/**
 * meta_tracking.js
 * A standalone module to capture and persist Meta attribution signals (fbclid, _fbp) in cookies.
 * 
 * Logic adapted for legacy environment (no React hooks).
 * - Checks URL for `fbclid` and sets `_fbc` cookie.
 * - Checks for `_fbp` cookie; if missing, generates and sets it.
 */

(function (window, document) {
    'use strict';

    var MetaTracking = {
        init: function () {
            var location = window.location;
            this.handleFbc(location.search);
            this.handleFbp();
            this.handleUtm(location.search);
        },

        // 1. Parsing and storing _fbc (Click ID)
        handleFbc: function (searchParams) {
            var fbclid = this.getQueryParam('fbclid', searchParams);

            if (fbclid) {
                var version = 'fb';
                var subdomainIndex = 1; // 1 = example.com
                var creationTime = new Date().getTime(); // Unix timestamp in ms

                // Format: fb.1.timestamp.id
                var fbcValue = version + '.' + subdomainIndex + '.' + creationTime + '.' + fbclid;

                this.setCookie('_fbc', fbcValue, 90);
            }
        },

        handleUtm: function (searchParams) {
            var self = this;
            if (!searchParams) return;

            // Logically, we want to capture all utm_ parameters.
            // We can either iterate a list or dynamic regex. 
            // Given the requirement to be robust, let's look for "utm_"

            var query = searchParams.substring(1); // remove '?'
            var vars = query.split('&');
            for (var i = 0; i < vars.length; i++) {
                var pair = vars[i].split('=');
                if (pair.length === 2) {
                    var key = decodeURIComponent(pair[0]);
                    var value = decodeURIComponent(pair[1]);
                    if (key.indexOf('utm_') === 0) {
                        self.setCookie(key, value, 90);
                    }
                }
            }
        },

        // 2. Handling _fbp (Browser ID)
        handleFbp: function () {
            if (!this.getCookie('_fbp')) {
                var version = 'fb';
                var subdomainIndex = 1;
                var creationTime = new Date().getTime();
                var randomInt = Math.floor(Math.random() * 10000000000); // 10-digit random number

                // Format: fb.1.timestamp.randomDigits
                var fbpValue = version + '.' + subdomainIndex + '.' + creationTime + '.' + randomInt;

                this.setCookie('_fbp', fbpValue, 90);
            }
        },

        // Helper: Get query param by name
        getQueryParam: function (name, search) {
            name = name.replace(/[\[]/, '\\[').replace(/[\]]/, '\\]');
            var regex = new RegExp('[\\?&]' + name + '=([^&#]*)');
            var results = regex.exec(search);
            return results === null ? '' : decodeURIComponent(results[1].replace(/\+/g, ' '));
        },

        // Helper: Set cookie
        setCookie: function (name, value, days) {
            var expires = "";
            if (days) {
                var date = new Date();
                date.setTime(date.getTime() + (days * 24 * 60 * 60 * 1000));
                expires = "; expires=" + date.toUTCString();
            }
            // Ensure path is root and domain is included if needed (defaults to current host)
            document.cookie = name + "=" + (value || "") + expires + "; path=/";
        },

        // Helper: Get cookie
        getCookie: function (name) {
            var nameEQ = name + "=";
            var ca = document.cookie.split(';');
            for (var i = 0; i < ca.length; i++) {
                var c = ca[i];
                while (c.charAt(0) == ' ') c = c.substring(1, c.length);
                if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length, c.length);
            }
            return null;
        }
    };

    // Initialize on ready
    if (document.readyState === 'complete' || document.readyState === 'interactive') {
        MetaTracking.init();
    } else {
        // IE9+ support for DOMContentLoaded
        document.addEventListener('DOMContentLoaded', function () {
            MetaTracking.init();
        });
    }

})(window, document);