/**
 * Utility class for accessibility-related checks and helpers.
 * Provides methods to detect user preferences for reduced motion,
 * screen reader usage, and other accessibility settings.
 */
export default class AccessibilityUtils {
	private static _shouldSkipAnimation: boolean | null = null;
	private static _hasScreenReader: boolean | null = null;
	private static _hasForcedColors: boolean | null = null;
	private static _prefersReducedMotion: boolean | null = null;

	/**
	 * Checks if animations should be skipped for accessibility reasons.
	 * Results are cached after first call for performance.
	 *
	 * Returns true if:
	 * - User prefers reduced motion (OS setting)
	 * - Screen reader is likely active (detected via various heuristics)
	 * - High contrast / forced colors mode is active
	 */
	static shouldSkipAnimation(): boolean {
		// Return cached result if available
		if (this._shouldSkipAnimation !== null) {
			return this._shouldSkipAnimation;
		}

		// SSR safety check
		if (typeof window === 'undefined') {
			return false;
		}

		let shouldSkip = false;

		// Check for reduced motion preference
		if (this.prefersReducedMotion()) {
			shouldSkip = true;
		}

		// Check for screen reader
		if (!shouldSkip && this.hasScreenReader()) {
			shouldSkip = true;
		}

		// 3. Check for forced-colors mode (high contrast) - often used with screen readers
		if (!shouldSkip && this.hasForcedColors()) {
			shouldSkip = true;
		}

		// Cache the result
		this._shouldSkipAnimation = shouldSkip;

		return shouldSkip;
	}

	/**
	 * Clears the cached accessibility check result.
	 * Useful if you need to re-evaluate after user changes settings.
	 */
	static clearCache(): void {
		this._shouldSkipAnimation = null;
		this._hasScreenReader = null;
		this._hasForcedColors = null;
		this._prefersReducedMotion = null;
	}

	/**
	 * Checks if the user prefers reduced motion.
	 * This is a simpler check that only looks at the OS preference.
	 */
	static prefersReducedMotion(): boolean {
		if (this._prefersReducedMotion != null) {
			return this._prefersReducedMotion;
		}

		if (typeof window === 'undefined') {
			return false;
		}

		this._prefersReducedMotion = window.matchMedia?.('(prefers-reduced-motion: reduce)').matches ?? false;
		return this._prefersReducedMotion;
	}

	/**
	 * Checks if high contrast / forced colors mode is active.
	 */
	static hasForcedColors(): boolean {
		if (this._hasForcedColors != null) {
			return this._hasForcedColors;
		}

		if (typeof window === 'undefined') {
			return false;
		}

		this._hasForcedColors = window.matchMedia?.('(forced-colors: active)').matches ?? false;
		return this._hasForcedColors;
	}

	/**
	 * Checks if screen reader is active
	 * Note: Direct screen reader detection is intentionally limited for privacy,
	 * but these heuristics catch common cases
	 */
	static hasScreenReader(): boolean {
		if (this._hasScreenReader != null) {
			return this._hasScreenReader;
		}

		if (typeof window === 'undefined') {
			return false;
		}

		// 1. Check if accessibility object model is available and indicates assistive tech
		if ((navigator as any).accessibilityFeatures?.screenReader?.enabled) {
			this._hasScreenReader = true;
			return true;
		}

		const ua = navigator.userAgent.toLowerCase();
		if (ua.includes('nvda') || ua.includes('jaws') || ua.includes('voiceover')) {
			this._hasScreenReader = true;
			return true;
		}

		this._hasScreenReader = false;
		return false;
	}
}