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import snowflake.connector
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import serialization

from airflow.hooks.dbapi_hook import DbApiHook


class SnowflakeHook(DbApiHook):
    """
    Interact with Snowflake.

    get_sqlalchemy_engine() depends on snowflake-sqlalchemy

    """

    conn_name_attr = 'snowflake_conn_id'
    default_conn_name = 'snowflake_default'
    supports_autocommit = True

    def __init__(self, *args, **kwargs):
        super(SnowflakeHook, self).__init__(*args, **kwargs)
        self.account = kwargs.pop("account", None)
        self.warehouse = kwargs.pop("warehouse", None)
        self.database = kwargs.pop("database", None)
        self.region = kwargs.pop("region", None)
        self.role = kwargs.pop("role", None)
        self.schema = kwargs.pop("schema", None)

    def _get_conn_params(self):
        """
        one method to fetch connection params as a dict
        used in get_uri() and get_connection()
        """
        conn = self.get_connection(self.snowflake_conn_id)
        account = conn.extra_dejson.get('account', None)
        warehouse = conn.extra_dejson.get('warehouse', None)
        database = conn.extra_dejson.get('database', None)
        region = conn.extra_dejson.get("region", None)
        role = conn.extra_dejson.get('role', None)

        conn_config = {
            "user": conn.login,
            "password": conn.password or '',
            "schema": self.schema or conn.schema or '',
            "database": self.database or database or '',
            "account": self.account or account or '',
            "warehouse": self.warehouse or warehouse or '',
            "region": self.region or region or '',
            "role": self.role or role or ''

        }

        """
        If private_key_file is specified in the extra json, load the contents of the file as a private
        key and specify that in the connection configuration. The connection password then becomes the
        passphrase for the private key. If your private key file is not encrypted (not recommended), then
        leave the password empty.
        """
        private_key_file = conn.extra_dejson.get('private_key_file', None)
        if private_key_file:
            with open(private_key_file, "rb") as key:
                passphrase = None
                if conn.password:
                    passphrase = conn.password.strip().encode()

                p_key = serialization.load_pem_private_key(
                    key.read(),
                    password=passphrase,
                    backend=default_backend()
                )

            pkb = p_key.private_bytes(encoding=serialization.Encoding.DER,
                                      format=serialization.PrivateFormat.PKCS8,
                                      encryption_algorithm=serialization.NoEncryption())

            conn_config['private_key'] = pkb
            conn_config.pop('password', None)

        return conn_config

    def get_uri(self):
        """
        override DbApiHook get_uri method for get_sqlalchemy_engine()
        """
        conn_config = self._get_conn_params()
        uri = 'snowflake://{user}:{password}@{account}/{database}/'
        uri += '{schema}?warehouse={warehouse}&role={role}'
        return uri.format(**conn_config)

    def get_conn(self):
        """
        Returns a snowflake.connection object
        """
        conn_config = self._get_conn_params()
        conn = snowflake.connector.connect(**conn_config)
        return conn

    def _get_aws_credentials(self):
        """
        returns aws_access_key_id, aws_secret_access_key
        from extra

        intended to be used by external import and export statements
        """
        if self.snowflake_conn_id:
            connection_object = self.get_connection(self.snowflake_conn_id)
            if 'aws_secret_access_key' in connection_object.extra_dejson:
                aws_access_key_id = connection_object.extra_dejson.get(
                    'aws_access_key_id')
                aws_secret_access_key = connection_object.extra_dejson.get(
                    'aws_secret_access_key')
        return aws_access_key_id, aws_secret_access_key

    def set_autocommit(self, conn, autocommit):
        conn.autocommit(autocommit)
