# Copyright (c) 2022 Contrast Security, Inc. See https://www.contrastsecurity.com/enduser-terms-0317a for more details.
# frozen_string_literal: true

require 'contrast/components/scope'
require 'contrast/utils/object_share'

module Contrast
  module Agent
    module Patching
      module Policy
        # This class functions to translate our policy.json into an actionable
        # Ruby object, allowing for dynamic patching over hardcoded patching.
        #
        # @abstract
        class PolicyNode
          include Contrast::Components::Scope::InstanceMethods
          JSON_METHOD_VISIBILITY = 'method_visibility'
          JSON_PROPERTIES = 'properties'
          JSON_METHOD_NAME = 'method_name'
          JSON_METHOD_SCOPE = 'scope'
          # The keys used to read from policy.json to create the individual
          # policy nodes. These are common across node types
          JSON_CLASS_NAME = 'class_name'
          JSON_INSTANCE_METHOD = 'instance_method'
          def initialize policy_hash = {}
            @class_name = policy_hash[JSON_CLASS_NAME]
            @instance_method = policy_hash[JSON_INSTANCE_METHOD]
            @method_name = policy_hash[JSON_METHOD_NAME]
            @method_scope = policy_hash[JSON_METHOD_SCOPE]
            @method_visibility = policy_hash[JSON_METHOD_VISIBILITY]
            @properties = policy_hash[JSON_PROPERTIES]
            symbolize
          end

          # Name of the class in which the method is being invoked.
          attr_accessor :class_name
          # Check for instance method.
          #
          # @return true | false
          attr_accessor :instance_method
          # The symbol representation of the invoked method.
          attr_accessor :method_name
          # Visibility of the invoked method [Private, Public, Protected]
          attr_accessor :method_visibility
          # Properties parsed from our JSON policy.
          attr_reader :properties
          # Scope of the method parsed from our JSON policy.
          attr_reader :method_scope

          # @raise [NoMethodError] This is being raised if any of the implementing subclasses does not have
          #     that method implemented, but is being called on.
          def node_class
            raise(NoMethodError, 'specify the type of the feature for which this node patches')
          end

          # @raise [NoMethodError] This is being raised if any of the implementing subclasses does not have
          #     that method implemented, but is being called on.
          def feature
            raise(NoMethodError, 'specify the name of the feature for which this node patches')
          end

          def id
            @_id ||= "#{ feature }:#{ node_class }:#{ class_name }#{ instance_method? ? '#' : '.' }#{ method_name }"
          end

          # Don't let nodes be created that will be missing things we need
          # later on. Really, if they don't have these things, they couldn't have
          # done their jobs anyway.
          #
          # @raise [ArgumentError] Validates if the created nodes have everything that we'll need now or later on.
          def validate
            unless class_name
              raise(ArgumentError, "#{ node_class } #{ id } did not have a proper class name. Unable to create.")
            end
            unless method_name
              raise(ArgumentError, "#{ node_class } #{ id } did not have a proper method name. Unable to create.")
            end
            unless method_name.is_a?(Symbol)
              raise(ArgumentError, "#{ node_class } #{ id } has a non symbol @method_name value. Unable to create.")
            end

            unless method_visibility.is_a?(Symbol)
              raise(ArgumentError,
                    "#{ node_class } #{ id } has a non symbol @method_visibility value. Unable to create.")
            end
            unless method_scope.nil? || Contrast::Agent::Scope.valid_scope?(method_scope)
              raise(ArgumentError, "#{ node_class } #{ id } requires an undefined scope. Unable to create.")
            end

            nil
          end

          # just turns this into a ruby-ism
          def instance_method?
            instance_method
          end

          private

          # Convert strings to symbols here, once, to avoid doing so on every
          # comparison at runtime
          def symbolize
            @method_name = @method_name.to_sym if @method_name
            @method_visibility = @method_visibility.to_sym if @method_visibility
            @method_scope = @method_scope.to_sym if @method_scope
          end
        end
      end
    end
  end
end