// FCS Glass - dx.cpp
//
// Implements: HC4, W1, E2, E3, G1, G2, R6.  (Research notes in dx.h; every
// signature and behaviour there was measured before being written.)

#include "device/dx.h"

#include <cstdio>

namespace fcs {

// D-26 / D-24. The buffer is a D3D11_FEATURE_DATA_FORMAT_SUPPORT struct, NOT a
// bare DXGI_FORMAT - passing the latter returns E_INVALIDARG and silently
// downgrades every quality decision.
bool D3D11SupportsFormat(ID3D11Device* dev, DXGI_FORMAT fmt) {
  if (!dev) return false;
  D3D11_FEATURE_DATA_FORMAT_SUPPORT data = {};
  data.InFormat = fmt;
  HRESULT hr = dev->CheckFeatureSupport(D3D11_FEATURE_FORMAT_SUPPORT, &data, sizeof(data));
  if (FAILED(hr)) return false;
  return (data.OutFormatSupport & D3D11_FORMAT_SUPPORT_RENDER_TARGET) != 0;
}

// D-22. The DComp device is created from an IDXGIDevice, NOT by
// QueryInterface on the D3D11 device - that returns E_NOINTERFACE every time.
HRESULT CreateCompositionDeviceFor(IDXGIDevice* dxgi, IDCompositionDevice** out) {
  if (!dxgi || !out) return E_POINTER;
  *out = nullptr;
  return ::DCompositionCreateDevice(dxgi, IID_PPV_ARGS(out));
}

DxDevice::~DxDevice() { Destroy(); }

void DxDevice::ReportFailure(const char* where, HRESULT hr) {
  info_.last_failure = hr;
  // Reported through the project's single HRESULT funnel so the probe can
  // surface file/line/expr rather than a bare code.
  FCS_CHECK_HR(hr);
  (void)where;
}

// REQ HC4 - hardware, then WARP. Both paths are attempted before giving up.
bool DxDevice::Create() {
  Destroy();
  if (!CreateDeviceInternal()) return false;
  if (!CreateCompositionInternal()) {
    Destroy();
    return false;
  }
  return true;
}

// REQ E3 - rebuild for device removed/reset. Caller keeps its own state.
bool DxDevice::Recreate() { return Create(); }

// E3 injection seam - the single point through which a frame is presented, so a
// DXGI_ERROR_DEVICE_REMOVED can be synthesised. Placed BEFORE the chain check
// deliberately: when a device really is lost, the chain is usually already gone,
// and an injection that returned "no chain" would be testing the wrong branch.
HRESULT DxDevice::Present(UINT flags) {
  if (injected_removals_ > 0) {
    --injected_removals_;
    return DXGI_ERROR_DEVICE_REMOVED;
  }
  IDXGISwapChain1* chain = swap_chain_.Get();
  if (chain == nullptr) return DXGI_ERROR_DEVICE_REMOVED;
  return chain->Present(0, flags);
}

bool DxDevice::CreateDeviceInternal() {
  static const D3D_FEATURE_LEVEL kLevels[] = {
      D3D_FEATURE_LEVEL_11_0, D3D_FEATURE_LEVEL_10_1, D3D_FEATURE_LEVEL_10_0,
      D3D_FEATURE_LEVEL_9_3,  D3D_FEATURE_LEVEL_9_2,  D3D_FEATURE_LEVEL_9_1,
  };
  // BGRA_SUPPORT is required: the R7 font atlas is built with GDI and the D2D
  // interop depends on it.
  const UINT flags = D3D11_CREATE_DEVICE_BGRA_SUPPORT;

  D3D_DRIVER_TYPE order[] = {D3D_DRIVER_TYPE_HARDWARE, D3D_DRIVER_TYPE_WARP};
  DriverKind kinds[] = {DriverKind::Hardware, DriverKind::Warp};

  HRESULT last = E_FAIL;
  for (int attempt = 0; attempt < 2; ++attempt) {
    device_.Reset();
    context_.Reset();
    D3D_FEATURE_LEVEL got = D3D_FEATURE_LEVEL_9_1;
    last = ::D3D11CreateDevice(nullptr, order[attempt], nullptr, flags, kLevels,
                              ARRAYSIZE(kLevels), D3D11_SDK_VERSION, device_.GetAddressOf(), &got,
                              context_.GetAddressOf());
    if (SUCCEEDED(last)) {
      info_.driver = kinds[attempt];
      info_.feature_level = got;
      info_.last_failure = S_OK;

      // D-22: the D3D device must hand us its IDXGIDevice for DComp.
      HRESULT q = device_.QueryInto<IDXGIDevice>(dxgi_device_.GetAddressOf());
      if (FAILED(q)) {
        ReportFailure("QueryInterface(IDXGIDevice)", q);
        return false;
      }

      // G2: measured, not assumed. Both were confirmed available on hardware
      // AND on WARP, so this is a capability check that can legitimately fail
      // on some future driver rather than a hard-coded tier mapping. (D-26)
      info_.supports_r10g10b10a2 =
          D3D11SupportsFormat(device_.Get(), DXGI_FORMAT_R10G10B10A2_UNORM);
      info_.supports_b8g8r8a8 =
          D3D11SupportsFormat(device_.Get(), DXGI_FORMAT_B8G8R8A8_UNORM);
      return true;
    }
  }

  ReportFailure("D3D11CreateDevice(hardware+WARP)", last);
  return false;
}

bool DxDevice::CreateCompositionInternal() {
  HRESULT hr = CreateCompositionDeviceFor(dxgi_device_.Get(), dcomp_.GetAddressOf());
  if (FAILED(hr)) {
    ReportFailure("DCompositionCreateDevice", hr);
    return false;
  }
  // IID_PPV_ARGS expands straight to the SDK's IID_PPV_ARGS_Helper, which only
  // overloads for T**, so a ComPtr<T>* is passed via GetAddressOf() rather
  // than through IID_PPV_ARGS.
  hr = ::CreateDXGIFactory2(0, IID_PPV_ARGS(factory_.GetAddressOf()));
  if (FAILED(hr)) {
    ReportFailure("CreateDXGIFactory2", hr);
    return false;
  }
  return true;
}
// REQ G2 / J5 - the PRESENTED swap chain is always B8G8R8A8_UNORM.
//
// X28: this previously returned R10G10B10A2_UNORM for QualityTier::Full, and
// CreateSwapChain assigned it to the swap chain while also setting
// DXGI_ALPHA_MODE_PREMULTIPLIED. R10G10B10A2 has a 2-BIT alpha channel, so a
// premultiplied alpha of 0.045, 0.30 or 0.72 would quantise to 0, 0.33, 0.67
// or 1 - every translucent tint would have been wrong from M3 onward. G2 and
// G1 cannot both hold on a swap chain (C-8), and the later rule (J5) wins.
//
// R10G10B10A2 remains correct, and is still used, for INTERNAL OPAQUE targets
// (backdrop, blur pyramid) whose alpha is unused - which is what G2 actually
// asked for. That is a separate accessor so the two cannot be confused again.
DXGI_FORMAT DxDevice::RenderTargetFormat(QualityTier tier) const {
  (void)tier;   // J5: the presented format does not vary by tier
  return DXGI_FORMAT_B8G8R8A8_UNORM;
}

// REQ G2 - format for an internal opaque render target, where the 2-bit alpha
// of R10G10B10A2 is harmless and its wider colour depth is wanted. Returns
// B8G8R8A8 when the format is genuinely unsupported (D-26 made this a
// measurement rather than an assumption).
DXGI_FORMAT DxDevice::InternalOpaqueFormat() const {
  if (info_.supports_r10g10b10a2) return DXGI_FORMAT_R10G10B10A2_UNORM;
  return DXGI_FORMAT_B8G8R8A8_UNORM;
}

// REQ W1 / G1 - the composition swap chain.
bool DxDevice::CreateSwapChain(HWND hwnd, UINT width, UINT height, QualityTier tier) {
  if (!hwnd || !device_ || !dcomp_ || !factory_) {
    info_.last_failure = E_INVALIDARG;
    return false;
  }
  if (width == 0 || height == 0) {
    // E2: a zero-size swap chain is invalid, and ResizeBuffers(0,0) is
    // E_INVALIDARG (D-25), so refuse rather than hand DXGI a bad call.
    info_.last_failure = E_INVALIDARG;
    return false;
  }

  DXGI_SWAP_CHAIN_DESC1 desc = {};
  desc.Width = width;
  desc.Height = height;
  desc.Format = RenderTargetFormat(tier);
  desc.SampleDesc.Count = 1;
  desc.BufferUsage = DXGI_USAGE_RENDER_TARGET_OUTPUT;
  desc.BufferCount = 2;
  desc.Scaling = DXGI_SCALING_STRETCH;
  // MANDATORY for a composition swap chain: DISCARD returns
  // DXGI_ERROR_INVALID_CALL (D-25).
  desc.SwapEffect = DXGI_SWAP_EFFECT_FLIP_SEQUENTIAL;
  // G1: premultiplied end to end, which is what prevents a dark fringe on
  // antialiased edges. Note the API does NOT enforce this - D-17's lesson
  // applies - so setting it is entirely our responsibility.
  desc.AlphaMode = DXGI_ALPHA_MODE_PREMULTIPLIED;

  swap_chain_.Reset();
  rtv_.Reset();
  HRESULT hr = factory_->CreateSwapChainForComposition(device_.Get(), &desc, nullptr,
                                                       swap_chain_.GetAddressOf());
  if (FAILED(hr)) {
    ReportFailure("CreateSwapChainForComposition", hr);
    return false;
  }

  // D-23: the method is CreateVisual; there is no CreateRootVisual.
  //
  // OWNERSHIP: this function OWNS the composition tree for the window - the
  // target, the root visual, and the SetContent link. The caller in main.cpp
  // previously built a SECOND target/visual over the SAME swap chain, which
  // meant two DComp targets for one HWND fighting over one root. `topmost`
  // also differed (TRUE here, FALSE there), so which tree won was undefined.
  //
  // The fix is that the tree is built HERE and ONLY here. AttachContent() below
  // re-establishes the link after a ResizeBuffers without rebuilding the tree.
  ComPtr<IDCompositionTarget> target;
  hr = dcomp_->CreateTargetForHwnd(hwnd, /*topmost=*/TRUE, target.GetAddressOf());
  if (FAILED(hr)) {
    ReportFailure("CreateTargetForHwnd", hr);
    return false;
  }
  ComPtr<IDCompositionVisual> root;
  hr = dcomp_->CreateVisual(root.GetAddressOf());
  if (FAILED(hr)) {
    ReportFailure("CreateVisual", hr);
    return false;
  }
  hr = root->SetContent(swap_chain_.Get());
  if (FAILED(hr)) {
    ReportFailure("IDCompositionVisual::SetContent", hr);
    return false;
  }
  hr = target->SetRoot(root.Get());
  if (FAILED(hr)) {
    ReportFailure("IDCompositionTarget::SetRoot", hr);
    return false;
  }
  hr = dcomp_->Commit();
  if (FAILED(hr)) {
    ReportFailure("IDCompositionDevice::Commit", hr);
    return false;
  }
  // The tree outlives this call, so both objects are retained. Without these the
  // ComPtrs release here and DComp is left holding a tree it can no longer
  // reason about on the next Commit. Swap, not assignment: ComPtr is move-only
  // and has a deleted copy-assignment (C2280).
  target_.Swap(target);
  root_.Swap(root);

  width_ = width;
  height_ = height;
  has_swap_chain_ = true;
  return true;
}

// REQ W1 / E2 - re-attach the back buffer after ResizeBuffers.
//
// ResizeBuffers detaches the buffers, so the root visual's content reference
// has to be re-established or the window goes black. The target and visual
// themselves are reused: rebuilding them on every resize is what produced a
// second target per HWND in the first place.
bool DxDevice::AttachContent() {
  if (!has_swap_chain_ || !dcomp_ || !root_) return false;
  HRESULT hr = root_->SetContent(swap_chain_.Get());
  if (FAILED(hr)) {
    ReportFailure("IDCompositionVisual::SetContent (reattach)", hr);
    return false;
  }
  hr = dcomp_->Commit();
  if (FAILED(hr)) {
    ReportFailure("IDCompositionDevice::Commit (reattach)", hr);
    return false;
  }
  return true;
}

void DxDevice::DestroySwapChain() {
  rtv_.Reset();
  // Order matters. The chain is a child of root_ in the composition graph, so
  // it must be released BEFORE the target that commits it - otherwise the
  // target holds a frame reference and Commit/destroy can stall or fault.
  swap_chain_.Reset();
  // Release the composition tree too. Leaving target_/root_ alive here is what
  // let a destroyed chain keep a target bound to the HWND, so the next
  // CreateSwapChain built a SECOND target for the same window. Resetting here
  // keeps "DxDevice owns exactly one tree per swap chain" (W1) true across a
  // rebuild, not just across a resize.
  root_.Reset();
  target_.Reset();
  has_swap_chain_ = false;
  width_ = 0;
  height_ = 0;
}

ID3D11RenderTargetView* DxDevice::AcquireRtv(HRESULT* hr_out) {
  if (hr_out) *hr_out = S_OK;
  if (!has_swap_chain_ || !device_) {
    if (hr_out) *hr_out = E_UNEXPECTED;
    return nullptr;
  }
  if (rtv_) return rtv_.Get();

  ComPtr<ID3D11Texture2D> back;
  HRESULT hr = swap_chain_->GetBuffer(0, IID_PPV_ARGS(back.GetAddressOf()));
  if (FAILED(hr)) {
    ReportFailure("IDXGISwapChain1::GetBuffer", hr);
    if (hr_out) *hr_out = hr;
    return nullptr;
  }
  hr = device_->CreateRenderTargetView(back.Get(), nullptr, rtv_.GetAddressOf());
  if (FAILED(hr)) {
    ReportFailure("CreateRenderTargetView", hr);
    if (hr_out) *hr_out = hr;
    return nullptr;
  }
  return rtv_.Get();
}

// REQ E2 - ResizeBuffers only when the size is genuinely non-zero. Measured:
// ResizeBuffers(0, 0, ...) is E_INVALIDARG, so the guard is required.
bool DxDevice::ResizeSwapChain(UINT width, UINT height) {
  if (!has_swap_chain_) {
    info_.last_failure = E_UNEXPECTED;
    return false;
  }
  if (width == 0 || height == 0) return true;  // nothing to do, not an error

  // BUG-29: release every reference to the back buffer BEFORE ResizeBuffers.
  // Dropping the RTV object is not enough: the device context still holds a
  // reference while the RTV is bound to the output-merger stage, and
  // PresentFrame binds it every frame and never unbinds. DXGI documents that
  // ResizeBuffers fails (DXGI_ERROR_INVALID_CALL) while the back buffer is still
  // referenced. Latent rather than observed - every resize on this host had
  // happened to succeed - but now load-bearing: the whole BUG-26 drag fix is
  // built on ResizeBuffers being reliable.
  // ComPtr has an explicit operator bool and operator! but NO operator==, so
  // `context_ != nullptr` is C2678 (main.cpp research note 5a).
  if (context_) context_->OMSetRenderTargets(0, nullptr, nullptr);
  rtv_.Reset();
  // P3-12: D3D11 releases objects lazily; flush so the runtime drops its back-buffer
  // reference before ResizeBuffers (the usual resize pattern in the DirectX samples).
  if (context_) context_->Flush();
  HRESULT hr = swap_chain_->ResizeBuffers(0, width, height, DXGI_FORMAT_UNKNOWN, 0);
  if (FAILED(hr)) {
    ReportFailure("IDXGISwapChain1::ResizeBuffers", hr);
    return false;
  }
  width_ = width;
  height_ = height;
  return true;
}

// REQ E2 - the size DXGI actually granted, not the size we asked for.
//
// Cached width_/height_ record intent. This reads DXGI_SWAP_CHAIN_DESC back out
// of the chain, so it is the only value that can prove the back buffer really
// covers the client area. The M0 capture showed a 443 px uncovered strip, and
// nothing in the cached fields would have revealed it: we had asked for a size
// and believed we got it.
bool DxDevice::SwapChainBufferSize(UINT* out_w, UINT* out_h) const {
  if (out_w) *out_w = 0;
  if (out_h) *out_h = 0;
  if (!swap_chain_) return false;
  DXGI_SWAP_CHAIN_DESC desc = {};
  HRESULT hr = swap_chain_->GetDesc(&desc);
  if (FAILED(hr)) return false;
  if (out_w) *out_w = desc.BufferDesc.Width;
  if (out_h) *out_h = desc.BufferDesc.Height;
  return true;
}

// REQ R6 - 60 fps Full, 30 fps Basic.
int DxDevice::TargetFrameMs(QualityTier tier) const {
  switch (tier) {
    case QualityTier::Full:     return 16;  // ~60 Hz
    case QualityTier::Balanced: return 16;
    case QualityTier::Basic:    return 33;  // ~30 Hz
    default:                    return 16;
  }
}

void DxDevice::Destroy() {
  DestroySwapChain();
  factory_.Reset();
  dcomp_.Reset();
  dxgi_device_.Reset();
  context_.Reset();
  device_.Reset();
  info_ = DeviceInfo();
}

}  // namespace fcs