import DOMPurify from 'isomorphic-dompurify';

/**
 * Splits plain text into paragraphs based on newlines.
 * Double newlines create new paragraphs, single newlines become <br>.
 * If the content already contains HTML block elements, returns as-is.
 */
function wrapInParagraphs(text: string): string {
	// Check if content already has block-level HTML elements
	const hasBlockElements = /<(p|div|h[1-6]|ul|ol|blockquote|pre|table|hr)[>\s]/i.test(text);
	if (hasBlockElements) {
		return text;
	}

	// Split on double newlines (paragraph breaks)
	const paragraphs = text.split(/\n\s*\n/);

	return paragraphs
		.map((para) => {
			const trimmed = para.trim();
			if (!trimmed) return '';
			// Convert single newlines to <br> within paragraphs
			const withBreaks = trimmed.replace(/\n/g, '<br>');
			return `<p>${withBreaks}</p>`;
		})
		.filter(Boolean)
		.join('\n');
}

/**
 * Sanitizes chapter HTML content with extended allowed tags.
 * More permissive than the description sanitizer to support
 * formatted novel content including headings, lists, and images.
 * Also wraps plain text in paragraph tags for better browser translate support.
 */
export function sanitizeChapterHtml(html: string): string {
	// First wrap in paragraphs if needed, then sanitize
	const wrapped = wrapInParagraphs(html);
	return DOMPurify.sanitize(wrapped, {
		ALLOWED_TAGS: [
			// Basic formatting
			'b',
			'i',
			'em',
			'strong',
			'u',
			's',
			'strike',
			'del',
			'ins',
			// Structure
			'p',
			'br',
			'hr',
			'div',
			'span',
			// Headings
			'h1',
			'h2',
			'h3',
			'h4',
			'h5',
			'h6',
			// Lists
			'ul',
			'ol',
			'li',
			// Quotes
			'blockquote',
			'q',
			'cite',
			// Preformatted
			'pre',
			'code',
			// Ruby (for Asian language annotations)
			'ruby',
			'rt',
			'rp',
			// Images
			'img',
			// Tables
			'table',
			'thead',
			'tbody',
			'tr',
			'th',
			'td'
		],
		ALLOWED_ATTR: [
			// Image attributes
			'src',
			'alt',
			'title',
			'width',
			'height',
			// Table attributes
			'colspan',
			'rowspan',
			// Generic styling (limited)
			'class'
		],
		ALLOW_DATA_ATTR: false
	});
}