/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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/. */

#ifndef MOZILLA_GFX_TEXTURECLIENTPOOL_H
#define MOZILLA_GFX_TEXTURECLIENTPOOL_H

#include "mozilla/gfx/Types.h"
#include "mozilla/gfx/Point.h"
#include "mozilla/RefPtr.h"
#include "mozilla/layers/KnowsCompositor.h"
#include "TextureClient.h"
#include "nsITimer.h"
#include <stack>
#include <list>

namespace mozilla {
namespace layers {

class ISurfaceAllocator;
class TextureForwarder;
class TextureReadLock;

class TextureClientAllocator {
 protected:
  virtual ~TextureClientAllocator() = default;

 public:
  NS_INLINE_DECL_REFCOUNTING(TextureClientAllocator)

  virtual already_AddRefed<TextureClient> GetTextureClient() = 0;

  /**
   * Return a TextureClient that is not yet ready to be reused, but will be
   * imminently.
   */
  virtual void ReturnTextureClientDeferred(TextureClient* aClient) = 0;

  virtual void ReportClientLost() = 0;
};

class TextureClientPool final : public TextureClientAllocator {
  virtual ~TextureClientPool();

 public:
  TextureClientPool(KnowsCompositor* aKnowsCompositor,
                    gfx::SurfaceFormat aFormat, gfx::IntSize aSize,
                    TextureFlags aFlags, uint32_t aShrinkTimeoutMsec,
                    uint32_t aClearTimeoutMsec, uint32_t aInitialPoolSize,
                    uint32_t aPoolUnusedSize, TextureForwarder* aAllocator);

  /**
   * Gets an allocated TextureClient of size and format that are determined
   * by the initialisation parameters given to the pool. This will either be
   * a cached client that was returned to the pool, or a newly allocated
   * client if one isn't available.
   *
   * All clients retrieved by this method should be returned using the return
   * functions, or reported lost so that the pool can manage its size correctly.
   */
  already_AddRefed<TextureClient> GetTextureClient() override;

  /**
   * Return a TextureClient that is no longer being used and is ready for
   * immediate re-use or destruction.
   */
  void ReturnTextureClient(TextureClient* aClient);

  /**
   * Return a TextureClient that is not yet ready to be reused, but will be
   * imminently.
   */
  void ReturnTextureClientDeferred(TextureClient* aClient) override;

  /**
   * Return any clients to the pool that were previously returned in
   * ReturnTextureClientDeferred.
   */
  void ReturnDeferredClients();

  /**
   * Attempt to shrink the pool so that there are no more than
   * mInitialPoolSize outstanding.
   */
  void ShrinkToMaximumSize();

  /**
   * Report that a client retrieved via GetTextureClient() has become
   * unusable, so that it will no longer be tracked.
   */
  void ReportClientLost() override;

  /**
   * Calling this will cause the pool to attempt to relinquish any unused
   * clients.
   */
  void Clear();

  LayersBackend GetBackend() const {
    return mKnowsCompositor->GetCompositorBackendType();
  }
  int32_t GetMaxTextureSize() const {
    return mKnowsCompositor->GetMaxTextureSize();
  }
  gfx::SurfaceFormat GetFormat() { return mFormat; }
  TextureFlags GetFlags() const { return mFlags; }

  /**
   * Clear the pool and put it in a state where it won't recycle any new
   * texture.
   */
  void Destroy();

 private:
  void ReturnUnlockedClients();

  /// Allocate a single TextureClient to be returned from the pool.
  void AllocateTextureClient();

  /// Reset and/or initialise timers for shrinking/clearing the pool.
  void ResetTimers();

  /// KnowsCompositor passed to the TextureClient for buffer creation.
  RefPtr<KnowsCompositor> mKnowsCompositor;

  /// Format is passed to the TextureClient for buffer creation.
  gfx::SurfaceFormat mFormat;

  /// The width and height of the tiles to be used.
  gfx::IntSize mSize;

  /// Flags passed to the TextureClient for buffer creation.
  const TextureFlags mFlags;

  /// How long to wait after a TextureClient is returned before trying
  /// to shrink the pool to its maximum size of mPoolUnusedSize.
  uint32_t mShrinkTimeoutMsec;

  /// How long to wait after a TextureClient is returned before trying
  /// to clear the pool.
  uint32_t mClearTimeoutMsec;

  // The initial number of unused texture clients to seed the pool with
  // on construction
  uint32_t mInitialPoolSize;

  // How many unused texture clients to try and keep around if we go over
  // the initial allocation
  uint32_t mPoolUnusedSize;

  /// This is a total number of clients in the wild and in the stack of
  /// deferred clients (see below).  So, the total number of clients in
  /// existence is always mOutstandingClients + the size of mTextureClients.
  uint32_t mOutstandingClients;

  std::stack<RefPtr<TextureClient>> mTextureClients;

  std::list<RefPtr<TextureClient>> mTextureClientsDeferred;
  RefPtr<nsITimer> mShrinkTimer;
  RefPtr<nsITimer> mClearTimer;
  // This mSurfaceAllocator owns us, so no need to hold a ref to it
  TextureForwarder* mSurfaceAllocator;

  // Keep track of whether this pool has been destroyed or not. If it has,
  // we won't accept returns of TextureClients anymore, and the refcounting
  // should take care of their destruction.
  bool mDestroyed;
};

}  // namespace layers
}  // namespace mozilla

#endif /* MOZILLA_GFX_TEXTURECLIENTPOOL_H */