/* Copyright (C) 2010-2016 The RetroArch team
 *
 * ---------------------------------------------------------------------------------------------
 * The following license statement only applies to this libretro API header (libretro_vulkan.h)
 * ---------------------------------------------------------------------------------------------
 *
 * Permission is hereby granted, free of charge,
 * to any person obtaining a copy of this software and associated documentation files (the
 * "Software"),
 * to deal in the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software,
 * and to permit persons to whom the Software is furnished to do so, subject to the following
 * conditions:
 *
 * The above copyright notice and this permission notice shall be included in all copies or
 * substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

#ifndef LIBRETRO_VULKAN_H__
#define LIBRETRO_VULKAN_H__

#include "ext/vulkan/vulkan.h"
#include "libretro.h"

#define RETRO_HW_RENDER_INTERFACE_VULKAN_VERSION 5
#define RETRO_HW_RENDER_CONTEXT_NEGOTIATION_INTERFACE_VULKAN_VERSION 1

struct retro_vulkan_image
{
  VkImageView image_view;
  VkImageLayout image_layout;
  VkImageViewCreateInfo create_info;
};

typedef void (*retro_vulkan_set_image_t)(void* handle, const struct retro_vulkan_image* image,
                                         uint32_t num_semaphores, const VkSemaphore* semaphores,
                                         uint32_t src_queue_family);

typedef uint32_t (*retro_vulkan_get_sync_index_t)(void* handle);
typedef uint32_t (*retro_vulkan_get_sync_index_mask_t)(void* handle);
typedef void (*retro_vulkan_set_command_buffers_t)(void* handle, uint32_t num_cmd,
                                                   const VkCommandBuffer* cmd);
typedef void (*retro_vulkan_wait_sync_index_t)(void* handle);
typedef void (*retro_vulkan_lock_queue_t)(void* handle);
typedef void (*retro_vulkan_unlock_queue_t)(void* handle);
typedef void (*retro_vulkan_set_signal_semaphore_t)(void* handle, VkSemaphore semaphore);

typedef const VkApplicationInfo* (*retro_vulkan_get_application_info_t)(void);

struct retro_vulkan_context
{
  VkPhysicalDevice gpu;
  VkDevice device;
  VkQueue queue;
  uint32_t queue_family_index;
  VkQueue presentation_queue;
  uint32_t presentation_queue_family_index;
};

typedef bool (*retro_vulkan_create_device_t)(
    struct retro_vulkan_context* context, VkInstance instance, VkPhysicalDevice gpu,
    VkSurfaceKHR surface, PFN_vkGetInstanceProcAddr get_instance_proc_addr,
    const char** required_device_extensions, unsigned num_required_device_extensions,
    const char** required_device_layers, unsigned num_required_device_layers,
    const VkPhysicalDeviceFeatures* required_features);

typedef void (*retro_vulkan_destroy_device_t)(void);

/* Note on thread safety:
 * The Vulkan API is heavily designed around multi-threading, and
 * the libretro interface for it should also be threading friendly.
 * A core should be able to build command buffers and submit
 * command buffers to the GPU from any thread.
 */

struct retro_hw_render_context_negotiation_interface_vulkan
{
  /* Must be set to RETRO_HW_RENDER_CONTEXT_NEGOTIATION_INTERFACE_VULKAN. */
  enum retro_hw_render_context_negotiation_interface_type interface_type;
  /* Must be set to RETRO_HW_RENDER_CONTEXT_NEGOTIATION_INTERFACE_VULKAN_VERSION. */
  unsigned interface_version;

  /* If non-NULL, returns a VkApplicationInfo struct that the frontend can use instead of
   * its "default" application info.
   */
  retro_vulkan_get_application_info_t get_application_info;

  /* If non-NULL, the libretro core will choose one or more physical devices,
   * create one or more logical devices and create one or more queues.
   * The core must prepare a designated PhysicalDevice, Device, Queue and queue family index
   * which the frontend will use for its internal operation.
   *
   * If gpu is not VK_NULL_HANDLE, the physical device provided to the frontend must be this
   * PhysicalDevice.
   * The core is still free to use other physical devices.
   *
   * The frontend will request certain extensions and layers for a device which is created.
   * The core must ensure that the queue and queue_family_index support GRAPHICS and COMPUTE.
   *
   * If surface is not VK_NULL_HANDLE, the core must consider presentation when creating the queues.
   * If presentation to "surface" is supported on the queue, presentation_queue must be equal to
   * queue.
   * If not, a second queue must be provided in presentation_queue and presentation_queue_index.
   * If surface is not VK_NULL_HANDLE, the instance from frontend will have been created with
   * supported for
   * VK_KHR_surface extension.
   *
   * The core is free to set its own queue priorities.
   * Device provided to frontend is owned by the frontend, but any additional device resources must
   * be freed by core
   * in destroy_device callback.
   *
   * If this function returns true, a PhysicalDevice, Device and Queues are initialized.
   * If false, none of the above have been initialized and the frontend will attempt
   * to fallback to "default" device creation, as if this function was never called.
   */
  retro_vulkan_create_device_t create_device;

  /* If non-NULL, this callback is called similar to context_destroy for HW_RENDER_INTERFACE.
   * However, it will be called even if context_reset was not called.
   * This can happen if the context never succeeds in being created.
   * destroy_device will always be called before the VkInstance
   * of the frontend is destroyed if create_device was called successfully so that the core has a
   * chance of
   * tearing down its own device resources.
   *
   * Only auxillary resources should be freed here, i.e. resources which are not part of
   * retro_vulkan_context.
   */
  retro_vulkan_destroy_device_t destroy_device;
};

struct retro_hw_render_interface_vulkan
{
  /* Must be set to RETRO_HW_RENDER_INTERFACE_VULKAN. */
  enum retro_hw_render_interface_type interface_type;
  /* Must be set to RETRO_HW_RENDER_INTERFACE_VULKAN_VERSION. */
  unsigned interface_version;

  /* Opaque handle to the Vulkan backend in the frontend
   * which must be passed along to all function pointers
   * in this interface.
   *
   * The rationale for including a handle here (which libretro v1
   * doesn't currently do in general) is:
   *
   * - Vulkan cores should be able to be freely threaded without lots of fuzz.
   *   This would break frontends which currently rely on TLS
   *   to deal with multiple cores loaded at the same time.
   * - Fixing this in general is TODO for an eventual libretro v2.
   */
  void* handle;

  /* The Vulkan instance the context is using. */
  VkInstance instance;
  /* The physical device used. */
  VkPhysicalDevice gpu;
  /* The logical device used. */
  VkDevice device;

  /* Allows a core to fetch all its needed symbols without having to link
   * against the loader itself. */
  PFN_vkGetDeviceProcAddr get_device_proc_addr;
  PFN_vkGetInstanceProcAddr get_instance_proc_addr;

  /* The queue the core must use to submit data.
   * This queue and index must remain constant throughout the lifetime
   * of the context.
   *
   * This queue will be the queue that supports graphics and compute
   * if the device supports compute.
   */
  VkQueue queue;
  unsigned queue_index;

  /* Before calling retro_video_refresh_t with RETRO_HW_FRAME_BUFFER_VALID,
   * set which image to use for this frame.
   *
   * If num_semaphores is non-zero, the frontend will wait for the
   * semaphores provided to be signaled before using the results further
   * in the pipeline.
   *
   * Semaphores provided by a single call to set_image will only be
   * waited for once (waiting for a semaphore resets it).
   * E.g. set_image, video_refresh, and then another
   * video_refresh without set_image,
   * but same image will only wait for semaphores once.
   *
   * For this reason, ownership transfer will only occur if semaphores
   * are waited on for a particular frame in the frontend.
   *
   * Using semaphores is optional for synchronization purposes,
   * but if not using
   * semaphores, an image memory barrier in vkCmdPipelineBarrier
   * should be used in the graphics_queue.
   * Example:
   *
   * vkCmdPipelineBarrier(cmd,
   *    srcStageMask = VK_PIPELINE_STAGE_ALL_GRAPHICS_BIT,
   *    dstStageMask = VK_PIPELINE_STAGE_FRAGMENT_SHADER_BIT,
   *    image_memory_barrier = {
   *       srcAccessMask = VK_ACCESS_COLOR_ATTACHMENT_WRITE_BIT,
   *       dstAccessMask = VK_ACCESS_SHADER_READ_BIT,
   *    });
   *
   * The use of pipeline barriers instead of semaphores is encouraged
   * as it is simpler and more fine-grained. A layout transition
   * must generally happen anyways which requires a
   * pipeline barrier.
   *
   * The image passed to set_image must have imageUsage flags set to at least
   * VK_IMAGE_USAGE_TRANSFER_SRC_BIT and VK_IMAGE_USAGE_SAMPLED_BIT.
   * The core will naturally want to use flags such as
   * VK_IMAGE_USAGE_COLOR_ATTACHMENT_BIT and/or
   * VK_IMAGE_USAGE_TRANSFER_DST_BIT depending
   * on how the final image is created.
   *
   * The image must also have been created with MUTABLE_FORMAT bit set if
   * 8-bit formats are used, so that the frontend can reinterpret sRGB
   * formats as it sees fit.
   *
   * Images passed to set_image should be created with TILING_OPTIMAL.
   * The image layout should be transitioned to either
   * VK_IMAGE_LAYOUT_GENERIC or VK_IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL.
   * The actual image layout used must be set in image_layout.
   *
   * The image must be a 2D texture which may or not be layered
   * and/or mipmapped.
   *
   * The image must be suitable for linear sampling.
   * While the image_view is typically the only field used,
   * the frontend may want to reinterpret the texture as sRGB vs.
   * non-sRGB for example so the VkImageViewCreateInfo used to
   * create the image view must also be passed in.
   *
   * The data in the pointer to the image struct will not be copied
   * as the pNext field in create_info cannot be reliably deep-copied.
   * The image pointer passed to set_image must be valid until
   * retro_video_refresh_t has returned.
   *
   * If frame duping is used when passing NULL to retro_video_refresh_t,
   * the frontend is free to either use the latest image passed to
   * set_image or reuse the older pointer passed to set_image the
   * frame RETRO_HW_FRAME_BUFFER_VALID was last used.
   *
   * Essentially, the lifetime of the pointer passed to
   * set_image should be extended if frame duping is used
   * so that the frontend can reuse the older pointer.
   *
   * The image itself however, must not be touched by the core until
   * wait_sync_index has been completed later. The frontend may perform
   * layout transitions on the image, so even read-only access is not defined.
   * The exception to read-only rule is if GENERAL layout is used for the image.
   * In this case, the frontend is not allowed to perform any layout transitions,
   * so concurrent reads from core and frontend are allowed.
   *
   * If frame duping is used, or if set_command_buffers is used,
   * the frontend will not wait for any semaphores.
   *
   * The src_queue_family is used to specify which queue family
   * the image is currently owned by. If using multiple queue families
   * (e.g. async compute), the frontend will need to acquire ownership of the
   * image before rendering with it and release the image afterwards.
   *
   * If src_queue_family is equal to the queue family (queue_index),
   * no ownership transfer will occur.
   * Similarly, if src_queue_family is VK_QUEUE_FAMILY_IGNORED,
   * no ownership transfer will occur.
   *
   * The frontend will always release ownership back to src_queue_family.
   * Waiting for frontend to complete with wait_sync_index() ensures that
   * the frontend has released ownership back to the application.
   * Note that in Vulkan, transfering ownership is a two-part process.
   *
   * Example frame:
   *  - core releases ownership from src_queue_index to queue_index with VkImageMemoryBarrier.
   *  - core calls set_image with src_queue_index.
   *  - Frontend will acquire the image with src_queue_index -> queue_index as well, completing the
   * ownership transfer.
   *  - Frontend renders the frame.
   *  - Frontend releases ownership with queue_index -> src_queue_index.
   *  - Next time image is used, core must acquire ownership from queue_index ...
   *
   * Since the frontend releases ownership, we cannot necessarily dupe the frame because
   * the core needs to make the roundtrip of ownership transfer.
   */
  retro_vulkan_set_image_t set_image;

  /* Get the current sync index for this frame which is obtained in
   * frontend by calling e.g. vkAcquireNextImageKHR before calling
   * retro_run().
   *
   * This index will correspond to which swapchain buffer is currently
   * the active one.
   *
   * Knowing this index is very useful for maintaining safe asynchronous CPU
   * and GPU operation without stalling.
   *
   * The common pattern for synchronization is to receive fences when
   * submitting command buffers to Vulkan (vkQueueSubmit) and add this fence
   * to a list of fences for frame number get_sync_index().
   *
   * Next time we receive the same get_sync_index(), we can wait for the
   * fences from before, which will usually return immediately as the
   * frontend will generally also avoid letting the GPU run ahead too much.
   *
   * After the fence has signaled, we know that the GPU has completed all
   * GPU work related to work submitted in the frame we last saw get_sync_index().
   *
   * This means we can safely reuse or free resources allocated in this frame.
   *
   * In theory, even if we wait for the fences correctly, it is not technically
   * safe to write to the image we earlier passed to the frontend since we're
   * not waiting for the frontend GPU jobs to complete.
   *
   * The frontend will guarantee that the appropriate pipeline barrier
   * in graphics_queue has been used such that
   * VK_PIPELINE_STAGE_COLOR_ATTACHMENT_OUTPUT_BIT cannot
   * start until the frontend is done with the image.
   */
  retro_vulkan_get_sync_index_t get_sync_index;

  /* Returns a bitmask of how many swapchain images we currently have
   * in the frontend.
   *
   * If bit #N is set in the return value, get_sync_index can return N.
   * Knowing this value is useful for preallocating per-frame management
   * structures ahead of time.
   *
   * While this value will typically remain constant throughout the
   * applications lifecycle, it may for example change if the frontend
   * suddently changes fullscreen state and/or latency.
   *
   * If this value ever changes, it is safe to assume that the device
   * is completely idle and all synchronization objects can be deleted
   * right away as desired.
   */
  retro_vulkan_get_sync_index_mask_t get_sync_index_mask;

  /* Instead of submitting the command buffer to the queue first, the core
   * can pass along its command buffer to the frontend, and the frontend
   * will submit the command buffer together with the frontends command buffers.
   *
   * This has the advantage that the overhead of vkQueueSubmit can be
   * amortized into a single call. For this mode, semaphores in set_image
   * will be ignored, so vkCmdPipelineBarrier must be used to synchronize
   * the core and frontend.
   *
   * The command buffers in set_command_buffers are only executed once,
   * even if frame duping is used.
   *
   * If frame duping is used, set_image should be used for the frames
   * which should be duped instead.
   *
   * Command buffers passed to the frontend with set_command_buffers
   * must not actually be submitted to the GPU until retro_video_refresh_t
   * is called.
   *
   * The frontend must submit the command buffer before submitting any
   * other command buffers provided by set_command_buffers. */
  retro_vulkan_set_command_buffers_t set_command_buffers;

  /* Waits on CPU for device activity for the current sync index to complete.
   * This is useful since the core will not have a relevant fence to sync with
   * when the frontend is submitting the command buffers. */
  retro_vulkan_wait_sync_index_t wait_sync_index;

  /* If the core submits command buffers itself to any of the queues provided
   * in this interface, the core must lock and unlock the frontend from
   * racing on the VkQueue.
   *
   * Queue submission can happen on any thread.
   * Even if queue submission happens on the same thread as retro_run(),
   * the lock/unlock functions must still be called.
   *
   * NOTE: Queue submissions are heavy-weight. */
  retro_vulkan_lock_queue_t lock_queue;
  retro_vulkan_unlock_queue_t unlock_queue;

  /* Sets a semaphore which is signaled when the image in set_image can safely be reused.
   * The semaphore is consumed next call to retro_video_refresh_t.
   * The semaphore will be signalled even for duped frames.
   * The semaphore will be signalled only once, so set_signal_semaphore should be called every
   * frame.
   * The semaphore may be VK_NULL_HANDLE, which disables semaphore signalling for next call to
   * retro_video_refresh_t.
   *
   * This is mostly useful to support use cases where you're rendering to a single image that
   * is recycled in a ping-pong fashion with the frontend to save memory (but potentially less
   * throughput).
   */
  retro_vulkan_set_signal_semaphore_t set_signal_semaphore;
};

#endif
