/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/*
 * 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 .
 */

#pragma once

#include <sal/types.h>
#include <com/sun/star/uno/XInterface.hpp>
#include <memory>
#include <vector>

class Size;
class SdrPage;

namespace sd::slidesorter::cache {

class BitmapCache;

/** Provide and manage the preview bitmap caches for all slide sorter
    instances.  There is one cache per active slide sorter plus a small
    number of caches that are no longer in use.  The later are kept to speed
    up the switching between views.
*/
class PageCacheManager
{
public:
    typedef std::vector< std::pair<Size, std::shared_ptr<BitmapCache> > > BestFittingPageCaches;
    typedef css::uno::Reference<css::uno::XInterface> DocumentKey;

    /** Return the one instance of the PageCacheManager class.
    */
    static std::shared_ptr<PageCacheManager> Instance();

    /** Look up the cache for the given model in which the previews have the
        specified size.  If no such cache exists, then one is created.  When
        a new BitmapCache is created its Recycle() method is called with a
        sorted list of existing caches from which the new one initialize its
        previews.
        @return
            The returned cache lives as long as somebody keeps a shared
            pointer and the ReleaseCache() method has not been called.
    */
    std::shared_ptr<BitmapCache> GetCache (
        const  DocumentKey& pDocument,
        const Size& rPreviewSize);

    /** Tell the cache manager to release its own reference to the specified
        cache.  After that the cache will live as long as the caller (and
        maybe others) holds its reference.
    */
    void ReleaseCache (const std::shared_ptr<BitmapCache>& rpCache);

    /** This is an information to the cache manager that the size of preview
        bitmaps in the specified cache has changed.

    */
    std::shared_ptr<BitmapCache> ChangeSize (
        const std::shared_ptr<BitmapCache>& rpCache,
        const Size& rOldPreviewSize,
        const Size& rNewPreviewSize);

    /** Invalidate the preview bitmap for one slide that belongs to the
        specified document.  The bitmaps for this slide in all caches are
        marked as out-of-date and will be re-created when they are requested
        the next time.
    */
    bool InvalidatePreviewBitmap (
        const DocumentKey& pDocument,
        const SdrPage* pPage);

    /** Invalidate the preview bitmaps for all slides that belong to the
        specified document.  This is necessary after model changes that
        affect e.g. page number fields.
    */
    void InvalidateAllPreviewBitmaps (const DocumentKey& pDocument);

    /** Invalidate all the caches that are currently in use and destroy
        those that are not.  This is used for example when the high contrast
        mode is turned on or off.
    */
    void InvalidateAllCaches();

    /** Call this method when a page has been deleted and its preview
        is not needed anymore.
    */
    void ReleasePreviewBitmap (const SdrPage* pPage);

private:
    /** Singleton instance of the cache manager.  Note that this is a weak
        pointer.  The (implementation class of) ViewShellBase holds a
        shared_ptr so that the cache manager has the same life time as the
        ViewShellBase.
    */
    static std::weak_ptr<PageCacheManager> mpInstance;

    /// List of active caches.
    class PageCacheContainer;
    std::unique_ptr<PageCacheContainer> mpPageCaches;

    /// List of inactive, recently used caches.
    class RecentlyUsedPageCaches;
    std::unique_ptr<RecentlyUsedPageCaches> mpRecentlyUsedPageCaches;

    /** The maximal number of recently used caches that are kept alive after
        they have become inactive, i.e. after they are not used anymore by a
        slide sorter.
    */
    static const sal_uInt32 mnMaximalRecentlyCacheCount = 2;

    PageCacheManager();
    ~PageCacheManager();

    class Deleter;
    friend class Deleter;

    std::shared_ptr<BitmapCache> GetRecentlyUsedCache(
        const DocumentKey& pDocument,
        const Size& rSize);

    /** Add the given cache to the list of recently used caches for the
        document.  There is one such list per document.  Each least has at
        most mnMaximalRecentlyCacheCount members.
    */
    void PutRecentlyUsedCache(
        DocumentKey const & pDocument,
        const Size& rPreviewSize,
        const std::shared_ptr<BitmapCache>& rpCache);

    /** This method is used internally to initialize a newly created
        BitmapCache with already existing previews.
    */
    void Recycle (
        const std::shared_ptr<BitmapCache>& rpCache,
        const DocumentKey& pDocument,
        const Size& rPreviewSize);
};

} // end of namespace ::sd::slidesorter::cache

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