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"""A sample KmsClient implementation."""
import argparse
import base64
import os

import requests

import pyarrow as pa
import pyarrow.parquet as pq
import pyarrow.parquet.encryption as pe


class VaultClient(pe.KmsClient):
    """An example of a KmsClient implementation with master keys
    managed by Hashicorp Vault KMS.
    See Vault documentation: https://www.vaultproject.io/api/secret/transit
    Not for production use!
    """
    JSON_MEDIA_TYPE = "application/json; charset=utf-8"
    DEFAULT_TRANSIT_ENGINE = "/v1/transit/"
    WRAP_ENDPOINT = "encrypt/"
    UNWRAP_ENDPOINT = "decrypt/"
    TOKEN_HEADER = "X-Vault-Token"

    def __init__(self, kms_connection_config):
        """Create a VaultClient instance.

        Parameters
        ----------
        kms_connection_config : KmsConnectionConfig
           configuration parameters to connect to vault,
           e.g. URL and access token
        """
        pe.KmsClient.__init__(self)
        self.kms_url = kms_connection_config.kms_instance_url + \
            VaultClient.DEFAULT_TRANSIT_ENGINE
        self.kms_connection_config = kms_connection_config

    def wrap_key(self, key_bytes, master_key_identifier):
        """Call Vault to wrap key key_bytes with key
        identified by master_key_identifier."""
        endpoint = self.kms_url + VaultClient.WRAP_ENDPOINT
        headers = {VaultClient.TOKEN_HEADER:
                   self.kms_connection_config.key_access_token}
        r = requests.post(endpoint + master_key_identifier,
                          headers=headers,
                          data={'plaintext': base64.b64encode(key_bytes)})
        r.raise_for_status()
        r_dict = r.json()
        wrapped_key = r_dict['data']['ciphertext']
        return wrapped_key

    def unwrap_key(self, wrapped_key, master_key_identifier):
        """Call Vault to unwrap wrapped_key with key
        identified by master_key_identifier"""
        endpoint = self.kms_url + VaultClient.UNWRAP_ENDPOINT
        headers = {VaultClient.TOKEN_HEADER:
                   self.kms_connection_config.key_access_token}
        r = requests.post(endpoint + master_key_identifier,
                          headers=headers,
                          data={'ciphertext': wrapped_key})
        r.raise_for_status()
        r_dict = r.json()
        plaintext = r_dict['data']['plaintext']
        key_bytes = base64.b64decode(plaintext)
        return key_bytes


def parquet_write_read_with_vault(parquet_filename):
    """An example for writing an encrypted parquet and reading an
    encrypted parquet using master keys managed by Hashicorp Vault KMS.
    Note that for this implementation requests dependency is needed
    and environment properties VAULT_URL and VAULT_TOKEN should be set.
    Please enable the transit engine.
    """
    path = parquet_filename

    table = pa.Table.from_pydict({
        'a': pa.array([1, 2, 3]),
        'b': pa.array(['a', 'b', 'c']),
        'c': pa.array(['x', 'y', 'z'])
    })

    # Encrypt the footer with the footer key,
    # encrypt column `a` with one key
    # and column `b` with another key,
    # keep `c` plaintext
    footer_key_name = "footer_key"
    col_a_key_name = "col_a_key"
    col_b_key_name = "col_b_key"

    encryption_config = pe.EncryptionConfiguration(
        footer_key=footer_key_name,
        column_keys={
            col_a_key_name: ["a"],
            col_b_key_name: ["b"],
        })

    kms_connection_config = pe.KmsConnectionConfig(
        kms_instance_url=os.environ.get('VAULT_URL', ''),
        key_access_token=os.environ.get('VAULT_TOKEN', ''),
    )

    def kms_factory(kms_connection_configuration):
        return VaultClient(kms_connection_configuration)

    # Write with encryption properties
    crypto_factory = pe.CryptoFactory(kms_factory)
    file_encryption_properties = crypto_factory.file_encryption_properties(
        kms_connection_config, encryption_config)
    with pq.ParquetWriter(path,
                          table.schema,
                          encryption_properties=file_encryption_properties) \
            as writer:
        writer.write_table(table)

    # Read with decryption properties
    file_decryption_properties = crypto_factory.file_decryption_properties(
        kms_connection_config)
    result = pq.ParquetFile(
        path, decryption_properties=file_decryption_properties)
    result_table = result.read()
    assert table.equals(result_table)


def main():
    parser = argparse.ArgumentParser(
        description="Write and read an encrypted parquet using master keys "
        "managed by Hashicorp Vault.\nBefore using please enable the "
        "transit engine in Vault and set VAULT_URL and VAULT_TOKEN "
        "environment variables.")
    parser.add_argument('--filename', dest='filename', type=str,
                        default='/tmp/encrypted_table.vault.parquet',
                        help='Filename of the parquet file to be created '
                             '(default: /tmp/encrypted_table.vault.parquet')
    args = parser.parse_args()
    filename = args.filename
    parquet_write_read_with_vault(filename)


if __name__ == '__main__':
    main()