[ONOS-6170] Implement codec for MappingInstruction primitives

Change-Id: Ib372de863e6d730c55326ef3450d6f79478592b5
diff --git a/apps/mappingmanagement/web/src/main/java/org/onosproject/mapping/web/codec/DecodeMappingInstructionCodecHelper.java b/apps/mappingmanagement/web/src/main/java/org/onosproject/mapping/web/codec/DecodeMappingInstructionCodecHelper.java
new file mode 100644
index 0000000..9519439
--- /dev/null
+++ b/apps/mappingmanagement/web/src/main/java/org/onosproject/mapping/web/codec/DecodeMappingInstructionCodecHelper.java
@@ -0,0 +1,113 @@
+/*
+ * Copyright 2017-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.mapping.web.codec;
+
+import com.fasterxml.jackson.databind.node.ObjectNode;
+import org.onosproject.codec.CodecContext;
+import org.onosproject.mapping.instructions.MappingInstruction;
+import org.onosproject.mapping.instructions.MappingInstructions;
+import org.onosproject.mapping.instructions.MulticastMappingInstruction;
+import org.onosproject.mapping.instructions.UnicastMappingInstruction;
+
+import static org.onlab.util.Tools.nullIsIllegal;
+
+/**
+ * Decoding portion of the mapping instruction codec.
+ */
+public final class DecodeMappingInstructionCodecHelper {
+    private final ObjectNode json;
+    private final CodecContext context;
+
+    /**
+     * Creates a decode mapping instruction codec object.
+     *
+     * @param json    JSON object to decode
+     * @param context codec context
+     */
+    public DecodeMappingInstructionCodecHelper(ObjectNode json, CodecContext context) {
+        this.json = json;
+        this.context = context;
+    }
+
+    /**
+     * Decodes an unicast mapping instruction.
+     *
+     * @return mapping instruction object decoded from the JSON
+     * @throws IllegalArgumentException if the JSON is invalid
+     */
+    private MappingInstruction decodeUnicast() {
+        String subType = nullIsIllegal(json.get(MappingInstructionCodec.SUBTYPE),
+                MappingInstructionCodec.SUBTYPE + MappingInstructionCodec.ERROR_MESSAGE).asText();
+
+        if (subType.equals(UnicastMappingInstruction.UnicastType.WEIGHT.name())) {
+            int weight = nullIsIllegal(json.get(MappingInstructionCodec.UNICAST_WEIGHT),
+                    MappingInstructionCodec.UNICAST_WEIGHT +
+                            MappingInstructionCodec.MISSING_MEMBER_MESSAGE).asInt();
+            return MappingInstructions.unicastWeight(weight);
+        } else if (subType.equals(UnicastMappingInstruction.UnicastType.PRIORITY.name())) {
+            int priority = nullIsIllegal(json.get(MappingInstructionCodec.UNICAST_PRIORITY),
+                    MappingInstructionCodec.UNICAST_PRIORITY +
+                            MappingInstructionCodec.MISSING_MEMBER_MESSAGE).asInt();
+            return MappingInstructions.unicastPriority(priority);
+        }
+        throw new IllegalArgumentException("Unicast MappingInstruction subtype "
+                + subType + " is not supported");
+    }
+
+    /**
+     * Decodes a multicast mapping instruction.
+     *
+     * @return mapping instruction object decoded from the JSON
+     * @throws IllegalArgumentException if the JSON is invalid
+     */
+    private MappingInstruction decodeMulticast() {
+        String subType = nullIsIllegal(json.get(MappingInstructionCodec.SUBTYPE),
+                MappingInstructionCodec.SUBTYPE + MappingInstructionCodec.ERROR_MESSAGE).asText();
+
+        if (subType.equals(MulticastMappingInstruction.MulticastType.WEIGHT.name())) {
+            int weight = nullIsIllegal(json.get(MappingInstructionCodec.MULTICAST_WEIGHT),
+                    MappingInstructionCodec.MULTICAST_WEIGHT +
+                            MappingInstructionCodec.MISSING_MEMBER_MESSAGE).asInt();
+            return MappingInstructions.multicastWeight(weight);
+        } else if (subType.equals(MulticastMappingInstruction.MulticastType.PRIORITY.name())) {
+            int priority = nullIsIllegal(json.get(MappingInstructionCodec.MULTICAST_PRIORITY),
+                    MappingInstructionCodec.MULTICAST_PRIORITY +
+                            MappingInstructionCodec.MISSING_MEMBER_MESSAGE).asInt();
+            return MappingInstructions.multicastPriority(priority);
+        }
+        throw new IllegalArgumentException("Multicast MappingInstruction subtype "
+                + subType + " is not supported");
+    }
+
+    /**
+     * Decodes the JSON into a mapping instruction object.
+     *
+     * @return MappingInstruction object
+     * @throws IllegalArgumentException if the JSON is invalid
+     */
+    public MappingInstruction decode() {
+        String type = nullIsIllegal(json.get(MappingInstructionCodec.TYPE),
+                MappingInstructionCodec.TYPE + MappingInstructionCodec.ERROR_MESSAGE).asText();
+
+        if (type.equals(MappingInstruction.Type.UNICAST.name())) {
+            return decodeUnicast();
+        } else if (type.equals(MappingInstruction.Type.MULTICAST.name())) {
+            return decodeMulticast();
+        }
+        throw new IllegalArgumentException("MappingInstruction type "
+                + type + " is not supported");
+    }
+}