/**
 * Lightweight markdown to HTML converter for uni-app rich-text component.
 * Supports: headings, bold, italic, inline code, code blocks,
 *           unordered lists, ordered lists, blockquotes, horizontal rules, line breaks.
 */

function escapeHtml(str) {
	return str
		.replace(/&/g, '&')
		.replace(/</g, '&lt;')
		.replace(/>/g, '&gt;')
		.replace(/"/g, '&quot;')
}

/**
 * Convert markdown string to HTML string.
 * @param {string} text
 * @returns {string}
 */
export function renderMarkdown(text) {
	if (!text) return ''

	// 1. Protect code blocks first (```)
	const codeBlocks = []
	let html = text.replace(/```([\w]*)\n?([\s\S]*?)```/g, (_, lang, code) => {
		const idx = codeBlocks.length
		const escaped = escapeHtml(code.replace(/^\n/, '').replace(/\n$/, ''))
		const langAttr = lang ? ` class="language-${lang}"` : ''
		codeBlocks.push(`<pre><code${langAttr}>${escaped}</code></pre>`)
		return `\x00CODE${idx}\x00`
	})

	// 2. Escape remaining HTML to prevent injection
	html = html.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;')

	// 3. Protect inline code (`)
	const inlineCodes = []
	html = html.replace(/`([^`\n]+)`/g, (_, code) => {
		const idx = inlineCodes.length
		inlineCodes.push(`<code>${escapeHtml(code)}</code>`)
		return `\x00INLINE${idx}\x00`
	})

	// 4. Headings (must be at line start)
	html = html.replace(/^#{4,6} (.+)$/gm, '<h6>$1</h6>')
	html = html.replace(/^### (.+)$/gm, '<h3>$1</h3>')
	html = html.replace(/^## (.+)$/gm, '<h2>$1</h2>')
	html = html.replace(/^# (.+)$/gm, '<h1>$1</h1>')

	// 5. Horizontal rules
	html = html.replace(/^[ \t]*(?:---+|===+|\*\*\*+)[ \t]*$/gm, '<hr/>')

	// 6. Blockquotes
	html = html.replace(/^&gt; ?(.*)$/gm, '<blockquote>$1</blockquote>')

	// 7. Bold + Italic
	html = html.replace(/\*\*\*(.+?)\*\*\*/g, '<strong><em>$1</em></strong>')
	html = html.replace(/___(.+?)___/g, '<strong><em>$1</em></strong>')

	// 8. Bold
	html = html.replace(/\*\*(.+?)\*\*/g, '<strong>$1</strong>')
	html = html.replace(/__(.+?)__/g, '<strong>$1</strong>')

	// 9. Italic
	html = html.replace(/\*(.+?)\*/g, '<em>$1</em>')
	html = html.replace(/_(.+?)_/g, '<em>$1</em>')

	// 10. Lists — collect consecutive list lines into <ul> or <ol>
	const lines = html.split('\n')
	const result = []
	let inUl = false
	let inOl = false

	for (let i = 0; i < lines.length; i++) {
		const line = lines[i]
		const ulMatch = line.match(/^[ \t]*[-*+] (.+)$/)
		const olMatch = line.match(/^[ \t]*\d+\. (.+)$/)

		if (ulMatch) {
			if (!inUl) {
				if (inOl) { result.push('</ol>'); inOl = false }
				result.push('<ul>')
				inUl = true
			}
			result.push(`<li>${ulMatch[1]}</li>`)
		} else if (olMatch) {
			if (!inOl) {
				if (inUl) { result.push('</ul>'); inUl = false }
				result.push('<ol>')
				inOl = true
			}
			result.push(`<li>${olMatch[1]}</li>`)
		} else {
			if (inUl) { result.push('</ul>'); inUl = false }
			if (inOl) { result.push('</ol>'); inOl = false }
			result.push(line)
		}
	}
	if (inUl) result.push('</ul>')
	if (inOl) result.push('</ol>')

	html = result.join('\n')

	// 11. Paragraphs — split by blank lines, wrap plain text blocks in <p>
	const blocks = html.split(/\n{2,}/)
	html = blocks.map(block => {
		block = block.trim()
		if (!block) return ''
		// Already wrapped in a block-level tag — leave as-is
		if (/^<(h[1-6]|ul|ol|li|pre|blockquote|hr)[\s/>]/.test(block)) return block
		// Has multiple lines → join with <br/>
		block = block.replace(/\n/g, '<br/>')
		return `<p>${block}</p>`
	}).join('\n')

	// 12. Restore inline codes and code blocks
	inlineCodes.forEach((code, idx) => {
		html = html.replace(`\x00INLINE${idx}\x00`, code)
	})
	codeBlocks.forEach((code, idx) => {
		html = html.replace(`\x00CODE${idx}\x00`, code)
	})

	return html
}