add metadata.json functionality

pkg/metadata/metadata.go

@@ -0,0 +1,61 @@
+/*
+Copyright 2021 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package metadata
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"io/ioutil"
+)
+
+type CustomJSON struct {
+	data map[string]string
+}
+
+func NewCustomJSON(from io.Reader) (*CustomJSON, error) {
+	meta := &CustomJSON{}
+	if from != nil {
+		dataBytes, err := ioutil.ReadAll(from)
+		if err != nil {
+			return nil, err
+		}
+		if err := json.Unmarshal(dataBytes, &meta.data); err != nil {
+			return nil, err
+		}
+	}
+	return meta, nil
+}
+
+func (m *CustomJSON) Add(key, value string) error {
+	if m.data == nil {
+		m.data = map[string]string{}
+	}
+	if _, exists := m.data[key]; exists {
+		return fmt.Errorf("key %s already exists in the metadata", key)
+	}
+	m.data[key] = value
+	return nil
+}
+
+func (m *CustomJSON) Write(writer io.Writer) error {
+	data, err := json.Marshal(m.data)
+	if err == nil {
+		_, err = writer.Write(data)
+	}
+	return err
+}

pkg/metadata/metadata_test.go

@@ -0,0 +1,65 @@
+/*
+Copyright 2021 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package metadata
+
+import (
+	"bytes"
+	"encoding/json"
+	"reflect"
+	"strings"
+	"testing"
+)
+
+func TestCustomJSON_AddWrite(t *testing.T) {
+	meta := CustomJSON{}
+	if err := meta.Add("foo", "bar"); err != nil {
+		t.Errorf("did not expect an error, but got: %v", err)
+	}
+	if err := meta.Add("baz", "qwe"); err != nil {
+		t.Errorf("did not expect an error, but got: %v", err)
+	}
+
+	var buff bytes.Buffer
+	if err := meta.Write(&buff); err != nil {
+		t.Errorf("did not expect an error, but got: %v", err)
+	}
+
+	actualBytes := buff.Bytes()
+
+	expectedBytes, err := json.Marshal(meta.data)
+	if err != nil {
+		t.Errorf("did not expect an error, but got: %v", err)
+	}
+	if !bytes.Equal(buff.Bytes(), expectedBytes) {
+		t.Errorf("mismatched metadata bytes, got: %v, want: %v", actualBytes, expectedBytes)
+	}
+}
+
+func TestNewCustomJSON(t *testing.T) {
+	json := `{"baz":"qwe","foo":"bar"}`
+	meta, err := NewCustomJSON(strings.NewReader(json))
+	if err != nil {
+		t.Errorf("did not expect an error, but got: %v", err)
+	}
+	expectedData := map[string]string{
+		"foo": "bar",
+		"baz": "qwe",
+	}
+	if !reflect.DeepEqual(meta.data, expectedData) {
+		t.Errorf("mismatched metadata bytes, got: %v, want: %v", meta.data, expectedData)
+	}
+}