import { promises as fs } from 'fs'
import path from 'path'
import { randomUUID } from 'crypto'

export interface EmailAttachment {
  filename: string
  content: Buffer
  cid: string
}

interface AgentEmailParams {
  agentName: string
  content: string
  appUrl: string
  userName?: string
}

/**
 * Read a local image file from the public directory.
 */
async function readLocalImage(relativePath: string): Promise<Buffer | null> {
  try {
    const filePath = path.join(process.cwd(), 'public', relativePath)
    return await fs.readFile(filePath)
  } catch {
    return null
  }
}

/**
 * Convert markdown to simple HTML suitable for email clients.
 * Replaces local image references with cid: placeholders for inline attachments.
 * Returns the HTML and a list of attachments to include.
 */
export async function markdownToEmailHtml(md: string, appUrl: string): Promise<{ html: string; attachments: EmailAttachment[] }> {
  let html = md
  const attachments: EmailAttachment[] = []
  const baseUrl = appUrl.replace(/\/$/, '')

  // Remove the execution footer (agent trace)
  html = html.replace(/\n---\n\n_\$Agent execution:[\s\S]*$/, '')
  html = html.replace(/\n---\n\n_Agent execution:[\s\S]*$/, '')

  // Horizontal rules
  html = html.replace(/^---+$/gm, '<hr style="border:none;border-top:1px solid #e5e7eb;margin:20px 0;">')

  // Headings
  html = html.replace(/^### (.+)$/gm, '<h3 style="margin:16px 0 8px;font-size:15px;font-weight:600;color:#1f2937;">$1</h3>')
  html = html.replace(/^## (.+)$/gm, '<h2 style="margin:20px 0 10px;font-size:16px;font-weight:700;color:#111827;">$1</h2>')
  html = html.replace(/^# (.+)$/gm, '<h1 style="margin:0 0 16px;font-size:18px;font-weight:700;color:#111827;">$1</h1>')

  // Bold and italic
  html = html.replace(/\*\*(.+?)\*\*/g, '<strong>$1</strong>')
  html = html.replace(/\*(.+?)\*/g, '<em style="color:#6b7280;">$1</em>')

  // Unordered list items
  html = html.replace(/^(\s*)[-*] (.+)$/gm, '$1<li style="margin:4px 0;padding-left:4px;">$2</li>')

  // Wrap consecutive <li> in <ul>
  html = html.replace(/((?:<li[^>]*>.*?<\/li>\s*)+)/g, (match) => {
    return '<ul style="margin:8px 0;padding-left:20px;list-style-type:disc;">' + match + '</ul>'
  })

  // Images ![alt](url) — local images become CID attachments, external stay as-is
  const imageMatches = [...html.matchAll(/!\[([^\]]*)\]\(([^)]+)\)/g)]
  for (const match of imageMatches) {
    const [fullMatch, alt, url] = match
    let imgTag: string

    if (url.startsWith('/uploads/')) {
      // Local image: read file and attach as CID
      const buffer = await readLocalImage(url)
      if (buffer) {
        const cid = `img-${randomUUID()}`
        const ext = path.extname(url).toLowerCase() || '.jpg'
        attachments.push({ filename: `image${ext}`, content: buffer, cid })
        imgTag = `<img src="cid:${cid}" alt="${alt}" style="max-width:100%;border-radius:8px;margin:12px 0;" />`
      } else {
        // Fallback to absolute URL if file not found
        imgTag = `<img src="${baseUrl}${url}" alt="${alt}" style="max-width:100%;border-radius:8px;margin:12px 0;" />`
      }
    } else {
      imgTag = `<img src="${url}" alt="${alt}" style="max-width:100%;border-radius:8px;margin:12px 0;" />`
    }
    html = html.replace(fullMatch, imgTag)
  }

  // Links
  html = html.replace(/\[([^\]]+)\]\(([^)]+)\)/g, (_match, text, url) => {
    const absoluteUrl = url.startsWith('/') ? `${baseUrl}${url}` : url
    return `<a href="${absoluteUrl}" style="color:#3b82f6;text-decoration:none;">${text}</a>`
  })

  // Paragraphs
  html = html.replace(/\n\n+/g, '</p><p style="margin:0 0 12px;">')
  html = html.replace(/\n/g, '<br>')
  html = '<p style="margin:0 0 12px;">' + html + '</p>'
  html = html.replace(/<p[^>]*>\s*<\/p>/g, '')

  return { html, attachments }
}

export async function getAgentEmailTemplate({ agentName, content, appUrl, userName }: AgentEmailParams): Promise<{ html: string; attachments: EmailAttachment[] }> {
  const greeting = userName ? `Bonjour ${userName},` : 'Bonjour,'
  const { html: htmlContent, attachments } = await markdownToEmailHtml(content, appUrl)

  // Extract a preview (first ~150 chars of plain text for subtitle)
  const plainText = content
    .replace(/^#{1,3}\s+/gm, '')
    .replace(/\*\*/g, '')
    .replace(/\[([^\]]+)\]\([^)]+\)/g, '$1')
    .replace(/[-*]\s+/g, '')
    .replace(/\n+/g, ' ')
    .trim()

  const html = `<!DOCTYPE html>
<html lang="fr">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>${agentName}</title>
  <style>
    body { font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif; line-height: 1.6; color: #374151; background: #f3f4f6; margin: 0; padding: 0; }
    .wrapper { width: 100%; background: #f3f4f6; padding: 32px 16px; }
    .container { max-width: 620px; margin: 0 auto; }
    .card { background: #ffffff; border-radius: 16px; overflow: hidden; box-shadow: 0 1px 3px rgba(0,0,0,0.08), 0 4px 12px rgba(0,0,0,0.04); }
    .card-header { background: linear-gradient(135deg, #1e293b 0%, #334155 100%); padding: 28px 32px; }
    .card-header h1 { margin: 0; font-size: 20px; font-weight: 700; color: #ffffff; }
    .card-header .subtitle { margin: 6px 0 0; font-size: 13px; color: #94a3b8; }
    .card-header .badge { display: inline-block; background: rgba(59,130,246,0.2); color: #93c5fd; font-size: 11px; font-weight: 600; padding: 3px 10px; border-radius: 9999px; margin-top: 10px; letter-spacing: 0.5px; text-transform: uppercase; }
    .card-body { padding: 28px 32px; font-size: 14px; color: #374151; }
    .card-footer { padding: 20px 32px; border-top: 1px solid #f1f5f9; text-align: center; background: #fafbfc; }
    .button { display: inline-block; padding: 12px 28px; background-color: #1e293b; color: #ffffff; text-decoration: none; border-radius: 10px; font-weight: 600; font-size: 14px; letter-spacing: 0.3px; }
    .button:hover { background-color: #334155; }
    .footer-text { margin-top: 20px; font-size: 12px; color: #9ca3af; text-align: center; }
    .footer-text a { color: #64748b; text-decoration: none; }
    .footer-text a:hover { text-decoration: underline; }
    .date { font-size: 12px; color: #9ca3af; margin-top: 4px; }
  </style>
</head>
<body>
  <div class="wrapper">
    <div class="container">
      <div class="card">
        <div class="card-header">
          <h1>${agentName}</h1>
          <div class="subtitle">${plainText.substring(0, 120)}${plainText.length > 120 ? '...' : ''}</div>
          <span class="badge">Synthèse automatique</span>
        </div>
        <div class="card-body">
          <p style="margin:0 0 8px;color:#6b7280;font-size:13px;">${greeting}</p>
          <p style="margin:0 0 20px;color:#6b7280;font-size:13px;">Votre agent <strong style="color:#1f2937;">${agentName}</strong> a terminé son exécution. Voici les résultats :</p>
          <hr style="border:none;border-top:1px solid #f1f5f9;margin:0 0 20px;">
          ${htmlContent}
        </div>
        <div class="card-footer">
          <a href="${appUrl}" class="button">Ouvrir dans Memento</a>
        </div>
      </div>
      <p class="footer-text">Cet email a été envoyé par votre agent Memento &middot; <a href="${appUrl}/agents">Gérer mes agents</a></p>
    </div>
  </div>
</body>
</html>`

  return { html, attachments }
}