/**
 * Cloudflare Email Worker — versebyversewithnate.us
 *
 * Receives inbound emails to hello@ and nate@, forwards to Gmail,
 * and POSTs a parsed copy to the site admin inbox.
 *
 * CLOUDFLARE SETUP:
 *   1. Go to Email > Email Routing > Routes in your Cloudflare dashboard
 *   2. Add two "Custom address" rules:
 *        hello@versebyversewithnate.us  →  Send to Worker  →  this worker
 *        nate@versebyversewithnate.us   →  Send to Worker  →  this worker
 *   3. Make sure nmemmert@gmail.com is listed as a verified destination address
 *      (Email Routing > Destination addresses)
 *
 * WORKER ENVIRONMENT VARIABLES (Workers & Pages > this worker > Settings > Variables):
 *   GMAIL_FORWARD_ADDRESS  =  nmemmert@gmail.com
 *   WEBHOOK_URL            =  https://versebyversewithnate.us/api/inbound-email
 *   WEBHOOK_SECRET         =  <a long random string — must match INBOUND_EMAIL_SECRET on the server>
 *
 * SERVER ENVIRONMENT VARIABLE (set in your server host / .env):
 *   INBOUND_EMAIL_SECRET   =  <same long random string as WEBHOOK_SECRET above>
 */

export default {
  async email(message, env, ctx) {
    const forwardPromise = message.forward(env.GMAIL_FORWARD_ADDRESS)

    const rawEmail = await streamToText(message.raw)

    const parsed = parseEmail(rawEmail, message)

    const webhookPromise = fetch(env.WEBHOOK_URL, {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
        'X-Webhook-Secret': env.WEBHOOK_SECRET,
      },
      body: JSON.stringify(parsed),
    }).catch(err => console.error('[email-worker] webhook failed:', err.message))

    await Promise.all([forwardPromise, webhookPromise])
  },
}

async function streamToText(stream) {
  const reader = stream.getReader()
  const chunks = []
  while (true) {
    const { done, value } = await reader.read()
    if (done) break
    chunks.push(value)
  }
  const bytes = new Uint8Array(chunks.reduce((acc, c) => acc + c.length, 0))
  let offset = 0
  for (const chunk of chunks) {
    bytes.set(chunk, offset)
    offset += chunk.length
  }
  return new TextDecoder().decode(bytes)
}

function parseEmail(raw, message) {
  const lines = raw.split(/\r?\n/)

  // Parse headers (everything before the first blank line)
  const headers = {}
  let bodyStart = 0
  for (let i = 0; i < lines.length; i++) {
    if (lines[i].trim() === '') {
      bodyStart = i + 1
      break
    }
    const colon = lines[i].indexOf(':')
    if (colon > 0) {
      const key = lines[i].slice(0, colon).trim().toLowerCase()
      const val = lines[i].slice(colon + 1).trim()
      if (!headers[key]) headers[key] = val
    }
  }

  const subject = decodeHeaderValue(headers['subject'] ?? '(no subject)')
  const from = message.from ?? headers['from'] ?? ''
  const to = message.to ?? headers['to'] ?? ''
  const date = headers['date'] ?? new Date().toISOString()
  const messageId = headers['message-id'] ?? ''

  // Extract plain text body — skip MIME boundaries and HTML parts
  const bodyLines = lines.slice(bodyStart)
  const plainText = extractPlainText(raw, bodyLines)

  return {
    from,
    to,
    subject,
    body: plainText,
    date,
    messageId,
    source: 'inbound-email',
  }
}

function extractPlainText(raw, bodyLines) {
  // Look for Content-Type: text/plain section in multipart emails
  const textPlainMatch = /Content-Type: text\/plain[^\r\n]*\r?\n(?:[^\r\n]+\r?\n)*\r?\n([\s\S]*?)(?=--|\z)/i.exec(raw)
  if (textPlainMatch) {
    return decodeEmailBody(textPlainMatch[1]).trim()
  }

  // Fallback: join body lines, strip HTML tags if present
  const joined = bodyLines.join('\n')
  if (/<[a-z][\s\S]*>/i.test(joined)) {
    return joined.replace(/<[^>]+>/g, '').replace(/&nbsp;/g, ' ').replace(/&amp;/g, '&').replace(/\s{3,}/g, '\n\n').trim()
  }

  return joined.trim()
}

function decodeEmailBody(text) {
  // Handle quoted-printable encoding (=XX hex sequences and soft line breaks)
  return text
    .replace(/=\r?\n/g, '')
    .replace(/=([0-9A-Fa-f]{2})/g, (_, hex) => String.fromCharCode(parseInt(hex, 16)))
}

function decodeHeaderValue(value) {
  // Handle encoded words: =?UTF-8?B?...?= or =?UTF-8?Q?...?=
  return value.replace(/=\?([^?]+)\?([BQ])\?([^?]*)\?=/gi, (_, charset, encoding, encoded) => {
    try {
      if (encoding.toUpperCase() === 'B') {
        const binary = atob(encoded)
        return new TextDecoder(charset).decode(Uint8Array.from(binary, c => c.charCodeAt(0)))
      }
      if (encoding.toUpperCase() === 'Q') {
        return encoded.replace(/_/g, ' ').replace(/=([0-9A-Fa-f]{2})/g, (_, hex) => String.fromCharCode(parseInt(hex, 16)))
      }
    } catch {
      return encoded
    }
    return encoded
  })
}