Refactor Flint index metadata

build.sbt

@@ -58,7 +58,12 @@ lazy val flintCore = (project in file("flint-core"))
       "org.opensearch.client" % "opensearch-rest-high-level-client" % opensearchVersion
         exclude ("org.apache.logging.log4j", "log4j-api"),
       "com.amazonaws" % "aws-java-sdk" % "1.12.397" % "provided"
-        exclude ("com.fasterxml.jackson.core", "jackson-databind")),
+        exclude ("com.fasterxml.jackson.core", "jackson-databind"),
+      "org.scalactic" %% "scalactic" % "3.2.15" % "test",
+      "org.scalatest" %% "scalatest" % "3.2.15" % "test",
+      "org.scalatest" %% "scalatest-flatspec" % "3.2.15" % "test",
+      "org.scalatestplus" %% "mockito-4-6" % "3.2.15.0" % "test",
+      "com.stephenn" %% "scalatest-json-jsonassert" % "0.2.5" % "test"),
     publish / skip := true)
 
 lazy val pplSparkIntegration = (project in file("ppl-spark-integration"))

docs/index.md

@@ -32,20 +32,17 @@ Currently, Flint metadata is only static configuration without version control a
 
 ```json
 {
-  "version": "0.1",
-  "indexConfig": {
-    "kind": "skipping",
-    "properties": {
-      "indexedColumns": [{
-        "kind": "...",
-        "columnName": "...",
-        "columnType": "..."
-      }]
-     }
-  },
-  "source": "alb_logs",
-  "state": "active",
-  "enabled": true
+  "version": "0.1.0",
+  "name": "...",
+  "kind": "skipping",
+  "source": "...",
+  "indexedColumns": [{
+    "kind": "...",
+    "columnName": "...",
+    "columnType": "..."
+  }],
+  "options": { },
+  "properties": { }
 }
 ```
 

flint-core/src/main/scala/org/opensearch/flint/core/metadata/FlintJsonHelper.scala

@@ -0,0 +1,132 @@
+/*
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package org.opensearch.flint.core.metadata
+
+import java.nio.charset.StandardCharsets.UTF_8
+
+import org.opensearch.common.bytes.BytesReference
+import org.opensearch.common.xcontent._
+import org.opensearch.common.xcontent.json.JsonXContent
+
+/**
+ * JSON parsing and building helper.
+ */
+object FlintJsonHelper {
+
+  /**
+   * Build JSON by creating JSON builder and pass it to the given function.
+   *
+   * @param block
+   *   building logic with JSON builder
+   * @return
+   *   JSON string
+   */
+  def buildJson(block: XContentBuilder => Unit): String = {
+    val builder: XContentBuilder = XContentFactory.jsonBuilder
+    builder.startObject
+    block(builder)
+    builder.endObject()
+    BytesReference.bytes(builder).utf8ToString
+  }
+
+  /**
+   * Add an object field of the name to the JSON builder and continue building it with the given
+   * function.
+   *
+   * @param builder
+   *   JSON builder
+   * @param name
+   *   field name
+   * @param block
+   *   building logic on the JSON field
+   */
+  def objectField(builder: XContentBuilder, name: String)(block: => Unit): Unit = {
+    builder.startObject(name)
+    block
+    builder.endObject()
+  }
+
+  /**
+   * Add an optional object field of the name to the JSON builder. Add an empty object field if
+   * the value is null.
+   *
+   * @param builder
+   *   JSON builder
+   * @param name
+   *   field name
+   * @param value
+   *   field value
+   */
+  def optionalObjectField(builder: XContentBuilder, name: String, value: AnyRef): Unit = {
+    if (value == null) {
+      builder.startObject(name).endObject()
+    } else {
+      builder.field(name, value)
+    }
+  }
+
+  /**
+   * Create a XContent JSON parser on the given JSON string.
+   *
+   * @param json
+   *   JSON string
+   * @return
+   *   JSON parser
+   */
+  def createJsonParser(json: String): XContentParser = {
+    JsonXContent.jsonXContent.createParser(
+      NamedXContentRegistry.EMPTY,
+      DeprecationHandler.IGNORE_DEPRECATIONS,
+      json.getBytes(UTF_8))
+  }
+
+  /**
+   * Parse the given JSON string by creating JSON parser and pass it to the parsing function.
+   *
+   * @param json
+   *   JSON string
+   * @param block
+   *   parsing logic with the parser
+   */
+  def parseJson(json: String)(block: (XContentParser, String) => Unit): Unit = {
+    val parser = createJsonParser(json)
+
+    // Read first root object token and start parsing
+    parser.nextToken()
+    parseObjectField(parser)(block)
+  }
+
+  /**
+   * Parse each inner field in the object field with the given parsing function.
+   *
+   * @param parser
+   *   JSON parser
+   * @param block
+   *   parsing logic on each inner field
+   */
+  def parseObjectField(parser: XContentParser)(block: (XContentParser, String) => Unit): Unit = {
+    while (parser.nextToken() != XContentParser.Token.END_OBJECT) {
+      val fieldName: String = parser.currentName()
+      parser.nextToken() // Move to the field value
+
+      block(parser, fieldName)
+    }
+  }
+
+  /**
+   * Parse each inner field in the array field.
+   *
+   * @param parser
+   *   JSON parser
+   * @param block
+   *   parsing logic on each inner field
+   */
+  def parseArrayField(parser: XContentParser)(block: => Unit): Unit = {
+    while (parser.nextToken() != XContentParser.Token.END_ARRAY) {
+      block
+    }
+  }
+}