// Copyright 2013 The Flutter Authors. All rights reserved.

// Use of this source code is governed by a BSD-style license that can be

// found in the LICENSE file.

#ifndef FLUTTER_SHELL_PLATFORM_ANDROID_IMAGE_LRU_H_

#define FLUTTER_SHELL_PLATFORM_ANDROID_IMAGE_LRU_H_

#include <array>

#include <cstddef>

#include "display_list/image/dl_image.h"

namespace flutter {

// This value needs to be larger than the number of swapchain images

// that a typical image reader will produce to ensure that we effectively

// cache. If the value is too small, we will unnecessarily churn through

// images, while if it is too large we may retain images longer than

// necessary.

static constexpr size_t kImageReaderSwapchainSize = 6u;

using HardwareBufferKey = uint64_t;

class ImageLRU {

public:

ImageLRU() = default;

~ImageLRU() = default;

/// @brief Retrieve the image associated with the given [key], or nullptr.

sk_sp<flutter::DlImage> FindImage(std::optional<HardwareBufferKey> key);

/// @brief Add a new image to the cache with a key, returning the key of the

/// LRU entry that was removed.

///

/// The value may be `0`, in which case nothing was removed.

HardwareBufferKey AddImage(const sk_sp<flutter::DlImage>& image,

HardwareBufferKey key);

/// @brief Remove all entires from the image cache.

void Clear();

private:

/// @brief Marks [key] as the most recently used.

void UpdateKey(const sk_sp<flutter::DlImage>& image, HardwareBufferKey key);

struct Data {

HardwareBufferKey key = 0u;

sk_sp<flutter::DlImage> value;

};

std::array<Data, kImageReaderSwapchainSize> images_;

};

} // namespace flutter

#endif // FLUTTER_SHELL_PLATFORM_ANDROID_IMAGE_LRU_H_