require "test_helper"

module Whitespace::ISA
  describe Readn do
    before do
      @vm = Whitespace::VM.new
      @stdin = Object.new
    end

    describe "#execute" do
      describe "when there is no character" do
        it "raises ArgumentError" do
          def @stdin.getc
          end

          console = Whitespace::Console.new(stdin: @stdin)
          e = expect { Readn.new(@vm, console).execute }.must_raise \
            ArgumentError
          expect(e.message).must_match /must be an integer/
        end
      end

      describe "when there is a character" do
        describe "when it is an integer" do
          before do
            def @stdin.getc
              @chars ||= ["-", "5", "\n"]
              @i ||= 0

              @i += 1
              @chars[@i - 1]
            end
          end

          describe "when the value stack is empty" do
            it "raises Whitespace::EmptyError" do
              expect(@vm.vstack.size).must_equal 0

              console = Whitespace::Console.new(stdin: @stdin)
              expect { Readn.new(@vm, console).execute }.must_raise \
                Whitespace::EmptyError
            end
          end

          describe "when the value stack has at least 1 element" do
            it "reads the integer and places it at the address in the heap" \
                "given by the top of the stack" do
              @vm.vstack.push :address
              expect(@vm.vstack.size).must_equal 1

              console = Whitespace::Console.new(stdin: @stdin)
              Readn.new(@vm, console).execute

              expect(@vm.memory[:address]).must_equal -5
              expect(@vm.vstack.size).must_equal 0
            end
          end
        end

        describe "when it is not an integer" do
          it "raises ArgumentError" do
            def @stdin.getc
              @chars ||= ["x"]
              @i ||= 0

              @i += 1
              @chars[@i - 1]
            end

            console = Whitespace::Console.new(stdin: @stdin)
            e = expect { Readn.new(@vm, console).execute }.must_raise \
              ArgumentError
            expect(e.message).must_match /must be an integer/
          end
        end
      end
    end
  end
end