Creating an expandable enum type, converting StorageClass

garrettjonesgoogle · garrettjonesgoogle · commit 6db00d34389b · 2017-04-18T09:23:52.000-07:00
diff --git a/google-cloud-core/src/main/java/com/google/cloud/StringEnumType.java b/google-cloud-core/src/main/java/com/google/cloud/StringEnumType.java
@@ -0,0 +1,80 @@
+/*
+ * Copyright 2017 Google Inc. All Rights Reserved.
+ *
+ * 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 com.google.cloud;
+
+import com.google.api.core.ApiFunction;
+import com.google.api.core.InternalApi;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * This represents a concept having a known set of acceptable String values, which can expand later
+ * due to new API features.
+ */
+@InternalApi
+public class StringEnumType<EnumT> {
+
+  private final String enumName;
+  private final ApiFunction<String, EnumT> constructor;
+  private Map<String, EnumT> knownValues = new HashMap<>();
+
+  public StringEnumType(String enumName, ApiFunction<String, EnumT> constructor) {
+    this.enumName = enumName;
+    this.constructor = constructor;
+  }
+
+  /**
+   * Create a new constant and register it in the known values.
+   */
+  public EnumT createAndRegister(String constant) {
+      EnumT instance = constructor.apply(constant);
+      knownValues.put(constant, instance);
+      return instance;
+  }
+
+  /**
+   * Get the enum object for the given String constant, and throw an exception if the constant is
+   * not recognized.
+   */
+  public EnumT valueOfStrict(String constant) {
+    EnumT value = knownValues.get(constant);
+    if (value != null) {
+      return value;
+    } else {
+      throw new IllegalArgumentException(
+          "Constant \"" + constant + "\" not found for enum \"" + enumName + "\"");
+    }
+  }
+
+  /**
+   * Get the enum object for the given String constant, and allow unrecognized values.
+   */
+  public EnumT valueOf(String constant) {
+    EnumT value = knownValues.get(constant);
+    if (value != null) {
+      return value;
+    } else {
+      return constructor.apply(constant);
+    }
+  }
+
+  /**
+   * Return the known values of this enum type.
+   */
+  public EnumT[] values() {
+    return (EnumT[]) knownValues.values().toArray();
+  }
+}
diff --git a/google-cloud-core/src/main/java/com/google/cloud/StringEnumValue.java b/google-cloud-core/src/main/java/com/google/cloud/StringEnumValue.java
@@ -0,0 +1,58 @@
+/*
+ * Copyright 2017 Google Inc. All Rights Reserved.
+ *
+ * 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 com.google.cloud;
+
+import com.google.api.core.InternalApi;
+import com.google.common.base.Preconditions;
+
+/**
+ * This represents a specific instance of a concept having a known set of acceptable String values,
+ * which can expand later due to new API features. Standard Java enums can't be used in such
+ * a context.
+ */
+public abstract class StringEnumValue {
+  private String constant;
+
+  @InternalApi
+  protected StringEnumValue(String constant) {
+    this.constant = Preconditions.checkNotNull(constant);
+  }
+
+  @Override
+  public String toString() {
+    return constant;
+  }
+
+  @Override
+  public boolean equals(Object that) {
+    if (that == null) {
+      return false;
+    }
+    if (this == that) {
+      return true;
+    }
+    if (!(that instanceof StringEnumValue)) {
+      return false;
+    }
+    StringEnumValue thatEnumValue = (StringEnumValue) that;
+    return this.constant.equals(thatEnumValue.constant);
+  }
+
+  @Override
+  public int hashCode() {
+    return constant.hashCode();
+  }
+}
diff --git a/google-cloud-storage/src/main/java/com/google/cloud/storage/StorageClass.java b/google-cloud-storage/src/main/java/com/google/cloud/storage/StorageClass.java
@@ -15,39 +15,82 @@
  */
 package com.google.cloud.storage;
 
+import com.google.api.core.ApiFunction;
+import com.google.cloud.StringEnumType;
+import com.google.cloud.StringEnumValue;
+
 /**
  * Enums for the storage classes.
  * See https://cloud.google.com/storage/docs/storage-classes for details.
  */
-public enum StorageClass {
+public class StorageClass extends StringEnumValue {
+
+  private StorageClass(String constant) {
+    super(constant);
+  }
+
+  private static ApiFunction<String, StorageClass> CONSTRUCTOR =
+      new ApiFunction<String, StorageClass>() {
+        @Override
+        public StorageClass apply(String constant) {
+          return new StorageClass(constant);
+        }
+      };
+
+  private static StringEnumType<StorageClass> type = new StringEnumType(
+      StorageClass.class.getName(),
+      CONSTRUCTOR);
 
   /**
    * Regional storage class.
    */
-  REGIONAL,
+  public static StorageClass REGIONAL = type.createAndRegister("REGIONAL");
 
   /**
    * Multi-regional storage class.
    */
-  MULTI_REGIONAL,
+  public static StorageClass MULTI_REGIONAL = type.createAndRegister("MULTI_REGIONAL");
 
   /**
    * Nearline storage class.
    */
-  NEARLINE,
+  public static StorageClass NEARLINE = type.createAndRegister("NEARLINE");
 
   /**
    * Coldline storage class.
    */
-  COLDLINE,
+  public static StorageClass COLDLINE = type.createAndRegister("COLDLINE");
 
   /**
    * Standard storage class.
    */
-  STANDARD,
+  public static StorageClass STANDARD = type.createAndRegister("STANDARD");
 
   /**
    * Durable Reduced Availability (deprecated)
    */
-  DURABLE_REDUCED_AVAILABILITY,
+  public static StorageClass DURABLE_REDUCED_AVAILABILITY = type.createAndRegister(
+      "DURABLE_REDUCED_AVAILABILITY");
+
+  /**
+   * Get the StorageClass for the given String constant, and throw an exception if the constant is
+   * not recognized.
+   */
+  public static StorageClass valueOfStrict(String constant) {
+    return type.valueOfStrict(constant);
+  }
+
+  /**
+   * Get the StorageClass for the given String constant, and allow unrecognized values.
+   */
+  public static StorageClass valueOf(String constant) {
+    return type.valueOf(constant);
+  }
+
+  /**
+   * Return the known values for StorageClass.
+   */
+  public static StorageClass[] values() {
+    return type.values();
+  }
 }
