#!/usr/bin/env npx tsx
/**
 * MCP Email Outreach Tool — Monetized with SettleGrid
 *
 * A complete MCP server that sends and validates emails via Resend.
 * Fork this template, add your Resend API key, and deploy.
 *
 * Setup:
 *   1. npm install @settlegrid/mcp
 *   2. Set RESEND_API_KEY, SENDER_EMAIL, and SETTLEGRID_API_KEY in your env
 *   3. Register your tool at settlegrid.ai/dashboard/tools
 *   4. Run: npx tsx mcp-email-outreach.ts
 *
 * Pricing: 2 cents per email, 3 cents per template send, 1 cent per validation
 *   - Resend costs ~$0.0004/email on Pro plan ($20/50K emails)
 *   - 2 cents = ~50x margin on raw sends
 *   - Template sends include rendering, 3 cents = ~33x margin
 *   - Validation is lightweight DNS lookup, 1 cent = pure margin
 *
 * Revenue: You keep 95-100% (100% on Free tier, 95% on paid tiers)
 */

import { settlegrid } from '@settlegrid/mcp'

// ── SettleGrid Setup ────────────────────────────────────────────────────────

const sg = settlegrid.init({
  toolSlug: 'my-email-outreach', // Replace with your tool slug
  pricing: {
    defaultCostCents: 2,
    methods: {
      send_email: { costCents: 2, displayName: 'Send Email' },
      send_template: { costCents: 3, displayName: 'Send Template' },
      validate_email: { costCents: 1, displayName: 'Validate Email' },
    },
  },
})

// ── Resend API Helper ───────────────────────────────────────────────────────

async function resendPost(path: string, body: Record<string, unknown>): Promise<Record<string, unknown>> {
  const response = await fetch(`https://api.resend.com${path}`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json', Authorization: `Bearer ${process.env.RESEND_API_KEY!}` },
    body: JSON.stringify(body),
  })
  if (!response.ok) throw new Error(`Resend API returned ${response.status}: ${response.statusText}`)
  return response.json()
}

// ── Validation ──────────────────────────────────────────────────────────────

const EMAIL_RE = /^[^\s@]+@[^\s@]+\.[^\s@]+$/
const BLOCKED_DOMAINS = ['example.com', 'test.com', 'localhost', 'mailinator.com', 'guerrillamail.com']

function validateEmailAddr(email: string): void {
  if (!email || !EMAIL_RE.test(email)) throw new Error('A valid email address is required')
  const domain = email.split('@')[1].toLowerCase()
  if (BLOCKED_DOMAINS.includes(domain)) throw new Error(`Email domain "${domain}" is blocked`)
}

// ── Email Methods ───────────────────────────────────────────────────────────

interface SendArgs { to: string; subject: string; body: string; replyTo?: string }

async function sendEmail(args: SendArgs): Promise<{ result: { messageId: string; status: string } }> {
  validateEmailAddr(args.to)
  if (!args.subject || args.subject.trim().length === 0) throw new Error('Subject must be non-empty')
  if (args.subject.length > 200) throw new Error('Subject must be 200 characters or fewer')
  if (!args.body || args.body.trim().length === 0) throw new Error('Email body must be non-empty')
  if (args.body.length > 50_000) throw new Error('Email body exceeds 50,000 character limit')
  const data = await resendPost('/emails', {
    from: process.env.SENDER_EMAIL!, to: [args.to], subject: args.subject, html: args.body, reply_to: args.replyTo,
  })
  return { result: { messageId: (data.id as string) ?? '', status: 'sent' } }
}

const TEMPLATES: Record<string, string> = {
  welcome: '<h1>Welcome, {{name}}!</h1><p>Thanks for signing up. {{message}}</p>',
  followup: '<p>Hi {{name}},</p><p>Following up on our conversation. {{message}}</p><p>Best,<br/>{{sender}}</p>',
  announcement: '<h2>{{headline}}</h2><p>{{message}}</p><p><a href="{{link}}">Learn more</a></p>',
}

interface TemplateArgs { to: string; subject: string; templateName: string; variables: Record<string, string> }

async function sendTemplate(args: TemplateArgs): Promise<{ result: { messageId: string; status: string } }> {
  validateEmailAddr(args.to)
  if (!args.subject || args.subject.length > 200) throw new Error('Subject must be 1-200 characters')
  if (!args.templateName || !TEMPLATES[args.templateName]) {
    throw new Error(`Unknown template. Available: ${Object.keys(TEMPLATES).join(', ')}`)
  }
  let html = TEMPLATES[args.templateName]
  for (const [key, value] of Object.entries(args.variables ?? {})) {
    html = html.replace(new RegExp(`\\{\\{${key}\\}\\}`, 'g'), value)
  }
  const data = await resendPost('/emails', {
    from: process.env.SENDER_EMAIL!, to: [args.to], subject: args.subject, html,
  })
  return { result: { messageId: (data.id as string) ?? '', status: 'sent' } }
}

interface ValidateArgs { email: string }

async function validateEmail(args: ValidateArgs): Promise<{
  result: { email: string; valid: boolean; mxRecords: boolean; format: boolean }
}> {
  if (!args.email) throw new Error('Email address is required')
  const formatValid = EMAIL_RE.test(args.email)
  const domain = args.email.split('@')[1] ?? ''
  let mxRecords = false
  if (formatValid && domain) {
    try {
      const resp = await fetch(`https://dns.google/resolve?name=${domain}&type=MX`)
      const data = await resp.json()
      mxRecords = Array.isArray(data.Answer) && data.Answer.length > 0
    } catch { /* DNS lookup failed */ }
  }
  return { result: { email: args.email, valid: formatValid && mxRecords, mxRecords, format: formatValid } }
}

// ── Wrap with SettleGrid Billing ─────────────────────────────────────────────

export const billedSend = sg.wrap(sendEmail, { method: 'send_email' })
export const billedTemplate = sg.wrap(sendTemplate, { method: 'send_template' })
export const billedValidate = sg.wrap(validateEmail, { method: 'validate_email' })

// ── REST Alternative ────────────────────────────────────────────────────────
// import { settlegridMiddleware } from '@settlegrid/mcp/rest'
//
// const withBilling = settlegridMiddleware({
//   toolSlug: 'my-email-outreach',
//   pricing: {
//     defaultCostCents: 2,
//     methods: {
//       send_email: { costCents: 2 },
//       send_template: { costCents: 3 },
//       validate_email: { costCents: 1 },
//     },
//   },
// })
//
// export async function POST(request: Request) {
//   return withBilling(request, async () => {
//     const body = await request.json()
//     const result = await sendEmail(body)
//     return Response.json(result)
//   }, 'send_email')
// }