHashInLogs(hash);
  }

  return reply.code(found ? 200 : 404).send();
}

export default async function (fastify, opts) {
  // Adds support for `application/x-www-form-urlencoded`
  fastify.register(import('@fastify/formbody'));

  // Serves files from `STATIC_PATH`
  fastify.register(import('@fastify/static'), {
    root: STATIC_PATH,
    prefix: '/static/',
  });

  // [GET] /
  fastify.get('/', index);

  // [POST] /
  fastify.post('/', capture);

  // [GET] /api/v1/hashes/check/:hash
  fastify.get('/api/v1/hashes/check/:hash', checkHash);
};