(function() {
    "use strict";

    var TRACKING_ID = "{{ $trackingId }}";
    var COLLECT_URL = "{{ $collectUrl }}";
    var SESSION_TIMEOUT = 30 * 60 * 1000;
    var STORAGE_PREFIX = "_ta_";

    // ---- Utilities ----

    function generateId() {
        try {
            var arr = new Uint8Array(16);
            crypto.getRandomValues(arr);
            return Array.from(arr, function(b) { return b.toString(16).padStart(2, "0"); }).join("");
        } catch(e) {
            return "xxxxxxxxxxxx4xxxyxxxxxxxxxxxxxxx".replace(/[xy]/g, function(c) {
                var r = Math.random() * 16 | 0;
                return (c === "x" ? r : (r & 0x3 | 0x8)).toString(16);
            });
        }
    }

    function getStore(key) {
        try { return localStorage.getItem(STORAGE_PREFIX + key); } catch(e) { return null; }
    }

    function setStore(key, value) {
        try { localStorage.setItem(STORAGE_PREFIX + key, value); } catch(e) {}
    }

    function now() { return Date.now(); }

    // ---- Visitor ID ----

    function getVisitorId() {
        var vid = getStore("vid");
        if (!vid) {
            vid = generateId();
            setStore("vid", vid);
        }
        return vid;
    }

    // ---- Session ID ----

    function getSessionId() {
        var sid = getStore("sid");
        var ts = parseInt(getStore("sid_ts"), 10) || 0;

        if (!sid || (now() - ts) > SESSION_TIMEOUT) {
            sid = generateId();
            setStore("sid", sid);
            setStore("is_new_session", "1");
        }

        setStore("sid_ts", String(now()));
        return sid;
    }

    function isNewSession() {
        var val = getStore("is_new_session");
        setStore("is_new_session", "0");
        return val === "1";
    }

    // ---- Device / Browser Detection ----

    function detectDevice() {
        var ua = navigator.userAgent || "";
        if (/Mobi|Android.*Mobile|iPhone|iPod/i.test(ua)) return "mobile";
        if (/iPad|Android(?!.*Mobile)|Tablet/i.test(ua)) return "tablet";
        return "desktop";
    }

    function detectBrowser() {
        var ua = navigator.userAgent || "";
        var m;

        if ((m = ua.match(/Edg(?:e|A|iOS)?\/(\S+)/))) return { name: "Edge", version: m[1] };
        if ((m = ua.match(/OPR\/(\S+)/))) return { name: "Opera", version: m[1] };
        if ((m = ua.match(/Chrome\/(\S+)/)) && !/Edg/.test(ua)) return { name: "Chrome", version: m[1] };
        if ((m = ua.match(/Safari\/(\S+)/)) && !/Chrome/.test(ua)) {
            var v = ua.match(/Version\/(\S+)/);
            return { name: "Safari", version: v ? v[1] : m[1] };
        }
        if ((m = ua.match(/Firefox\/(\S+)/))) return { name: "Firefox", version: m[1] };

        return { name: "Other", version: "" };
    }

    function detectOS() {
        var ua = navigator.userAgent || "";
        var m;

        if ((m = ua.match(/Windows NT (\d+\.\d+)/))) return { name: "Windows", version: m[1] };
        if ((m = ua.match(/Mac OS X (\d+[._]\d+[._]?\d*)/))) return { name: "macOS", version: m[1].replace(/_/g, ".") };
        if ((m = ua.match(/Android (\d+(\.\d+)*)/))) return { name: "Android", version: m[1] };
        if (/iPhone|iPad|iPod/.test(ua)) {
            m = ua.match(/OS (\d+[_]\d+[_]?\d*)/);
            return { name: "iOS", version: m ? m[1].replace(/_/g, ".") : "" };
        }
        if (/Linux/.test(ua)) return { name: "Linux", version: "" };

        return { name: "Other", version: "" };
    }

    // ---- UTM Parameters ----

    function getUtmParams() {
        var params = {};
        try {
            var sp = new URLSearchParams(window.location.search);
            ["utm_source", "utm_medium", "utm_campaign", "utm_term", "utm_content"].forEach(function(key) {
                var val = sp.get(key);
                if (val) params[key] = val;
            });
        } catch(e) {}
        return params;
    }

    function getReferrerDomain() {
        try {
            if (!document.referrer) return "";
            return new URL(document.referrer).hostname;
        } catch(e) {
            return "";
        }
    }

    // ---- Send Beacon ----

    function send(data) {
        var vid = getVisitorId();
        var sid = getSessionId();
        var browser = detectBrowser();
        var os = detectOS();
        var utm = getUtmParams();

        var payload = Object.assign({
            tid: TRACKING_ID,
            vid: vid,
            sid: sid,
            is_new_session: isNewSession(),
            url: window.location.href,
            path: window.location.pathname,
            title: document.title,
            referrer: document.referrer,
            ref_domain: getReferrerDomain(),
            sr: screen.width + "x" + screen.height,
            lang: (navigator.language || "").substring(0, 10),
            device: detectDevice(),
            browser: browser.name,
            browser_version: browser.version.substring(0, 20),
            os: os.name,
            os_version: os.version.substring(0, 20),
        }, utm, data);

        var blob = new Blob([JSON.stringify(payload)], { type: "application/json" });

        if (navigator.sendBeacon) {
            navigator.sendBeacon(COLLECT_URL, blob);
        } else {
            var xhr = new XMLHttpRequest();
            xhr.open("POST", COLLECT_URL, true);
            xhr.setRequestHeader("Content-Type", "application/json");
            xhr.send(JSON.stringify(payload));
        }
    }

    // ---- Time on Page ----

    var pageEnteredAt = now();

    function getTimeOnPage() {
        return Math.round((now() - pageEnteredAt) / 1000);
    }

    // ---- Track Page View ----

    function trackPageView() {
        pageEnteredAt = now();
        send({ type: "pageview" });
    }

    // ---- Track Event ----

    function trackEvent(name, params) {
        params = params || {};
        send({
            type: "event",
            event_name: name,
            event_category: params.category || null,
            event_action: params.action || null,
            event_label: params.label || null,
            event_value: params.value != null ? params.value : null,
            event_properties: params.properties || null,
        });
    }

    // ---- Send time-on-page before leaving ----

    function onPageLeave() {
        var top = getTimeOnPage();
        if (top > 0) {
            send({ type: "event", event_name: "page_leave", event_properties: { time_on_page: top } });
        }
    }

    document.addEventListener("visibilitychange", function() {
        if (document.visibilityState === "hidden") onPageLeave();
    });

    // ---- SPA Support: listen for pushState / popstate ----

    var originalPushState = history.pushState;
    history.pushState = function() {
        onPageLeave();
        originalPushState.apply(history, arguments);
        trackPageView();
    };

    window.addEventListener("popstate", function() {
        onPageLeave();
        trackPageView();
    });

    // ---- Public API ----

    window.ta = function(command, arg1, arg2) {
        switch(command) {
            case "event":
                trackEvent(arg1, arg2);
                break;
            case "pageview":
                trackPageView();
                break;
        }
    };

    // ---- Auto-track initial page view ----

    trackPageView();
})();