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orpets.js
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orpets.js
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const storageHours = 48;
var processedNodes = [];
const listings = document.getElementsByClassName("listing");
clearLocalStorage();
window.onload = doOnScroll;
window.onscroll = doOnScroll;
/**
* Fires on scroll
*/
async function doOnScroll() {
for (var i = listings.length - 1; i >= 0; i--) {
// for (var i = 1; i >= 0; i--) {
var listing = listings[i];
if (processedNodes.includes(listing) === false) {
if (isScrolledIntoView(listing) === true) {
processedNodes.push(listing);
let listUrl = getLink(listing);
let petText = await getPetText(listUrl);
appendPetText(listing, petText);
}
}
}
}
/**
* Determines whether given element is visible in the viewscreen
*
* @param {element} el DOM Element
* @returns bool
*/
function isScrolledIntoView(el) {
let elTop = el.getBoundingClientRect().top;
let elBottom = el.getBoundingClientRect().bottom;
let isVisible = elTop >= 0 && elBottom <= window.innerHeight;
return isVisible;
}
/**
* Pauses code execution for desired amount.
*
* @param {int} milliseconds Time to wait
* @returns promise
*/
function sleep(milliseconds) {
return new Promise((resolve) => setTimeout(resolve, milliseconds));
}
/**
* Get the link from listing element
*
* @param {html} listing
* @returns string
*/
function getLink(listing) {
const listingLink = listing.getElementsByClassName("listing__link");
const href = listingLink[0].href;
const baseURL = href.substring(0, href.indexOf("?"));
return baseURL;
}
/**
* Get the Pet Text for a given url
* Checks local storage first, and if not found, fetches the text from the given
* URL and stores it for the future.
*
* @param {string} url
* @returns string
*/
async function getPetText(url) {
let petText = getWithExpiry(url);
if (petText !== null) {
return petText;
} else {
let expires = storageHours * 60 * 60 * 1000;
petText = await scrapePetText(url);
setWithExpiry(url, petText, expires);
return petText;
}
}
/**
* Sets a localstorage item with expiration date
*
* @param {string} key Key name
* @param {string} value Value content
* @param {int} exp Expiration time (in milliseconds)
*/
function setWithExpiry(key, value, exp) {
const now = new Date().getTime();
const item = {
origin: "orpets",
value: value,
expiry: now + exp,
};
localStorage.setItem(key, JSON.stringify(item));
}
/**
* Get the Pet Text from local storage and check whether it has expired. Deletes
* the key/value if expired and returns null instead.
*
* @param {string} key Key to search for
* @returns Value or Null
*/
function getWithExpiry(key) {
const value = localStorage.getItem(key);
if (!value) {
return null;
}
const item = JSON.parse(value);
const now = new Date().getTime();
if (now > item.expiry) {
localStorage.removeItem(key);
return null;
}
return item.value;
}
/**
*
* @param {string} url URL of hotel general info to scrape
* @returns {string} Pet text in <li> form
*/
async function scrapePetText(url) {
console.log("Scraping"); // DEBUG
// Limit the rate of hits to be polite.
await sleep(Math.random() * 3000 + 1000); // wait 1 to 3 seconds
let response = await fetch(url);
if (!response.ok) {
throw new Error(`HTTP error! status: ${response.status}`);
}
var parsedResponse = new window.DOMParser().parseFromString(await response.text(), "text/html");
var petText = parsedResponse.querySelector("[itemprop=petsAllowed]").innerHTML;
return petText;
}
/**
*
* @param {element} listing HTML Element
* @param {string} petText <li> listings of pet text info
*/
function appendPetText(listing, petText) {
const petContent = document.createElement("ul");
petContent.innerHTML = petText;
listing.appendChild(petContent);
}
/**
* Houseclaning function to clear all Orpets data that is expired on each load
*/
function clearLocalStorage() {
const now = new Date().getTime();
for (let i = 0; i < localStorage.length; i++) {
const key = localStorage.key(i);
let item;
try {
item = JSON.parse(localStorage.getItem(key));
} catch (e) {
item = {};
}
if (item.origin === "orpets" && item.exipiry < now) {
localStorage.removeItem(key);
}
// Nuclear Option
// if (item.origin === "orpets") {
// localStorage.removeItem(key);
// }
}
}