// Lightweight safe Markdown to HTML parsing function — shared by blog posts and AI itinerary results.
export function renderMarkdownToHtml(md: string): string {
  if (!md) return ''
  let html = md
    .replace(/&/g, '&')
    .replace(/</g, '&lt;')
    .replace(/>/g, '&gt;')

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

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

  // Headings
  html = html.replace(/^### (.*?)$/gm, '<h4 class="text-base font-heading font-bold text-pine mt-6 mb-2 lowercase">$1</h4>')
  html = html.replace(/^## (.*?)$/gm, '<h3 class="text-lg font-heading font-extrabold text-pine mt-8 mb-3 lowercase">$1</h3>')
  html = html.replace(/^# (.*?)$/gm, '<h2 class="text-xl font-heading font-extrabold text-pine mt-10 mb-4 lowercase">$1</h2>')

  // Bullet Lists
  html = html.replace(/^\* (.*?)$/gm, '<li class="ml-4 list-disc text-sm text-ink/80 leading-relaxed">$1</li>')
  html = html.replace(/^- (.*?)$/gm, '<li class="ml-4 list-disc text-sm text-ink/80 leading-relaxed">$1</li>')

  // Blockquotes
  html = html.replace(/^&gt; (.*?)$/gm, '<blockquote class="border-l-2 border-turquoise/40 pl-4 italic text-sm text-shutter my-3">$1</blockquote>')

  // Links
  html = html.replace(/\[(.*?)\]\((.*?)\)/g, '<a href="$2" class="text-turquoise hover:underline" target="_blank" rel="noopener">$1</a>')

  // Paragraphs
  const blocks = html.split(/\n\n+/)
  html = blocks.map(block => {
    const trimmed = block.trim()
    if (!trimmed) return ''
    if (trimmed.startsWith('<h') || trimmed.startsWith('<li') || trimmed.startsWith('<ul') || trimmed.startsWith('<ol') || trimmed.startsWith('<blockquote')) {
      return trimmed
    }
    return `<p class="leading-relaxed mb-4 text-sm sm:text-base text-ink/80 font-medium">${trimmed.replace(/\n/g, '<br/>')}</p>`
  }).join('\n')

  return html
}