common: refactor build states into a separate file

These states will be used for tracking the image builds and compose
states in the rest of our codebase. There should be no change in the
behavior. It is a 1 to 1 replacement with the only difference of using
type alias instead of plain string.

internal/common/states.go

@@ -0,0 +1,79 @@
+package common
+
+import (
+	"encoding/json"
+)
+
+func getStateMapping() []string {
+	return []string{"WAITING", "RUNNING", "FINISHED", "FAILED"}
+}
+
+type ImageBuildState int
+
+const (
+	IBWaiting ImageBuildState = iota
+	IBRunning
+	IBFinished
+	IBFailed
+)
+
+// ToString converts ImageBuildState into a human readable string
+func (ibs ImageBuildState) ToString() string {
+	return getStateMapping()[int(ibs)]
+}
+
+func unmarshalStateHelper(data []byte, mapping []string) (int, error) {
+	var stringInput string
+	err := json.Unmarshal(data, &stringInput)
+	if err != nil {
+		return 0, err
+	}
+	for n, str := range getStateMapping() {
+		if str == stringInput {
+			return n, nil
+		}
+	}
+	return 0, &CustomJsonConversionError{"invalid image build status:" + stringInput}
+}
+
+// UnmarshalJSON converts a JSON string into an ImageBuildState
+func (ibs *ImageBuildState) UnmarshalJSON(data []byte) error {
+	val, err := unmarshalStateHelper(data, getStateMapping())
+	if err != nil {
+		return err
+	}
+	*ibs = ImageBuildState(val)
+	return nil
+}
+
+func (ibs ImageBuildState) MarshalJSON() ([]byte, error) {
+	return json.Marshal(getStateMapping()[ibs])
+}
+
+type ComposeState int
+
+const (
+	CWaiting ComposeState = iota
+	CRunning
+	CFinished
+	CFailed
+)
+
+// ToString converts ImageBuildState into a human readable string
+func (cs ComposeState) ToString() string {
+	return getStateMapping()[int(cs)]
+}
+
+// UnmarshalJSON converts a JSON string into an ImageBuildState
+func (ibs *ComposeState) UnmarshalJSON(data []byte) error {
+	val, err := unmarshalStateHelper(data, getStateMapping())
+	if err != nil {
+		return err
+	}
+	*ibs = ComposeState(val)
+	return nil
+}
+
+func (ibs ComposeState) MarshalJSON() ([]byte, error) {
+	return json.Marshal(getStateMapping()[ibs])
+}

internal/common/states_test.go

@@ -0,0 +1,59 @@
+package common
+
+import (
+	"encoding/json"
+	"reflect"
+	"testing"
+)
+
+func TestJSONConversions(t *testing.T) {
+	type TestJson struct {
+		Ibs ImageBuildState `json:"ibs"`
+		Cs ComposeState `json:"cs"`
+	}
+	typedCases := []TestJson{
+		{
+			Ibs: IBWaiting,
+			Cs: CWaiting,
+		},
+		{
+			Ibs: IBRunning,
+			Cs: CFailed,
+		},
+	}
+	strCases := []string{
+		`{"ibs": "WAITING", "cs": "WAITING"}`,
+		`{"ibs": "RUNNING", "cs": "FAILED"}`,
+	}
+
+	for n, c := range strCases {
+		var inputStringAsStruct *TestJson
+		err := json.Unmarshal([]byte(c), &inputStringAsStruct)
+		if err != nil {
+			t.Fatal("Failed to unmarshal:", err)
+		}
+		if reflect.DeepEqual(inputStringAsStruct, typedCases[n]) {
+			t.Error("Unmarshaled compose request is not the one expected")
+		}
+	}
+
+	var byteArrays [][]byte
+	for _, c := range typedCases {
+		data, err := json.Marshal(c)
+		if err != nil {
+			t.Fatal("Failed to marshal state:", err)
+		}
+		byteArrays = append(byteArrays, data)
+	}
+	for n, b := range byteArrays {
+		var inputStringAsStruct *TestJson
+		err := json.Unmarshal(b, &inputStringAsStruct)
+		if err != nil {
+			t.Fatal("Failed to unmarshal:", err)
+		}
+		if reflect.DeepEqual(inputStringAsStruct, typedCases[n]) {
+			t.Error("Unmarshaled compose request is not the one expected")
+		}
+	}
+	
+}