merge-register = mv-reg with user defined merge strategy

Author: mweberUKL

build.gradle

@@ -1,5 +1,5 @@
 group 'eu.antidotedb'
-version '0.2.0'
+version '0.2.1'
 
 apply plugin: 'java'
 apply plugin: 'maven'

src/main/java/eu/antidotedb/client/Key.java

@@ -270,6 +270,14 @@ public static FlagKey flag_dw(String key) {
         return flag_ew(ByteString.copyFromUtf8(key));
     }
 
+    public static <V> MergeRegisterKey<V> mergeRegister(ByteString key, ValueCoder<V> format, MergeRegisterKey.ValueMerger<V> merger) {
+        return new MergeRegisterKey<>(key, format, merger);
+    }
+
+    public static <V> MergeRegisterKey<V> mergeRegister(String key, ValueCoder<V> format, MergeRegisterKey.ValueMerger<V> merger) {
+        return mergeRegister(ByteString.copyFromUtf8(key), format, merger);
+    }
+
 
     AntidotePB.ApbMapKey.Builder toApbMapKey() {
         AntidotePB.ApbMapKey.Builder builder = AntidotePB.ApbMapKey.newBuilder();

src/main/java/eu/antidotedb/client/MergeRegisterKey.java

@@ -0,0 +1,26 @@
+package eu.antidotedb.client;
+
+import com.google.protobuf.ByteString;
+import eu.antidotedb.antidotepb.AntidotePB;
+
+import java.util.List;
+
+public class MergeRegisterKey<V> extends Key<V> {
+    public interface ValueMerger<V> {
+        V merge(List<V> concValues);
+    }
+
+    private ValueCoder<V> format;
+    private ValueMerger<V> merger;
+
+    MergeRegisterKey(ByteString key, ValueCoder<V> format, ValueMerger<V> merger) {
+        super(AntidotePB.CRDT_type.MVREG, key);
+        this.format = format;
+        this.merger = merger;
+    }
+
+    @Override
+    V readResponseToValue(AntidotePB.ApbReadObjectResp resp) {
+        return merger.merge(ResponseDecoder.multiValueRegister(format).readResponseToValue(resp));
+    }
+}