L402: Pay-per-call APIs

import express, { type Request as ExpressRequest, type Response as ExpressResponse } from 'express'
import { withPayment } from '@moneydevkit/replit/server/express'

const app = express()

function expressToFetchRequest(req: ExpressRequest): Request {
  const headers = new Headers()
  for (const [key, value] of Object.entries(req.headers)) {
    if (key.toLowerCase() === 'content-length') {
      continue
    }

    if (Array.isArray(value)) {
      value.forEach((item) => headers.append(key, item))
    } else if (value !== undefined) {
      headers.set(key, value)
    }
  }

  return new Request(`${req.protocol}://${req.get('host')}${req.originalUrl}`, {
    method: req.method,
    headers,
  })
}

async function sendFetchResponse(res: ExpressResponse, response: Response) {
  response.headers.forEach((value, key) => res.setHeader(key, value))
  res.status(response.status).send(Buffer.from(await response.arrayBuffer()))
}

const handler = async (req: Request) => {
  return Response.json({ content: 'Premium data' })
}

const paidHandler = withPayment(
  { amount: 100, currency: 'SAT' },
  handler,
)

app.get('/api/premium', async (req, res) => {
  const response = await paidHandler(expressToFetchRequest(req))
  await sendFetchResponse(res, response)
})

import express, { type Request as ExpressRequest, type Response as ExpressResponse } from 'express'
import { withDeferredSettlement, type SettleResult } from '@moneydevkit/replit/server/express'

const app = express()
app.use(express.json())

function expressToFetchRequest(req: ExpressRequest): Request {
  const headers = new Headers()
  for (const [key, value] of Object.entries(req.headers)) {
    if (key.toLowerCase() === 'content-length') {
      continue
    }

    if (Array.isArray(value)) {
      value.forEach((item) => headers.append(key, item))
    } else if (value !== undefined) {
      headers.set(key, value)
    }
  }

  const init: RequestInit = {
    method: req.method,
    headers,
  }

  if (req.method !== 'GET' && req.method !== 'HEAD' && req.body !== undefined) {
    init.body = typeof req.body === 'string' || Buffer.isBuffer(req.body)
      ? req.body
      : JSON.stringify(req.body)
  }

  return new Request(`${req.protocol}://${req.get('host')}${req.originalUrl}`, init)
}

async function sendFetchResponse(res: ExpressResponse, response: Response) {
  response.headers.forEach((value, key) => res.setHeader(key, value))
  res.status(response.status).send(Buffer.from(await response.arrayBuffer()))
}

const handler = async (req: Request, settle: () => Promise<SettleResult>) => {
  const { prompt } = await req.json()

  const result = await runAiInference(prompt)

  const { settled } = await settle()
  if (!settled) {
    return Response.json({ error: 'settlement_failed' }, { status: 500 })
  }

  return Response.json({ result })
}

const paidHandler = withDeferredSettlement(
  { amount: 100, currency: 'SAT' },
  handler,
)

app.post('/api/ai', async (req, res) => {
  const response = await paidHandler(expressToFetchRequest(req))
  await sendFetchResponse(res, response)
})