Expose WriteRequest.RefreshPolicy string representation (#23106)

This commit changes the RefreshPolicy enum so that string representation are exposed. This will help the high level rest client to simply use  refreshPolicy.getValue() to get the corresponding parameter value of a given refresh policy.

core/src/main/java/org/elasticsearch/action/support/WriteRequest.java

@@ -65,36 +65,43 @@ public interface WriteRequest<R extends WriteRequest<R>> extends Streamable {
         /**
          * Don't refresh after this request. The default.
          */
-        NONE,
+        NONE("false"),
         /**
          * Force a refresh as part of this request. This refresh policy does not scale for high indexing or search throughput but is useful
          * to present a consistent view to for indices with very low traffic. And it is wonderful for tests!
          */
-        IMMEDIATE,
+        IMMEDIATE("true"),
         /**
          * Leave this request open until a refresh has made the contents of this request visible to search. This refresh policy is
          * compatible with high indexing and search throughput but it causes the request to wait to reply until a refresh occurs.
          */
-        WAIT_UNTIL;
+        WAIT_UNTIL("wait_for");
+
+        private final String value;
+
+        RefreshPolicy(String value) {
+            this.value = value;
+        }
+
+        public String getValue() {
+            return value;
+        }
 
         /**
          * Parse the string representation of a refresh policy, usually from a request parameter.
          */
-        public static RefreshPolicy parse(String string) {
-            switch (string) {
-            case "false":
-                return NONE;
-            /*
-             * Empty string is IMMEDIATE because that makes "POST /test/test/1?refresh" perform a refresh which reads well and is what folks
-             * are used to.
-             */
-            case "":
-            case "true":
-                return IMMEDIATE;
-            case "wait_for":
-                return WAIT_UNTIL;
+        public static RefreshPolicy parse(String value) {
+            for (RefreshPolicy policy : values()) {
+                if (policy.getValue().equals(value)) {
+                    return policy;
+                }
             }
-            throw new IllegalArgumentException("Unknown value for refresh: [" + string + "].");
+            if ("".equals(value)) {
+                // Empty string is IMMEDIATE because that makes "POST /test/test/1?refresh" perform
+                // a refresh which reads well and is what folks are used to.
+                return IMMEDIATE;
+            }
+            throw new IllegalArgumentException("Unknown value for refresh: [" + value + "].");
         }
 
         public static RefreshPolicy readFrom(StreamInput in) throws IOException {

core/src/test/java/org/elasticsearch/action/support/RefreshPolicyTests.java

@@ -0,0 +1,54 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you 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 org.elasticsearch.action.support;
+
+import org.elasticsearch.common.io.stream.BytesStreamOutput;
+import org.elasticsearch.common.io.stream.StreamInput;
+import org.elasticsearch.test.ESTestCase;
+
+import java.io.IOException;
+
+public class RefreshPolicyTests extends ESTestCase {
+
+    public void testSerialization() throws IOException {
+        final WriteRequest.RefreshPolicy refreshPolicy = randomFrom(WriteRequest.RefreshPolicy.values());
+        try (BytesStreamOutput out = new BytesStreamOutput()) {
+            refreshPolicy.writeTo(out);
+            try (StreamInput in = out.bytes().streamInput()) {
+                WriteRequest.RefreshPolicy deserializedRefreshPolicy = WriteRequest.RefreshPolicy.readFrom(in);
+                assertEquals(refreshPolicy, deserializedRefreshPolicy);
+            }
+        }
+    }
+
+    public void testParse() throws IOException {
+        final String refreshPolicyValue = randomFrom(WriteRequest.RefreshPolicy.values()).getValue();
+        assertEquals(refreshPolicyValue, WriteRequest.RefreshPolicy.parse(refreshPolicyValue).getValue());
+    }
+
+    public void testParseEmpty() throws IOException {
+        assertEquals(WriteRequest.RefreshPolicy.IMMEDIATE, WriteRequest.RefreshPolicy.parse(""));
+    }
+
+    public void testParseUnknown() throws IOException {
+        IllegalArgumentException e = expectThrows(IllegalArgumentException.class, () -> WriteRequest.RefreshPolicy.parse("unknown"));
+        assertEquals("Unknown value for refresh: [unknown].", e.getMessage());
+    }
+}