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/*
 * Copyright Terracotta, Inc.
 *
 * 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.terracotta.management.registry;

import org.terracotta.management.call.Parameter;
import org.terracotta.management.capabilities.context.CapabilityContext;
import org.terracotta.management.capabilities.descriptors.Descriptor;
import org.terracotta.management.context.Context;
import org.terracotta.management.registry.action.ExposedObject;
import org.terracotta.management.registry.action.Named;
import org.terracotta.management.registry.action.RequiredContext;
import org.terracotta.management.stats.Statistic;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Map;
import java.util.Queue;
import java.util.concurrent.ConcurrentLinkedQueue;

/**
 * @author Mathieu Carbou
 */
public abstract class AbstractManagementProvider implements ManagementProvider {

  protected final Queue> managedObjects = new ConcurrentLinkedQueue>();

  private final String capabilityName;
  private final Class managedType;
  private final CapabilityContext capabilityContext;

  public AbstractManagementProvider(Class managedType) {
    this.managedType = managedType;
    this.capabilityName = buildCapabilityName();
    this.capabilityContext = buildCapabilityContext();
  }

  @Override
  public final Class getManagedType() {
    return managedType;
  }

  @Override
  public final String getCapabilityName() {
    return capabilityName;
  }

  @Override
  public final CapabilityContext getCapabilityContext() {
    return capabilityContext;
  }

  @Override
  public final void register(T managedObject) {
    this.managedObjects.add(wrap(managedObject));
  }

  @Override
  public final void unregister(T managedObject) {
    for (ExposedObject exposedObject : managedObjects) {
      if (exposedObject.getTarget() == managedObject) {
        if (this.managedObjects.remove(exposedObject)) {
          dispose(exposedObject);
        }
      }
    }
  }

  @Override
  public final void close() {
    while (!managedObjects.isEmpty()) {
      dispose(managedObjects.poll());
    }
  }

  @Override
  public final boolean supports(Context context) {
    return findExposedObject(context) != null;
  }

  @Override
  public Map> collectStatistics(Context context, Collection statisticNames, long since) {
    throw new UnsupportedOperationException("Not a statistics provider : " + getCapabilityName());
  }

  @Override
  public final void callAction(Context context, String methodName, Parameter... parameters) {
    callAction(context, methodName, Object.class, parameters);
  }

  @Override
  public  V callAction(Context context, String methodName, Class returnType, Parameter... parameters) {
    throw new UnsupportedOperationException("Not an action provider : " + getCapabilityName());
  }

  @Override
  public Collection getDescriptors() {
    return Collections.emptyList();
  }

  protected String buildCapabilityName() {
    Named named = getClass().getAnnotation(Named.class);
    return named == null ? getClass().getSimpleName() : named.value();
  }

  // first try to find annotation on managedType, which might not be there, in this case tries to find from this subclass
  protected CapabilityContext buildCapabilityContext() {
    Collection attrs = new ArrayList();
    RequiredContext requiredContext = getManagedType().getAnnotation(RequiredContext.class);
    if (requiredContext == null) {
      requiredContext = getClass().getAnnotation(RequiredContext.class);
    }
    if (requiredContext == null) {
      throw new IllegalStateException("@RequiredContext not found on " + getManagedType().getName() + " or " + getClass().getName());
    }
    for (Named n : requiredContext.value()) {
      attrs.add(new CapabilityContext.Attribute(n.value(), true));
    }
    return new CapabilityContext(attrs);
  }

  protected void dispose(ExposedObject exposedObject) {
  }

  protected abstract ExposedObject wrap(T managedObject);

  protected final ExposedObject findExposedObject(Context context) {
    if (!contextValid(context)) {
      return null;
    }
    for (ExposedObject managedObject : managedObjects) {
      if (managedObject.matches(context)) {
        return managedObject;
      }
    }
    return null;
  }

  private boolean contextValid(Context context) {
    if (context == null) {
      return false;
    }
    for (CapabilityContext.Attribute attribute : getCapabilityContext().getAttributes()) {
      if (context.get(attribute.getName()) == null) {
        return false;
      }
    }
    return true;
  }

}