module Lotus
  module Validations
    # A single validation error for an attribute
    #
    # @since 0.1.0
    class Error
      # @since 0.2.4
      # @api private
      NAMESPACE_SEPARATOR = '.'.freeze

      # The name of the attribute
      #
      # @return [Symbol] the name of the attribute
      #
      # @since 0.2.4
      #
      # @see Lotus::Validations::Error#attribute
      #
      # @example
      #   error = Error.new(:name, :presence, true, nil, 'author')
      #
      #   error.attribute      # => "author.name"
      #   error.attribute_name # => "name"
      attr_reader :attribute_name

      # The name of the validation
      #
      # @return [Symbol] the name of the validation
      #
      # @since 0.1.0
      attr_reader :validation

      # The expected value
      #
      # @return [Object] the expected value
      #
      # @since 0.1.0
      attr_reader :expected

      # The actual value
      #
      # @return [Object] the actual value
      #
      # @since 0.1.0
      attr_reader :actual

      # Returns the namespaced attribute name
      #
      # In cases where the error was pulled up from nested validators,
      # `attribute` will be a namespaced string containing
      # parent attribute names separated by a period.
      #
      # @since 0.1.0
      #
      # @see Lotus::Validations::Error#attribute_name
      #
      # @example
      #   error = Error.new(:name, :presence, true, nil, 'author')
      #
      #   error.attribute      # => "author.name"
      #   error.attribute_name # => "name"
      attr_accessor :attribute

      # Initialize a validation error
      #
      # @param attribute_name [Symbol] the name of the attribute
      # @param validation [Symbol] the name of the validation
      # @param expected [Object] the expected value
      # @param actual [Object] the actual value
      # @param namespace [String] the optional namespace
      #
      # @since 0.1.0
      # @api private
      def initialize(attribute_name, validation, expected, actual, namespace = nil)
        @attribute_name = attribute_name.to_s
        @validation = validation
        @expected = expected
        @actual = actual
        @namespace = namespace
        @attribute = [@namespace, attribute_name].compact.join(NAMESPACE_SEPARATOR)
      end

      # Check if self equals to `other`
      #
      # @since 0.1.0
      def ==(other)
        other.is_a?(self.class) &&
          other.attribute  == attribute  &&
          other.validation == validation &&
          other.expected   == expected   &&
          other.actual     == actual
      end
    end
  end
end