// Copyright 2016 Dolphin Emulator Project
// SPDX-License-Identifier: GPL-2.0-or-later

#include "VideoCommon/RenderState.h"

#include <algorithm>
#include <array>

#include "VideoCommon/BPMemory.h"
#include "VideoCommon/TextureConfig.h"

void RasterizationState::Generate(const BPMemory& bp, PrimitiveType primitive_type)
{
  cullmode = bp.genMode.cullmode;
  primitive = primitive_type;

  // Back-face culling should be disabled for points/lines.
  if (primitive_type != PrimitiveType::Triangles && primitive_type != PrimitiveType::TriangleStrip)
    cullmode = CullMode::None;
}

void DepthState::Generate(const BPMemory& bp)
{
  testenable = bp.zmode.testenable.Value();
  updateenable = bp.zmode.updateenable.Value();
  func = bp.zmode.func.Value();
}

static bool IsDualSrc(SrcBlendFactor factor)
{
  return factor == SrcBlendFactor::SrcAlpha || factor == SrcBlendFactor::InvSrcAlpha;
}

static bool IsDualSrc(DstBlendFactor factor)
{
  return factor == DstBlendFactor::SrcAlpha || factor == DstBlendFactor::InvSrcAlpha;
}

bool BlendingState::RequiresDualSrc() const
{
  bool requires_dual_src = false;
  requires_dual_src |= IsDualSrc(srcfactor) || IsDualSrc(srcfactoralpha);
  requires_dual_src |= IsDualSrc(dstfactor) || IsDualSrc(dstfactoralpha);
  requires_dual_src &= blendenable && usedualsrc;
  return requires_dual_src;
}

// If the framebuffer format has no alpha channel, it is assumed to
// ONE on blending. As the backends may emulate this framebuffer
// configuration with an alpha channel, we just drop all references
// to the destination alpha channel.
static SrcBlendFactor RemoveDstAlphaUsage(SrcBlendFactor factor)
{
  switch (factor)
  {
  case SrcBlendFactor::DstAlpha:
    return SrcBlendFactor::One;
  case SrcBlendFactor::InvDstAlpha:
    return SrcBlendFactor::Zero;
  default:
    return factor;
  }
}

static DstBlendFactor RemoveDstAlphaUsage(DstBlendFactor factor)
{
  switch (factor)
  {
  case DstBlendFactor::DstAlpha:
    return DstBlendFactor::One;
  case DstBlendFactor::InvDstAlpha:
    return DstBlendFactor::Zero;
  default:
    return factor;
  }
}

// We separate the blending parameter for rgb and alpha. For blending
// the alpha component, CLR and ALPHA are indentical. So just always
// use ALPHA as this makes it easier for the backends to use the second
// alpha value of dual source blending.
static DstBlendFactor RemoveSrcColorUsage(DstBlendFactor factor)
{
  switch (factor)
  {
  case DstBlendFactor::SrcClr:
    return DstBlendFactor::SrcAlpha;
  case DstBlendFactor::InvSrcClr:
    return DstBlendFactor::InvSrcAlpha;
  default:
    return factor;
  }
}

// Same as RemoveSrcColorUsage, but because of the overlapping enum,
// this must be written as another function.
static SrcBlendFactor RemoveDstColorUsage(SrcBlendFactor factor)
{
  switch (factor)
  {
  case SrcBlendFactor::DstClr:
    return SrcBlendFactor::DstAlpha;
  case SrcBlendFactor::InvDstClr:
    return SrcBlendFactor::InvDstAlpha;
  default:
    return factor;
  }
}

void BlendingState::Generate(const BPMemory& bp)
{
  // Start with everything disabled.
  hex = 0;

  const bool target_has_alpha = bp.zcontrol.pixel_format == PixelFormat::RGBA6_Z24;
  const bool alpha_test_may_succeed = bp.alpha_test.TestResult() != AlphaTestResult::Fail;

  colorupdate = bp.blendmode.colorupdate && alpha_test_may_succeed;
  alphaupdate = bp.blendmode.alphaupdate && target_has_alpha && alpha_test_may_succeed;
  const bool dstalpha = bp.dstalpha.enable && alphaupdate;
  usedualsrc = true;

  if (bp.blendmode.blendenable)
  {
    if (bp.blendmode.subtract)
    {
      blendenable = true;
      subtractAlpha = subtract = true;
      srcfactoralpha = srcfactor = SrcBlendFactor::One;
      dstfactoralpha = dstfactor = DstBlendFactor::One;

      if (dstalpha)
      {
        subtractAlpha = false;
        srcfactoralpha = SrcBlendFactor::One;
        dstfactoralpha = DstBlendFactor::Zero;
      }
    }
    else
    {
      blendenable = true;
      srcfactor = bp.blendmode.srcfactor;
      dstfactor = bp.blendmode.dstfactor;
      if (!target_has_alpha)
      {
        // uses ONE instead of DSTALPHA
        srcfactor = RemoveDstAlphaUsage(srcfactor);
        dstfactor = RemoveDstAlphaUsage(dstfactor);
      }
      // replaces SrcClr with SrcAlpha and DstClr with DstAlpha, it is important to
      // use the dst function for the src factor and vice versa
      srcfactoralpha = RemoveDstColorUsage(srcfactor);
      dstfactoralpha = RemoveSrcColorUsage(dstfactor);

      if (dstalpha)
      {
        srcfactoralpha = SrcBlendFactor::One;
        dstfactoralpha = DstBlendFactor::Zero;
      }
    }
  }
  else if (bp.blendmode.logicopenable)
  {
    if (bp.blendmode.logicmode == LogicOp::NoOp)
    {
      // Fast path for Kirby's Return to Dreamland, they use it with dstAlpha.
      colorupdate = false;
      alphaupdate = alphaupdate && dstalpha;
    }
    else
    {
      logicopenable = true;
      logicmode = bp.blendmode.logicmode;

      if (dstalpha)
      {
        // TODO: Not supported by backends.
      }
    }
  }

  // If we aren't writing color or alpha, don't blend it.
  // Intel GPUs on D3D12 seem to have issues with dual-source blend if the second source is used in
  // the blend state but not actually written (i.e. the alpha src or dst factor is src alpha, but
  // alpha update is disabled). So, change the blending configuration to not use a dual-source
  // factor. Note that in theory, disabling writing should render these irrelevant.
  if (!colorupdate)
  {
    srcfactor = SrcBlendFactor::Zero;
    dstfactor = DstBlendFactor::One;
  }
  if (!alphaupdate)
  {
    srcfactoralpha = SrcBlendFactor::Zero;
    dstfactoralpha = DstBlendFactor::One;
  }
}

void BlendingState::ApproximateLogicOpWithBlending()
{
  struct LogicOpApproximation
  {
    bool blendEnable;
    bool subtract;
    SrcBlendFactor srcfactor;
    DstBlendFactor dstfactor;
  };
  // TODO: This previously had a warning about SRC and DST being aliased and not to mix them,
  // but INVSRCCLR and INVDSTCLR were also aliased and were mixed.
  // Thus, NOR, EQUIV, INVERT, COPY_INVERTED, and OR_INVERTED duplicate(d) other values.
  static constexpr std::array<LogicOpApproximation, 16> approximations = {{
      // clang-format off
      {false, false, SrcBlendFactor::One,       DstBlendFactor::Zero},        // CLEAR (Shader outputs 0)
      {true,  false, SrcBlendFactor::DstClr,    DstBlendFactor::Zero},        // AND
      {true,  true,  SrcBlendFactor::One,       DstBlendFactor::InvSrcClr},   // AND_REVERSE
      {false, false, SrcBlendFactor::One,       DstBlendFactor::Zero},        // COPY
      {true,  true,  SrcBlendFactor::DstClr,    DstBlendFactor::One},         // AND_INVERTED
      {true,  false, SrcBlendFactor::Zero,      DstBlendFactor::One},         // NOOP
      {true,  false, SrcBlendFactor::InvDstClr, DstBlendFactor::InvSrcClr},   // XOR
      {true,  false, SrcBlendFactor::InvDstClr, DstBlendFactor::One},         // OR
      {true,  false, SrcBlendFactor::InvDstClr, DstBlendFactor::InvSrcClr},   // NOR
      {true,  false, SrcBlendFactor::InvDstClr, DstBlendFactor::Zero},        // EQUIV
      {true,  false, SrcBlendFactor::InvDstClr, DstBlendFactor::Zero},        // INVERT (Shader outputs 255)
      {true,  false, SrcBlendFactor::One,       DstBlendFactor::InvDstAlpha}, // OR_REVERSE
      {false, false, SrcBlendFactor::One,       DstBlendFactor::Zero},        // COPY_INVERTED (Shader inverts)
      {true,  false, SrcBlendFactor::InvDstClr, DstBlendFactor::One},         // OR_INVERTED
      {true,  false, SrcBlendFactor::InvDstClr, DstBlendFactor::InvSrcClr},   // NAND
      {false, false, SrcBlendFactor::One,       DstBlendFactor::Zero},        // SET (Shader outputs 255)
      // clang-format on
  }};

  logicopenable = false;
  usedualsrc = false;
  const LogicOpApproximation& approximation = approximations[static_cast<u32>(logicmode.Value())];
  if (approximation.blendEnable)
  {
    blendenable = true;
    subtract = approximation.subtract;
    srcfactor = approximation.srcfactor;
    srcfactoralpha = approximation.srcfactor;
    dstfactor = approximation.dstfactor;
    dstfactoralpha = approximation.dstfactor;
  }
}

bool BlendingState::LogicOpApproximationIsExact()
{
  switch (logicmode.Value())
  {
  case LogicOp::Clear:
  case LogicOp::Set:
  case LogicOp::NoOp:
  case LogicOp::Invert:
  case LogicOp::CopyInverted:
  case LogicOp::Copy:
    return true;
  default:
    return false;
  }
}

bool BlendingState::LogicOpApproximationWantsShaderHelp()
{
  switch (logicmode.Value())
  {
  case LogicOp::Clear:
  case LogicOp::Set:
  case LogicOp::NoOp:
  case LogicOp::Invert:
  case LogicOp::CopyInverted:
    return true;
  default:
    return false;
  }
}

void SamplerState::Generate(const BPMemory& bp, u32 index)
{
  auto tex = bp.tex.GetUnit(index);
  const TexMode0& bp_tm0 = tex.texMode0;
  const TexMode1& bp_tm1 = tex.texMode1;

  // GX can configure the mip filter to none. However, D3D and Vulkan can't express this in their
  // sampler states. Therefore, we set the min/max LOD to zero if this option is used.
  tm0.min_filter = bp_tm0.min_filter;
  tm0.mipmap_filter =
      bp_tm0.mipmap_filter == MipMode::Linear ? FilterMode::Linear : FilterMode::Near;
  tm0.mag_filter = bp_tm0.mag_filter;

  // If mipmaps are disabled, clamp min/max lod
  if (bp_tm0.mipmap_filter == MipMode::None)
  {
    tm1.max_lod = 0;
    tm1.min_lod = 0;
    tm0.lod_bias = 0;
  }
  else
  {
    // NOTE: When comparing, max is checked first, then min; if max is less than min, max wins
    tm1.max_lod = bp_tm1.max_lod.Value();
    tm1.min_lod = std::min(tm1.max_lod.Value(), bp_tm1.min_lod.Value());
    tm0.lod_bias = bp_tm0.lod_bias * (256 / 32);
  }

  // Wrap modes
  // Hardware testing indicates that wrap_mode set to 3 behaves the same as clamp.
  auto filter_invalid_wrap = [](WrapMode mode) {
    return (mode <= WrapMode::Mirror) ? mode : WrapMode::Clamp;
  };
  tm0.wrap_u = filter_invalid_wrap(bp_tm0.wrap_s);
  tm0.wrap_v = filter_invalid_wrap(bp_tm0.wrap_t);

  tm0.diag_lod = bp_tm0.diag_lod;
  tm0.anisotropic_filtering = false;  // TODO: Respect BP anisotropic filtering mode
  tm0.lod_clamp = bp_tm0.lod_clamp;   // TODO: What does this do?
}

namespace RenderState
{
RasterizationState GetInvalidRasterizationState()
{
  RasterizationState state;
  state.hex = UINT32_C(0xFFFFFFFF);
  return state;
}

RasterizationState GetNoCullRasterizationState(PrimitiveType primitive)
{
  RasterizationState state = {};
  state.cullmode = CullMode::None;
  state.primitive = primitive;
  return state;
}

RasterizationState GetCullBackFaceRasterizationState(PrimitiveType primitive)
{
  RasterizationState state = {};
  state.cullmode = CullMode::Back;
  state.primitive = primitive;
  return state;
}

DepthState GetInvalidDepthState()
{
  DepthState state;
  state.hex = UINT32_C(0xFFFFFFFF);
  return state;
}

DepthState GetNoDepthTestingDepthState()
{
  DepthState state = {};
  state.testenable = false;
  state.updateenable = false;
  state.func = CompareMode::Always;
  return state;
}

DepthState GetAlwaysWriteDepthState()
{
  DepthState state = {};
  state.testenable = true;
  state.updateenable = true;
  state.func = CompareMode::Always;
  return state;
}

BlendingState GetInvalidBlendingState()
{
  BlendingState state;
  state.hex = UINT32_C(0xFFFFFFFF);
  return state;
}

BlendingState GetNoBlendingBlendState()
{
  BlendingState state = {};
  state.usedualsrc = false;
  state.blendenable = false;
  state.srcfactor = SrcBlendFactor::One;
  state.srcfactoralpha = SrcBlendFactor::One;
  state.dstfactor = DstBlendFactor::Zero;
  state.dstfactoralpha = DstBlendFactor::Zero;
  state.logicopenable = false;
  state.colorupdate = true;
  state.alphaupdate = true;
  return state;
}

BlendingState GetNoColorWriteBlendState()
{
  BlendingState state = {};
  state.usedualsrc = false;
  state.blendenable = false;
  state.srcfactor = SrcBlendFactor::One;
  state.srcfactoralpha = SrcBlendFactor::One;
  state.dstfactor = DstBlendFactor::Zero;
  state.dstfactoralpha = DstBlendFactor::Zero;
  state.logicopenable = false;
  state.colorupdate = false;
  state.alphaupdate = false;
  return state;
}

SamplerState GetInvalidSamplerState()
{
  SamplerState state;
  state.tm0.hex = 0xFFFFFFFF;
  state.tm1.hex = 0xFFFFFFFF;
  return state;
}

SamplerState GetPointSamplerState()
{
  SamplerState state = {};
  state.tm0.min_filter = FilterMode::Near;
  state.tm0.mag_filter = FilterMode::Near;
  state.tm0.mipmap_filter = FilterMode::Near;
  state.tm0.wrap_u = WrapMode::Clamp;
  state.tm0.wrap_v = WrapMode::Clamp;
  state.tm1.min_lod = 0;
  state.tm1.max_lod = 255;
  state.tm0.lod_bias = 0;
  state.tm0.anisotropic_filtering = false;
  state.tm0.diag_lod = LODType::Edge;
  state.tm0.lod_clamp = false;
  return state;
}

SamplerState GetLinearSamplerState()
{
  SamplerState state = {};
  state.tm0.min_filter = FilterMode::Linear;
  state.tm0.mag_filter = FilterMode::Linear;
  state.tm0.mipmap_filter = FilterMode::Linear;
  state.tm0.wrap_u = WrapMode::Clamp;
  state.tm0.wrap_v = WrapMode::Clamp;
  state.tm1.min_lod = 0;
  state.tm1.max_lod = 255;
  state.tm0.lod_bias = 0;
  state.tm0.anisotropic_filtering = false;
  state.tm0.diag_lod = LODType::Edge;
  state.tm0.lod_clamp = false;
  return state;
}

FramebufferState GetColorFramebufferState(AbstractTextureFormat format)
{
  FramebufferState state = {};
  state.color_texture_format = format;
  state.depth_texture_format = AbstractTextureFormat::Undefined;
  state.per_sample_shading = false;
  state.samples = 1;
  state.additional_color_attachment_count = 0;
  return state;
}

FramebufferState GetRGBA8FramebufferState()
{
  return GetColorFramebufferState(AbstractTextureFormat::RGBA8);
}

}  // namespace RenderState