Create interfaces for Policy Distribution

Created interfaces and some skeletal implementations. Implememtations to
be further developed in subsequent stories

Change-Id: If55be78e34c8783451cb9aa755a563bc0850e569
Issue-ID: POLICY-1029
Signed-off-by: mmis <michael.morris@ericsson.com>

5 files changed, 307 insertions, 0 deletions

diff --git a/reception/src/main/java/org/onap/policy/distribution/reception/decoding/PolicyDecoder.java b/reception/src/main/java/org/onap/policy/distribution/reception/decoding/PolicyDecoder.java
new file mode 100644
index 00000000..8306b630
--- /dev/null
+++ b/reception/src/main/java/org/onap/policy/distribution/reception/decoding/PolicyDecoder.java
@@ -0,0 +1,52 @@
+/*-
+ * ============LICENSE_START=======================================================
+ *  Copyright (C) 2018 Ericsson. All rights reserved.
+ * ================================================================================
+ * 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.
+ * 
+ * SPDX-License-Identifier: Apache-2.0
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.distribution.reception.decoding;
+
+import java.util.Collection;
+import org.onap.policy.distribution.model.Policy;
+import org.onap.policy.distribution.model.PolicyInput;
+
+/**
+ * Decodes polices from a given input.
+ *
+ * @param <T> the type of policy that will be created
+ * @param <S> the type of input to be decoded
+ */
+public interface PolicyDecoder<S extends PolicyInput, T extends Policy> {
+
+    /**
+     * Can the decoder handle input of the specified type.
+     * 
+     * @param policyInput the type
+     * @return <code>true</code if the decoder can handle the specified type
+     */
+    boolean canHandle(PolicyInput policyInput);
+
+    /**
+     * Decode policies from the given input
+     * 
+     * @param input the input
+     * @return the generated policies
+     * @throws PolicyDecodingException if an error occurs during decoding
+     */
+    Collection<T> decode(S input) throws PolicyDecodingException;
+
+}
diff --git a/reception/src/main/java/org/onap/policy/distribution/reception/decoding/PolicyDecodingException.java b/reception/src/main/java/org/onap/policy/distribution/reception/decoding/PolicyDecodingException.java
new file mode 100644
index 00000000..5f2923d8
--- /dev/null
+++ b/reception/src/main/java/org/onap/policy/distribution/reception/decoding/PolicyDecodingException.java
@@ -0,0 +1,49 @@
+/*-
+ * ============LICENSE_START=======================================================
+ *  Copyright (C) 2018 Ericsson. All rights reserved.
+ * ================================================================================
+ * 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.
+ * 
+ * SPDX-License-Identifier: Apache-2.0
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.distribution.reception.decoding;
+
+/**
+ * An error has occured while decoding a policy.
+ */
+public class PolicyDecodingException extends Exception {
+
+    private static final long serialVersionUID = 3809376274411309160L;
+
+    /**
+     * Construct an instance with the given message.
+     * 
+     * @param message the error message
+     */
+    public PolicyDecodingException(String message) {
+        super(message);
+    }
+
+    /**
+     * Construct an instance with the given message and cause.
+     * 
+     * @param message the error message
+     * @param cause the cause
+     */
+    public PolicyDecodingException(String message, Throwable cause) {
+        super(message, cause);
+    }
+
+}
diff --git a/reception/src/main/java/org/onap/policy/distribution/reception/handling/AbstractReceptionHandler.java b/reception/src/main/java/org/onap/policy/distribution/reception/handling/AbstractReceptionHandler.java
new file mode 100644
index 00000000..f728fc33
--- /dev/null
+++ b/reception/src/main/java/org/onap/policy/distribution/reception/handling/AbstractReceptionHandler.java
@@ -0,0 +1,99 @@
+/*-
+ * ============LICENSE_START=======================================================
+ *  Copyright (C) 2018 Ericsson. All rights reserved.
+ * ================================================================================
+ * 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.
+ * 
+ * SPDX-License-Identifier: Apache-2.0
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.distribution.reception.handling;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import org.onap.policy.distribution.forwarding.PolicyForwarder;
+import org.onap.policy.distribution.forwarding.PolicyForwardingException;
+import org.onap.policy.distribution.model.Policy;
+import org.onap.policy.distribution.model.PolicyInput;
+import org.onap.policy.distribution.reception.decoding.PolicyDecoder;
+import org.onap.policy.distribution.reception.decoding.PolicyDecodingException;
+import org.slf4j.ext.XLogger;
+import org.slf4j.ext.XLoggerFactory;
+
+/***
+ * Base implementation of {@link ReceptionHandler}. All reception handlers should extend this base
+ * class by implementing the {@link #initializeReception(String)} method to perform the
+ * specific initialization required to receive inputs and by invoking
+ * {@link #inputReceived(PolicyInput)} when the reception handler receives input
+ */
+public abstract class AbstractReceptionHandler implements ReceptionHandler {
+
+    private static final XLogger LOGGER = XLoggerFactory.getXLogger(AbstractReceptionHandler.class);
+
+    private PluginHandler pluginHandler;
+
+    @Override
+    public void initialize(String parameterGroupName) {
+        pluginHandler = new PluginHandler(parameterGroupName);
+        initializeReception(parameterGroupName);
+    }
+
+    /**
+     * Sub classes must implement this method to perform the specific initialization required to
+     * receive inputs, for example setting up subscriptions
+     * 
+     * @param parameterGroupName the parameter group name
+     */
+    protected abstract void initializeReception(String parameterGroupName);
+
+    /**
+     * Handle input that has been received. The given input shall be decoded using the
+     * {@link PolicyDecoder}s configured for this reception handler and forwarded using the
+     * {@link PolicyForwarder}s configured for this reception handler.
+     * 
+     * @param policyInput the input that has been received
+     * @throws PolicyDecodingException if an error occurs in decoding a policy from the received
+     *         input
+     */
+    protected void inputReceived(PolicyInput policyInput) throws PolicyDecodingException {
+
+        Collection<Policy> policies = new ArrayList<>();
+        for (PolicyDecoder<PolicyInput, Policy> policyDecoder : getRelevantPolicyDecoders(policyInput)) {
+            policies.addAll(policyDecoder.decode(policyInput));
+        }
+
+        for (PolicyForwarder policyForwarder : pluginHandler.getPolicyForwarders()) {
+            try {
+                policyForwarder.forward(policies);
+            } catch (PolicyForwardingException policyForwardingException) {
+                LOGGER.error("Error when forwarding policies to " + policyForwarder, policyForwardingException);
+            }
+        }
+    }
+
+    private Collection<PolicyDecoder<PolicyInput, Policy>> getRelevantPolicyDecoders(PolicyInput policyInput)
+            throws PolicyDecodingException {
+        Collection<PolicyDecoder<PolicyInput, Policy>> relevantPolicyDecoders = new ArrayList<>();
+        for (PolicyDecoder<PolicyInput, Policy> policyDecoder : pluginHandler.getPolicyDecoders()) {
+            if (policyDecoder.canHandle(policyInput)) {
+                relevantPolicyDecoders.add(policyDecoder);
+            }
+        }
+        if (relevantPolicyDecoders.isEmpty()) {
+            throw new PolicyDecodingException("No decoder available matching requirements");
+        }
+        return relevantPolicyDecoders;
+    }
+
+}
diff --git a/reception/src/main/java/org/onap/policy/distribution/reception/handling/PluginHandler.java b/reception/src/main/java/org/onap/policy/distribution/reception/handling/PluginHandler.java
new file mode 100644
index 00000000..d10fe0b0
--- /dev/null
+++ b/reception/src/main/java/org/onap/policy/distribution/reception/handling/PluginHandler.java
@@ -0,0 +1,66 @@
+/*-
+ * ============LICENSE_START=======================================================
+ *  Copyright (C) 2018 Ericsson. All rights reserved.
+ * ================================================================================
+ * 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.
+ * 
+ * SPDX-License-Identifier: Apache-2.0
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.distribution.reception.handling;
+
+import java.util.Collection;
+import org.onap.policy.distribution.forwarding.PolicyForwarder;
+import org.onap.policy.distribution.model.Policy;
+import org.onap.policy.distribution.model.PolicyInput;
+import org.onap.policy.distribution.reception.decoding.PolicyDecoder;
+
+/**
+ * Handles the plugins to policy distribution.
+ */
+public class PluginHandler {
+
+    private Collection<PolicyDecoder<PolicyInput, Policy>> policyDecoders;
+    private Collection<PolicyForwarder> policyForwarders;
+
+    /**
+     * Create an instance to instantiate plugins based on the given parameter group.
+     * 
+     * @param parameterGroupName the name of the parameter group
+     */
+    public PluginHandler(String parameterGroupName) {
+        // Read configuration using common/common-parameters and instantiate decoders and forwarders
+    }
+
+    /**
+     * Get the policy decoders.
+     * 
+     * @return the policy decoders
+     */
+    public Collection<PolicyDecoder<PolicyInput, Policy>> getPolicyDecoders() {
+        return policyDecoders;
+    }
+
+    /**
+     * Get the policy forwarders.
+     * 
+     * @return the policy forwarders
+     */
+    public Collection<PolicyForwarder> getPolicyForwarders() {
+        return policyForwarders;
+    }
+
+
+
+}
diff --git a/reception/src/main/java/org/onap/policy/distribution/reception/handling/ReceptionHandler.java b/reception/src/main/java/org/onap/policy/distribution/reception/handling/ReceptionHandler.java
new file mode 100644
index 00000000..85cc1db1
--- /dev/null
+++ b/reception/src/main/java/org/onap/policy/distribution/reception/handling/ReceptionHandler.java
@@ -0,0 +1,41 @@
+/*-
+ * ============LICENSE_START=======================================================
+ *  Copyright (C) 2018 Ericsson. All rights reserved.
+ * ================================================================================
+ * 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.
+ * 
+ * SPDX-License-Identifier: Apache-2.0
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.distribution.reception.handling;
+
+/**
+ * Handles input into Policy Distribution which may be decoded into a Policy.
+ */
+public interface ReceptionHandler {
+
+    /**
+     * Initialize the reception handler with the given parameters
+     * 
+     * @param parameterGroupName the name of the parameter group containing the configuration for
+     *        the reception handler
+     */
+    void initialize(String parameterGroupName);
+
+    /**
+     * Destroy the reception handler, removing any subscriptions and releasing all resources
+     */
+    void destroy();
+
+}