/**
 * E2EE helpers — server never decrypts; only detects envelopes and opaques previews.
 */

const E2EE_PREVIEW = '🔒 پیام رمزنگاری‌شده'

function isE2eeEnvelope(content) {
  if (!content || typeof content !== 'string') return false
  const trimmed = content.trim()
  if (!trimmed.startsWith('{')) return false
  try {
    const parsed = JSON.parse(trimmed)
    return Boolean(parsed && parsed.e2ee === true && parsed.ciphertext)
  } catch {
    return false
  }
}

function opaquePreview(content, maxLen = 80) {
  if (isE2eeEnvelope(content)) return E2EE_PREVIEW
  const text = String(content || 'پیام')
  return text.slice(0, maxLen)
}

module.exports = {
  E2EE_PREVIEW,
  isE2eeEnvelope,
  opaquePreview
}