git/odb: introduce const ObjectType enumeration

git/odb/object_type.go

@@ -0,0 +1,45 @@
+package odb
+
+import "strings"
+
+// ObjectType is a constant enumeration type for identifying the kind of object
+// type an implementing instance of the Object interface is.
+type ObjectType uint8
+
+const (
+	UnknownObjectType ObjectType = iota
+	BlobObjectType
+	TreeObjectType
+	CommitObjectType
+)
+
+// ObjectTypeFromString converts from a given string to an ObjectType
+// enumeration instance.
+func ObjectTypeFromString(s string) ObjectType {
+	switch strings.ToLower(s) {
+	case "blob":
+		return BlobObjectType
+	case "tree":
+		return TreeObjectType
+	case "commit":
+		return CommitObjectType
+	default:
+		return UnknownObjectType
+	}
+}
+
+// String implements the fmt.Stringer interface and returns a string
+// representation of the ObjectType enumeration instance.
+func (t ObjectType) String() string {
+	switch t {
+	case UnknownObjectType:
+		return "unknown"
+	case BlobObjectType:
+		return "blob"
+	case TreeObjectType:
+		return "tree"
+	case CommitObjectType:
+		return "commit"
+	}
+	return "<unknown>"
+}

git/odb/object_type_test.go

@@ -0,0 +1,35 @@
+package odb
+
+import (
+	"math"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestObjectTypeFromString(t *testing.T) {
+	for str, typ := range map[string]ObjectType{
+		"blob":           BlobObjectType,
+		"tree":           TreeObjectType,
+		"commit":         CommitObjectType,
+		"something else": UnknownObjectType,
+	} {
+		t.Run(str, func(t *testing.T) {
+			assert.Equal(t, typ, ObjectTypeFromString(str))
+		})
+	}
+}
+
+func TestObjectTypeToString(t *testing.T) {
+	for typ, str := range map[ObjectType]string{
+		BlobObjectType:            "blob",
+		TreeObjectType:            "tree",
+		CommitObjectType:          "commit",
+		UnknownObjectType:         "unknown",
+		ObjectType(math.MaxUint8): "<unknown>",
+	} {
+		t.Run(str, func(t *testing.T) {
+			assert.Equal(t, str, typ.String())
+		})
+	}
+}