Support pretty option for _explain request

* Added a formatter to print explain response in pretty format of json.

* Added pretty option for _explain request.

* Added integration test.

* Added unittest.

src/main/java/com/amazon/opendistroforelasticsearch/sql/plugin/RestSqlAction.java

@@ -23,6 +23,7 @@
 import com.amazon.opendistroforelasticsearch.sql.executor.ActionRequestRestExecutorFactory;
 import com.amazon.opendistroforelasticsearch.sql.executor.RestExecutor;
 import com.amazon.opendistroforelasticsearch.sql.executor.format.ErrorMessage;
+import com.amazon.opendistroforelasticsearch.sql.utils.JsonPrettyFormatter;
 import com.amazon.opendistroforelasticsearch.sql.metrics.MetricName;
 import com.amazon.opendistroforelasticsearch.sql.metrics.Metrics;
 import com.amazon.opendistroforelasticsearch.sql.query.QueryAction;
@@ -139,11 +140,18 @@ private static QueryAction explainRequest(final NodeClient client, final SqlRequ
 
     private void executeSqlRequest(final RestRequest request, final QueryAction queryAction,
                                    final Client client, final RestChannel channel) throws Exception {
+        Map<String, String> params = request.params();
         if (isExplainRequest(request)) {
             final String jsonExplanation = queryAction.explain().explain();
-            channel.sendResponse(new BytesRestResponse(OK, "application/json; charset=UTF-8", jsonExplanation));
+            String result;
+            if (params.containsKey("pretty")
+                    && ("".equals(params.get("pretty")) || "true".equals(params.get("pretty")))) {
+                result = JsonPrettyFormatter.format(jsonExplanation);
+            } else {
+                result = jsonExplanation;
+            }
+            channel.sendResponse(new BytesRestResponse(OK, "application/json; charset=UTF-8", result));
         } else {
-            Map<String, String> params = request.params();
             RestExecutor restExecutor = ActionRequestRestExecutorFactory.createExecutor(params.get("format"),
                     queryAction);
             //doing this hack because elasticsearch throws exception for un-consumed props

src/main/java/com/amazon/opendistroforelasticsearch/sql/utils/JsonPrettyFormatter.java

@@ -0,0 +1,53 @@
+/*
+ *   Copyright 2019 Amazon.com, Inc. or its affiliates. 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.
+ *   A copy of the License is located at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *   or in the "license" file accompanying this file. This file 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.amazon.opendistroforelasticsearch.sql.utils;
+
+import org.elasticsearch.common.Strings;
+import org.elasticsearch.common.xcontent.LoggingDeprecationHandler;
+import org.elasticsearch.common.xcontent.NamedXContentRegistry;
+import org.elasticsearch.common.xcontent.XContentBuilder;
+import org.elasticsearch.common.xcontent.XContentFactory;
+import org.elasticsearch.common.xcontent.XContentParser;
+import org.elasticsearch.common.xcontent.XContentType;
+
+import java.io.IOException;
+
+/**
+ * Utility Class for formatting Json string pretty.
+ */
+public class JsonPrettyFormatter {
+
+    /**
+     * @param jsonString Json string without/with pretty format
+     * @return A standard and pretty formatted json string
+     * @throws IOException
+     */
+    public static String format(String jsonString) throws IOException {
+        //turn _explain response into pretty formatted Json
+        XContentBuilder contentBuilder = XContentFactory.jsonBuilder().prettyPrint();
+        try (
+                XContentParser contentParser = XContentFactory.xContent(XContentType.JSON)
+                        .createParser(NamedXContentRegistry.EMPTY, LoggingDeprecationHandler.INSTANCE, jsonString)
+        ){
+            contentBuilder.copyCurrentStructure(contentParser);
+        }
+        return Strings.toString(contentBuilder);
+    }
+
+    private JsonPrettyFormatter() {
+        throw new AssertionError(getClass().getCanonicalName() + " is a utility class and must not be initialized");
+    }
+}

src/test/java/com/amazon/opendistroforelasticsearch/sql/esintgtest/PrettyFormatterIT.java

@@ -0,0 +1,72 @@
+/*
+ *   Copyright 2019 Amazon.com, Inc. or its affiliates. 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.
+ *   A copy of the License is located at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *   or in the "license" file accompanying this file. This file 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.amazon.opendistroforelasticsearch.sql.esintgtest;
+
+import com.amazon.opendistroforelasticsearch.sql.utils.StringUtils;
+import com.google.common.io.Files;
+import org.elasticsearch.client.Request;
+import org.elasticsearch.client.Response;
+import org.elasticsearch.client.RestClient;
+import org.elasticsearch.test.ESIntegTestCase;
+import org.junit.Test;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+
+import static com.amazon.opendistroforelasticsearch.sql.esintgtest.TestsConstants.TEST_INDEX_ACCOUNT;
+import static org.hamcrest.Matchers.equalTo;
+
+public class PrettyFormatterIT extends SQLIntegTestCase{
+
+    @Override
+    protected void init() throws Exception {
+        loadIndex(Index.ACCOUNT);
+    }
+
+    @Test
+    public void assertExplainPrettyFormatted() throws IOException {
+        String query = StringUtils.format("SELECT firstname FROM %s", TEST_INDEX_ACCOUNT);
+
+        String notPrettyExplainOutputFilePath = TestUtils.getResourceFilePath(
+                "src/test/resources/expectedOutput/explainIT_format_not_pretty.json");
+        String notPrettyExplainOutput = Files.toString(new File(notPrettyExplainOutputFilePath), StandardCharsets.UTF_8);
+
+        assertThat(executeExplainRequest(query, ""), equalTo(notPrettyExplainOutput));
+        assertThat(executeExplainRequest(query, "pretty=false"), equalTo(notPrettyExplainOutput));
+
+        String prettyExplainOutputFilePath = TestUtils.getResourceFilePath(
+                "src/test/resources/expectedOutput/explainIT_format_pretty.json");
+        String prettyExplainOutput = Files.toString(new File(prettyExplainOutputFilePath), StandardCharsets.UTF_8);
+
+        assertThat(executeExplainRequest(query, "pretty"), equalTo(prettyExplainOutput));
+        assertThat(executeExplainRequest(query, "pretty=true"), equalTo(prettyExplainOutput));
+    }
+
+    private String executeExplainRequest(String query, String explainParam) throws IOException {
+        String endpoint = "/_opendistro/_sql/_explain?" + explainParam;
+        String request = makeRequest(query);
+
+        Request sqlRequest = new Request("POST", endpoint);
+        sqlRequest.setJsonEntity(request);
+
+        RestClient restClient = ESIntegTestCase.getRestClient();
+        Response response = restClient.performRequest(sqlRequest);
+        String responseString = TestUtils.getResponseBody(response, true);
+
+        return responseString;
+    }
+}

src/test/java/com/amazon/opendistroforelasticsearch/sql/unittest/PrettyFormatterTest.java

@@ -0,0 +1,68 @@
+/*
+ *   Copyright 2019 Amazon.com, Inc. or its affiliates. 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.
+ *   A copy of the License is located at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *   or in the "license" file accompanying this file. This file 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.amazon.opendistroforelasticsearch.sql.unittest;
+
+import com.amazon.opendistroforelasticsearch.sql.esintgtest.TestUtils;
+import com.amazon.opendistroforelasticsearch.sql.utils.JsonPrettyFormatter;
+import com.google.common.io.Files;
+import org.junit.Test;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.equalTo;
+
+public class PrettyFormatterTest {
+
+    @Test
+    public void assertFormatterWithoutContentInside() throws IOException {
+        String noContentInput = "{ }";
+        String expectedOutput = "{ }";
+        String result = JsonPrettyFormatter.format(noContentInput);
+        assertThat(result, equalTo(expectedOutput));
+    }
+
+    @Test
+    public void assertFormatterOutputsPrettyJson() throws IOException {
+        String explainFormattedPrettyFilePath = TestUtils.getResourceFilePath(
+                "/src/test/resources/expectedOutput/explain_format_pretty.json");
+        String explainFormattedPretty = Files.toString(new File(explainFormattedPrettyFilePath), StandardCharsets.UTF_8);
+
+        String explainFormattedOnelineFilePath = TestUtils.getResourceFilePath(
+                "/src/test/resources/explain_format_oneline.json");
+        String explainFormattedOneline = Files.toString(new File(explainFormattedOnelineFilePath), StandardCharsets.UTF_8);
+        String result = JsonPrettyFormatter.format(explainFormattedOneline);
+
+        assertThat(result, equalTo(explainFormattedPretty));
+    }
+
+    @Test(expected = IOException.class)
+    public void illegalInputOfNull() throws IOException {
+        JsonPrettyFormatter.format("");
+    }
+
+    @Test(expected = IOException.class)
+    public void illegalInputOfUnpairedBrace() throws IOException {
+        JsonPrettyFormatter.format("{\"key\" : \"value\"");
+    }
+
+    @Test(expected = IOException.class)
+    public void illegalInputOfWrongBraces() throws IOException {
+        JsonPrettyFormatter.format("<\"key\" : \"value\">");
+    }
+}

src/test/resources/expectedOutput/explainIT_format_not_pretty.json

@@ -0,0 +1 @@
+{"from":0,"size":200,"_source":{"includes":["firstname"],"excludes":[]}}

src/test/resources/expectedOutput/explainIT_format_pretty.json

@@ -0,0 +1,10 @@
+{
+  "from" : 0,
+  "size" : 200,
+  "_source" : {
+    "includes" : [
+      "firstname"
+    ],
+    "excludes" : [ ]
+  }
+}

src/test/resources/expectedOutput/explain_format_pretty.json

@@ -0,0 +1,10 @@
+{
+  "from" : 0,
+  "size" : 200,
+  "_source" : {
+    "includes" : [
+      "firstname"
+    ],
+    "excludes" : [ ]
+  }
+}

src/test/resources/explain_format_oneline.json

@@ -0,0 +1 @@
+{"from" : 0, "size" : 200, "_source" : {"includes" : ["firstname"], "excludes" : [ ]}}