Violentmonkey / Greasemonkey / Tampermonkey script to notify on new ads on eBay Kleinanzeigen

ebay-kleinanzeigen-notifier.js

// ==UserScript==
// @name        eBay Kleinanzeigen Notifier
// @namespace   www.ebay-kleinanzeigen.de
// @description eBay Kleinanzeigen Notifier
// @version     1.0.0
// @icon        https://www.ebay-kleinanzeigen.de/static/img/favicon.png
// @match       https://www.ebay-kleinanzeigen.de/*
// @grant       GM_getValue
// @grant       GM_setValue
// @grant       GM_addStyle
// @grant       GM_notification
// ==/UserScript==

const config = {
  queryParamName: 'notify',
  reloadInterval: 10_000,
  actions: [
    'playSound',
    'showNotification',
  ],
};

const shouldPlaySound = config.actions.indexOf('playSound') !== -1;
const shouldShowNotification = config.actions.indexOf('showNotification') !== -1;

const storageItem = (k) => {
  const key = `ebay-kleinanzeigen-notifier_${k}`;
  return {
    read: () => {
      return window.GM_getValue(key, null);
    },
    write: (data) => {
      return window.GM_setValue(key, data);
    },
  };
};

const ensureCanPlaySound = (cb) => {
  const canPlay = (cb) => {
    const timeout = window.setTimeout(() => {
      cb(false);
    }, 500);
    const ctx = new window.AudioContext();
    try {
      ctx.resume().then(() => {
        window.clearTimeout(timeout);
        return cb(ctx.state === 'running');
      });
    } catch (e) {
      window.clearTimeout(timeout);
      return cb(false);
    }
  };

  const elem = window.GM_addStyle('body { visibility: hidden; background-color: red; }');
  canPlay((can) => {
    if (can) {
      elem.remove();
    }
    cb(can);
  });
};

const playSound = () => {
  const start = 0;
  const end = 2_000;

  const audioCtx = new window.AudioContext();
  const osc = audioCtx.createOscillator();
  osc.connect(audioCtx.destination);
  osc.type = 'sine';
  osc.frequency.value = start;
  osc.start();

  const wave = () => {
    for (let i = start; i <= end; i++) { window.setTimeout(() => { osc.frequency.value = i; }, i ); }
    for (let i = end; i >= start; i--) { window.setTimeout(() => { osc.frequency.value = i; }, 2*end - i ); }
  };

  wave();
  window.setInterval(wave, 2*end);
};

const showNotification = () => {
  const n = window.GM_notification({
    title: 'New ad on eBay Kleinanzeigen',
    text: 'Found a new ad on eBay Kleinanzeigen',
    image: 'https://www.ebay-kleinanzeigen.de/static/img/favicon.png',
  });
};

const foundNew = () => {
  if (shouldPlaySound) { playSound(); }
  if (shouldShowNotification) { showNotification(); }
};

const go = () => {
  const s = storageItem(window.location.pathname);
  const ids = s.read() || [];

  const ads = window.document.querySelectorAll('.ad-listitem:not(.badge-topad, .is-topad, .is-highlight) .aditem');
  const latestAd = ads[0];
  if (!latestAd) {
    return;
  }
  const latestAdID = latestAd.getAttribute('data-adid');

  let found = false;
  ids.every((id) => {
    if (id === latestAdID) {
      found = true;
      return false;
    }
    return true;
  });

  if (!found) {
    ids.push(latestAdID);
    s.write(ids);

    foundNew();
  }

  window.setTimeout(() => { window.document.location.reload(); }, config.reloadInterval);
};

if ((new window.URLSearchParams(window.location.search)).has(config.queryParamName)) {
  if (!shouldPlaySound) {
    go();
  } else {
    ensureCanPlaySound((can) => {
      if (can) {
        go();
      } else {
        window.onclick = () => { window.document.location.reload(); };
        window.alert('Can\'t play sound as user interaction didn\'t happen yet. Please click anywhere on the page to reload.');
      }
    });
  }
}