// Copyright 2009 Dolphin Emulator Project
// SPDX-License-Identifier: GPL-2.0-or-later

#include "VideoCommon/BPFunctions.h"

#include <algorithm>
#include <cmath>
#include <string_view>

#include "Common/Assert.h"
#include "Common/CommonTypes.h"
#include "Common/Logging/Log.h"
#include "Common/SmallVector.h"

#include "VideoCommon/AbstractFramebuffer.h"
#include "VideoCommon/AbstractGfx.h"
#include "VideoCommon/BPMemory.h"
#include "VideoCommon/FramebufferManager.h"
#include "VideoCommon/RenderBase.h"
#include "VideoCommon/RenderState.h"
#include "VideoCommon/VertexManagerBase.h"
#include "VideoCommon/VertexShaderManager.h"
#include "VideoCommon/VideoCommon.h"
#include "VideoCommon/VideoConfig.h"
#include "VideoCommon/XFMemory.h"

namespace BPFunctions
{
// ----------------------------------------------
// State translation lookup tables
// Reference: Yet Another GameCube Documentation
// ----------------------------------------------

void FlushPipeline()
{
  g_vertex_manager->Flush();
}

void SetGenerationMode()
{
  g_vertex_manager->SetRasterizationStateChanged();
}

int ScissorRect::GetArea() const
{
  return rect.GetWidth() * rect.GetHeight();
}

int ScissorResult::GetViewportArea(const ScissorRect& rect) const
{
  int x0 = std::clamp<int>(rect.rect.left + rect.x_off, viewport_left, viewport_right);
  int x1 = std::clamp<int>(rect.rect.right + rect.x_off, viewport_left, viewport_right);

  int y0 = std::clamp<int>(rect.rect.top + rect.y_off, viewport_top, viewport_bottom);
  int y1 = std::clamp<int>(rect.rect.bottom + rect.y_off, viewport_top, viewport_bottom);

  return (x1 - x0) * (y1 - y0);
}

// Compare so that a sorted collection of rectangles has the best one last, so that if they're drawn
// in order, the best one is the one that is drawn last (and thus over the rest).
// The exact iteration order on hardware hasn't been tested, but silly things can happen where a
// polygon can intersect with itself; this only applies outside of the viewport region (in areas
// that would normally be affected by clipping).  No game is known to care about this.
bool ScissorResult::IsWorse(const ScissorRect& lhs, const ScissorRect& rhs) const
{
  // First, penalize any rect that is not in the viewport
  int lhs_area = GetViewportArea(lhs);
  int rhs_area = GetViewportArea(rhs);

  if (lhs_area != rhs_area)
    return lhs_area < rhs_area;

  // Now compare on total areas, without regard for the viewport
  return lhs.GetArea() < rhs.GetArea();
}

namespace
{
using RangeList = Common::SmallVector<ScissorRange, 9>;

static RangeList ComputeScissorRanges(int start, int end, int offset, int efb_dim)
{
  RangeList ranges;

  for (int extra_off = -4096; extra_off <= 4096; extra_off += 1024)
  {
    int new_off = offset + extra_off;
    int new_start = std::clamp(start - new_off, 0, efb_dim);
    int new_end = std::clamp(end - new_off + 1, 0, efb_dim);
    if (new_start < new_end)
    {
      ranges.emplace_back(new_off, new_start, new_end);
    }
  }

  return ranges;
}
}  // namespace

ScissorResult::ScissorResult(const BPMemory& bpmemory, const XFMemory& xfmemory)
    : ScissorResult(bpmemory,
                    std::minmax(xfmemory.viewport.xOrig - xfmemory.viewport.wd,
                                xfmemory.viewport.xOrig + xfmemory.viewport.wd),
                    std::minmax(xfmemory.viewport.yOrig - xfmemory.viewport.ht,
                                xfmemory.viewport.yOrig + xfmemory.viewport.ht))
{
}
ScissorResult::ScissorResult(const BPMemory& bpmemory, std::pair<float, float> viewport_x,
                             std::pair<float, float> viewport_y)
    : scissor_tl{.hex = bpmemory.scissorTL.hex}, scissor_br{.hex = bpmemory.scissorBR.hex},
      scissor_off{.hex = bpmemory.scissorOffset.hex}, viewport_left(viewport_x.first),
      viewport_right(viewport_x.second), viewport_top(viewport_y.first),
      viewport_bottom(viewport_y.second)
{
  // Range is [left, right] and [top, bottom] (closed intervals)
  const int left = scissor_tl.x;
  const int right = scissor_br.x;
  const int top = scissor_tl.y;
  const int bottom = scissor_br.y;
  // When left > right or top > bottom, nothing renders (even with wrapping from the offsets)
  if (left > right || top > bottom)
    return;

  // Note that both the offsets and the coordinates have 342 added to them internally by GX
  // functions (for the offsets, this is before they are divided by 2/right shifted). This code
  // could undo both sets of offsets, but it doesn't need to since they cancel out when subtracting
  // (and those offsets actually matter for the left > right and top > bottom checks).
  const int x_off = scissor_off.x << 1;
  const int y_off = scissor_off.y << 1;

  RangeList x_ranges = ComputeScissorRanges(left, right, x_off, EFB_WIDTH);
  RangeList y_ranges = ComputeScissorRanges(top, bottom, y_off, EFB_HEIGHT);

  m_result.reserve(x_ranges.size() * y_ranges.size());

  // Now we need to form actual rectangles from the x and y ranges,
  // which is a simple Cartesian product of x_ranges_clamped and y_ranges_clamped.
  // Each rectangle is also a Cartesian product of x_range and y_range, with
  // the rectangles being half-open (of the form [x0, x1) X [y0, y1)).
  for (const auto& x_range : x_ranges)
  {
    DEBUG_ASSERT(x_range.start < x_range.end);
    DEBUG_ASSERT(static_cast<u32>(x_range.end) <= EFB_WIDTH);
    for (const auto& y_range : y_ranges)
    {
      DEBUG_ASSERT(y_range.start < y_range.end);
      DEBUG_ASSERT(static_cast<u32>(y_range.end) <= EFB_HEIGHT);
      m_result.emplace_back(x_range, y_range);
    }
  }

  auto cmp = [&](const ScissorRect& lhs, const ScissorRect& rhs) { return IsWorse(lhs, rhs); };
  std::ranges::sort(m_result, cmp);
}

ScissorRect ScissorResult::Best() const
{
  // For now, simply choose the best rectangle (see ScissorResult::IsWorse).
  // This does mean we calculate all rectangles and only choose one, which is not optimal, but this
  // is called infrequently.  Eventually, all backends will support multiple scissor rects.
  if (!m_result.empty())
  {
    return m_result.back();
  }
  else
  {
    // But if we have no rectangles, use a bogus one that's out of bounds.
    // Ideally, all backends will support multiple scissor rects, in which case this won't be
    // needed.
    return ScissorRect(ScissorRange{0, 1000, 1001}, ScissorRange{0, 1000, 1001});
  }
}

ScissorResult ComputeScissorRects()
{
  return ScissorResult{bpmem, xfmem};
}

void SetScissorAndViewport()
{
  auto native_rc = ComputeScissorRects().Best();

  auto target_rc = g_framebuffer_manager->ConvertEFBRectangle(native_rc.rect);
  auto converted_rc = g_gfx->ConvertFramebufferRectangle(target_rc, g_gfx->GetCurrentFramebuffer());
  g_gfx->SetScissorRect(converted_rc);

  float raw_x = (xfmem.viewport.xOrig - native_rc.x_off) - xfmem.viewport.wd;
  float raw_y = (xfmem.viewport.yOrig - native_rc.y_off) + xfmem.viewport.ht;
  float raw_width = 2.0f * xfmem.viewport.wd;
  float raw_height = -2.0f * xfmem.viewport.ht;
  if (g_ActiveConfig.UseVertexRounding())
  {
    // Round the viewport to match full 1x IR pixels as well.
    // This eliminates a line in the archery mode in Wii Sports Resort at 3x IR and higher.
    raw_x = std::round(raw_x);
    raw_y = std::round(raw_y);
    raw_width = std::round(raw_width);
    raw_height = std::round(raw_height);
  }

  float x = g_framebuffer_manager->EFBToScaledXf(raw_x);
  float y = g_framebuffer_manager->EFBToScaledYf(raw_y);
  float width = g_framebuffer_manager->EFBToScaledXf(raw_width);
  float height = g_framebuffer_manager->EFBToScaledYf(raw_height);
  float min_depth = (xfmem.viewport.farZ - xfmem.viewport.zRange) / 16777216.0f;
  float max_depth = xfmem.viewport.farZ / 16777216.0f;
  if (width < 0.f)
  {
    x += width;
    width *= -1;
  }
  if (height < 0.f)
  {
    y += height;
    height *= -1;
  }

  // The maximum depth that is written to the depth buffer should never exceed this value.
  // This is necessary because we use a 2^24 divisor for all our depth values to prevent
  // floating-point round-trip errors. However the console GPU doesn't ever write a value
  // to the depth buffer that exceeds 2^24 - 1.
  constexpr float GX_MAX_DEPTH = 16777215.0f / 16777216.0f;
  if (!g_ActiveConfig.backend_info.bSupportsDepthClamp)
  {
    // There's no way to support oversized depth ranges in this situation. Let's just clamp the
    // range to the maximum value supported by the console GPU and hope for the best.
    min_depth = std::clamp(min_depth, 0.0f, GX_MAX_DEPTH);
    max_depth = std::clamp(max_depth, 0.0f, GX_MAX_DEPTH);
  }

  if (VertexShaderManager::UseVertexDepthRange())
  {
    // We need to ensure depth values are clamped the maximum value supported by the console GPU.
    // Taking into account whether the depth range is inverted or not.
    if (xfmem.viewport.zRange < 0.0f && g_ActiveConfig.backend_info.bSupportsReversedDepthRange)
    {
      min_depth = GX_MAX_DEPTH;
      max_depth = 0.0f;
    }
    else
    {
      min_depth = 0.0f;
      max_depth = GX_MAX_DEPTH;
    }
  }

  float near_depth, far_depth;
  if (g_ActiveConfig.backend_info.bSupportsReversedDepthRange)
  {
    // Set the reversed depth range.
    near_depth = max_depth;
    far_depth = min_depth;
  }
  else
  {
    // We use an inverted depth range here to apply the Reverse Z trick.
    // This trick makes sure we match the precision provided by the 1:0
    // clipping depth range on the hardware.
    near_depth = 1.0f - max_depth;
    far_depth = 1.0f - min_depth;
  }

  // Lower-left flip.
  if (g_ActiveConfig.backend_info.bUsesLowerLeftOrigin)
    y = static_cast<float>(g_gfx->GetCurrentFramebuffer()->GetHeight()) - y - height;

  g_gfx->SetViewport(x, y, width, height, near_depth, far_depth);
}

void SetDepthMode()
{
  g_vertex_manager->SetDepthStateChanged();
}

void SetBlendMode()
{
  g_vertex_manager->SetBlendingStateChanged();
}

/* Explanation of the magic behind ClearScreen:
  There's numerous possible formats for the pixel data in the EFB.
  However, in the HW accelerated backends we're always using RGBA8
  for the EFB format, which causes some problems:
  - We're using an alpha channel although the game doesn't
  - If the actual EFB format is RGBA6_Z24 or R5G6B5_Z16, we are using more bits per channel than the
  native HW

  To properly emulate the above points, we're doing the following:
  (1)
    - disable alpha channel writing of any kind of rendering if the actual EFB format doesn't use an
  alpha channel
    - NOTE: Always make sure that the EFB has been cleared to an alpha value of 0xFF in this case!
    - Same for color channels, these need to be cleared to 0x00 though.
  (2)
    - convert the RGBA8 color to RGBA6/RGB8/RGB565 and convert it to RGBA8 again
    - convert the Z24 depth value to Z16 and back to Z24
*/
void ClearScreen(const MathUtil::Rectangle<int>& rc)
{
  bool colorEnable = (bpmem.blendmode.colorupdate != 0);
  bool alphaEnable = (bpmem.blendmode.alphaupdate != 0);
  bool zEnable = (bpmem.zmode.updateenable != 0);
  auto pixel_format = bpmem.zcontrol.pixel_format;

  // (1): Disable unused color channels
  if (pixel_format == PixelFormat::RGB8_Z24 || pixel_format == PixelFormat::RGB565_Z16 ||
      pixel_format == PixelFormat::Z24)
  {
    alphaEnable = false;
  }

  if (colorEnable || alphaEnable || zEnable)
  {
    u32 color = (bpmem.clearcolorAR << 16) | bpmem.clearcolorGB;
    u32 z = bpmem.clearZValue;

    // (2) drop additional accuracy
    if (pixel_format == PixelFormat::RGBA6_Z24)
    {
      color = RGBA8ToRGBA6ToRGBA8(color);
    }
    else if (pixel_format == PixelFormat::RGB565_Z16)
    {
      color = RGBA8ToRGB565ToRGBA8(color);
      z = Z24ToZ16ToZ24(z);
    }
    g_framebuffer_manager->ClearEFB(rc, colorEnable, alphaEnable, zEnable, color, z);
  }
}

void OnPixelFormatChange()
{
  // TODO : Check for Z compression format change
  // When using 16bit Z, the game may enable a special compression format which we might need to
  // handle. Only a few games like RS2 and RS3 even use z compression but it looks like they
  // always use ZFAR when using 16bit Z (on top of linear 24bit Z)

  // Besides, we currently don't even emulate 16bit depth and force it to 24bit.

  /*
   * When changing the EFB format, the pixel data won't get converted to the new format but stays
   * the same.
   * Since we are always using an RGBA8 buffer though, this causes issues in some games.
   * Thus, we reinterpret the old EFB data with the new format here.
   */
  if (!g_ActiveConfig.bEFBEmulateFormatChanges)
    return;

  const auto old_format = g_framebuffer_manager->GetPrevPixelFormat();
  const auto new_format = bpmem.zcontrol.pixel_format;
  g_framebuffer_manager->StorePixelFormat(new_format);

  DEBUG_LOG_FMT(VIDEO, "pixelfmt: pixel={}, zc={}", new_format, bpmem.zcontrol.zformat);

  // no need to reinterpret pixel data in these cases
  if (new_format == old_format || old_format == PixelFormat::INVALID_FMT)
    return;

  // Check for pixel format changes
  switch (old_format)
  {
  case PixelFormat::RGB8_Z24:
  case PixelFormat::Z24:
  {
    // Z24 and RGB8_Z24 are treated equal, so just return in this case
    if (new_format == PixelFormat::RGB8_Z24 || new_format == PixelFormat::Z24)
      return;

    if (new_format == PixelFormat::RGBA6_Z24)
    {
      g_renderer->ReinterpretPixelData(EFBReinterpretType::RGB8ToRGBA6);
      return;
    }
    else if (new_format == PixelFormat::RGB565_Z16)
    {
      g_renderer->ReinterpretPixelData(EFBReinterpretType::RGB8ToRGB565);
      return;
    }
  }
  break;

  case PixelFormat::RGBA6_Z24:
  {
    if (new_format == PixelFormat::RGB8_Z24 || new_format == PixelFormat::Z24)
    {
      g_renderer->ReinterpretPixelData(EFBReinterpretType::RGBA6ToRGB8);
      return;
    }
    else if (new_format == PixelFormat::RGB565_Z16)
    {
      g_renderer->ReinterpretPixelData(EFBReinterpretType::RGBA6ToRGB565);
      return;
    }
  }
  break;

  case PixelFormat::RGB565_Z16:
  {
    if (new_format == PixelFormat::RGB8_Z24 || new_format == PixelFormat::Z24)
    {
      g_renderer->ReinterpretPixelData(EFBReinterpretType::RGB565ToRGB8);
      return;
    }
    else if (new_format == PixelFormat::RGBA6_Z24)
    {
      g_renderer->ReinterpretPixelData(EFBReinterpretType::RGB565ToRGBA6);
      return;
    }
  }
  break;

  default:
    break;
  }

  ERROR_LOG_FMT(VIDEO, "Unhandled EFB format change: {} to {}", old_format, new_format);
}

void SetInterlacingMode(const BPCmd& bp)
{
  // TODO
  switch (bp.address)
  {
  case BPMEM_FIELDMODE:
  {
    // SDK always sets bpmem.lineptwidth.lineaspect via BPMEM_LINEPTWIDTH
    // just before this cmd
    DEBUG_LOG_FMT(VIDEO, "BPMEM_FIELDMODE texLOD:{} lineaspect:{}", bpmem.fieldmode.texLOD,
                  bpmem.lineptwidth.adjust_for_aspect_ratio);
  }
  break;
  case BPMEM_FIELDMASK:
  {
    // Determines if fields will be written to EFB (always computed)
    DEBUG_LOG_FMT(VIDEO, "BPMEM_FIELDMASK even:{} odd:{}", bpmem.fieldmask.even,
                  bpmem.fieldmask.odd);
  }
  break;
  default:
    ERROR_LOG_FMT(VIDEO, "SetInterlacingMode default");
    break;
  }
}
}  // namespace BPFunctions
