// Input validation utilities
import { SESSION_TITLE_MAX_LENGTH, MESSAGE_MAX_LENGTH } from './constants';

/**
 * Validate session title
 * @param title Session title to validate
 * @returns Error message if invalid, null if valid
 */
export function validateSessionTitle(title: string): string | null {
	const trimmed = title.trim();

	if (trimmed.length === 0) {
		return 'Session title cannot be empty';
	}

	if (trimmed.length > SESSION_TITLE_MAX_LENGTH) {
		return `Session title must be ${SESSION_TITLE_MAX_LENGTH} characters or less`;
	}

	return null;
}

/**
 * Validate message content
 * @param content Message content to validate
 * @returns Error message if invalid, null if valid
 */
export function validateMessageContent(content: string): string | null {
	const trimmed = content.trim();

	if (trimmed.length === 0) {
		return 'Message cannot be empty';
	}

	if (trimmed.length > MESSAGE_MAX_LENGTH) {
		return `Message must be ${MESSAGE_MAX_LENGTH} characters or less`;
	}

	return null;
}

/**
 * Validate email format
 * @param email Email address to validate
 * @returns True if valid email format, false otherwise
 */
export function isValidEmail(email: string): boolean {
	const emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
	return emailRegex.test(email);
}

/**
 * Validate UUID format
 * @param uuid UUID string to validate
 * @returns True if valid UUID v4 format, false otherwise
 */
export function isValidUUID(uuid: string): boolean {
	const uuidRegex =
		/^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i;
	return uuidRegex.test(uuid);
}

/**
 * Sanitize HTML to prevent XSS
 * @param html HTML string to sanitize
 * @returns Sanitized HTML with dangerous tags removed
 */
export function sanitizeHtml(html: string): string {
	const div = document.createElement('div');
	div.textContent = html;
	return div.innerHTML;
}

/**
 * Truncate text to specified length with ellipsis
 * @param text Text to truncate
 * @param maxLength Maximum length
 * @returns Truncated text with ellipsis if needed
 */
export function truncate(text: string, maxLength: number): string {
	if (text.length <= maxLength) {
		return text;
	}
	return text.substring(0, maxLength - 3) + '...';
}