/**
 * Client analytics: GTM bootstrap, Consent Mode v2, dataLayer helpers.
 *
 * Setup (ops) — also documented on PUBLIC_GTM_ID in root `.env.example`:
 * 1. Create a GA4 property in Google Analytics.
 * 2. Create a GTM web container; set PUBLIC_GTM_ID=GTM-XXXX in root `.env`.
 * 3. In GTM: GA4 Configuration tag with Consent Settings requiring
 *    analytics_storage (and ad_* for ads tags); publish the container.
 * 4. SPA page views: Custom Event trigger `page_view` (from afterNavigate).
 *    Do NOT also enable GTM History Change / enhanced measurement page_view —
 *    that would double-count.
 *
 * Primary loading is GTM only — do not hard-code a GA measurement ID here.
 */

import { browser } from "$app/environment";
import { env } from "$env/dynamic/public";
import {
	CONSENT_STORAGE_KEY,
	CONSENT_WAIT_FOR_UPDATE_MS,
	DENIED_CONSENT_DEFAULTS,
	parseStoredConsent,
	preferencesToConsentSignals,
	type ConsentModeSignals,
	type ConsentPreferences
} from "./analytics/consent-mode";
import { resolveGtmId } from "./analytics/gtm-id";
import {
	toEcommerceObject,
	type Ga4EcommerceFields
} from "./analytics/ecommerce";

export type { ConsentModeSignals, ConsentPreferences };
export type { Ga4EcommerceFields, Ga4EcommerceItem, Ga4ItemCategory } from "./analytics/ecommerce";
export {
	CONSENT_STORAGE_KEY,
	CONSENT_VERSION,
	acceptAllPreferences,
	estimatedSkusBucket,
	parseStoredConsent,
	preferencesToConsentSignals,
	rejectNonEssentialPreferences,
	serializeConsent
} from "./analytics/consent-mode";
export { resolveGtmId } from "./analytics/gtm-id";
export {
	buildCreditPackEcommerce,
	buildSubscriptionEcommerce,
	claimPurchaseTracking,
	resolveCheckoutEcommerceFromParams,
	safeCheckoutSessionId
} from "./analytics/ecommerce";

type DataLayer = Array<Record<string, unknown> | IArguments | unknown[]>;

declare global {
	interface Window {
		dataLayer?: DataLayer;
		gtag?: (...args: unknown[]) => void;
		__descrybeGtmLoaded?: string;
		__descrybeConsentDefaulted?: boolean;
	}
}

function ensureDataLayer(): DataLayer {
	if (!browser) return [];
	window.dataLayer = window.dataLayer ?? [];
	return window.dataLayer;
}

function ensureGtag(): void {
	if (!browser) return;
	ensureDataLayer();
	if (typeof window.gtag === "function") return;
	window.gtag = function gtag(...args: unknown[]) {
		ensureDataLayer().push(args);
	};
}

/** True when the user granted analytics_storage via the CMP. */
export function isAnalyticsGranted(): boolean {
	if (!browser) return false;
	try {
		const stored = parseStoredConsent(localStorage.getItem(CONSENT_STORAGE_KEY));
		return stored?.analytics === true;
	} catch {
		return false;
	}
}

/** Call before GTM injects — EU/EEA default denied until CMP update. */
export function ensureConsentDefaults(): void {
	if (!browser || window.__descrybeConsentDefaulted) return;
	ensureGtag();
	window.gtag?.("consent", "default", {
		...DENIED_CONSENT_DEFAULTS,
		wait_for_update: CONSENT_WAIT_FOR_UPDATE_MS
	});
	window.__descrybeConsentDefaulted = true;
}

export function updateConsentMode(prefs: ConsentPreferences): void {
	if (!browser) return;
	ensureGtag();
	ensureConsentDefaults();
	const signals = preferencesToConsentSignals(prefs);
	window.gtag?.("consent", "update", signals);
	pushDataLayer({
		event: "consent_update",
		analytics_storage: signals.analytics_storage,
		ad_storage: signals.ad_storage,
		ad_user_data: signals.ad_user_data,
		ad_personalization: signals.ad_personalization
	});
}

export function pushDataLayer(payload: Record<string, unknown>): void {
	if (!browser) return;
	ensureDataLayer().push(payload);
}

/**
 * Custom event helper. No-ops until analytics_storage is granted via CMP.
 * Never pass email, password, tokens, names, phone, SKU/GTIN/title, or API keys.
 */
export function trackEvent(event: string, params?: Record<string, unknown>): void {
	if (!browser) return;
	if (!isAnalyticsGranted()) return;
	const name = event.trim();
	if (!name) return;
	pushDataLayer({
		event: name,
		...(params ?? {})
	});
}

/**
 * GA4 ecommerce custom event (GTM). Clears prior ecommerce, then pushes
 * `{ event, ecommerce: { currency?, value?, transaction_id?, items } }`.
 * Consent-gated like trackEvent. Never pass PII (email, cus_*, names).
 */
export function trackEcommerceEvent(
	event: string,
	ecommerce: Ga4EcommerceFields,
	extra?: Record<string, unknown>
): void {
	if (!browser) return;
	if (!isAnalyticsGranted()) return;
	const name = event.trim();
	if (!name) return;
	pushDataLayer({ ecommerce: null });
	pushDataLayer({
		event: name,
		ecommerce: toEcommerceObject(ecommerce),
		...(extra ?? {})
	});
}

/**
 * SPA page_view for GTM (Custom Event trigger: page_view).
 * Gated on analytics consent. Prefer this over GTM History Change.
 */
export function trackPageview(path: string, opts?: { title?: string; location?: string }): void {
	if (!browser) return;
	if (!isAnalyticsGranted()) return;
	pushDataLayer({
		event: "page_view",
		page_path: path,
		page_title: opts?.title ?? document.title,
		page_location: opts?.location ?? window.location.href
	});
}

export function resolveConfiguredGtmId(): string | null {
	return resolveGtmId(env.PUBLIC_GTM_ID);
}

/** Load GTM container once when PUBLIC_GTM_ID is a valid GTM-XXXX id. */
export function loadGoogleTagManager(gtmId = resolveConfiguredGtmId()): string | null {
	if (!browser) return null;
	const id = resolveGtmId(gtmId);
	if (!id) return null;
	if (window.__descrybeGtmLoaded === id) return id;

	ensureConsentDefaults();
	ensureDataLayer().push({ "gtm.start": Date.now(), event: "gtm.js" });

	const script = document.createElement("script");
	script.async = true;
	script.src = `https://www.googletagmanager.com/gtm.js?id=${encodeURIComponent(id)}`;
	document.head.appendChild(script);

	window.__descrybeGtmLoaded = id;
	return id;
}