/*
  ==============================================================================

   This file is part of the JUCE framework.
   Copyright (c) Raw Material Software Limited

   JUCE is an open source framework subject to commercial or open source
   licensing.

   By downloading, installing, or using the JUCE framework, or combining the
   JUCE framework with any other source code, object code, content or any other
   copyrightable work, you agree to the terms of the JUCE End User Licence
   Agreement, and all incorporated terms including the JUCE Privacy Policy and
   the JUCE Website Terms of Service, as applicable, which will bind you. If you
   do not agree to the terms of these agreements, we will not license the JUCE
   framework to you, and you must discontinue the installation or download
   process and cease use of the JUCE framework.

   JUCE End User Licence Agreement: https://juce.com/legal/juce-9-licence/
   JUCE Privacy Policy: https://juce.com/juce-privacy-policy
   JUCE Website Terms of Service: https://juce.com/juce-website-terms-of-service/

   Or:

   You may also use this code under the terms of the AGPLv3:
   https://www.gnu.org/licenses/agpl-3.0.en.html

   THE JUCE FRAMEWORK IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL
   WARRANTIES, WHETHER EXPRESSED OR IMPLIED, INCLUDING WARRANTY OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, ARE DISCLAIMED.

  ==============================================================================
*/

namespace juce
{

//==============================================================================
/**
    Holds a list of ChangeListeners, and sends messages to them when instructed.

    @see ChangeListener

    @tags{Events}
*/
class JUCE_API  ChangeBroadcaster
{
public:
    //==============================================================================
    /** Creates an ChangeBroadcaster. */
    ChangeBroadcaster() noexcept;

    /** Destructor. */
    virtual ~ChangeBroadcaster();

    //==============================================================================
    /** Registers a listener to receive change callbacks from this broadcaster.
        Trying to add a listener that's already on the list will have no effect.
    */
    void addChangeListener (ChangeListener* listener);

    /** Unregisters a listener from the list.
        If the listener isn't on the list, this won't have any effect.
    */
    void removeChangeListener (ChangeListener* listener);

    /** Removes all listeners from the list. */
    void removeAllChangeListeners();

    //==============================================================================
    /** Causes an asynchronous change message to be sent to all the registered listeners.

        The message will be delivered asynchronously by the main message thread, so this
        method will return immediately. To call the listeners synchronously use
        sendSynchronousChangeMessage().
    */
    void sendChangeMessage();

    /** Sends a synchronous change message to all the registered listeners.

        This will immediately call all the listeners that are registered. For thread-safety
        reasons, you must only call this method on the main message thread.

        @see dispatchPendingMessages
    */
    void sendSynchronousChangeMessage();

    /** If a change message has been sent but not yet dispatched, this will call
        sendSynchronousChangeMessage() to make the callback immediately.

        For thread-safety reasons, you must only call this method on the main message thread.
    */
    void dispatchPendingMessages();

private:
    //==============================================================================
    class ChangeBroadcasterCallback  : public AsyncUpdater
    {
    public:
        ChangeBroadcasterCallback();
        ~ChangeBroadcasterCallback() override { cancelPendingUpdate(); }
        void handleAsyncUpdate() override;

        ChangeBroadcaster* owner;
    };

    friend class ChangeBroadcasterCallback;
    ChangeBroadcasterCallback broadcastCallback;
    ListenerList <ChangeListener> changeListeners;

    std::atomic<bool> anyListeners { false };

    void callListeners();

    JUCE_DECLARE_NON_COPYABLE (ChangeBroadcaster)
};

} // namespace juce
