module ActiveRecord #:nodoc:
  class Base
    # Transparently encrypt and decrypt values stored via ActiveRecord.
    #
    # Parameters:
    # * Symbolic names of each method to create which has a corresponding
    #   method already defined in rails starting with: encrypted_
    # * Followed by an optional hash:
    #     :random_iv [true|false]
    #       Whether the encrypted value should use a random IV every time the
    #       field is encrypted.
    #       It is recommended to set this to true where feasible. If the encrypted
    #       value could be used as part of a SQL where clause, or as part
    #       of any lookup, then it must be false.
    #       Setting random_iv to true will result in a different encrypted output for
    #       the same input string.
    #       Note: Only set to true if the field will never be used as part of
    #         the where clause in an SQL query.
    #       Note: When random_iv is true it will add a 8 byte header, plus the bytes
    #         to store the random IV in every returned encrypted string, prior to the
    #         encoding if any.
    #       Default: false
    #       Highly Recommended where feasible: true
    #
    #     :type [Symbol]
    #       The type for this field, #see SymmetricEncryption::COERCION_TYPES
    #       Default: :string
    #
    #     :compress [true|false]
    #       Whether to compress str before encryption
    #       Should only be used for large strings since compression overhead and
    #       the overhead of adding the 'magic' header may exceed any benefits of
    #       compression
    #       Note: Adds a 6 byte header prior to encoding, only if :random_iv is false
    #       Default: false
    def self.attr_encrypted(*params)
      # Ensure ActiveRecord has created all its methods first
      # Ignore failures since the table may not yet actually exist
      begin
        define_attribute_methods
      rescue StandardError
        nil
      end

      options = params.last.is_a?(Hash) ? params.pop.dup : {}

      params.each do |attribute|
        SymmetricEncryption::Generator.generate_decrypted_accessors(self, attribute, "encrypted_#{attribute}", options)
        encrypted_attributes[attribute.to_sym] = "encrypted_#{attribute}".to_sym
      end
    end

    # Contains a hash of encrypted attributes with virtual attribute names as keys and real attribute
    # names as values
    #
    # Example
    #
    #   class User < ActiveRecord::Base
    #     attr_encrypted :email
    #   end
    #
    #   User.encrypted_attributes  =>  { email: encrypted_email }
    def self.encrypted_attributes
      @encrypted_attributes ||= superclass.respond_to?(:encrypted_attributes) ? superclass.encrypted_attributes.dup : {}
    end

    # Return the name of all encrypted virtual attributes as an Array of symbols
    # Example: [:email, :password]
    def self.encrypted_keys
      @encrypted_keys ||= encrypted_attributes.keys
    end

    # Return the name of all encrypted columns as an Array of symbols
    # Example: [:encrypted_email, :encrypted_password]
    def self.encrypted_columns
      @encrypted_columns ||= encrypted_attributes.values
    end

    # Returns whether an attribute has been configured to be encrypted
    #
    # Example
    #
    #   class User < ActiveRecord::Base
    #     attr_accessor :name
    #     attr_encrypted :email
    #   end
    #
    #   User.encrypted_attribute?(:name) # false
    #   User.encrypted_attribute?(:email) # true
    def self.encrypted_attribute?(attribute)
      encrypted_keys.include?(attribute)
    end

    # Returns whether the attribute is the database column to hold the
    # encrypted data for a matching encrypted attribute
    #
    # Example
    #
    #   class User < ActiveRecord::Base
    #     attr_accessor :name
    #     attr_encrypted :email
    #   end
    #
    #   User.encrypted_column?(:encrypted_name) # false
    #   User.encrypted_column?(:encrypted_email) # true
    def self.encrypted_column?(attribute)
      encrypted_columns.include?(attribute)
    end
  end
end