Add Flint client and index management API

flint/build.sbt

@@ -54,7 +54,13 @@ lazy val root = (project in file("."))
 
 lazy val flintCore = (project in file("flint-core"))
   .disablePlugins(AssemblyPlugin)
-  .settings(name := "flint-core", scalaVersion := scala212)
+  .settings(
+    name := "flint-core",
+    scalaVersion := scala212,
+    libraryDependencies ++= Seq(
+      "org.opensearch.client" % "opensearch-rest-client" % opensearchVersion,
+      "org.opensearch.client" % "opensearch-rest-high-level-client" % opensearchVersion)
+  )
 
 lazy val flintSparkIntegration = (project in file("flint-spark-integration"))
   .dependsOn(flintCore)
@@ -64,8 +70,6 @@ lazy val flintSparkIntegration = (project in file("flint-spark-integration"))
     name := "flint-spark-integration",
     scalaVersion := scala212,
     libraryDependencies ++= Seq(
-      "org.opensearch.client" % "opensearch-rest-client" % opensearchVersion,
-      "org.opensearch.client" % "opensearch-rest-high-level-client" % opensearchVersion,
       "org.testcontainers" % "testcontainers" % "1.18.0" % "test",
       "org.scalactic" %% "scalactic" % "3.2.15",
       "org.scalatest" %% "scalatest" % "3.2.15" % "test",
@@ -98,6 +102,7 @@ lazy val integtest = (project in file("integ-test"))
     scalaVersion := scala212,
     libraryDependencies ++= Seq(
       "org.scalactic" %% "scalactic" % "3.2.15",
-      "org.scalatest" %% "scalatest" % "3.2.15" % "test"),
+      "org.scalatest" %% "scalatest" % "3.2.15" % "test",
+      "com.stephenn" %% "scalatest-json-jsonassert" % "0.2.5" % "test"),
     libraryDependencies ++= deps(sparkVersion),
     Test / fullClasspath += (flintSparkIntegration / assembly).value)

flint/flint-core/src/main/scala/org/opensearch/flint/core/FlintClient.java

@@ -0,0 +1,39 @@
+/*
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package org.opensearch.flint.core;
+
+import org.opensearch.flint.core.metadata.FlintMetadata;
+
+/**
+ * Flint index client that provides API for metadata and data operations
+ * on a Flint index regardless of concrete storage.
+ */
+public interface FlintClient {
+
+  /**
+   * Create a Flint index with the metadata given.
+   *
+   * @param indexName index name
+   * @param metadata  index metadata
+   */
+  void createIndex(String indexName, FlintMetadata metadata);
+
+  /**
+   * Does Flint index with the given name exist
+   *
+   * @param indexName index name
+   * @return true if the index exists, otherwise false
+   */
+  boolean exists(String indexName);
+
+  /**
+   * Retrieve metadata in a Flint index.
+   *
+   * @param indexName index name
+   * @return index metadata
+   */
+  FlintMetadata getIndexMetadata(String indexName);
+}

flint/flint-core/src/main/scala/org/opensearch/flint/core/metadata/FlintMetadata.java

@@ -0,0 +1,24 @@
+/*
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package org.opensearch.flint.core.metadata;
+
+/**
+ * Flint metadata follows Flint index specification and defines metadata
+ * for a Flint index regardless of query engine integration and storage.
+ */
+public class FlintMetadata {
+
+  // TODO: define metadata format and create strong-typed class
+  private final String content;
+
+  public FlintMetadata(String content) {
+    this.content = content;
+  }
+
+  public String getContent() {
+    return content;
+  }
+}

flint/flint-core/src/main/scala/org/opensearch/flint/core/storage/FlintOpenSearchClient.java

@@ -0,0 +1,78 @@
+/*
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package org.opensearch.flint.core.storage;
+
+import java.io.IOException;
+import org.apache.http.HttpHost;
+import org.opensearch.client.RequestOptions;
+import org.opensearch.client.RestClient;
+import org.opensearch.client.RestHighLevelClient;
+import org.opensearch.client.indices.CreateIndexRequest;
+import org.opensearch.client.indices.GetIndexRequest;
+import org.opensearch.client.indices.GetMappingsRequest;
+import org.opensearch.client.indices.GetMappingsResponse;
+import org.opensearch.cluster.metadata.MappingMetadata;
+import org.opensearch.common.xcontent.XContentType;
+import org.opensearch.flint.core.FlintClient;
+import org.opensearch.flint.core.metadata.FlintMetadata;
+
+/**
+ * Flint client implementation for OpenSearch storage.
+ */
+public class FlintOpenSearchClient implements FlintClient {
+
+  /** OpenSearch host name. */
+  private final String host;
+
+  /** OpenSearch port number. */
+  private final int port;
+
+  public FlintOpenSearchClient(String host, int port) {
+    this.host = host;
+    this.port = port;
+  }
+
+  @Override
+  public void createIndex(String indexName, FlintMetadata metadata) {
+    try (RestHighLevelClient client = createClient()) {
+      CreateIndexRequest request = new CreateIndexRequest(indexName);
+      request.mapping(metadata.getContent(), XContentType.JSON);
+
+      client.indices().create(request, RequestOptions.DEFAULT);
+    } catch (Exception e) {
+      throw new IllegalStateException("Failed to create Flint index", e);
+    }
+  }
+
+  @Override
+  public boolean exists(String indexName) {
+    try (RestHighLevelClient client = createClient()) {
+      return client.indices()
+          .exists(new GetIndexRequest(indexName), RequestOptions.DEFAULT);
+    } catch (IOException e) {
+      throw new IllegalStateException("Failed to check if Flint index exists", e);
+    }
+  }
+
+  @Override
+  public FlintMetadata getIndexMetadata(String indexName) {
+    try (RestHighLevelClient client = createClient()) {
+      GetMappingsRequest request = new GetMappingsRequest().indices(indexName);
+      GetMappingsResponse response =
+          client.indices().getMapping(request, RequestOptions.DEFAULT);
+
+      MappingMetadata mapping = response.mappings().get(indexName);
+      return new FlintMetadata(mapping.source().string());
+    } catch (Exception e) {
+      throw new IllegalStateException("Failed to get Flint index metadata", e);
+    }
+  }
+
+  private RestHighLevelClient createClient() {
+    return new RestHighLevelClient(
+        RestClient.builder(new HttpHost(host, port, "http")));
+  }
+}

flint/integ-test/src/test/scala/org/opensearch/flint/OpenSearchSuite.scala

@@ -0,0 +1,56 @@
+/*
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package org.opensearch.flint
+
+import org.apache.http.HttpHost
+import org.opensearch.action.admin.indices.delete.DeleteIndexRequest
+import org.opensearch.client.{RequestOptions, RestClient, RestHighLevelClient}
+import org.opensearch.testcontainers.OpenSearchContainer
+import org.scalatest.{BeforeAndAfterAll, Suite}
+
+/**
+ * Test required OpenSearch domain should extend OpenSearchSuite.
+ */
+trait OpenSearchSuite extends BeforeAndAfterAll {
+  self: Suite =>
+
+  protected lazy val container = new OpenSearchContainer()
+
+  protected lazy val openSearchPort: Int = container.port()
+
+  protected lazy val openSearchHost: String = container.getHost
+
+  protected lazy val openSearchClient = new RestHighLevelClient(
+    RestClient.builder(new HttpHost(openSearchHost, openSearchPort, "http")))
+
+  protected lazy val openSearchOptions =
+    Map("host" -> openSearchHost, "port" -> s"$openSearchPort")
+
+  override def beforeAll(): Unit = {
+    container.start()
+    super.beforeAll()
+  }
+
+  override def afterAll(): Unit = {
+    container.close()
+    super.afterAll()
+  }
+
+  /**
+   * Delete index `indexNames` after calling `f`.
+   */
+  protected def withIndexName(indexNames: String*)(f: => Unit): Unit = {
+    try {
+      f
+    } finally {
+      indexNames.foreach { indexName =>
+        openSearchClient
+          .indices()
+          .delete(new DeleteIndexRequest(indexName), RequestOptions.DEFAULT)
+      }
+    }
+  }
+}

flint/integ-test/src/test/scala/org/opensearch/flint/core/FlintOpenSearchClientSuite.scala

@@ -0,0 +1,48 @@
+/*
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package org.opensearch.flint.core
+
+import com.stephenn.scalatest.jsonassert.JsonMatchers.matchJson
+import org.opensearch.flint.OpenSearchSuite
+import org.opensearch.flint.core.metadata.FlintMetadata
+import org.opensearch.flint.core.storage.FlintOpenSearchClient
+import org.scalatest.flatspec.AnyFlatSpec
+import org.scalatest.matchers.should.Matchers
+
+class FlintOpenSearchClientSuite
+    extends AnyFlatSpec
+    with OpenSearchSuite
+    with Matchers {
+
+  /** Lazy initialize after container started. */
+  lazy val flintClient = new FlintOpenSearchClient(openSearchHost, openSearchPort)
+
+  behavior of "Flint OpenSearch client"
+
+  it should "create index successfully" in {
+    val indexName = "test"
+    val content =
+      """ {
+        |   "_meta": {
+        |     "kind": "SkippingIndex"
+        |   },
+        |   "properties": {
+        |     "age": {
+        |       "type": "integer"
+        |     }
+        |   }
+        | }
+        |""".stripMargin
+    flintClient.createIndex(indexName, new FlintMetadata(content))
+
+    flintClient.exists(indexName) shouldBe true
+    flintClient.getIndexMetadata(indexName).getContent should matchJson (content)
+  }
+
+  it should "return false if index not exist" in {
+    flintClient.exists("non-exist-index") shouldBe false
+  }
+}