How to use the @aws-crypto/client-node.decrypt function in @aws-crypto/client-node

export async function kmsRegionalDiscoveryLimitTest (ciphertext: string|Buffer) {
  const discovery = true
  // This provider will *only* decrypt for keys in the us-east-1 region.
  const clientProvider = limitRegions(['us-east-1'], getKmsClient)
  const keyring = new KmsKeyringNode({ clientProvider, discovery })

  const cleartext = await decrypt(keyring, ciphertext)

  return { ciphertext, cleartext }
}

}

  /* Find data to encrypt.  A simple string. */
  const cleartext = 'asdf'

  /* Encrypt the data. */
  const { result } = await encrypt(keyring, cleartext, { encryptionContext: context })

  /* Decrypt the data.
   * This decrypt call could be done with **any** of the 3 keyrings.
   * Here we use the multi-keyring, but
   * decrypt(kmsKeyring, result)
   * decrypt(aesKeyring, result)
   * would both work as well.
   */
  const { plaintext, messageHeader } = await decrypt(keyring, result)

  /* Grab the encryption context so you can verify it. */
  const { encryptionContext } = messageHeader

  /* Verify the encryption context.
   * If you use an algorithm suite with signing,
   * the Encryption SDK adds a name-value pair to the encryption context that contains the public key.
   * Because the encryption context might contain additional key-value pairs,
   * do not add a test that requires that all key-value pairs match.
   * Instead, verify that the key-value pairs you expect match.
   */
  Object
    .entries(context)
    .forEach(([key, value]) => {
      if (encryptionContext[key] !== value) throw new Error('Encryption Context does not match expected values')
    })

* See: https://docs.aws.amazon.com/encryption-sdk/latest/developer-guide/concepts.html#encryption-context
   */
  const context = {
    stage: 'demo',
    purpose: 'simple demonstration app',
    origin: 'us-west-2'
  }

  /* Find data to encrypt.  A simple string. */
  const cleartext = 'asdf'

  /* Encrypt the data. */
  const { result } = await encrypt(keyring, cleartext, { encryptionContext: context })

  /* Decrypt the data. */
  const { plaintext, messageHeader } = await decrypt(keyring, result)

  /* Grab the encryption context so you can verify it. */
  const { encryptionContext } = messageHeader

  /* Verify the encryption context.
   * If you use an algorithm suite with signing,
   * the Encryption SDK adds a name-value pair to the encryption context that contains the public key.
   * Because the encryption context might contain additional key-value pairs,
   * do not add a test that requires that all key-value pairs match.
   * Instead, verify that the key-value pairs you expect match.
   */
  Object
    .entries(context)
    .forEach(([key, value]) => {
      if (encryptionContext[key] !== value) throw new Error('Encryption Context does not match expected values')
    })

* the origin can identify a malicious actor.
   * See: https://docs.aws.amazon.com/encryption-sdk/latest/developer-guide/concepts.html#encryption-context
   */
  const context = {
    stage: 'demo',
    purpose: 'simple demonstration app',
    origin: 'us-west-2'
  }

  /* Find data to encrypt.  A simple string. */
  const cleartext = 'asdf'

  /* Encrypt the data. */
  const { result } = await encrypt(keyring, cleartext, { encryptionContext: context })
  /* Decrypt the data. */
  const { plaintext, messageHeader } = await decrypt(keyring, result)

  /* Grab the encryption context so you can verify it. */
  const { encryptionContext } = messageHeader

  /* Verify the encryption context.
   * If you use an algorithm suite with signing,
   * the Encryption SDK adds a name-value pair to the encryption context that contains the public key.
   * Because the encryption context might contain additional key-value pairs,
   * do not add a test that requires that all key-value pairs match.
   * Instead, verify that the key-value pairs you expect match.
   */
  Object
    .entries(context)
    .forEach(([key, value]) => {
      if (encryptionContext[key] !== value) throw new Error('Encryption Context does not match expected values')
    })

export async function kmsRegionalDiscoveryExcludeTest (ciphertext: string|Buffer) {
  const discovery = true
  // This provider will decrypt for keys in any region except us-east-1.
  const clientProvider = excludeRegions(['us-east-1'], getKmsClient)
  const keyring = new KmsKeyringNode({ clientProvider, discovery })

  const cleartext = await decrypt(keyring, ciphertext)

  return { ciphertext, cleartext }
}

* the origin can identify a malicious actor.
   * See: https://docs.aws.amazon.com/encryption-sdk/latest/developer-guide/concepts.html#encryption-context
   */
  const context = {
    stage: 'demo',
    purpose: 'simple demonstration app',
    origin: 'us-west-2'
  }

  /* Find data to encrypt.  A simple string. */
  const cleartext = 'asdf'

  /* Encrypt the data. */
  const { result } = await encrypt(keyring, cleartext, { encryptionContext: context })
  /* Decrypt the data. */
  const { plaintext, messageHeader } = await decrypt(keyring, result)

  /* Grab the encryption context so you can verify it. */
  const { encryptionContext } = messageHeader

  /* Verify the encryption context.
   * If you use an algorithm suite with signing,
   * the Encryption SDK adds a name-value pair to the encryption context that contains the public key.
   * Because the encryption context might contain additional key-value pairs,
   * do not add a test that requires that all key-value pairs match.
   * Instead, verify that the key-value pairs you expect match.
   */
  Object
    .entries(context)
    .forEach(([key, value]) => {
      if (encryptionContext[key] !== value) throw new Error('Encryption Context does not match expected values')
    })

export async function testDecryptVector ({ name, keysInfo, plainTextStream, cipherStream }: TestVectorInfo): Promise {
  try {
    const cmm = decryptMaterialsManagerNode(keysInfo)
    const knowGood: Buffer[] = []
    plainTextStream.on('data', (chunk: Buffer) => knowGood.push(chunk))
    const { plaintext } = await decrypt(cmm, cipherStream)
    const result = Buffer.concat(knowGood).equals(plaintext)
    return { result, name }
  } catch (err) {
    return { result: false, name, err }
  }
}