Add logic to fetch previousClusterUUID

Signed-off-by: Sooraj Sinha <soosinha@amazon.com>

server/src/main/java/org/opensearch/gateway/remote/ClusterMetadataManifest.java

@@ -41,6 +41,7 @@ public class ClusterMetadataManifest implements Writeable, ToXContentFragment {
     private static final ParseField NODE_ID_FIELD = new ParseField("node_id");
     private static final ParseField COMMITTED_FIELD = new ParseField("committed");
     private static final ParseField INDICES_FIELD = new ParseField("indices");
+    private static final ParseField PREVIOUS_CLUSTER_UUID = new ParseField("previous_cluster_uuid");
 
     private static long term(Object[] fields) {
         return (long) fields[0];
@@ -74,6 +75,10 @@ private static List<UploadedIndexMetadata> indices(Object[] fields) {
         return (List<UploadedIndexMetadata>) fields[7];
     }
 
+    private static String previousClusterUUID(Object[] fields) {
+        return (String) fields[8];
+    }
+
     private static final ConstructingObjectParser<ClusterMetadataManifest, Void> PARSER = new ConstructingObjectParser<>(
         "cluster_metadata_manifest",
         fields -> new ClusterMetadataManifest(
@@ -84,7 +89,8 @@ private static List<UploadedIndexMetadata> indices(Object[] fields) {
             opensearchVersion(fields),
             nodeId(fields),
             committed(fields),
-            indices(fields)
+            indices(fields),
+            previousClusterUUID(fields)
         )
     );
 
@@ -101,6 +107,7 @@ private static List<UploadedIndexMetadata> indices(Object[] fields) {
             (p, c) -> UploadedIndexMetadata.fromXContent(p),
             INDICES_FIELD
         );
+        PARSER.declareString(ConstructingObjectParser.constructorArg(), PREVIOUS_CLUSTER_UUID);
     }
 
     private final List<UploadedIndexMetadata> indices;
@@ -111,6 +118,7 @@ private static List<UploadedIndexMetadata> indices(Object[] fields) {
     private final Version opensearchVersion;
     private final String nodeId;
     private final boolean committed;
+    private final String previousClusterUUID;
 
     public List<UploadedIndexMetadata> getIndices() {
         return indices;
@@ -144,6 +152,10 @@ public boolean isCommitted() {
         return committed;
     }
 
+    public String getPreviousClusterUUID() {
+        return previousClusterUUID;
+    }
+
     public ClusterMetadataManifest(
         long clusterTerm,
         long version,
@@ -152,7 +164,8 @@ public ClusterMetadataManifest(
         Version opensearchVersion,
         String nodeId,
         boolean committed,
-        List<UploadedIndexMetadata> indices
+        List<UploadedIndexMetadata> indices,
+        String previousClusterUUID
     ) {
         this.clusterTerm = clusterTerm;
         this.stateVersion = version;
@@ -162,6 +175,7 @@ public ClusterMetadataManifest(
         this.nodeId = nodeId;
         this.committed = committed;
         this.indices = Collections.unmodifiableList(indices);
+        this.previousClusterUUID = previousClusterUUID;
     }
 
     public ClusterMetadataManifest(StreamInput in) throws IOException {
@@ -173,6 +187,7 @@ public ClusterMetadataManifest(StreamInput in) throws IOException {
         this.nodeId = in.readString();
         this.committed = in.readBoolean();
         this.indices = Collections.unmodifiableList(in.readList(UploadedIndexMetadata::new));
+        this.previousClusterUUID = in.readString();
     }
 
     public static Builder builder() {
@@ -199,6 +214,7 @@ public XContentBuilder toXContent(XContentBuilder builder, Params params) throws
             }
         }
         builder.endArray();
+        builder.field(PREVIOUS_CLUSTER_UUID.getPreferredName(), getPreviousClusterUUID());
         return builder;
     }
 
@@ -212,6 +228,7 @@ public void writeTo(StreamOutput out) throws IOException {
         out.writeString(nodeId);
         out.writeBoolean(committed);
         out.writeCollection(indices);
+        out.writeString(previousClusterUUID);
     }
 
     @Override
@@ -230,12 +247,23 @@ public boolean equals(Object o) {
             && Objects.equals(stateUUID, that.stateUUID)
             && Objects.equals(opensearchVersion, that.opensearchVersion)
             && Objects.equals(nodeId, that.nodeId)
-            && Objects.equals(committed, that.committed);
+            && Objects.equals(committed, that.committed)
+            && Objects.equals(previousClusterUUID, that.previousClusterUUID);
     }
 
     @Override
     public int hashCode() {
-        return Objects.hash(indices, clusterTerm, stateVersion, clusterUUID, stateUUID, opensearchVersion, nodeId, committed);
+        return Objects.hash(
+            indices,
+            clusterTerm,
+            stateVersion,
+            clusterUUID,
+            stateUUID,
+            opensearchVersion,
+            nodeId,
+            committed,
+            previousClusterUUID
+        );
     }
 
     @Override
@@ -261,6 +289,7 @@ public static class Builder {
         private String stateUUID;
         private Version opensearchVersion;
         private String nodeId;
+        private String previousClusterUUID;
         private boolean committed;
 
         public Builder indices(List<UploadedIndexMetadata> indices) {
@@ -307,6 +336,11 @@ public List<UploadedIndexMetadata> getIndices() {
             return indices;
         }
 
+        public Builder previousClusterUUID(String previousClusterUUID) {
+            this.previousClusterUUID = previousClusterUUID;
+            return this;
+        }
+
         public Builder() {
             indices = new ArrayList<>();
         }
@@ -320,6 +354,7 @@ public Builder(ClusterMetadataManifest manifest) {
             this.nodeId = manifest.nodeId;
             this.committed = manifest.committed;
             this.indices = new ArrayList<>(manifest.indices);
+            this.previousClusterUUID = manifest.previousClusterUUID;
         }
 
         public ClusterMetadataManifest build() {
@@ -331,7 +366,8 @@ public ClusterMetadataManifest build() {
                 opensearchVersion,
                 nodeId,
                 committed,
-                indices
+                indices,
+                previousClusterUUID
             );
         }