dry-rb/dry-logic

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lib/dry/logic/rule/interface.rb

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# frozen_string_literal: true

module Dry
  module Logic
    class Rule
      class Interface < ::Module
        SPLAT = ["*rest"].freeze

        attr_reader :arity

        attr_reader :curried

        def initialize(arity, curried)
          @arity = arity
          @curried = curried

          if !variable_arity? && curried > arity
            raise ArgumentError, "wrong number of arguments (#{curried} for #{arity})"
          end

          define_constructor if curried?

          if constant?
            define_constant_application
          else
            define_application
          end
        end

        def constant?
          arity.zero?
        end

        def variable_arity?
          arity.negative?
        end

        def curried?
          !curried.zero?
        end

        def unapplied
          if variable_arity?
            unapplied = arity.abs - 1 - curried

            if unapplied.negative?
              0
            else
              unapplied
            end
          else
            arity - curried
          end
        end

        def name
          if constant?
            "Constant"
          else
            arity_str =
              if variable_arity?
                "Variable#{arity.abs - 1}Arity"
              else
                "#{arity}Arity"
              end

            curried_str =
              if curried?
                "#{curried}Curried"
              else
                EMPTY_STRING
              end

            "#{arity_str}#{curried_str}"
          end
        end

        def define_constructor
          assignment =
            if curried.equal?(1)
              "@arg0 = @args[0]"
            else
              "#{curried_args.join(", ")} = @args"
            end

          module_eval(<<~RUBY, __FILE__, __LINE__ + 1)
            def initialize(*)
              super

              #{assignment}
            end
          RUBY
        end

        def define_constant_application
          module_exec do
            def call(*)
              if @predicate[]
                Result::SUCCESS
              else
                Result.new(false, id) { ast }
              end
            end

            def [](*)
              @predicate[]
            end
          end
        end

        def define_application
          splat = variable_arity? ? SPLAT : EMPTY_ARRAY
          parameters = (unapplied_args + splat).join(", ")
          application = "@predicate[#{(curried_args + unapplied_args + splat).join(", ")}]"

          module_eval(<<~RUBY, __FILE__, __LINE__ + 1)
            def call(#{parameters})
              if #{application}
                Result::SUCCESS
              else
                Result.new(false, id) { ast(#{parameters}) }
              end
            end

            def [](#{parameters})
              #{application}
            end
          RUBY
        end

        def curried_args
          @curried_args ||= ::Array.new(curried) { |i| "@arg#{i}" }
        end

        def unapplied_args
          @unapplied_args ||= ::Array.new(unapplied) { |i| "input#{i}" }
        end
      end
    end
  end
end