resources: Add a utility to map from struct fields

For GAPI front ends that want to know what fields they can use and which
they map to, these two functions can be used.

resources/util_test.go

@@ -152,3 +152,89 @@ func TestMiscEncodeDecode2(t *testing.T) {
 		t.Error("The input and output Res values do not match!")
 	}
 }
+
+func TestStructTagToFieldName0(t *testing.T) {
+	type TestStruct struct {
+		// TODO: switch this to TestRes when it is in git master
+		NoopRes        // so that this struct implements `Res`
+		Alpha   bool   `lang:"alpha" yaml:"nope"`
+		Beta    string `yaml:"beta"`
+		Gamma   string
+		Delta   int `lang:"surprise"`
+	}
+
+	mapping, err := StructTagToFieldName(&TestStruct{})
+	if err != nil {
+		t.Errorf("failed: %+v", err)
+		return
+	}
+
+	expected := map[string]string{
+		"alpha":    "Alpha",
+		"surprise": "Delta",
+	}
+
+	if !reflect.DeepEqual(mapping, expected) {
+		t.Errorf("expected: %+v", expected)
+		t.Errorf("received: %+v", mapping)
+	}
+}
+
+func TestLowerStructFieldNameToFieldName0(t *testing.T) {
+	type TestStruct struct {
+		// TODO: switch this to TestRes when it is in git master
+		NoopRes   // so that this struct implements `Res`
+		Alpha     bool
+		skipMe    bool
+		Beta      string
+		IAmACamel uint
+		pass      *string
+		Gamma     string
+		Delta     int
+	}
+
+	mapping, err := LowerStructFieldNameToFieldName(&TestStruct{})
+	if err != nil {
+		t.Errorf("failed: %+v", err)
+		return
+	}
+
+	expected := map[string]string{
+		"noopres": "NoopRes", // TODO: switch this to TestRes when it is in git master
+		"alpha":   "Alpha",
+		//"skipme": "skipMe",
+		"beta":      "Beta",
+		"iamacamel": "IAmACamel",
+		//"pass": "pass",
+		"gamma": "Gamma",
+		"delta": "Delta",
+	}
+
+	if !reflect.DeepEqual(mapping, expected) {
+		t.Errorf("expected: %+v", expected)
+		t.Errorf("received: %+v", mapping)
+	}
+}
+
+func TestLowerStructFieldNameToFieldName1(t *testing.T) {
+	type TestStruct struct {
+		// TODO: switch this to TestRes when it is in git master
+		NoopRes // so that this struct implements `Res`
+		Alpha   bool
+		skipMe  bool
+		Beta    string
+		// these two should collide
+		DoubleWord bool
+		Doubleword string
+		IAmACamel  uint
+		pass       *string
+		Gamma      string
+		Delta      int
+	}
+
+	mapping, err := LowerStructFieldNameToFieldName(&TestStruct{})
+	if err == nil {
+		t.Errorf("expected failure, but passed with: %+v", mapping)
+		return
+	}
+}