// Copyright 2017 Citra Emulator Project
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.

#include <algorithm>
#include "common/assert.h"
#include "common/color.h"
#include "common/common_types.h"
#include "common/logging/log.h"
#include "common/vector_math.h"
#include "core/hw/gpu.h"
#include "core/memory.h"
#include "video_core/pica_state.h"
#include "video_core/regs_framebuffer.h"
#include "video_core/swrasterizer/framebuffer.h"
#include "video_core/utils.h"
#include "video_core/video_core.h"

namespace Pica::Rasterizer {

void DrawPixel(int x, int y, const Common::Vec4<u8>& color) {
    const auto& framebuffer = g_state.regs.framebuffer.framebuffer;
    const PAddr addr = framebuffer.GetColorBufferPhysicalAddress();

    // Similarly to textures, the render framebuffer is laid out from bottom to top, too.
    // NOTE: The framebuffer height register contains the actual FB height minus one.
    y = framebuffer.height - y;

    const u32 coarse_y = y & ~7;
    u32 bytes_per_pixel =
        GPU::Regs::BytesPerPixel(GPU::Regs::PixelFormat(framebuffer.color_format.Value()));
    u32 dst_offset = VideoCore::GetMortonOffset(x, y, bytes_per_pixel) +
                     coarse_y * framebuffer.width * bytes_per_pixel;
    u8* dst_pixel = VideoCore::Memory()->GetPhysicalPointer(addr) + dst_offset;

    switch (framebuffer.color_format) {
    case FramebufferRegs::ColorFormat::RGBA8:
        Color::EncodeRGBA8(color, dst_pixel);
        break;

    case FramebufferRegs::ColorFormat::RGB8:
        Color::EncodeRGB8(color, dst_pixel);
        break;

    case FramebufferRegs::ColorFormat::RGB5A1:
        Color::EncodeRGB5A1(color, dst_pixel);
        break;

    case FramebufferRegs::ColorFormat::RGB565:
        Color::EncodeRGB565(color, dst_pixel);
        break;

    case FramebufferRegs::ColorFormat::RGBA4:
        Color::EncodeRGBA4(color, dst_pixel);
        break;

    default:
        LOG_CRITICAL(Render_Software, "Unknown framebuffer color format {:x}",
                     static_cast<u32>(framebuffer.color_format.Value()));
        UNIMPLEMENTED();
    }
}

const Common::Vec4<u8> GetPixel(int x, int y) {
    const auto& framebuffer = g_state.regs.framebuffer.framebuffer;
    const PAddr addr = framebuffer.GetColorBufferPhysicalAddress();

    y = framebuffer.height - y;

    const u32 coarse_y = y & ~7;
    u32 bytes_per_pixel =
        GPU::Regs::BytesPerPixel(GPU::Regs::PixelFormat(framebuffer.color_format.Value()));
    u32 src_offset = VideoCore::GetMortonOffset(x, y, bytes_per_pixel) +
                     coarse_y * framebuffer.width * bytes_per_pixel;
    u8* src_pixel = VideoCore::Memory()->GetPhysicalPointer(addr) + src_offset;

    switch (framebuffer.color_format) {
    case FramebufferRegs::ColorFormat::RGBA8:
        return Color::DecodeRGBA8(src_pixel);

    case FramebufferRegs::ColorFormat::RGB8:
        return Color::DecodeRGB8(src_pixel);

    case FramebufferRegs::ColorFormat::RGB5A1:
        return Color::DecodeRGB5A1(src_pixel);

    case FramebufferRegs::ColorFormat::RGB565:
        return Color::DecodeRGB565(src_pixel);

    case FramebufferRegs::ColorFormat::RGBA4:
        return Color::DecodeRGBA4(src_pixel);

    default:
        LOG_CRITICAL(Render_Software, "Unknown framebuffer color format {:x}",
                     static_cast<u32>(framebuffer.color_format.Value()));
        UNIMPLEMENTED();
    }

    return {0, 0, 0, 0};
}

u32 GetDepth(int x, int y) {
    const auto& framebuffer = g_state.regs.framebuffer.framebuffer;
    const PAddr addr = framebuffer.GetDepthBufferPhysicalAddress();
    u8* depth_buffer = VideoCore::Memory()->GetPhysicalPointer(addr);

    y = framebuffer.height - y;

    const u32 coarse_y = y & ~7;
    u32 bytes_per_pixel = FramebufferRegs::BytesPerDepthPixel(framebuffer.depth_format);
    u32 stride = framebuffer.width * bytes_per_pixel;

    u32 src_offset = VideoCore::GetMortonOffset(x, y, bytes_per_pixel) + coarse_y * stride;
    u8* src_pixel = depth_buffer + src_offset;

    switch (framebuffer.depth_format) {
    case FramebufferRegs::DepthFormat::D16:
        return Color::DecodeD16(src_pixel);
    case FramebufferRegs::DepthFormat::D24:
        return Color::DecodeD24(src_pixel);
    case FramebufferRegs::DepthFormat::D24S8:
        return Color::DecodeD24S8(src_pixel).x;
    default:
        LOG_CRITICAL(HW_GPU, "Unimplemented depth format {}",
                     static_cast<u32>(framebuffer.depth_format.Value()));
        UNIMPLEMENTED();
        return 0;
    }
}

u8 GetStencil(int x, int y) {
    const auto& framebuffer = g_state.regs.framebuffer.framebuffer;
    const PAddr addr = framebuffer.GetDepthBufferPhysicalAddress();
    u8* depth_buffer = VideoCore::Memory()->GetPhysicalPointer(addr);

    y = framebuffer.height - y;

    const u32 coarse_y = y & ~7;
    u32 bytes_per_pixel = Pica::FramebufferRegs::BytesPerDepthPixel(framebuffer.depth_format);
    u32 stride = framebuffer.width * bytes_per_pixel;

    u32 src_offset = VideoCore::GetMortonOffset(x, y, bytes_per_pixel) + coarse_y * stride;
    u8* src_pixel = depth_buffer + src_offset;

    switch (framebuffer.depth_format) {
    case FramebufferRegs::DepthFormat::D24S8:
        return Color::DecodeD24S8(src_pixel).y;

    default:
        LOG_WARNING(
            HW_GPU,
            "GetStencil called for function which doesn't have a stencil component (format {})",
            static_cast<u32>(framebuffer.depth_format.Value()));
        return 0;
    }
}

void SetDepth(int x, int y, u32 value) {
    const auto& framebuffer = g_state.regs.framebuffer.framebuffer;
    const PAddr addr = framebuffer.GetDepthBufferPhysicalAddress();
    u8* depth_buffer = VideoCore::Memory()->GetPhysicalPointer(addr);

    y = framebuffer.height - y;

    const u32 coarse_y = y & ~7;
    u32 bytes_per_pixel = FramebufferRegs::BytesPerDepthPixel(framebuffer.depth_format);
    u32 stride = framebuffer.width * bytes_per_pixel;

    u32 dst_offset = VideoCore::GetMortonOffset(x, y, bytes_per_pixel) + coarse_y * stride;
    u8* dst_pixel = depth_buffer + dst_offset;

    switch (framebuffer.depth_format) {
    case FramebufferRegs::DepthFormat::D16:
        Color::EncodeD16(value, dst_pixel);
        break;

    case FramebufferRegs::DepthFormat::D24:
        Color::EncodeD24(value, dst_pixel);
        break;

    case FramebufferRegs::DepthFormat::D24S8:
        Color::EncodeD24X8(value, dst_pixel);
        break;

    default:
        LOG_CRITICAL(HW_GPU, "Unimplemented depth format {}",
                     static_cast<u32>(framebuffer.depth_format.Value()));
        UNIMPLEMENTED();
        break;
    }
}

void SetStencil(int x, int y, u8 value) {
    const auto& framebuffer = g_state.regs.framebuffer.framebuffer;
    const PAddr addr = framebuffer.GetDepthBufferPhysicalAddress();
    u8* depth_buffer = VideoCore::Memory()->GetPhysicalPointer(addr);

    y = framebuffer.height - y;

    const u32 coarse_y = y & ~7;
    u32 bytes_per_pixel = Pica::FramebufferRegs::BytesPerDepthPixel(framebuffer.depth_format);
    u32 stride = framebuffer.width * bytes_per_pixel;

    u32 dst_offset = VideoCore::GetMortonOffset(x, y, bytes_per_pixel) + coarse_y * stride;
    u8* dst_pixel = depth_buffer + dst_offset;

    switch (framebuffer.depth_format) {
    case Pica::FramebufferRegs::DepthFormat::D16:
    case Pica::FramebufferRegs::DepthFormat::D24:
        // Nothing to do
        break;

    case Pica::FramebufferRegs::DepthFormat::D24S8:
        Color::EncodeX24S8(value, dst_pixel);
        break;

    default:
        LOG_CRITICAL(HW_GPU, "Unimplemented depth format {}",
                     static_cast<u32>(framebuffer.depth_format.Value()));
        UNIMPLEMENTED();
        break;
    }
}

u8 PerformStencilAction(FramebufferRegs::StencilAction action, u8 old_stencil, u8 ref) {
    switch (action) {
    case FramebufferRegs::StencilAction::Keep:
        return old_stencil;

    case FramebufferRegs::StencilAction::Zero:
        return 0;

    case FramebufferRegs::StencilAction::Replace:
        return ref;

    case FramebufferRegs::StencilAction::Increment:
        // Saturated increment
        return std::min<u8>(old_stencil, 254) + 1;

    case FramebufferRegs::StencilAction::Decrement:
        // Saturated decrement
        return std::max<u8>(old_stencil, 1) - 1;

    case FramebufferRegs::StencilAction::Invert:
        return ~old_stencil;

    case FramebufferRegs::StencilAction::IncrementWrap:
        return old_stencil + 1;

    case FramebufferRegs::StencilAction::DecrementWrap:
        return old_stencil - 1;

    default:
        LOG_CRITICAL(HW_GPU, "Unknown stencil action {:x}", (int)action);
        UNIMPLEMENTED();
        return 0;
    }
}

Common::Vec4<u8> EvaluateBlendEquation(const Common::Vec4<u8>& src,
                                       const Common::Vec4<u8>& srcfactor,
                                       const Common::Vec4<u8>& dest,
                                       const Common::Vec4<u8>& destfactor,
                                       FramebufferRegs::BlendEquation equation) {
    Common::Vec4<int> result;

    auto src_result = (src * srcfactor).Cast<int>();
    auto dst_result = (dest * destfactor).Cast<int>();

    switch (equation) {
    case FramebufferRegs::BlendEquation::Add:
        result = (src_result + dst_result) / 255;
        break;

    case FramebufferRegs::BlendEquation::Subtract:
        result = (src_result - dst_result) / 255;
        break;

    case FramebufferRegs::BlendEquation::ReverseSubtract:
        result = (dst_result - src_result) / 255;
        break;

    // TODO: How do these two actually work?  OpenGL doesn't include the blend factors in the
    //       min/max computations, but is this what the 3DS actually does?
    case FramebufferRegs::BlendEquation::Min:
        result.r() = std::min(src.r(), dest.r());
        result.g() = std::min(src.g(), dest.g());
        result.b() = std::min(src.b(), dest.b());
        result.a() = std::min(src.a(), dest.a());
        break;

    case FramebufferRegs::BlendEquation::Max:
        result.r() = std::max(src.r(), dest.r());
        result.g() = std::max(src.g(), dest.g());
        result.b() = std::max(src.b(), dest.b());
        result.a() = std::max(src.a(), dest.a());
        break;

    default:
        LOG_CRITICAL(HW_GPU, "Unknown RGB blend equation 0x{:x}", static_cast<u8>(equation));
        UNIMPLEMENTED();
    }

    return Common::Vec4<u8>(std::clamp(result.r(), 0, 255), std::clamp(result.g(), 0, 255),
                            std::clamp(result.b(), 0, 255), std::clamp(result.a(), 0, 255));
};

u8 LogicOp(u8 src, u8 dest, FramebufferRegs::LogicOp op) {
    switch (op) {
    case FramebufferRegs::LogicOp::Clear:
        return 0;

    case FramebufferRegs::LogicOp::And:
        return src & dest;

    case FramebufferRegs::LogicOp::AndReverse:
        return src & ~dest;

    case FramebufferRegs::LogicOp::Copy:
        return src;

    case FramebufferRegs::LogicOp::Set:
        return 255;

    case FramebufferRegs::LogicOp::CopyInverted:
        return ~src;

    case FramebufferRegs::LogicOp::NoOp:
        return dest;

    case FramebufferRegs::LogicOp::Invert:
        return ~dest;

    case FramebufferRegs::LogicOp::Nand:
        return ~(src & dest);

    case FramebufferRegs::LogicOp::Or:
        return src | dest;

    case FramebufferRegs::LogicOp::Nor:
        return ~(src | dest);

    case FramebufferRegs::LogicOp::Xor:
        return src ^ dest;

    case FramebufferRegs::LogicOp::Equiv:
        return ~(src ^ dest);

    case FramebufferRegs::LogicOp::AndInverted:
        return ~src & dest;

    case FramebufferRegs::LogicOp::OrReverse:
        return src | ~dest;

    case FramebufferRegs::LogicOp::OrInverted:
        return ~src | dest;
    }

    UNREACHABLE();
};

// Decode/Encode for shadow map format. It is similar to D24S8 format, but the depth field is in
// big-endian
static const Common::Vec2<u32> DecodeD24S8Shadow(const u8* bytes) {
    return {static_cast<u32>((bytes[0] << 16) | (bytes[1] << 8) | bytes[2]), bytes[3]};
}

static void EncodeD24X8Shadow(u32 depth, u8* bytes) {
    bytes[2] = depth & 0xFF;
    bytes[1] = (depth >> 8) & 0xFF;
    bytes[0] = (depth >> 16) & 0xFF;
}

static void EncodeX24S8Shadow(u8 stencil, u8* bytes) {
    bytes[3] = stencil;
}

void DrawShadowMapPixel(int x, int y, u32 depth, u8 stencil) {
    const auto& framebuffer = g_state.regs.framebuffer.framebuffer;
    const auto& shadow = g_state.regs.framebuffer.shadow;
    const PAddr addr = framebuffer.GetColorBufferPhysicalAddress();

    y = framebuffer.height - y;

    const u32 coarse_y = y & ~7;
    u32 bytes_per_pixel = 4;
    u32 dst_offset = VideoCore::GetMortonOffset(x, y, bytes_per_pixel) +
                     coarse_y * framebuffer.width * bytes_per_pixel;
    u8* dst_pixel = VideoCore::Memory()->GetPhysicalPointer(addr) + dst_offset;

    auto ref = DecodeD24S8Shadow(dst_pixel);
    u32 ref_z = ref.x;
    u32 ref_s = ref.y;

    if (depth < ref_z) {
        if (stencil == 0) {
            EncodeD24X8Shadow(depth, dst_pixel);
        } else {
            float16 constant = float16::FromRaw(shadow.constant);
            float16 linear = float16::FromRaw(shadow.linear);
            float16 x = float16::FromFloat32(static_cast<float>(depth) / ref_z);
            float16 stencil_new = float16::FromFloat32(stencil) / (constant + linear * x);
            stencil = static_cast<u8>(std::clamp(stencil_new.ToFloat32(), 0.0f, 255.0f));

            if (stencil < ref_s)
                EncodeX24S8Shadow(stencil, dst_pixel);
        }
    }
}

} // namespace Pica::Rasterizer
