base.py

import json
from typing import Optional, Union

from aws_lambda_powertools.utilities._data_masking.provider import BaseProvider


class DataMasking:
    """
    Note: This utility is currently in a Non-General Availability (Non-GA) phase and may have limitations.
    Please DON'T USE THIS utility in production environments.
    Keep in mind that when we transition to General Availability (GA), there might be breaking changes introduced.

    A utility class for masking sensitive data within various data types.

    This class provides methods for masking sensitive information, such as personal
    identifiers or confidential data, within different data types such as strings,
    dictionaries, lists, and more. It helps protect sensitive information while
    preserving the structure of the original data.

    Usage:
    Instantiate an object of this class and use its methods to mask sensitive data
    based on the data type. Supported data types include strings, dictionaries,
    and more.

    Example:
    ```
    from aws_lambda_powertools.utilities.data_masking.base import DataMasking

    def lambda_handler(event, context):
        masker = DataMasking()

        data = {
            "project": "powertools",
            "sensitive": "xxxxxxxxxx"
        }

        masked = masker.mask(data,fields=["sensitive"])

        return masked

    ```
    """

    def __init__(self, provider: Optional[BaseProvider] = None):
        self.provider = provider or BaseProvider()

    def encrypt(self, data, fields=None, **provider_options):
        return self._apply_action(data, fields, self.provider.encrypt, **provider_options)

    def decrypt(self, data, fields=None, **provider_options):
        return self._apply_action(data, fields, self.provider.decrypt, **provider_options)

    def mask(self, data, fields=None, **provider_options):
        return self._apply_action(data, fields, self.provider.mask, **provider_options)

    def _apply_action(self, data, fields, action, **provider_options):
        """
        Helper method to determine whether to apply a given action to the entire input data
        or to specific fields if the 'fields' argument is specified.

        Parameters
        ----------
        data : any
            The input data to process.
        fields : Optional[List[any]] = None
            A list of fields to apply the action to. If 'None', the action is applied to the entire 'data'.
        action : Callable
           The action to apply to the data. It should be a callable that performs an operation on the data
           and returns the modified value.

        Returns
        -------
        any
            The modified data after applying the action.
        """

        if fields is not None:
            return self._apply_action_to_fields(data, fields, action, **provider_options)
        else:
            return action(data, **provider_options)

    def _apply_action_to_fields(
        self,
        data: Union[dict, str],
        fields: list,
        action,
        **provider_options,
    ) -> Union[dict, str]:
        """
        This method takes the input data, which can be either a dictionary or a JSON string,
        and applies a mask, an encryption, or a decryption to the specified fields.

        Parameters
        ----------
            data : Union[dict, str])
                The input data to process. It can be either a dictionary or a JSON string.
            fields : List
                A list of fields to apply the action to. Each field can be specified as a string or
                a list of strings representing nested keys in the dictionary.
            action : Callable
                The action to apply to the fields. It should be a callable that takes the current
                value of the field as the first argument and any additional arguments that might be required
                for the action. It performs an operation on the current value using the provided arguments and
                returns the modified value.
            **provider_options:
                Additional keyword arguments to pass to the 'action' function.

        Returns
        -------
            dict
                The modified dictionary after applying the action to the
            specified fields.

        Raises
        -------
            ValueError
                If 'fields' parameter is None.
            TypeError
                If the 'data' parameter is not a traversable type

        Example
        -------
        ```python
        >>> data = {'a': {'b': {'c': 1}}, 'x': {'y': 2}}
        >>> fields = ['a.b.c', 'a.x.y']
        # The function will transform the value at 'a.b.c' (1) and 'a.x.y' (2)
        # and store the result as:
        new_dict = {'a': {'b': {'c': 'transformed_value'}}, 'x': {'y': 'transformed_value'}}
        ```
        """

        if fields is None:
            raise ValueError("No fields specified.")

        if isinstance(data, str):
            # Parse JSON string as dictionary
            my_dict_parsed = json.loads(data)
        elif isinstance(data, dict):
            # In case their data has keys that are not strings (i.e. ints), convert it all into a JSON string
            my_dict_parsed = json.dumps(data)
            # Turn back into dict so can parse it
            my_dict_parsed = json.loads(my_dict_parsed)
        else:
            raise TypeError(
                f"Unsupported data type for 'data' parameter. Expected a traversable type, but got {type(data)}.",
            )

        # For example: ['a.b.c'] in ['a.b.c', 'a.x.y']
        for nested_key in fields:
            # Prevent overriding loop variable
            curr_nested_key = nested_key

            # If the nested_key is not a string, convert it to a string representation
            if not isinstance(curr_nested_key, str):
                curr_nested_key = json.dumps(curr_nested_key)

            # Split the nested key string into a list of nested keys
            # ['a.b.c'] -> ['a', 'b', 'c']
            keys = curr_nested_key.split(".")

            # Initialize a current dictionary to the root dictionary
            curr_dict = my_dict_parsed

            # Traverse the dictionary hierarchy by iterating through the list of nested keys
            for key in keys[:-1]:
                curr_dict = curr_dict[key]

            # Retrieve the final value of the nested field
            valtochange = curr_dict[(keys[-1])]

            # Apply the specified 'action' to the target value
            curr_dict[keys[-1]] = action(valtochange, **provider_options)

        return my_dict_parsed