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

    var storageKey = 'iouAnalyticsCampaign';
    var scrollMilestones = [25, 50, 75, 100];

    function safeJsonParse(value) {
        try {
            return JSON.parse(value);
        } catch (error) {
            return null;
        }
    }

    function safeStorageGet() {
        try {
            return window.localStorage.getItem(storageKey);
        } catch (error) {
            return null;
        }
    }

    function safeStorageSet(value) {
        try {
            window.localStorage.setItem(storageKey, value);
        } catch (error) {
            return;
        }
    }

    function sanitizeValue(value) {
        if (value === null || value === undefined || value === '') {
            return null;
        }

        return String(value).replace(/\s+/g, ' ').trim().substring(0, 100);
    }

    function cleanParams(params) {
        var cleaned = {};
        var key;

        for (key in params) {
            if (!Object.prototype.hasOwnProperty.call(params, key)) {
                continue;
            }

            if (typeof params[key] === 'boolean' || typeof params[key] === 'number') {
                cleaned[key] = params[key];
                continue;
            }

            var sanitized = sanitizeValue(params[key]);
            if (sanitized !== null) {
                cleaned[key] = sanitized;
            }
        }

        return cleaned;
    }

    function getQueryParams() {
        return new window.URLSearchParams(window.location.search);
    }

    function getCampaignFromQuery(queryParams) {
        var campaign = {
            source: sanitizeValue(queryParams.get('utm_source')),
            medium: sanitizeValue(queryParams.get('utm_medium')),
            campaign: sanitizeValue(queryParams.get('utm_campaign')),
            term: sanitizeValue(queryParams.get('utm_term')),
            content: sanitizeValue(queryParams.get('utm_content')),
            gclid: sanitizeValue(queryParams.get('gclid')),
            fbclid: sanitizeValue(queryParams.get('fbclid'))
        };

        if (campaign.source || campaign.medium || campaign.campaign || campaign.term || campaign.content || campaign.gclid || campaign.fbclid) {
            campaign.capturedAt = new Date().toISOString();
            return campaign;
        }

        return null;
    }

    function getStoredCampaign() {
        return safeJsonParse(safeStorageGet()) || {};
    }

    function persistCampaign(campaign) {
        if (!campaign) {
            return;
        }

        safeStorageSet(JSON.stringify(campaign));
    }

    function buildBaseContext(options) {
        var queryParams = getQueryParams();
        var campaign = getStoredCampaign();
        var locale = sanitizeValue(options.locale || queryParams.get('locale') || document.documentElement.lang);
        var debugModeEnabled = !!window.iouAnalyticsDebugMode;

        return cleanParams({
            page_type: options.pageType,
            page_location: window.location.href,
            page_path: window.location.pathname,
            page_title: document.title,
            locale: locale,
            debug_mode: debugModeEnabled,
            campaign_source: campaign.source,
            campaign_medium: campaign.medium,
            campaign_name: campaign.campaign,
            campaign_term: campaign.term,
            campaign_content: campaign.content
        });
    }

    function dispatchEvent(name, params) {
        var eventParams = cleanParams(params || {});

        if (typeof window.gtag === 'function') {
            window.gtag('event', name, eventParams);
            return;
        }

        if (Array.isArray(window.dataLayer)) {
            window.dataLayer.push(Object.assign({ event: name }, eventParams));
        }
    }

    function trackEvent(name, options, params) {
        dispatchEvent(name, Object.assign({}, buildBaseContext(options), params || {}));
    }

    function trackLandingSignals(options) {
        var queryParams = getQueryParams();
        var campaignFromQuery = getCampaignFromQuery(queryParams);
        var referrerHost = null;

        persistCampaign(campaignFromQuery);

        if (document.referrer) {
            try {
                referrerHost = new window.URL(document.referrer).hostname;
            } catch (error) {
                referrerHost = sanitizeValue(document.referrer);
            }
        }

        trackEvent('page_context', options, {
            has_utm: !!campaignFromQuery,
            has_referrer: !!document.referrer,
            referrer_host: referrerHost
        });

        if (campaignFromQuery || document.referrer) {
            trackEvent('traffic_origin_detected', options, {
                origin_type: campaignFromQuery ? 'campaign' : 'referrer_only',
                referrer_host: referrerHost
            });
        }
    }

    function bindTrackedClicks(options, clickDefinitions) {
        (clickDefinitions || []).forEach(function (definition) {
            var elements = document.querySelectorAll(definition.selector);

            Array.prototype.forEach.call(elements, function (element) {
                element.addEventListener('click', function () {
                    var params = typeof definition.params === 'function'
                        ? definition.params(element)
                        : (definition.params || {});

                    trackEvent(definition.eventName, options, params);
                });
            });
        });
    }

    function observeSections(options, sections) {
        if (!window.IntersectionObserver || !sections || !sections.length) {
            return;
        }

        var seenSections = {};
        var observer = new window.IntersectionObserver(function (entries) {
            entries.forEach(function (entry) {
                var sectionName = entry.target.getAttribute('data-analytics-section') || entry.target.id;

                if (!entry.isIntersecting || seenSections[sectionName]) {
                    return;
                }

                seenSections[sectionName] = true;
                trackEvent('section_view', options, {
                    section_name: sectionName
                });
            });
        }, {
            threshold: 0.55
        });

        sections.forEach(function (selector) {
            var element = document.querySelector(selector);
            if (element) {
                observer.observe(element);
            }
        });
    }

    function trackScrollDepth(options) {
        var triggered = {};

        function handler() {
            var doc = document.documentElement;
            var scrollHeight = Math.max(doc.scrollHeight, document.body.scrollHeight) - window.innerHeight;
            var progress = scrollHeight > 0 ? Math.round((window.scrollY / scrollHeight) * 100) : 100;

            scrollMilestones.forEach(function (milestone) {
                if (!triggered[milestone] && progress >= milestone) {
                    triggered[milestone] = true;
                    trackEvent('scroll_depth', options, {
                        percent_scrolled: milestone
                    });
                }
            });
        }

        window.addEventListener('scroll', handler, { passive: true });
        handler();
    }

    function decorateShareUrl(baseUrl, params) {
        var url = new window.URL(baseUrl, window.location.origin);

        Object.keys(params).forEach(function (key) {
            if (params[key] !== null && params[key] !== undefined && params[key] !== '') {
                url.searchParams.set(key, params[key]);
            }
        });

        return url.toString();
    }

    window.iouAnalytics = {
        init: function (options) {
            var settings = options || {};

            trackLandingSignals(settings);
            bindTrackedClicks(settings, settings.clicks || []);
            observeSections(settings, settings.sections || []);

            if (settings.trackScrollDepth) {
                trackScrollDepth(settings);
            }
        },
        track: function (eventName, options, params) {
            trackEvent(eventName, options || {}, params || {});
        },
        decorateShareUrl: decorateShareUrl
    };
})(window, document);