// Dear ImGui: standalone example application for Win32 + OpenGL 3
// If you are new to Dear ImGui, read documentation from the docs/ folder + read the top of imgui.cpp.
// Read online: https://github.com/ocornut/imgui/tree/master/docs

#include "imgui.h"
#include "imgui_impl_opengl3.h"
#include "imgui_impl_win32.h"
#ifndef WIN32_LEAN_AND_MEAN
#define WIN32_LEAN_AND_MEAN
#endif
#include <windows.h>
#include <GL/GL.h>
#include <tchar.h>

// Data stored per platform window
struct RendererData
{
    HDC hDC;
};

// Data
static HGLRC        g_hRC;
static RendererData g_MainWindow;
static int          g_Width;
static int          g_Height;

// Forward declarations of helper functions
bool CreateDeviceOpenGL2(HWND hWnd, RendererData* data);
void CleanupDeviceOpenGL2(HWND hWnd, RendererData* data);
void ResetDevice();
LRESULT WINAPI WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);

static void Win32_CreateWindow(ImGuiViewport* viewport)
{
    assert(viewport->RendererUserData == NULL);

    RendererData* data = IM_NEW(RendererData);
    CreateDeviceOpenGL2((HWND)viewport->PlatformHandle, data);
    viewport->RendererUserData = data;
}

static void Win32_DestroyWindow(ImGuiViewport* viewport)
{
    if (viewport->RendererUserData != NULL)
    {
        RendererData* data = (RendererData*)viewport->RendererUserData;
        CleanupDeviceOpenGL2((HWND)viewport->PlatformHandle, data);
        IM_DELETE(data);
        viewport->RendererUserData = NULL;
    }
}

static void Win32_RenderWindow(ImGuiViewport* viewport, void*)
{
    // Activate the platform window DC in the OpenGL rendering context
    RendererData* data = (RendererData*)viewport->RendererUserData;
    if (data)
        wglMakeCurrent(data->hDC, g_hRC);
}

static void Win32_SwapBuffers(ImGuiViewport* viewport, void*)
{
    RendererData* data = (RendererData*)viewport->RendererUserData;
    if (data)
        ::SwapBuffers(data->hDC);
}

// Main code
int main(int, char**)
{
    // Create application window
    //ImGui_ImplWin32_EnableDpiAwareness();
    WNDCLASSEXW wc = { sizeof(wc), CS_OWNDC, WndProc, 0L, 0L, GetModuleHandle(NULL), NULL, NULL, NULL, NULL, L"ImGui Example", NULL };
    ::RegisterClassExW(&wc);
    HWND hwnd = ::CreateWindowW(wc.lpszClassName, L"Dear ImGui Win32+OpenGL3 Example", WS_OVERLAPPEDWINDOW, 100, 100, 1280, 800, NULL, NULL, wc.hInstance, NULL);

    // Initialize OpenGL
    if (!CreateDeviceOpenGL2(hwnd, &g_MainWindow))
    {
        CleanupDeviceOpenGL2(hwnd, &g_MainWindow);
        ::DestroyWindow(hwnd);
        ::UnregisterClassW(wc.lpszClassName, wc.hInstance);
        return 1;
    }
    wglMakeCurrent(g_MainWindow.hDC, g_hRC);

    // Show the window
    ::ShowWindow(hwnd, SW_SHOWDEFAULT);
    ::UpdateWindow(hwnd);

    // Setup Dear ImGui context
    IMGUI_CHECKVERSION();
    ImGui::CreateContext();
    ImGuiIO& io = ImGui::GetIO(); (void)io;
    io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
    io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
    io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;         // Enable Docking
    io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable;       // Enable Multi-Viewport / Platform Windows
    //io.ConfigViewportsNoAutoMerge = true;
    //io.ConfigViewportsNoTaskBarIcon = true;

    // Setup Dear ImGui style
    ImGui::StyleColorsDark();
    //ImGui::StyleColorsClassic();

    // When viewports are enabled we tweak WindowRounding/WindowBg so platform windows can look identical to regular ones.
    ImGuiStyle& style = ImGui::GetStyle();
    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
    {
        style.WindowRounding = 0.0f;
        style.Colors[ImGuiCol_WindowBg].w = 1.0f;
    }

    // Setup Platform/Renderer backends
    ImGui_ImplWin32_Init(hwnd);// , true);
    ImGui_ImplOpenGL3_Init();

    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
    {
        ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();
        IM_ASSERT(platform_io.Renderer_CreateWindow == NULL);
        IM_ASSERT(platform_io.Renderer_DestroyWindow == NULL);
        IM_ASSERT(platform_io.Renderer_SwapBuffers == NULL);
        IM_ASSERT(platform_io.Platform_RenderWindow == NULL);
        platform_io.Renderer_CreateWindow = Win32_CreateWindow;
        platform_io.Renderer_DestroyWindow = Win32_DestroyWindow;
        platform_io.Renderer_SwapBuffers = Win32_SwapBuffers;
        platform_io.Platform_RenderWindow = Win32_RenderWindow;
    }

    // Load Fonts
    // - If no fonts are loaded, dear imgui will use the default font. You can also load multiple fonts and use ImGui::PushFont()/PopFont() to select them.
    // - AddFontFromFileTTF() will return the ImFont* so you can store it if you need to select the font among multiple.
    // - If the file cannot be loaded, the function will return NULL. Please handle those errors in your application (e.g. use an assertion, or display an error and quit).
    // - The fonts will be rasterized at a given size (w/ oversampling) and stored into a texture when calling ImFontAtlas::Build()/GetTexDataAsXXXX(), which ImGui_ImplXXXX_NewFrame below will call.
    // - Use '#define IMGUI_ENABLE_FREETYPE' in your imconfig file to use Freetype for higher quality font rendering.
    // - Read 'docs/FONTS.md' for more instructions and details.
    // - Remember that in C/C++ if you want to include a backslash \ in a string literal you need to write a double backslash \\ !
    //io.Fonts->AddFontDefault();
    //io.Fonts->AddFontFromFileTTF("c:\\Windows\\Fonts\\segoeui.ttf", 18.0f);
    //io.Fonts->AddFontFromFileTTF("../../misc/fonts/DroidSans.ttf", 16.0f);
    //io.Fonts->AddFontFromFileTTF("../../misc/fonts/Roboto-Medium.ttf", 16.0f);
    //io.Fonts->AddFontFromFileTTF("../../misc/fonts/Cousine-Regular.ttf", 15.0f);
    //ImFont* font = io.Fonts->AddFontFromFileTTF("c:\\Windows\\Fonts\\ArialUni.ttf", 18.0f, NULL, io.Fonts->GetGlyphRangesJapanese());
    //IM_ASSERT(font != NULL);

    // Our state
    bool show_demo_window = true;
    bool show_another_window = false;
    ImVec4 clear_color = ImVec4(0.45f, 0.55f, 0.60f, 1.00f);

    // Main loop
    bool done = false;
    while (!done)
    {
        // Poll and handle messages (inputs, window resize, etc.)
        // See the WndProc() function below for our to dispatch events to the Win32 backend.
        MSG msg;
        while (::PeekMessage(&msg, NULL, 0U, 0U, PM_REMOVE))
        {
            ::TranslateMessage(&msg);
            ::DispatchMessage(&msg);
            if (msg.message == WM_QUIT)
                done = true;
        }
        if (done)
            break;

        // Start the Dear ImGui frame
        ImGui_ImplOpenGL3_NewFrame();
        ImGui_ImplWin32_NewFrame();
        ImGui::NewFrame();

        // 1. Show the big demo window (Most of the sample code is in ImGui::ShowDemoWindow()! You can browse its code to learn more about Dear ImGui!).
        if (show_demo_window)
            ImGui::ShowDemoWindow(&show_demo_window);

        // 2. Show a simple window that we create ourselves. We use a Begin/End pair to create a named window.
        {
            static float f = 0.0f;
            static int counter = 0;

            ImGui::Begin("Hello, world!");                          // Create a window called "Hello, world!" and append into it.

            ImGui::Text("This is some useful text.");               // Display some text (you can use a format strings too)
            ImGui::Checkbox("Demo Window", &show_demo_window);      // Edit bools storing our window open/close state
            ImGui::Checkbox("Another Window", &show_another_window);

            ImGui::SliderFloat("float", &f, 0.0f, 1.0f);            // Edit 1 float using a slider from 0.0f to 1.0f
            ImGui::ColorEdit3("clear color", (float*)&clear_color); // Edit 3 floats representing a color

            if (ImGui::Button("Button"))                            // Buttons return true when clicked (most widgets return true when edited/activated)
                counter++;
            ImGui::SameLine();
            ImGui::Text("counter = %d", counter);

            ImGui::Text("Application average %.3f ms/frame (%.1f FPS)", 1000.0f / io.Framerate, io.Framerate);
            ImGui::End();
        }

        // 3. Show another simple window.
        if (show_another_window)
        {
            ImGui::Begin("Another Window", &show_another_window);   // Pass a pointer to our bool variable (the window will have a closing button that will clear the bool when clicked)
            ImGui::Text("Hello from another window!");
            if (ImGui::Button("Close Me"))
                show_another_window = false;
            ImGui::End();
        }

        // Rendering
        ImGui::Render();
        glViewport(0, 0, g_Width, g_Height);
        glClearColor(clear_color.x, clear_color.y, clear_color.z, clear_color.w);
        glClear(GL_COLOR_BUFFER_BIT);
        ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());

        // Update and Render additional Platform Windows
        if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
        {
            ImGui::UpdatePlatformWindows();
            ImGui::RenderPlatformWindowsDefault();

            // Restore the OpenGL rendering context to the main window DC, since platform windows might have changed it.
            wglMakeCurrent(g_MainWindow.hDC, g_hRC);
        }

        // Present
        ::SwapBuffers(g_MainWindow.hDC);
    }

    ImGui_ImplOpenGL3_Shutdown();
    ImGui_ImplWin32_Shutdown();
    ImGui::DestroyContext();

    CleanupDeviceOpenGL2(hwnd, &g_MainWindow);
    wglDeleteContext(g_hRC);
    ::DestroyWindow(hwnd);
    ::UnregisterClassW(wc.lpszClassName, wc.hInstance);

    return 0;
}

bool ActivateOpenGL2(HWND hWnd)
{
    HDC hDc = GetDC(hWnd);

    PIXELFORMATDESCRIPTOR pfd = { 0 };

    pfd.nSize = sizeof(pfd);
    pfd.nVersion = 1;
    pfd.dwFlags = PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER;
    pfd.iPixelType = PFD_TYPE_RGBA;
    pfd.cColorBits = 32;

    int pf = ChoosePixelFormat(hDc, &pfd);
    if (pf == 0)
        return false;

    if (::SetPixelFormat(hDc, pf, &pfd) == FALSE)
        return false;

    ::ReleaseDC(hWnd, hDc);
    return true;
}

// Helper functions

bool CreateDeviceOpenGL2(HWND hWnd, RendererData* data)
{
    if (!ActivateOpenGL2(hWnd))
        return false;
    data->hDC = ::GetDC(hWnd);
    if (!g_hRC)
        g_hRC = wglCreateContext(data->hDC);
    return true;
}

void CleanupDeviceOpenGL2(HWND hWnd, RendererData* data)
{
    wglMakeCurrent(NULL, NULL);
    ::ReleaseDC(hWnd, data->hDC);
}

#ifndef WM_DPICHANGED
#define WM_DPICHANGED 0x02E0 // From Windows SDK 8.1+ headers
#endif

// Forward declare message handler from imgui_impl_win32.cpp
extern IMGUI_IMPL_API LRESULT ImGui_ImplWin32_WndProcHandler(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);

// Win32 message handler
// You can read the io.WantCaptureMouse, io.WantCaptureKeyboard flags to tell if dear imgui wants to use your inputs.
// - When io.WantCaptureMouse is true, do not dispatch mouse input data to your main application, or clear/overwrite your copy of the mouse data.
// - When io.WantCaptureKeyboard is true, do not dispatch keyboard input data to your main application, or clear/overwrite your copy of the keyboard data.
// Generally you may always pass all inputs to dear imgui, and hide them from your application based on those two flags.
LRESULT WINAPI WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    if (ImGui_ImplWin32_WndProcHandler(hWnd, msg, wParam, lParam))
        return true;

    switch (msg)
    {
    case WM_SIZE:
        if (wParam != SIZE_MINIMIZED)
        {
            g_Width = LOWORD(lParam);
            g_Height = HIWORD(lParam);
        }
        return 0;
    case WM_SYSCOMMAND:
        if ((wParam & 0xfff0) == SC_KEYMENU) // Disable ALT application menu
            return 0;
        break;
    case WM_DESTROY:
        ::PostQuitMessage(0);
        return 0;
    case WM_DPICHANGED:
        if (ImGui::GetIO().ConfigFlags & ImGuiConfigFlags_DpiEnableScaleViewports)
        {
            //const int dpi = HIWORD(wParam);
            //printf("WM_DPICHANGED to %d (%.0f%%)\n", dpi, (float)dpi / 96.0f * 100.0f);
            const RECT* suggested_rect = (RECT*)lParam;
            ::SetWindowPos(hWnd, NULL, suggested_rect->left, suggested_rect->top, suggested_rect->right - suggested_rect->left, suggested_rect->bottom - suggested_rect->top, SWP_NOZORDER | SWP_NOACTIVATE);
        }
        break;
    }
    return ::DefWindowProc(hWnd, msg, wParam, lParam);
}