IAEngine/Src/IAEngine/imp/cpp/Rendering/Renderer.cpp

// IAEngine: 2D Game Engine by IA
// Copyright (C) 2025 IAS (ias@iasoft.dev)
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.

#include <IAEngine/IAEngine.hpp>
#include <IAEngine/Rendering/Camera.hpp>
#include <IAEngine/Rendering/GPUBuffer.hpp>
#include <IAEngine/Rendering/GPUTexture.hpp>
#include <IAEngine/Rendering/Pipeline/UnlitMesh.hpp>
#include <IAEngine/Rendering/Renderer.hpp>

#include <SDL3/SDL_gpu.h>

#include <backends/imgui_impl_sdl3.h>
#include <backends/imgui_impl_sdlgpu3.h>

namespace ia::iae
{
    struct Mesh
    {
        INT32 IndexCount{};
        RefPtr<GPUBuffer> IndexBuffer;
        RefPtr<GPUBuffer> VertexBuffer;
    };

    struct RenderState
    {
        BOOL FlippedH{false};
        BOOL FlippedV{false};
        BOOL CameraRelative{true};
        BOOL ScissorEnabled{false};
        glm::vec2 TextureOffset{0.0f, 0.0f};
        SDL_Rect Scissor{0, 0, 0, 0};
    };

    Vector<Mesh> g_meshes{};
    RenderState g_renderState{};
} // namespace ia::iae

namespace ia::iae
{
    EXTERN SDL_Window *g_windowHandle;

    INT32 Renderer::s_width{};
    INT32 Renderer::s_height{};
    Vector<Renderer::DebugUIWindow> Renderer::s_debugUIWindows;

    SDL_GPUDevice *g_gpuDevice{};

    // Render State
    SDL_GPUCommandBuffer *g_cmdBuffer{};
    SDL_GPURenderPass *g_renderPass{};
    SDL_GPUTexture *g_swpChainTexture{};
    SDL_GPUTexture *g_depthBufferTexture{};

    // ImGUI State
    ImGuiIO g_imGUIIO{};
    ImDrawData *g_imDrawData{};

    RefPtr<Pipeline_UnlitMesh> g_pipelineUnlitMesh;

    Camera2D g_camera{};

    glm::mat4 matProjection{1.0f};
    glm::mat4 matView{1.0f};
    glm::mat4 matModel{1.0f};

    glm::mat4 matIdentity{1.0f};

    SDL_Rect g_defaultScissor{};

    Handle g_meshHandleQuad{};

    RefPtr<GPUTexture> g_whiteTexture{};

    BOOL Renderer::Initialize()
    {
        SDL_GetWindowSizeInPixels(g_windowHandle, &s_width, &s_height);

        if (!(g_gpuDevice = SDL_CreateGPUDevice(SDL_GPU_SHADERFORMAT_SPIRV, Engine::IsDebugMode, nullptr)))
        {
            IAE_LOG_ERROR("Couldn't create SDL3 GPU Device: ", SDL_GetError());
            return false;
        }

        if (!SDL_ClaimWindowForGPUDevice(g_gpuDevice, g_windowHandle))
        {
            IAE_LOG_ERROR("Couldn't initialize SDL3 GPU for the window: ", SDL_GetError());
            return false;
        }
        SDL_SetGPUSwapchainParameters(g_gpuDevice, g_windowHandle, SDL_GPU_SWAPCHAINCOMPOSITION_SDR,
                                      SDL_GPU_PRESENTMODE_VSYNC);

        const auto mainScale = SDL_GetDisplayContentScale(SDL_GetPrimaryDisplay());

        IMGUI_CHECKVERSION();
        ImGui::CreateContext();
        g_imGUIIO = ImGui::GetIO();
        g_imGUIIO.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;
        g_imGUIIO.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;

        ImGui::StyleColorsClassic();

        ImGuiStyle &style = ImGui::GetStyle();
        style.ScaleAllSizes(mainScale);
        style.FontScaleDpi = mainScale;

        ImGui_ImplSDLGPU3_InitInfo initInfo{.Device = g_gpuDevice,
                                            .ColorTargetFormat =
                                                SDL_GetGPUSwapchainTextureFormat(g_gpuDevice, g_windowHandle),
                                            .PresentMode = SDL_GPU_PRESENTMODE_VSYNC};
        ImGui_ImplSDL3_InitForSDLGPU(g_windowHandle);
        ImGui_ImplSDLGPU3_Init(&initInfo);

        if (!GPUBuffer::InitializeStagingBuffer())
            return false;

        {
            SDL_GPUTextureCreateInfo createInfo{.type = SDL_GPU_TEXTURETYPE_2D,
                                                .format = SDL_GPU_TEXTUREFORMAT_D16_UNORM,
                                                .usage = SDL_GPU_TEXTUREUSAGE_DEPTH_STENCIL_TARGET,
                                                .width = (UINT32) s_width,
                                                .height = (UINT32) s_height,
                                                .layer_count_or_depth = 1,
                                                .num_levels = 1,
                                                .sample_count = SDL_GPU_SAMPLECOUNT_1};
            g_depthBufferTexture = SDL_CreateGPUTexture(g_gpuDevice, &createInfo);
        }

        GPUTexture::Initialize();

        g_pipelineUnlitMesh = Pipeline_UnlitMesh::Create();

        matProjection = glm::orthoLH(0.0f, (FLOAT32) s_width, (FLOAT32) s_height, 0.0f, -1000.0f, 1000.0f);

        g_defaultScissor.x = 0;
        g_defaultScissor.y = 0;
        g_defaultScissor.w = s_width;
        g_defaultScissor.h = s_height;

        {
            constexpr auto l = 100;
            const auto data = new UINT32[l * l];
            for (SIZE_T i = 0; i < l * l; i++)
                data[i] = 0xFFFFFFFF;
            g_whiteTexture = GPUTexture::Create((PCUINT8) data, l, l);
            delete[] data;
        }

        g_meshHandleQuad = CreateMesh(
            {
                {glm::vec3{0, 1, 0}, glm::vec2{0, 1}, glm::vec4{1.0f, 1.0f, 1.0f, 1.0f}},
                {glm::vec3{1, 1, 0}, glm::vec2{1, 1}, glm::vec4{1.0f, 1.0f, 1.0f, 1.0f}},
                {glm::vec3{1, 0, 0}, glm::vec2{1, 0}, glm::vec4{1.0f, 1.0f, 1.0f, 1.0f}},
                {glm::vec3{0, 0, 0}, glm::vec2{0, 0}, glm::vec4{1.0f, 1.0f, 1.0f, 1.0f}},
            },
            {0, 1, 2, 2, 3, 0});

        return true;
    }

    VOID Renderer::Terminate()
    {
        SDL_WaitForGPUIdle(g_gpuDevice);

        for (auto &mesh : g_meshes)
        {
            mesh.VertexBuffer.reset();
            mesh.IndexBuffer.reset();
        }

        g_pipelineUnlitMesh.reset();

        g_whiteTexture.reset();

        GPUTexture::Terminate();

        GPUBuffer::TerminateStagingBuffer();

        SDL_ReleaseGPUTexture(g_gpuDevice, g_depthBufferTexture);

        ImGui_ImplSDL3_Shutdown();
        ImGui_ImplSDLGPU3_Shutdown();
        ImGui::DestroyContext();

        SDL_ReleaseWindowFromGPUDevice(g_gpuDevice, g_windowHandle);
        SDL_DestroyGPUDevice(g_gpuDevice);
    }

    VOID Renderer::AddDebugUIWindow(IN PCCHAR title, IN CONST glm::vec2 &position, IN CONST glm::vec2 &size,
                                    IN std::function<VOID()> contentDrawCallback)
    {
        s_debugUIWindows.pushBack(DebugUIWindow{title, position, size, contentDrawCallback});
    }

    VOID Renderer::BeginFrame()
    {
        ImGui_ImplSDLGPU3_NewFrame();
        ImGui_ImplSDL3_NewFrame();
        ImGui::NewFrame();
        for (const auto &w : s_debugUIWindows)
        {
            ImGui::Begin(w.Title);
            ImGui::SetWindowPos({w.Position.x, w.Position.y});
            ImGui::SetWindowSize({w.Size.x, w.Size.y});
            w.ContentDrawCallback();
            ImGui::End();
        }
        ImGui::Render();

        if (!(g_cmdBuffer = SDL_AcquireGPUCommandBuffer(g_gpuDevice)))
        {
            IAE_LOG_ERROR("Couldn't acquire SDL3 GPU command buffer: ", SDL_GetError());
            return;
        }

        if (!SDL_WaitAndAcquireGPUSwapchainTexture(g_cmdBuffer, g_windowHandle, &g_swpChainTexture, (PUINT32) &s_width,
                                                   (PUINT32) &s_height))
        {
            IAE_LOG_ERROR("Couldn't acquire SDL3 GPU Swapchain texture: ", SDL_GetError());
            return;
        }

        if (!g_swpChainTexture)
            return;

        g_imDrawData = ImGui::GetDrawData();

        ImGui_ImplSDLGPU3_PrepareDrawData(g_imDrawData, g_cmdBuffer);

        SDL_GPUColorTargetInfo colorTargetInfo = {0};
        colorTargetInfo.texture = g_swpChainTexture;
        colorTargetInfo.clear_color = SDL_FColor{0.33f, 0.33f, 0.33f, 1.0f};
        colorTargetInfo.load_op = SDL_GPU_LOADOP_CLEAR;
        colorTargetInfo.store_op = SDL_GPU_STOREOP_STORE;

        SDL_GPUDepthStencilTargetInfo depthStencilTargetInfo = {0};
        depthStencilTargetInfo.texture = g_depthBufferTexture;
        depthStencilTargetInfo.cycle = true;
        depthStencilTargetInfo.clear_depth = 0;
        depthStencilTargetInfo.clear_stencil = 0;
        depthStencilTargetInfo.load_op = SDL_GPU_LOADOP_CLEAR;
        depthStencilTargetInfo.store_op = SDL_GPU_STOREOP_STORE;
        depthStencilTargetInfo.stencil_load_op = SDL_GPU_LOADOP_CLEAR;
        depthStencilTargetInfo.stencil_store_op = SDL_GPU_STOREOP_STORE;

        g_renderPass = SDL_BeginGPURenderPass(g_cmdBuffer, &colorTargetInfo, 1, &depthStencilTargetInfo);

        g_pipelineUnlitMesh->Bind((Handle) g_renderPass);
        SDL_PushGPUVertexUniformData(g_cmdBuffer, 0, &matProjection, sizeof(matProjection));
        matView = g_camera.GetViewMatrix();
        SDL_PushGPUVertexUniformData(g_cmdBuffer, 1, &matView, sizeof(matView));
    }

    VOID Renderer::EndFrame()
    {
        if (!g_swpChainTexture)
            return;

        ImGui_ImplSDLGPU3_RenderDrawData(g_imDrawData, g_cmdBuffer, g_renderPass);
        SDL_EndGPURenderPass(g_renderPass);
        SDL_SubmitGPUCommandBuffer(g_cmdBuffer);
    }

    VOID Renderer::SetState_FlippedH(IN BOOL value)
    {
        g_renderState.FlippedH = value;
    }

    VOID Renderer::SetState_FlippedV(IN BOOL value)
    {
        g_renderState.FlippedV = value;
    }

    VOID Renderer::SetState_CameraRelative(IN BOOL value)
    {
        g_renderState.CameraRelative = value;
    }

    VOID Renderer::SetState_ScissorEnabled(IN BOOL value)
    {
        g_renderState.ScissorEnabled = value;
    }

    VOID Renderer::SetState_Scissor(IN CONST glm::vec4 &region)
    {
        g_renderState.Scissor.x = region.x;
        g_renderState.Scissor.y = region.y;
        g_renderState.Scissor.w = region.z;
        g_renderState.Scissor.h = region.w;
    }

    VOID Renderer::SetState_TextureOffset(IN FLOAT32 u, IN FLOAT32 v)
    {
        g_renderState.TextureOffset = {u, v};
    }

    Camera2D *Renderer::GetCamera()
    {
        return &g_camera;
    }
} // namespace ia::iae

namespace ia::iae
{
    Handle Renderer::GetMesh_Quad()
    {
        return g_meshHandleQuad;
    }

    Handle Renderer::CreateMesh(IN CONST Vector<MeshVertex> &vertices, IN CONST Vector<INT32> &indices)
    {
        Mesh mesh{};
        mesh.VertexBuffer = GPUBuffer::Create(GPUBuffer::Usage::VERTEX, vertices.data(),
                                              static_cast<UINT32>(vertices.size() * sizeof(vertices[0])));
        mesh.IndexBuffer = GPUBuffer::Create(GPUBuffer::Usage::INDEX, indices.data(),
                                             static_cast<UINT32>(indices.size() * sizeof(indices[0])));
        mesh.IndexCount = static_cast<UINT32>(indices.size());
        g_meshes.pushBack(mesh);
        return static_cast<Handle>(g_meshes.size() - 1);
    }

    VOID Renderer::Draw(IN Handle meshHandle, IN Handle textureHandle, IN CONST glm::vec2 &position,
                        IN CONST glm::vec2 &scale, IN FLOAT32 rotation, IN UINT8 layerIndex, IN INT16 sortIndex,
                        IN CONST glm::vec4 &colorOverlay)
    {
        IA_ASSERT(sortIndex <= 0x1FFF);

#pragma pack(push, 1)

        STATIC struct
        {
            INT32 FlippedH{false};
            INT32 FlippedV{false};
            glm::vec2 TextureOffset{0.0f, 0.0f};
            glm::vec4 ColorOverlay{1.0f, 1.0f, 1.0f, 1.0f};
        } s_fragmentUniform{};

#pragma pack(pop)

        if (g_renderState.CameraRelative)
            SDL_PushGPUVertexUniformData(g_cmdBuffer, 1, &matView, sizeof(matView));
        else
            SDL_PushGPUVertexUniformData(g_cmdBuffer, 1, &matIdentity, sizeof(matIdentity));
        if (Engine::GetActiveScene()->YSortingEnabled())
            sortIndex += static_cast<INT16>(position.y);
        matModel =
            glm::translate(glm::mat4(1.0f), glm::vec3{position.x, position.y,
                                                      static_cast<FLOAT32>((layerIndex << 13) | (sortIndex & 0x1FFF))});
        matModel = glm::rotate(matModel, rotation, glm::vec3(0.0f, 0.0f, 1.0f));
        matModel = glm::scale(matModel, glm::vec3{scale.x, scale.y, 1.0f});
        SDL_PushGPUVertexUniformData(g_cmdBuffer, 2, &matModel, sizeof(matModel));

        s_fragmentUniform.ColorOverlay = colorOverlay;
        s_fragmentUniform.FlippedH = g_renderState.FlippedH;
        s_fragmentUniform.FlippedV = g_renderState.FlippedV;
        s_fragmentUniform.TextureOffset = g_renderState.TextureOffset;
        SDL_GPUTextureSamplerBinding textureBinding{
            .texture = (SDL_GPUTexture *) (textureHandle ? textureHandle : g_whiteTexture->GetHandle()),
            .sampler = (SDL_GPUSampler *) GPUTexture::GetDefaultSampler()};
        SDL_BindGPUFragmentSamplers(g_renderPass, 0, &textureBinding, 1);
        SDL_PushGPUFragmentUniformData(g_cmdBuffer, 0, &s_fragmentUniform, sizeof(s_fragmentUniform));

        if (g_renderState.ScissorEnabled)
            SDL_SetGPUScissor(g_renderPass, &g_renderState.Scissor);
        else
            SDL_SetGPUScissor(g_renderPass, &g_defaultScissor);

        const auto &mesh = g_meshes[meshHandle];
        SDL_GPUBufferBinding bufferBindings[] = {
            {.buffer = (SDL_GPUBuffer *) mesh.VertexBuffer->GetHandle(), .offset = 0},
            {.buffer = (SDL_GPUBuffer *) mesh.IndexBuffer->GetHandle(), .offset = 0}};
        SDL_BindGPUVertexBuffers(g_renderPass, 0, bufferBindings, 1);
        SDL_BindGPUIndexBuffer(g_renderPass, &bufferBindings[1], SDL_GPU_INDEXELEMENTSIZE_32BIT);
        SDL_DrawGPUIndexedPrimitives(g_renderPass, mesh.IndexCount, 1, 0, 0, 0);
    }
} // namespace ia::iae