Adding metadata to support shard split and to resolve shard ids based on child shard hash

Signed-off-by: vikasvb90 <vikasvb@amazon.com>

Author: vikasvb90

server/src/main/java/org/opensearch/cluster/metadata/IndexMetadata.java

@@ -0,0 +1,134 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.cluster.metadata;
+
+import org.opensearch.common.annotation.ExperimentalApi;
+import org.opensearch.core.common.io.stream.StreamInput;
+import org.opensearch.core.common.io.stream.StreamOutput;
+import org.opensearch.core.common.io.stream.Writeable;
+import org.opensearch.core.xcontent.ToXContentFragment;
+import org.opensearch.core.xcontent.XContentBuilder;
+import org.opensearch.core.xcontent.XContentParser;
+
+import java.io.IOException;
+
+/**
+ * Represents the hash range assigned to a shard.
+ *
+ * @opensearch.experimental
+ */
+@ExperimentalApi
+public class ShardRange implements Comparable<ShardRange>, ToXContentFragment, Writeable {
+    private final int shardId;
+    private final int start;
+    private final int end;
+
+    public ShardRange(int shardId, int start, int end) {
+        this.shardId = shardId;
+        this.start = start;
+        this.end = end;
+    }
+
+    /**
+     * Constructs a new shard range from a stream.
+     * @param in the stream to read from
+     * @throws IOException if an error occurs while reading from the stream
+     * @see #writeTo(StreamOutput)
+     */
+    public ShardRange(StreamInput in) throws IOException {
+        shardId = in.readVInt();
+        start = in.readInt();
+        end = in.readInt();
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (!(o instanceof ShardRange)) return false;
+
+        ShardRange that = (ShardRange) o;
+
+        if (shardId != that.shardId) return false;
+        if (start != that.start) return false;
+        return end == that.end;
+    }
+
+    @Override
+    public int hashCode() {
+        int result = shardId;
+        result = 31 * result + start;
+        result = 31 * result + end;
+        return result;
+    }
+
+    public int getShardId() {
+        return shardId;
+    }
+
+    public int getStart() {
+        return start;
+    }
+
+    public int getEnd() {
+        return end;
+    }
+
+    public ShardRange copy() {
+        return new ShardRange(shardId, start, end);
+    }
+
+    public boolean contains(long hash) {
+        return hash >= start && hash <= end;
+    }
+
+    @Override
+    public int compareTo(ShardRange o) {
+        return Integer.compare(start, o.start);
+    }
+
+    @Override
+    public String toString() {
+        return "ShardRange{" + "shardId=" + shardId + ", start=" + start + ", end=" + end + '}';
+    }
+
+    @Override
+    public void writeTo(StreamOutput out) throws IOException {
+        out.writeVInt(shardId);
+        out.writeInt(start);
+        out.writeInt(end);
+    }
+
+    @Override
+    public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
+        builder.startObject().field("shard_id", shardId).field("start", start).field("end", end);
+        builder.endObject();
+        return builder;
+    }
+
+    public static ShardRange parse(XContentParser parser) throws IOException {
+        int shardId = -1, start = -1, end = -1;
+        XContentParser.Token token;
+        String fieldName = null;
+        while ((token = parser.nextToken()) != XContentParser.Token.END_OBJECT) {
+            if (token == XContentParser.Token.FIELD_NAME) {
+                fieldName = parser.currentName();
+            } else if (token == XContentParser.Token.VALUE_NUMBER) {
+                if ("shard_id".equals(fieldName)) {
+                    shardId = parser.intValue();
+                } else if ("start".equals(fieldName)) {
+                    start = parser.intValue();
+                } else if ("end".equals(fieldName)) {
+                    end = parser.intValue();
+                }
+            }
+        }
+
+        return new ShardRange(shardId, start, end);
+    }
+}