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/*
 * Copyright (C) 2014-2024 Philip Helger (www.helger.com)
 * philip[at]helger[dot]com
 *
 * 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 com.helger.photon.api;

import javax.annotation.Nonnull;
import javax.annotation.concurrent.GuardedBy;
import javax.annotation.concurrent.ThreadSafe;

import com.helger.commons.ValueEnforcer;
import com.helger.commons.annotation.UsedViaReflection;
import com.helger.commons.annotation.VisibleForTesting;
import com.helger.commons.string.ToStringGenerator;
import com.helger.web.scope.singleton.AbstractGlobalWebSingleton;

/**
 * Central API manager. Was reworked in v8.1.4 to clearly separate between
 * registry and invoker.
 *
 * @author Philip Helger
 */
@ThreadSafe
public class GlobalAPIInvoker extends AbstractGlobalWebSingleton
{
  @GuardedBy ("m_aRWLock")
  private IAPIRegistry m_aRegistry = new APIRegistry ();
  @GuardedBy ("m_aRWLock")
  private IAPIInvoker m_aInvoker = new APIInvoker ();

  @Deprecated (forRemoval = false)
  @UsedViaReflection
  public GlobalAPIInvoker ()
  {}

  @Nonnull
  public static GlobalAPIInvoker getInstance ()
  {
    return getGlobalSingleton (GlobalAPIInvoker.class);
  }

  /**
   * Reset all values to default. This is only intended for testing purposes.
   * ATTENTION: this removes ALL registrations!
   */
  @VisibleForTesting
  public void resetToDefault ()
  {
    m_aRegistry = new APIRegistry ();
    m_aInvoker = new APIInvoker ();
  }

  @Nonnull
  public IAPIRegistry getRegistry ()
  {
    return m_aRWLock.readLockedGet ( () -> m_aRegistry);
  }

  /**
   * Set the global registry to be used. Note: this API can only called BEFORE
   * registrations are performed. Afterwards an {@link IllegalStateException} is
   * thrown if this API is invoked.
   *
   * @param aRegistry
   *        The registry to use. May not be null.
   */
  public void setRegistry (@Nonnull final IAPIRegistry aRegistry)
  {
    ValueEnforcer.notNull (aRegistry, "Registry");
    if (m_aRWLock.readLockedBoolean ( () -> m_aRegistry.getAllAPIDescriptors ().isNotEmpty ()))
      throw new IllegalStateException ("Cannot change the registry after an API was registered!");

    m_aRWLock.writeLocked ( () -> m_aRegistry = aRegistry);
  }

  @Nonnull
  public IAPIInvoker getInvoker ()
  {
    return m_aRWLock.readLockedGet ( () -> m_aInvoker);
  }

  /**
   * Set the global invoker to be used. This can be changed during the runtime
   * of the application and is independent of the registry state. Use this to
   * e.g. increase the debug logging or tracing of the invocations.
   *
   * @param aInvoker
   *        The invoker to be used. May not be null.
   */
  public void setInvoker (@Nonnull final IAPIInvoker aInvoker)
  {
    ValueEnforcer.notNull (aInvoker, "Invoker");
    m_aRWLock.writeLocked ( () -> m_aInvoker = aInvoker);
  }

  @Override
  public String toString ()
  {
    return ToStringGenerator.getDerived (super.toString ())
                            .append ("Registry", m_aRegistry)
                            .append ("Invoker", m_aInvoker)
                            .getToString ();
  }
}