// Lightweight Postal API client
// Sends messages via Postal /api/v1/send/message
// Requires env: POSTAL_URL, POSTAL_API_KEY, POSTAL_FROM, optional POSTAL_FROM_NAME, POSTAL_REPLY_TO

import dotenv from 'dotenv'
dotenv.config()

let _fetch = null

async function getFetch() {
  if (typeof globalThis.fetch === 'function') return globalThis.fetch
  if (_fetch) return _fetch
  try {
    const mod = await import('node-fetch')
    _fetch = mod.default
    return _fetch
  } catch (e) {
    throw new Error('fetch is not available and node-fetch is not installed. Please install node-fetch or use Node 18+.')
  }
}

function ensureArray(v) {
  if (!v) return []
  if (Array.isArray(v)) return v
  if (typeof v === 'string') return v.split(/[;,]/).map(s => s.trim()).filter(Boolean)
  return [String(v)]
}

function fmtFromAddress(email, name) {
  const e = String(email || '').trim()
  const n = String(name || '').trim()
  if (!e) return ''
  return n ? `${n} <${e}>` : e
}

export async function sendPostalEmail({ to, subject, text, html, cc = [], bcc = [] }) {
  const base = (process.env.POSTAL_URL || '').replace(/\/$/, '')
  const apiKey = process.env.POSTAL_API_KEY || ''
  const fromEmail = process.env.POSTAL_FROM || ''
  const fromName = process.env.POSTAL_FROM_NAME || ''
  const replyTo = process.env.POSTAL_REPLY_TO || ''

  if (!base || !apiKey || !fromEmail) {
    throw new Error('Postal configuration missing: POSTAL_URL, POSTAL_API_KEY, POSTAL_FROM are required')
  }

  const endpoint = `${base}/api/v1/send/message`
  const payload = {
    api_key: apiKey,
    from: fmtFromAddress(fromEmail, fromName),
    to: ensureArray(to),
    subject: subject || '',
    html_body: html || undefined,
    plain_body: text || undefined,
  }
  const ccArr = ensureArray(cc)
  const bccArr = ensureArray(bcc)
  if (ccArr.length) payload.cc = ccArr
  if (bccArr.length) payload.bcc = bccArr
  if (replyTo) payload.reply_to = replyTo

  const fetchImpl = await getFetch()
  const res = await fetchImpl(endpoint, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify(payload),
  })

  let data
  try {
    data = await res.json()
  } catch (e) {
    throw new Error(`Postal response parse error: HTTP ${res.status}`)
  }
  if (!res.ok || data?.status !== 'success') {
    const errMsg = data?.data?.message || data?.message || JSON.stringify(data)
    throw new Error(`Postal send failed: ${errMsg}`)
  }
  return data
}