Create response for display

backend/handlers.go

@@ -66,7 +66,7 @@ func (hr *HandlerRepository) scaleMessageHandler() func(http.ResponseWriter, *ht
 			}).Infof("Scale new value: %0.2f", message.Value)
 		}
 
-		_, _ = w.Write([]byte("OK"))
+		_, _ = w.Write([]byte(hr.scale.GetPushResponse()))
 	}
 }
 

backend/pkg/scale/scale_beers_output.go

@@ -0,0 +1,23 @@
+package scale
+
+import (
+	"fmt"
+	"strings"
+)
+
+// GetPushResponse is a response for scale push event
+// Scale has display and it is able to display four digits
+func (s *Scale) GetPushResponse() string {
+	s.mux.RLock()
+	defer s.mux.RUnlock()
+
+	return leftPad(fmt.Sprintf("%d", s.beersLeft), " ", 4)
+}
+
+func leftPad(input string, padChar string, length int) string {
+	if len(input) >= length {
+		return input
+	}
+	padding := strings.Repeat(padChar, length-len(input))
+	return padding + input
+}

backend/pkg/scale/scale_beers_output_test.go

@@ -0,0 +1,32 @@
+package scale
+
+import (
+	"testing"
+)
+
+func TestScale_GetPushResponse(t *testing.T) {
+	cases := []struct {
+		beersLeft int
+		want      string
+	}{
+		{beersLeft: 0, want: "   0"},
+		{beersLeft: 1, want: "   1"},
+		{beersLeft: 10, want: "  10"},
+		{beersLeft: 66, want: "  66"},
+		{beersLeft: 100, want: " 100"},
+		{beersLeft: 222, want: " 222"},
+		{beersLeft: 1000, want: "1000"},
+		{beersLeft: 9999, want: "9999"},
+	}
+
+	for _, tt := range cases {
+		s := &Scale{
+			beersLeft: tt.beersLeft,
+		}
+
+		got := s.GetPushResponse()
+		if got != tt.want {
+			t.Errorf("Scale.GetPushResponse() = %v, want %v", got, tt.want)
+		}
+	}
+}