const base64url = require('base64-url')
const createHash = require('crypto').createHash
const forge = require('node-forge')
const NodeRSA = require('node-rsa')

const PRIVATE_KEY_PEM =
  '-----BEGIN RSA PRIVATE KEY-----\n' +
  'MIIEpAIBAAKCAQEApoocpO3bbUF6o8eyJlQCfwLahEsunWdVF++yOEyKu4Lp1j0m\n' +
  '2j/P7iHOtxBAkjdM2X2oW3qO1mR0sIFefqnm93g0q2nRuYEoS+W3o6X50wjOVm8f\n' +
  'r/tLqELzy5BoET0AQl7Axp1DNsb0HNOBcoIBt+xVY4I+k6uXJJJMzbgvahAgSLZ9\n' +
  'RW0Z0WT+dCHZpZUj0nLxNXIPdci65Bw6IognqXHP6AwKZXpT6jCzjzq9uyHxVcud\n' +
  'qw6j0kQw48/A5A6AN5fIVy1cKnd0sKdqRX1NUqVoiOrO4jaDB1IdLD+YmRE/JjOH\n' +
  'sWIMElYCPxKqnsNo6VCslGX/ziinArHhqRBrHwIDAQABAoIBAHAdmpsN5iLvafjI\n' +
  'f45+EBAhg6p8Uq102zx6CakNHniN8Y5hLL7RJtJRwDBNqKrGv93LUoQDRhXfGw+Y\n' +
  'iF0NVIhVTF/5pU8VPGOcCr0JB96ilwZpWRPIQW7NZAMu/GBeiMYls/IB/TXrSnv9\n' +
  'h6/nBfEkEXgkPqx7YA0m0L3NuV3U1lCY/LhBJY4Xvi0uRdqu3tTHXftehuPwC4UB\n' +
  '42eJTWv/qLeOlkCdUUV4f7+dNaES88Vdhj6lu/BusnNhvnwHQik4dNwzPCGeP8NV\n' +
  '5gaesWiNWFZuTURGKk1B65p5LzNPjsVT50RDuW8FnSZwIvNcohrX9ILPsmg/t0Kr\n' +
  'ozcOksECgYEA4XWOK4twx5RG162zveRHqU7H9RBWSz7/PzM9Eob9vx/tC/b1YqBR\n' +
  'VShk23vje19eNiYWAkxcpobIP4ek/0ZT8nHkJg8wl+J/hnXADcvwv2dKnoFnm5pn\n' +
  'rTBUKc8R3wrSlAV8XQAtdnxsfFa5AOQJ6WFVI9AdfH3Iw8XZk4gIIPMCgYEAvRlY\n' +
  'y80HnR3kwMOqY488V1qk41dmfNqa+YDL+zkPF1HhHI9VnK5BQuI7lyKJl984KwHu\n' +
  '0gbwx3Wp4XkD5JUboEpl5LnaLsjEWemjTaQWdvJHPd5wkJ0m/jRQ2YeT4g2gFu4y\n' +
  'Pi/pWkrzhnzQQVAmOdAm5Kj27LtDzp0lspw3uCUCgYEAw2YdvFGSgfZZW4147QeO\n' +
  'sAbON+9bysUjdMPUl10VR/LEgA0d6MdnFfX3S13Y7tDdlvJ1OrKxzcWcgaru7ism\n' +
  'kEXy5KVfiRNNUNx2gb6RvWEpA6zFfc9ZMXlkSAPlyjfX/1+tw/Bmdn0pjK2gk0wP\n' +
  '5wtrPameFInzWPD9O+a2nM8CgYBZ6UhgNs+M9B7FTQOiLQPa4R2PfwobCXIwef4D\n' +
  'KIE1bFgl1T02r2AWZi1BUkmr7ZXuVQ/xyx0HKbopm/mu4PruvxEtrPTB0/IQcleU\n' +
  'XhXUXqRjFXXePOrCaaubkqxNCn95B67aBLvmk8awxn3a4DocuQ0VIgWuT+gQwIWh\n' +
  'JEgWBQKBgQDKD+2Yh1/rUzu15lbPH0JSpozUinuFjePieR/4n+5CtEUxWJ2f0WeK\n' +
  's4XWWf2qgUccjpiGju2UR840mgWROoZ8BfSTd5tg1F7bo0HMgu2hu0RIRpZcRhsA\n' +
  'Cd0GrJvf1t0QIdDCXAy+RpgU1SLSq4Q6Lomc0WA5C5nBw9RKEUOV9A==\n' +
  '-----END RSA PRIVATE KEY-----\n'

const PUBLIC_KEY_PEM =
  '-----BEGIN PUBLIC KEY-----\n' +
  'MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEApoocpO3bbUF6o8eyJlQC\n' +
  'fwLahEsunWdVF++yOEyKu4Lp1j0m2j/P7iHOtxBAkjdM2X2oW3qO1mR0sIFefqnm\n' +
  '93g0q2nRuYEoS+W3o6X50wjOVm8fr/tLqELzy5BoET0AQl7Axp1DNsb0HNOBcoIB\n' +
  't+xVY4I+k6uXJJJMzbgvahAgSLZ9RW0Z0WT+dCHZpZUj0nLxNXIPdci65Bw6Iogn\n' +
  'qXHP6AwKZXpT6jCzjzq9uyHxVcudqw6j0kQw48/A5A6AN5fIVy1cKnd0sKdqRX1N\n' +
  'UqVoiOrO4jaDB1IdLD+YmRE/JjOHsWIMElYCPxKqnsNo6VCslGX/ziinArHhqRBr\n' +
  'HwIDAQAB\n' +
  '-----END PUBLIC KEY-----\n'

const createCertificate = ({
                             publicKey,
                             privateKey,
                             jwksOrigin
                           }) => {
  const cert = forge.pki.createCertificate()
  cert.publicKey = publicKey
  cert.serialNumber = '123'
  const attrs = [
    {
      name: 'commonName',
      value: `${jwksOrigin}`
    }
  ]
  cert.validity.notBefore = new Date()
  cert.validity.notAfter = new Date()
  cert.validity.notAfter.setFullYear(cert.validity.notBefore.getFullYear() + 1)
  cert.setSubject(attrs)
  cert.setIssuer(attrs)
  cert.sign(privateKey)
  return forge.pki.certificateToPem(cert)
}

const getCertThumbprint = (certificate) => {
  const shasum = createHash('sha1')
  const der = Buffer.from(certificate).toString('binary')
  shasum.update(der)
  return shasum.digest('base64')
}

const createKeyPair = () => {
  const privateKey = forge.pki.privateKeyFromPem(PRIVATE_KEY_PEM)
  const publicKey = forge.pki.publicKeyFromPem(PUBLIC_KEY_PEM)
  return {
    privateKey,
    publicKey
  }
}

const bnToB64 = (bn) => {
  let hex = BigInt(bn).toString(16)
  if (hex.length % 2) {
    hex = '0' + hex
  }

  const bin = []
  let i = 0
  let d
  let b
  while (i < hex.length) {
    d = parseInt(hex.slice(i, i + 2), 16)
    b = String.fromCharCode(d)
    bin.push(b)
    i += 2
  }

  return Buffer.from(bin.join(''), 'binary').toString('base64')
}

const setup = (jwksOrigin) => {
  const { privateKey, publicKey } = createKeyPair()
  const certPem = createCertificate({
    jwksOrigin,
    privateKey,
    publicKey
  })
  const certDer = forge.util.encode64(
    forge.asn1
      .toDer(forge.pki.certificateToAsn1(forge.pki.certificateFromPem(certPem)))
      .getBytes()
  )
  const thumbprint = base64url.encode(getCertThumbprint(certDer))

  const helperKey = new NodeRSA()
  helperKey.importKey(forge.pki.privateKeyToPem(privateKey))
  const { n: modulus, e: exponent } = helperKey.exportKey('components')

  return {
    privateKey: forge.pki.privateKeyToPem(privateKey),
    certDer: certDer,
    thumbPrint: thumbprint,
    exponent: bnToB64(exponent),
    modulus: modulus.toString('base64')
  }
}

module.exports = setup