/**
 ******************************************************************************
 * Xenia : Xbox 360 Emulator Research Project                                 *
 ******************************************************************************
 * Copyright 2020 Ben Vanik. All rights reserved.                             *
 * Released under the BSD license - see LICENSE in the root for more details. *
 ******************************************************************************
 */

#include "xenia/gpu/xenos.h"

#include <cmath>

#include "xenia/base/math.h"

namespace xe {
namespace gpu {
namespace xenos {

// https://github.com/Microsoft/DirectXTex/blob/master/DirectXTex/DirectXTexConvert.cpp

float Float7e3To32(uint32_t f10) {
  f10 &= 0x3FF;
  if (!f10) {
    return 0.0f;
  }
  uint32_t mantissa = f10 & 0x7F;
  uint32_t exponent = f10 >> 7;
  if (!exponent) {
    // Normalize the value in the resulting float.
    // do { Exponent--; Mantissa <<= 1; } while ((Mantissa & 0x80) == 0)
    uint32_t mantissa_lzcnt = xe::lzcnt(mantissa) - (32 - 8);
    exponent = uint32_t(1 - int32_t(mantissa_lzcnt));
    mantissa = (mantissa << mantissa_lzcnt) & 0x7F;
  }
  uint32_t f32 = ((exponent + 124) << 23) | (mantissa << 3);
  return *reinterpret_cast<const float*>(&f32);
}

// Based on CFloat24 from d3dref9.dll and the 6e4 code from:
// https://github.com/Microsoft/DirectXTex/blob/master/DirectXTex/DirectXTexConvert.cpp
// 6e4 has a different exponent bias allowing [0,512) values, 20e4 allows [0,2).

uint32_t Float32To20e4(float f32) {
  if (!(f32 > 0.0f)) {
    // Positive only, and not -0 or NaN.
    return 0;
  }
  uint32_t f32u32 = *reinterpret_cast<const uint32_t*>(&f32);
  if (f32u32 >= 0x3FFFFFF8) {
    // Saturate.
    return 0xFFFFFF;
  }
  if (f32u32 < 0x38800000) {
    // The number is too small to be represented as a normalized 20e4.
    // Convert it to a denormalized value.
    uint32_t shift = std::min(uint32_t(113 - (f32u32 >> 23)), uint32_t(24));
    f32u32 = (0x800000 | (f32u32 & 0x7FFFFF)) >> shift;
  } else {
    // Rebias the exponent to represent the value as a normalized 20e4.
    f32u32 += 0xC8000000u;
  }
  return ((f32u32 + 3 + ((f32u32 >> 3) & 1)) >> 3) & 0xFFFFFF;
}

float Float20e4To32(uint32_t f24) {
  f24 &= 0xFFFFFF;
  if (!f24) {
    return 0.0f;
  }
  uint32_t mantissa = f24 & 0xFFFFF;
  uint32_t exponent = f24 >> 20;
  if (!exponent) {
    // Normalize the value in the resulting float.
    // do { Exponent--; Mantissa <<= 1; } while ((Mantissa & 0x100000) == 0)
    uint32_t mantissa_lzcnt = xe::lzcnt(mantissa) - (32 - 21);
    exponent = uint32_t(1 - int32_t(mantissa_lzcnt));
    mantissa = (mantissa << mantissa_lzcnt) & 0xFFFFF;
  }
  uint32_t f32 = ((exponent + 112) << 23) | (mantissa << 3);
  return *reinterpret_cast<const float*>(&f32);
}

const char* GetColorRenderTargetFormatName(ColorRenderTargetFormat format) {
  switch (format) {
    case ColorRenderTargetFormat::k_8_8_8_8:
      return "k_8_8_8_8";
    case ColorRenderTargetFormat::k_8_8_8_8_GAMMA:
      return "k_8_8_8_8_GAMMA";
    case ColorRenderTargetFormat::k_2_10_10_10:
      return "k_2_10_10_10";
    case ColorRenderTargetFormat::k_2_10_10_10_FLOAT:
      return "k_2_10_10_10_FLOAT";
    case ColorRenderTargetFormat::k_16_16:
      return "k_16_16";
    case ColorRenderTargetFormat::k_16_16_16_16:
      return "k_16_16_16_16";
    case ColorRenderTargetFormat::k_16_16_FLOAT:
      return "k_16_16_FLOAT";
    case ColorRenderTargetFormat::k_16_16_16_16_FLOAT:
      return "k_16_16_16_16_FLOAT";
    case ColorRenderTargetFormat::k_2_10_10_10_AS_10_10_10_10:
      return "k_2_10_10_10_AS_10_10_10_10";
    case ColorRenderTargetFormat::k_2_10_10_10_FLOAT_AS_16_16_16_16:
      return "k_2_10_10_10_FLOAT_AS_16_16_16_16";
    case ColorRenderTargetFormat::k_32_FLOAT:
      return "k_32_FLOAT";
    case ColorRenderTargetFormat::k_32_32_FLOAT:
      return "k_32_32_FLOAT";
    default:
      return "kUnknown";
  }
}

const char* GetDepthRenderTargetFormatName(DepthRenderTargetFormat format) {
  switch (format) {
    case DepthRenderTargetFormat::kD24S8:
      return "kD24S8";
    case DepthRenderTargetFormat::kD24FS8:
      return "kD24FS8";
    default:
      return "kUnknown";
  }
}

}  // namespace xenos
}  // namespace gpu
}  // namespace xe