changedetection.io/changedetectionio/content_fetchers/res/xpath_element_scraper.js

// Copyright (C) 2021 Leigh Morresi (dgtlmoon@gmail.com)
// All rights reserved.

// @file Scrape the page looking for elements of concern (%ELEMENTS%)
// http://matatk.agrip.org.uk/tests/position-and-width/
// https://stackoverflow.com/questions/26813480/when-is-element-getboundingclientrect-guaranteed-to-be-updated-accurate
//
// Some pages like https://www.londonstockexchange.com/stock/NCCL/ncondezi-energy-limited/analysis
// will automatically force a scroll somewhere, so include the position offset
// Lets hope the position doesnt change while we iterate the bbox's, but this is better than nothing
var scroll_y = 0;
try {
    scroll_y = +document.documentElement.scrollTop || document.body.scrollTop
} catch (e) {
    console.log(e);
}


// Include the getXpath script directly, easier than fetching
function getxpath(e) {
    var n = e;
    if (n && n.id) return '//*[@id="' + n.id + '"]';
    for (var o = []; n && Node.ELEMENT_NODE === n.nodeType;) {
        for (var i = 0, r = !1, d = n.previousSibling; d;) d.nodeType !== Node.DOCUMENT_TYPE_NODE && d.nodeName === n.nodeName && i++, d = d.previousSibling;
        for (d = n.nextSibling; d;) {
            if (d.nodeName === n.nodeName) {
                r = !0;
                break
            }
            d = d.nextSibling
        }
        o.push((n.prefix ? n.prefix + ":" : "") + n.localName + (i || r ? "[" + (i + 1) + "]" : "")), n = n.parentNode
    }
    return o.length ? "/" + o.reverse().join("/") : ""
}

const findUpTag = (el) => {
    let r = el
    chained_css = [];
    depth = 0;

    //  Strategy 1: If it's an input, with name, and there's only one, prefer that
    if (el.name !== undefined && el.name.length) {
        var proposed = el.tagName + "[name=" + el.name + "]";
        var proposed_element = window.document.querySelectorAll(proposed);
        if (proposed_element.length) {
            if (proposed_element.length === 1) {
                return proposed;
            } else {
                // Some sites change ID but name= stays the same, we can hit it if we know the index
                // Find all the elements that match and work out the input[n]
                var n = Array.from(proposed_element).indexOf(el);
                // Return a Playwright selector for nthinput[name=zipcode]
                return proposed + " >> nth=" + n;
            }
        }
    }

    // Strategy 2: Keep going up until we hit an ID tag, imagine it's like  #list-widget div h4
    while (r.parentNode) {
        if (depth === 5) {
            break;
        }
        if ('' !== r.id) {
            chained_css.unshift("#" + CSS.escape(r.id));
            final_selector = chained_css.join(' > ');
            // Be sure theres only one, some sites have multiples of the same ID tag :-(
            if (window.document.querySelectorAll(final_selector).length === 1) {
                return final_selector;
            }
            return null;
        } else {
            chained_css.unshift(r.tagName.toLowerCase());
        }
        r = r.parentNode;
        depth += 1;
    }
    return null;
}


// @todo - if it's SVG or IMG, go into image diff mode
// %ELEMENTS% replaced at injection time because different interfaces use it with different settings

var size_pos = [];
// after page fetch, inject this JS
// build a map of all elements and their positions (maybe that only include text?)
var bbox;
console.log("Scanning %ELEMENTS%");

function collectVisibleElements(parent, visibleElements) {
    if (!parent) return; // Base case: if parent is null or undefined, return


    // Add the parent itself to the visible elements array if it's of the specified types
    const tagName = parent.tagName.toLowerCase();
    if ("%ELEMENTS%".split(',').includes(tagName)) {
        visibleElements.push(parent);
    }

    // Iterate over the parent's children
    const children = parent.children;
    for (let i = 0; i < children.length; i++) {
        const child = children[i];
        if (
            child.nodeType === Node.ELEMENT_NODE &&
            window.getComputedStyle(child).display !== 'none' &&
            window.getComputedStyle(child).visibility !== 'hidden' &&
            child.offsetWidth >= 0 &&
            child.offsetHeight >= 0 &&
            window.getComputedStyle(child).contentVisibility !== 'hidden'
        ) {
            // If the child is an element and is visible, recursively collect visible elements
            collectVisibleElements(child, visibleElements);
        }
    }
}

// Create an array to hold the visible elements
const visibleElementsArray = [];

// Call collectVisibleElements with the starting parent element
collectVisibleElements(document.body, visibleElementsArray);


visibleElementsArray.forEach(function (element) {

    bbox = element.getBoundingClientRect();

    // Skip really small ones, and where width or height ==0
    if (bbox['width'] * bbox['height'] < 10) {
        return
    }

    // Don't include elements that are offset from canvas
    if (bbox['top'] + scroll_y < 0 || bbox['left'] < 0) {
        return
    }

    // @todo the getXpath kind of sucks, it doesnt know when there is for example just one ID sometimes
    // it should not traverse when we know we can anchor off just an ID one level up etc..
    // maybe, get current class or id, keep traversing up looking for only class or id until there is just one match

    // 1st primitive - if it has class, try joining it all and select, if theres only one.. well thats us.
    xpath_result = false;
    try {
        var d = findUpTag(element);
        if (d) {
            xpath_result = d;
        }
    } catch (e) {
        console.log(e);
    }
    // You could swap it and default to getXpath and then try the smarter one
    // default back to the less intelligent one
    if (!xpath_result) {
        try {
            // I've seen on FB and eBay that this doesnt work
            // ReferenceError: getXPath is not defined at eval (eval at evaluate (:152:29), <anonymous>:67:20) at UtilityScript.evaluate (<anonymous>:159:18) at UtilityScript.<anonymous> (<anonymous>:1:44)
            xpath_result = getxpath(element);
        } catch (e) {
            console.log(e);
            return
        }
    }


    size_pos.push({
        xpath: xpath_result,
        width: Math.round(bbox['width']),
        height: Math.round(bbox['height']),
        left: Math.floor(bbox['left']),
        top: Math.floor(bbox['top']) + scroll_y,
        tagName: (element.tagName) ? element.tagName.toLowerCase() : '',
        tagtype: (element.tagName.toLowerCase() === 'input' && element.type) ? element.type.toLowerCase() : '',
        isClickable: window.getComputedStyle(element).cursor == "pointer"
    });

});


// Inject the current one set in the include_filters, which may be a CSS rule
// used for displaying the current one in VisualSelector, where its not one we generated.
if (include_filters.length) {
    // Foreach filter, go and find it on the page and add it to the results so we can visualise it again
    for (const f of include_filters) {
        bbox = false;
        q = false;

        if (!f.length) {
            console.log("xpath_element_scraper: Empty filter, skipping");
            continue;
        }

        try {
            // is it xpath?
            if (f.startsWith('/') || f.startsWith('xpath')) {
                var qry_f = f.replace(/xpath(:|\d:)/, '')
                console.log("[xpath] Scanning for included filter " + qry_f)
                q = document.evaluate(qry_f, document, null, XPathResult.FIRST_ORDERED_NODE_TYPE, null).singleNodeValue;
            } else {
                console.log("[css] Scanning for included filter " + f)
                q = document.querySelector(f);
            }
        } catch (e) {
            // Maybe catch DOMException and alert?
            console.log("xpath_element_scraper: Exception selecting element from filter " + f);
            console.log(e);
        }

        if (q) {
            // Try to resolve //something/text() back to its /something so we can atleast get the bounding box
            try {
                if (typeof q.nodeName == 'string' && q.nodeName === '#text') {
                    q = q.parentElement
                }
            } catch (e) {
                console.log(e)
                console.log("xpath_element_scraper: #text resolver")
            }

            // #1231 - IN the case XPath attribute filter is applied, we will have to traverse up and find the element.
            if (typeof q.getBoundingClientRect == 'function') {
                bbox = q.getBoundingClientRect();
                console.log("xpath_element_scraper: Got filter element, scroll from top was " + scroll_y)
            } else {
                try {
                    // Try and see we can find its ownerElement
                    bbox = q.ownerElement.getBoundingClientRect();
                    console.log("xpath_element_scraper: Got filter by ownerElement element, scroll from top was " + scroll_y)
                } catch (e) {
                    console.log(e)
                    console.log("xpath_element_scraper: error looking up q.ownerElement")
                }
            }
        }

        if (!q) {
            console.log("xpath_element_scraper: filter element " + f + " was not found");
        }

        if (bbox && bbox['width'] > 0 && bbox['height'] > 0) {
            size_pos.push({
                xpath: f,
                width: parseInt(bbox['width']),
                height: parseInt(bbox['height']),
                left: parseInt(bbox['left']),
                top: parseInt(bbox['top']) + scroll_y
            });
        }
    }
}

// Sort the elements so we find the smallest one first, in other words, we find the smallest one matching in that area
// so that we dont select the wrapping element by mistake and be unable to select what we want
size_pos.sort((a, b) => (a.width * a.height > b.width * b.height) ? 1 : -1)

// Window.width required for proper scaling in the frontend
return {'size_pos': size_pos, 'browser_width': window.innerWidth};