/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
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 * This file is part of the LibreOffice project.
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * This file incorporates work covered by the following license notice:
 *
 *   Licensed to the Apache Software Foundation (ASF) under one or more
 *   contributor license agreements. See the NOTICE file distributed
 *   with this work for additional information regarding copyright
 *   ownership. The ASF licenses this file to you 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 .
 */

#ifndef INCLUDED_SLIDESHOW_SOURCE_INC_INTERRUPTABLEDELAYEVENT_HXX
#define INCLUDED_SLIDESHOW_SOURCE_INC_INTERRUPTABLEDELAYEVENT_HXX

#include "delayevent.hxx"

namespace slideshow
{
    namespace internal
    {
        /** Event, which delays calling passed Event's fire() method
            the given amount of time.

            This is actually a facade around the passed event object,
            that passes on all calls to that object, and the sole
            contribution of itself is the delay.
        */
        class DelayFacade : public Event
        {
        public:
            DelayFacade( const EventSharedPtr&  rEvent,
                         double                 nTimeout    ) :
                Event("DelayFacade"),
                mpEvent( rEvent ),
                mnTimeout( nTimeout )
            {
            }

            virtual bool fire() override
            {
                if( mpEvent && isCharged() )
                {
                    // pass on directly - we're supposed to be called
                    // from EventQueue here, anyway - and if not,
                    // we're only keeping that incorrect transitively.
                    return mpEvent->fire();
                }

                return false;
            }

            virtual bool isCharged() const override
            {
                // pass on to wrappee - this ensures that we return
                // false on isCharged(), even if the other event has
                // been fired outside our own fire() method
                return mpEvent && mpEvent->isCharged();
            }

            virtual double getActivationTime( double nCurrentTime ) const override
            {
                // enforce _our_ timeout to our clients (this
                // overrides any timeout possibly set at the wrappee!)
                return nCurrentTime + mnTimeout;
            }

            virtual void dispose() override
            {
                mpEvent.reset();
            }

        private:
            EventSharedPtr  mpEvent;
            double          mnTimeout;
        };

        /// Return value for makeInterruptableDelay()
        struct InterruptableEventPair
        {
            /** This member contains a pointer to the timeout
                event. When enqueued, this event will fire the
                requested action only after the specified timeout.
             */
            EventSharedPtr  mpTimeoutEvent;

            /** This member contains a pointer to the interruption
                event. When enqueued, this event will fire
                immediately, interrupting a potentially waiting
                timeout event.
             */
            EventSharedPtr  mpImmediateEvent;
        };

        /** Generate an interruptable delay event.

            This function generates a pair of events, that are
            especially tailored to achieve the following behaviour: By
            default, the given functor is called after the specified
            timeout (after insertion of the event into the EventQueue,
            of course). But optionally, when the interruption event
            InterruptableEventPair::mpImmediateEvent is fired, the
            given functor is called <em>at once</em>, and the delay is
            ignored (that means, the given functor is guaranteed to be
            called at utmost once, and never twice. Furthermore, it is
            ensured that both events return false on isCharged(), once
            anyone of them has been fired already).

            @param rFunctor
            Functor to call when the event fires.

            @param nTimeout
            Timeout in seconds, to wait until functor is called.

            @returns a pair of events, where the first one waits the
            specified amount of time, and the other fires the given
            functor immediately.
         */
        template< typename Functor > InterruptableEventPair makeInterruptableDelay( const Functor&  rFunctor,
                                                                                    double          nTimeout    )
        {
            InterruptableEventPair aRes;

            aRes.mpImmediateEvent = makeEvent( rFunctor, "makeInterruptableDelay");
            aRes.mpTimeoutEvent = std::make_shared<DelayFacade>( aRes.mpImmediateEvent,
                                                        nTimeout );

            return aRes;
        }
    }
}

#endif // INCLUDED_SLIDESHOW_SOURCE_INC_INTERRUPTABLEDELAYEVENT_HXX

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