function initSquidTracking() {

    var agent = navigator.userAgent;
    var domain = window.location.hostname;
    var page = window.location.pathname;
    var timezone = Intl.DateTimeFormat().resolvedOptions().timeZone;
    var scrollPercentage = 0;
    var sessionId = sessionSet();
    var browserId = browserSet();
    var referrer = document.referrer;
    var endpoint = "https://icnsquid.work/api/UKbkUbuiYTc";
    // Enable checkout-specific event mapping.
    var enableCheckoutFormLogic = true;

    if (referrer === '') {
        referrer = 'direct';
    } 
    
    function isPageRefreshed() {
        return performance.navigation.type === 1;
    }

    /* get source of user i.e ppc */
    var queryString = window.location.search;
    var urlParams = new URLSearchParams(queryString);
    /*var squidSource = urlParams.get('squid_source');*/
    var squidSource = urlParams.get('utm_source');
    if(squidSource) {
        localStorage.setItem('squid_source', squidSource);
    } else {
        squidSource = localStorage.getItem('squid_source') ?? 'none';
    }
    var sources = JSON.parse(localStorage.getItem('squid_sources')) ?? [];
    if(urlParams.has('squid_source')) {
        squidSource = urlParams.get('squid_source');
        if(!sources.includes(squidSource)) {
            sources.push(squidSource);
            localStorage.setItem('squid_sources', JSON.stringify(sources));
        }
    }
    
    /* get email campaign if exists */
    var squidEmail = urlParams.get('squid_email');
    if(squidEmail) {
        localStorage.setItem('squid_email', squidEmail);
    } else {
        squidEmail = localStorage.getItem('squid_email') ?? null;
    }
    
    /* generate IDs */
    function randomString(length) {
        var chars = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
        var result = '';
        for (var i = length; i > 0; --i) result += chars[Math.floor(Math.random() * chars.length)];
        return result;
    }

    /* fetch or set sessionId */
    function sessionSet() {
        var sessionId = localStorage.getItem('session_id');
        if(!sessionId) {
            sessionId = randomString(24);
            var fetchPromise = fetch("https://icnsquid.work/api/checksessionid/"+sessionId);
            fetchPromise.then(response => {
                return response.json();
            }).then(res => {
                if(!res.OK) {
                    sessionId = res.session_id;
                } 
            });
            localStorage.setItem('session_id', sessionId);
        }
        return sessionId;
    }

    /* fetch or set browserId */
    function browserSet() {
        var browserId = localStorage.getItem('browser_id');
        if(!browserId) {
            browserId = randomString(24);
            var fetchPromise = fetch("https://icnsquid.work/api/checkbrowserid/"+browserId);
            fetchPromise.then(response => {
                return response.json();
            }).then(res => {
                if(!res.OK) {
                    browserId = res.browser_id;
                } 
            });
            localStorage.setItem('browser_id', browserId);
        }
        return browserId;
    }

    /* page views */
    function pageView() {
        setLatestEvent();
        if (!isPageRefreshed()) {
            uniqueData = {
                category: 'page_view'
            }
            sendData(uniqueData);
        } 
    }

    /* Track link clicks */
    var links = document.getElementsByTagName("a");
    for(var link of links) {
        link.addEventListener("click", function (e) {
            setLatestEvent();

            sendData({
                category: 'link',
                link: e.target.href,
            });
        });
    }

    /* Track button clicks */
    var buttons = document.getElementsByTagName("button");
    for(var button of buttons) {
        button.addEventListener("click", function (e) {
            setLatestEvent();

            sendData({
                category: 'button',
                button_text: e.target.innerText,
            });
        });
    }

    // Track Senso iframe Forms [!!] Doesn't work because of Cross-origin restrictions imposed by the external host of the source
    // var iframes = document.getElementsByTagName("iframe");
    // for(var iframe of iframes) {
        
    //     // Get the document object of the iframe
    //     var iframeDocument = iframe.contentDocument || iframe.contentWindow.document;
        
    //     // Find all form elements within the iframe document
    //     var formElements = iframeDocument.getElementsByTagName("form");
        
        
    //     // Add event listener for all iframe forms
    //     for(var ifrForm of formElements) {
    //         ifrForm.addEventListener("submit", function (e) {
    //             setLatestEvent();
    //             e.preventDefault();
    //             getFormData(e.target);
    //         });
    //     }
    // }

    var pendingForms = {}; // Holds form data while waiting for WPForms AJAX to finish

    function getFormKey(formEl) {
        return formEl.id ||
            formEl.getAttribute('data-formid') ||
            formEl.getAttribute('data-form-id') ||
            formEl.getAttribute('data-form') ||
            'unknown';
    }

    /* track form submits */
    var forms = document.getElementsByTagName("form");
    for(var form of forms) {
        form.addEventListener("submit", function (e) {
            // Do NOT prevent default. Just capture data.
            setLatestEvent();
            var formEl = e.target;
            var formKey = getFormKey(formEl);
            var formEventData = getFormData(formEl);

            if (!formEventData) {
                return;
            }

            if (formEl.classList.contains('wpforms-ajax-form')) {
                // Hold the data in memory until WPForms reports success/fail.
                pendingForms[formKey] = formEventData;
            } else {
                // Non-AJAX forms: send immediately as success.
                formEventData.success = true;
                sendData(formEventData, true);
            }
        });
    }

    if (typeof jQuery !== 'undefined') {
        // Form Success
        jQuery(document).on('wpformsAjaxSubmitSuccess', 'form.wpforms-ajax-form', function(e) {
            var formEl = e.target;
            var formKey = getFormKey(formEl);
            var formEventData = pendingForms[formKey] || getFormData(formEl);
            if (!formEventData) return;
            formEventData.success = true;
            sendData(formEventData, true);
            delete pendingForms[formKey];
        });

        // Form Failed (validation error, captcha failed, etc.)
        jQuery(document).on('wpformsAjaxSubmitFailed wpformsAjaxSubmitError', 'form.wpforms-ajax-form', function(e) {
            var formEl = e.target;
            var formKey = getFormKey(formEl);
            var formEventData = pendingForms[formKey] || getFormData(formEl);
            if (!formEventData) return;
            formEventData.success = false;
            sendData(formEventData, true);
            delete pendingForms[formKey];
        });
    }
    
    /* get form fill data */
    function getFormData(form) {
        var formName = form.id;
        var formData = {};
        Object.assign(formData, {form_class: formName});

        function getFormIdentifier(formEl) {
            var id = (formEl.id || '').trim();
            if (id) return id;

            var nameAttr = (formEl.getAttribute('name') || '').trim();
            if (nameAttr) return nameAttr;

            var dataId = (
                formEl.getAttribute('data-form-id') ||
                formEl.getAttribute('data-formid') ||
                formEl.getAttribute('data-form') ||
                ''
            ).trim();
            if (dataId) return dataId;

            var ariaLabel = (formEl.getAttribute('aria-label') || '').trim();
            if (ariaLabel) return ariaLabel;

            var title = (formEl.getAttribute('title') || '').trim();
            if (title) return title;

            var legend = '';
            var legendEl = formEl.querySelector('fieldset legend');
            if (legendEl && legendEl.textContent) {
                legend = legendEl.textContent.trim();
            }
            if (legend) return legend;

            var action = (formEl.getAttribute('action') || '').trim();
            if (action) return action;

            var className = (formEl.className || '').trim();
            if (className) return className;

            var formsList = Array.prototype.slice.call(document.getElementsByTagName('form'));
            var idx = formsList.indexOf(formEl);
            return idx >= 0 ? 'form_' + (idx + 1) : 'form_unknown';
        }

        var formIdentifier = getFormIdentifier(form);

        var inputs = form.getElementsByTagName('INPUT');
        var textAreas = form.getElementsByTagName('TEXTAREA');
        var fieldCounter = 0;

        function setFieldValue(key, value) {
            var normalizedKey = String(key || '').trim();
            if (!normalizedKey) {
                fieldCounter += 1;
                normalizedKey = 'field_' + fieldCounter;
            }
            formData[normalizedKey] = value;
        }

        function getFallbackFieldName(field) {
            return field.getAttribute('name') || field.id || field.getAttribute('placeholder') || field.type || '';
        }

        function getFieldValue(patterns) {
            var escaped = patterns.map(function(pattern) {
                return pattern.replace(/[-\/\\^$*+?.()|[\]{}]/g, '\\$&');
            });
            var selector = escaped.map(function(pattern) {
                return '[name*="' + pattern + '" i], [id*="' + pattern + '" i]';
            }).join(', ');
            var el = form.querySelector(selector);
            return el ? el.value : null;
        }

        function getEmailFromFormData() {
            var directEmail = getFieldValue(['email']);
            if (directEmail && String(directEmail).trim() !== '') {
                return String(directEmail).trim();
            }

            var emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
            for (var formKey in formData) {
                if (!Object.prototype.hasOwnProperty.call(formData, formKey)) continue;
                var formValue = formData[formKey];
                if (typeof formValue === 'string' && emailRegex.test(formValue.trim())) {
                    return formValue.trim();
                }
            }
            return null;
        }

        for(var input of inputs) {  
            var labels = input.labels;
            var hasLabels = !!(labels && labels.length);
            for(var label of Object.keys(labels || {})) {
                var labelName = labels[label].textContent;
                if (!labelName || String(labelName).trim() === '') continue;
                setFieldValue(labelName, input.value);
            }
            if (!hasLabels) {
                setFieldValue(getFallbackFieldName(input), input.value);
            }
        }
        for(var textArea of textAreas) {
            var labels = textArea.labels;
            var hasLabels = !!(labels && labels.length);
            for(var label of Object.keys(labels || {})) {
                var labelName = labels[label].textContent;
                if (!labelName || String(labelName).trim() === '') continue;
                setFieldValue(labelName, textArea.value);
            }
            if (!hasLabels) {
                setFieldValue(getFallbackFieldName(textArea), textArea.value);
            }
        }

        var extractedEmail = getEmailFromFormData();

        if (!enableCheckoutFormLogic) {
            return {
                category: 'form',
                email: extractedEmail,
                form_id: formIdentifier,
                form: formData,
            };
        }

        function toNumber(value) {
            if (value == null) return null;
            var cleaned = String(value).replace(/[^0-9.,-]/g, '');
            // Handle "1,234.56" and "1234,56"
            if (cleaned.indexOf(',') > -1 && cleaned.indexOf('.') > -1) {
                cleaned = cleaned.replace(/,/g, '');
            } else if (cleaned.indexOf(',') > -1 && cleaned.indexOf('.') === -1) {
                cleaned = cleaned.replace(',', '.');
            }
            var parsed = parseFloat(cleaned);
            return Number.isFinite(parsed) ? parsed : null;
        }

        function normalizeCurrency(value) {
            if (!value) return null;
            var currency = String(value).trim();
            if (currency === '£') return 'GBP';
            if (currency === '$') return 'USD';
            if (currency === '€') return 'EUR';
            if (currency.length === 3) return currency.toUpperCase();
            return currency.toUpperCase();
        }

        function getCheckoutFromTable() {
            var table = document.querySelector('table.shop_table.woocommerce-checkout-review-order-table');
            if (!table) return null;

            var totalRow = table.querySelector('tfoot tr.order-total');
            if (!totalRow) return null;

            var currencySymbolEl = totalRow.querySelector('.woocommerce-Price-currencySymbol');
            var currencyRaw = currencySymbolEl ? currencySymbolEl.textContent : null;
            var currency = normalizeCurrency(currencyRaw);

            var amountEl = totalRow.querySelector('.woocommerce-Price-amount bdi') || totalRow.querySelector('.woocommerce-Price-amount');
            var amountRaw = amountEl ? amountEl.textContent : null;
            var amount = toNumber(amountRaw);

            if (amount === null && !currency) return null;
            return {
                original_payment_amount: amount,
                original_payment_currency: currency
            };
        }

        var checkoutFromTable = getCheckoutFromTable();
        var checkoutConvertedAmount = toNumber(getFieldValue(['converted_payment_amount']));
        var checkoutOriginalCurrency = normalizeCurrency(getFieldValue(['original_payment_currency']));
        var checkoutOriginalAmount = toNumber(getFieldValue(['original_payment_amount']));
        var checkoutEmail = extractedEmail;
        var checkoutFormId = formIdentifier || 'checkout_form';
        var formId = (form.id || '').toLowerCase();
        var formNameAttr = (form.getAttribute('name') || '').toLowerCase();
        var formClass = (form.className || '').toLowerCase();
        var isCheckoutContext = (
            page.indexOf('/checkout') !== -1 ||
            formId.indexOf('checkout') !== -1 ||
            formNameAttr.indexOf('checkout') !== -1 ||
            formClass.indexOf('checkout') !== -1 ||
            checkoutFromTable !== null
        );

        if (!checkoutEmail) {
            var emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
            for (var formKey in formData) {
                if (!Object.prototype.hasOwnProperty.call(formData, formKey)) continue;
                var formValue = formData[formKey];
                if (typeof formValue === 'string' && emailRegex.test(formValue.trim())) {
                    checkoutEmail = formValue.trim();
                    break;
                }
            }
        }

        if (checkoutFromTable) {
            checkoutOriginalAmount = checkoutFromTable.original_payment_amount;
            checkoutOriginalCurrency = checkoutFromTable.original_payment_currency;
        }

        if (checkoutOriginalCurrency === 'GBP' && checkoutOriginalAmount !== null) {
            checkoutConvertedAmount = checkoutOriginalAmount;
        }

        var isCheckoutForm = (
            isCheckoutContext ||
            checkoutConvertedAmount !== null ||
            checkoutOriginalAmount !== null ||
            (checkoutOriginalCurrency && checkoutOriginalCurrency.length > 0)
        );

        if (isCheckoutForm) {
            return {
                category: 'checkout_form',
                form_id: checkoutFormId,
                email: checkoutEmail,
                converted_payment_amount: null,
                original_payment_currency: null,
                original_payment_amount: null,
                form: formData
            };
        }

        // Non-checkout forms continue to use generic form tracking.
        return {
            category: 'form',
            email: extractedEmail,
            form_id: formIdentifier,
            form: formData,
        };
    }

    /**  
     * track page scrolls
     * get current browser viewpane heigtht
     */
    function getWindowHeight() {
        return window.innerHeight || 
            document.documentElement.clientHeight ||
            document.body.clientHeight || 0;
    }

    /**
     * get current absolute window scroll position
     */
    function getWindowYScroll() {
        return window.pageYOffset || 
            document.body.scrollTop ||
            document.documentElement.scrollTop || 0;
    }

    /**
     * get current absolute document height
     */
    function getDocHeight() {
        return Math.max(
            document.body.scrollHeight || 0, 
            document.documentElement.scrollHeight || 0,
            document.body.offsetHeight || 0, 
            document.documentElement.offsetHeight || 0,
            document.body.clientHeight || 0, 
            document.documentElement.clientHeight || 0
        );
    }

    /**
     * get current vertical scroll percentage
     */
    function getScrollPercentage() {
        return (
            (getWindowYScroll() + getWindowHeight()) / getDocHeight()
        ) * 100;
    }

    var throttledListener = throttle(scrollListener, 25);
    window.addEventListener('scroll', throttledListener, {passive: true});
    function throttle(func, delay) { // allows [func] to run once every [delay] ms
        var func = func.bind(func),
            last = Date.now();
        return function() {
            if (Date.now() - last > delay) {
                func();
                last = Date.now();
            }
        }
    }
    function scrollListener() {
        if(scrollPercentage < Math.round(getScrollPercentage())) {

            scrollPercentage = Math.round(getScrollPercentage());
            var threshold = document.body.clientHeight * 0.6;

            if (window.pageYOffset >= threshold) {      
                window.removeEventListener('scroll', throttledListener);
            }

            sendData({
                category: 'scroll',
                scroll_percentage: scrollPercentage,
            });
        }
    }

    /* track video */
    var timer = null;
    var totalTime = 0;

    var players = document.getElementsByTagName("video");

    for(var player of players) {
        player.addEventListener("play", startPlaying);
        player.addEventListener("pause", pausePlaying);
    }

    function startPlaying() {
        timer = window.setInterval(function() {
            totalTime += 10;
        }, 10);
    }

    function pausePlaying() {
        if (timer) clearInterval(timer);

        sendData({
            category: 'video',
            'duration': totalTime
        });
    }
    
    /* reset session_id */
    function sessionReset() {
        localStorage.removeItem("session_id");
        sessionId = sessionSet();
    }

    /* track last event time */
    function setLatestEvent() {
        var now = Date.now();
        var latestEvent = localStorage.getItem("last_event") || now;

        if(now - latestEvent > 1800000) {
            sessionReset();
        }
        
        localStorage.setItem("last_event", now);
    }

    /* send all data to SQUID */
    async function sendData(uniqueData, preferBeacon) {
        eventData = {
            'squid': {
                time: Date.now(),
                timezone: timezone,
                page: page,
                domain: domain,
                referrer: referrer,
                source: squidSource,
                sources: sources,
                email: squidEmail,
                user_agent: agent,
                session_id: sessionId,
                browser_id: browserId
            }
        }

        Object.assign(eventData['squid'], uniqueData);
        
        console.log(eventData);
        
        var headersList = {
            "Accept": "*/*",
            "Content-Type": "application/json"
        }
        
        var blob = new Blob([JSON.stringify(eventData)], { type: 'application/json; charset=UTF-8' });
        var payload = JSON.stringify(eventData);

        if (preferBeacon && navigator.sendBeacon) {
            // sendBeacon is best for form submits/page unload
            if (navigator.sendBeacon(endpoint, payload)) {
                return;
            }
        }

        try {
            var response = await fetch(endpoint, { 
                method: "POST",
                body: blob,
                headers: headersList,
                keepalive: !!preferBeacon
            });

            var res = await response.text();
            console.log(res);
        } catch (error) {
            console.log('SQUID send failed', error);
        }
    }
    
    pageView();
}

// Check if the page is already loaded
if (document.readyState === 'complete' || document.readyState === 'interactive') {
    // The load event already fired, run immediately
    initSquidTracking();
} else {
    // The page is still loading, wait for it
    window.addEventListener('load', initSquidTracking);
}