// Copyright 2024 Dolphin Emulator Project
// SPDX-License-Identifier: GPL-2.0-or-later

#pragma once

#ifdef ENABLE_VR

#include <array>
#include <atomic>
#include <memory>
#include <vector>

#include <openxr/openxr.h>

#include "VideoCommon/AbstractFramebuffer.h"

// OpenXRManager owns the XrInstance, XrSystemId, XrSession, and reference XrSpace.
// It handles the OpenXR session state machine and per-frame timing.
//
// Backend-specific swapchain creation is handled by the respective backend class
// (D3DOpenXR for D3D11, VulkanOpenXR for Vulkan), which creates the XrSession
// with a graphics binding and then calls SetSession() + SetSwapchain() to
// transfer ownership here.

namespace VR
{
// Per-eye pose and field-of-view returned by xrLocateViews.
struct XREyeView
{
  XrPosef pose;
  XrFovf fov;
};

// Abstract interface for backend-specific per-eye swapchain management.
// Implemented by D3DOpenXR (D3D11) and VulkanOpenXR (Vulkan).
// Used by Presenter::RenderXFBToScreen() to blit game frames into the HMD's
// eye textures without depending on backend-specific types.
class IOpenXRSwapchain
{
public:
  virtual ~IOpenXRSwapchain() = default;

  // Acquire the next swapchain image for the given eye (0 = left, 1 = right).
  // Returns an AbstractFramebuffer* to render into, or nullptr on error.
  // Must be paired with ReleaseEyeTexture() after rendering is complete.
  virtual AbstractFramebuffer* AcquireEyeFramebuffer(uint32_t eye) = 0;

  // Signal the runtime that rendering into the given eye's current image is done.
  virtual void ReleaseEyeTexture(uint32_t eye) = 0;

  // Build the XrCompositionLayerProjection from the current eye poses and submit
  // via xrEndFrame. Call after both eyes have been rendered and released.
  virtual bool SubmitFrame() = 0;

  // Pixel dimensions of the eye render targets (typically HMD recommended resolution).
  virtual uint32_t GetEyeWidth() const = 0;
  virtual uint32_t GetEyeHeight() const = 0;
};

class OpenXRManager
{
public:
  OpenXRManager();
  ~OpenXRManager();

  OpenXRManager(const OpenXRManager&) = delete;
  OpenXRManager& operator=(const OpenXRManager&) = delete;

  // Step 1: Create XrInstance.
  // extra_extensions must include the graphics API extension (e.g. XR_KHR_D3D11_ENABLE_EXTENSION_NAME).
  bool CreateInstance(const std::vector<const char*>& extra_extensions = {});

  // Step 2: Locate the HMD system.
  bool InitializeSystem();

  // Step 2b: Query recommended per-eye render resolution.
  // Must be called before the backend creates swapchains.
  bool EnumerateViewConfigurations();

  // Step 3 (called by backend after creating session with graphics binding).
  void SetSession(XrSession session);

  // Step 3b: Register the backend swapchain implementation for use by the presenter.
  // Raw pointer — the backend object outlives the manager.
  void SetSwapchain(IOpenXRSwapchain* swapchain) { m_swapchain = swapchain; }
  IOpenXRSwapchain* GetSwapchain() const { return m_swapchain; }

  // Step 4: Create the local reference space used for head tracking.
  bool CreateReferenceSpace();

  // ---- Per-frame interface ----

  // Poll XrEvents and drive the session state machine.
  // Returns false if the render loop should stop.
  bool PollEvents();

  // xrWaitFrame — blocks until the runtime wants a new frame rendered.
  // Call at the start of each rendered frame.
  bool WaitFrame();

  // xrBeginFrame — signals the runtime that rendering has started.
  bool BeginFrame();

  // xrEndFrame — submits the completed layer stack to the compositor.
  bool EndFrame(const std::vector<XrCompositionLayerBaseHeader*>& layers);

  // xrLocateViews — fills m_eye_views with the predicted head pose for each eye.
  // Call between BeginFrame and rendering.
  bool LocateViews();

  // ---- Accessors ----

  XrInstance GetInstance() const { return m_instance; }
  XrSystemId GetSystemId() const { return m_system_id; }
  XrSession GetSession() const { return m_session; }
  XrSpace GetReferenceSpace() const { return m_reference_space; }

  XrTime GetPredictedDisplayTime() const { return m_frame_state.predictedDisplayTime; }
  bool IsSessionRunning() const { return m_session_running; }
  bool ShouldRender() const { return m_frame_state.shouldRender == XR_TRUE; }

  const std::array<XREyeView, 2>& GetEyeViews() const { return m_eye_views; }
  const std::array<XrViewConfigurationView, 2>& GetViewConfigViews() const
  {
    return m_view_config_views;
  }

  // Compute per-eye projection rows with head rotation and eye position baked in.
  //
  // out_proj_rows[0..1] = left-eye rows 0,1; [2..3] = right-eye rows 0,1.
  //   x_clip = dot(row0, viewPos),  y_clip = dot(row1, viewPos)
  //   Head rotation and eye position (scaled by units_per_meter) are baked in.
  //
  // out_z_rows[0..1] = left/right eye z-axis row.
  //   z_eye = dot(z_row, viewPos) gives eye-space depth for perspective divide
  //   (f.pos.w = -z_eye) and depth buffer recomputation.
  void GetEyeProjectionRows(
      float units_per_meter,
      std::array<std::array<float, 4>, 4>& out_proj_rows,
      std::array<std::array<float, 4>, 2>& out_z_rows) const;

  // Compute per-eye projection rows WITHOUT head rotation (for head-locked content).
  // Same layout as GetEyeProjectionRows but only includes the raw asymmetric frustum
  // projection and per-eye IPD offset. Content rendered with these rows follows
  // the user's head movements.
  void GetRawEyeProjectionRows(
      float units_per_meter,
      std::array<std::array<float, 4>, 4>& out_proj_rows) const;

  // Request recentering of the VR home position.
  // Applied on the OpenXR render thread during LocateViews.
  void RequestRecenter();

private:
  bool InitializeInputActions();
  void DestroyInputActions();
  void UpdateInputActions();
  void UpdateHaptics();
  void ResetInputActionsState();

  void HandleSessionStateChange(XrSessionState new_state);

  XrInstance m_instance = XR_NULL_HANDLE;
  XrSystemId m_system_id = XR_NULL_SYSTEM_ID;
  XrSession m_session = XR_NULL_HANDLE;
  XrSpace m_reference_space = XR_NULL_HANDLE;

  // Non-owning pointer; lifetime managed by the backend (D3DOpenXR).
  IOpenXRSwapchain* m_swapchain = nullptr;

  XrSessionState m_session_state = XR_SESSION_STATE_UNKNOWN;
  bool m_session_running = false;
  bool m_exit_render_loop = false;

  XrFrameState m_frame_state{XR_TYPE_FRAME_STATE};

  // OpenXR input action set used to expose VR controller input to Dolphin's
  // regular controller mapping UI.
  XrActionSet m_input_action_set = XR_NULL_HANDLE;
  std::array<XrPath, 2> m_input_hand_paths{XR_NULL_PATH, XR_NULL_PATH};
  XrAction m_action_primary_click = XR_NULL_HANDLE;
  XrAction m_action_secondary_click = XR_NULL_HANDLE;
  XrAction m_action_menu_click = XR_NULL_HANDLE;
  XrAction m_action_thumbstick_click = XR_NULL_HANDLE;
  XrAction m_action_trigger_click = XR_NULL_HANDLE;
  XrAction m_action_squeeze_click = XR_NULL_HANDLE;
  XrAction m_action_trigger_value = XR_NULL_HANDLE;
  XrAction m_action_squeeze_value = XR_NULL_HANDLE;
  XrAction m_action_thumbstick_x = XR_NULL_HANDLE;
  XrAction m_action_thumbstick_y = XR_NULL_HANDLE;
  XrAction m_action_aim_pose = XR_NULL_HANDLE;
  XrAction m_action_grip_pose = XR_NULL_HANDLE;
  XrAction m_action_haptic = XR_NULL_HANDLE;
  std::array<XrSpace, 2> m_aim_spaces{XR_NULL_HANDLE, XR_NULL_HANDLE};
  std::array<XrSpace, 2> m_grip_spaces{XR_NULL_HANDLE, XR_NULL_HANDLE};
  std::array<bool, 2> m_haptics_active{false, false};

  std::array<XrViewConfigurationView, 2> m_view_config_views{};
  std::array<XrView, 2> m_views{};
  std::array<XREyeView, 2> m_eye_views{};

  // "Home" head-center position, recorded on first LocateViews.
  // All positional tracking is relative to this to avoid floor-level offsets.
  mutable bool m_home_set{false};
  mutable XrVector3f m_home_position{0.f, 0.f, 0.f};
  std::atomic<bool> m_recenter_requested{false};
};

// Global instance — created by the backend during VideoBackend::Initialize().
extern std::unique_ptr<OpenXRManager> g_openxr;

}  // namespace VR

#endif  // ENABLE_VR