// ImGui Win32 + DirectX9 binding
// https://github.com/ocornut/imgui

#include <imgui.h>
#include "imgui_impl_dx9.h"

// DirectX
#include <d3dx9.h>
#define DIRECTINPUT_VERSION 0x0800
#include <dinput.h>

// Data
static HWND                     g_hWnd = 0;
static INT64                    g_Time = 0;
static INT64                    g_TicksPerSecond = 0;
static LPDIRECT3DDEVICE9        g_pd3dDevice = NULL;
static LPDIRECT3DVERTEXBUFFER9  g_pVB = NULL;

struct CUSTOMVERTEX
{
    D3DXVECTOR3 pos;
    D3DCOLOR    col;
    D3DXVECTOR2 uv;
};
#define D3DFVF_CUSTOMVERTEX (D3DFVF_XYZ|D3DFVF_DIFFUSE|D3DFVF_TEX1)

// This is the main rendering function that you have to implement and provide to ImGui (via setting up 'RenderDrawListsFn' in the ImGuiIO structure)
// If text or lines are blurry when integrating ImGui in your engine:
// - in your Render function, try translating your projection matrix by (0.5f,0.5f) or (0.375f,0.375f)
static void ImGui_ImplDX9_RenderDrawLists(ImDrawList** const cmd_lists, int cmd_lists_count)
{
    size_t total_vtx_count = 0;
    for (int n = 0; n < cmd_lists_count; n++)
        total_vtx_count += cmd_lists[n]->vtx_buffer.size();
    if (total_vtx_count == 0)
        return;

    // Copy and convert all vertices into a single contiguous buffer
    CUSTOMVERTEX* vtx_dst;
    if (g_pVB->Lock(0, (UINT)total_vtx_count, (void**)&vtx_dst, D3DLOCK_DISCARD) < 0)
        return;
    for (int n = 0; n < cmd_lists_count; n++)
    {
        const ImDrawList* cmd_list = cmd_lists[n];
        const ImDrawVert* vtx_src = &cmd_list->vtx_buffer[0];
        for (size_t i = 0; i < cmd_list->vtx_buffer.size(); i++)
        {
            vtx_dst->pos.x = vtx_src->pos.x;
            vtx_dst->pos.y = vtx_src->pos.y;
            vtx_dst->pos.z = 0.0f;
            vtx_dst->col = (vtx_src->col & 0xFF00FF00) | ((vtx_src->col & 0xFF0000)>>16) | ((vtx_src->col & 0xFF) << 16);     // RGBA --> ARGB for DirectX9
            vtx_dst->uv.x = vtx_src->uv.x;
            vtx_dst->uv.y = vtx_src->uv.y;
            vtx_dst++;
            vtx_src++;
        }
    }
    g_pVB->Unlock();

    g_pd3dDevice->SetStreamSource( 0, g_pVB, 0, sizeof( CUSTOMVERTEX ) );
    g_pd3dDevice->SetFVF( D3DFVF_CUSTOMVERTEX );

    // Setup render state: alpha-blending, no face culling, no depth testing
    g_pd3dDevice->SetRenderState( D3DRS_CULLMODE, D3DCULL_NONE );
    g_pd3dDevice->SetRenderState( D3DRS_LIGHTING, false );
    g_pd3dDevice->SetRenderState( D3DRS_ZENABLE, false );
    g_pd3dDevice->SetRenderState( D3DRS_ALPHABLENDENABLE, true );
    g_pd3dDevice->SetRenderState( D3DRS_BLENDOP, D3DBLENDOP_ADD );
    g_pd3dDevice->SetRenderState( D3DRS_ALPHATESTENABLE, false );
    g_pd3dDevice->SetRenderState( D3DRS_SRCBLEND, D3DBLEND_SRCALPHA );
    g_pd3dDevice->SetRenderState( D3DRS_DESTBLEND, D3DBLEND_INVSRCALPHA );
    g_pd3dDevice->SetRenderState( D3DRS_SCISSORTESTENABLE, true );
    g_pd3dDevice->SetTextureStageState( 0, D3DTSS_COLOROP, D3DTOP_SELECTARG1 );
    g_pd3dDevice->SetTextureStageState( 0, D3DTSS_COLORARG1, D3DTA_DIFFUSE );
    g_pd3dDevice->SetTextureStageState( 0, D3DTSS_ALPHAOP, D3DTOP_MODULATE );
    g_pd3dDevice->SetTextureStageState( 0, D3DTSS_ALPHAARG1, D3DTA_TEXTURE );
    g_pd3dDevice->SetTextureStageState( 0, D3DTSS_ALPHAARG2, D3DTA_DIFFUSE );
    g_pd3dDevice->SetSamplerState( 0, D3DSAMP_MINFILTER, D3DTEXF_LINEAR );
    g_pd3dDevice->SetSamplerState( 0, D3DSAMP_MAGFILTER, D3DTEXF_LINEAR );

    // Setup orthographic projection matrix
    D3DXMATRIXA16 mat;
    D3DXMatrixIdentity(&mat);
    g_pd3dDevice->SetTransform(D3DTS_WORLD, &mat);
    g_pd3dDevice->SetTransform(D3DTS_VIEW, &mat);
    D3DXMatrixOrthoOffCenterLH(&mat, 0.5f, ImGui::GetIO().DisplaySize.x+0.5f, ImGui::GetIO().DisplaySize.y+0.5f, 0.5f, -1.0f, +1.0f);
    g_pd3dDevice->SetTransform(D3DTS_PROJECTION, &mat);

    // Render command lists
    int vtx_offset = 0;
    for (int n = 0; n < cmd_lists_count; n++)
    {
        const ImDrawList* cmd_list = cmd_lists[n];
        for (size_t cmd_i = 0; cmd_i < cmd_list->commands.size(); cmd_i++)
        {
            const ImDrawCmd* pcmd = &cmd_list->commands[cmd_i];
            if (pcmd->user_callback)
            {
                pcmd->user_callback(cmd_list, pcmd);
            }
            else
            {
                const RECT r = { (LONG)pcmd->clip_rect.x, (LONG)pcmd->clip_rect.y, (LONG)pcmd->clip_rect.z, (LONG)pcmd->clip_rect.w };
                g_pd3dDevice->SetTexture( 0, (LPDIRECT3DTEXTURE9)pcmd->texture_id );
                g_pd3dDevice->SetScissorRect(&r);
                g_pd3dDevice->DrawPrimitive(D3DPT_TRIANGLELIST, vtx_offset, pcmd->vtx_count/3);
            }
            vtx_offset += pcmd->vtx_count;
        }
    }
}

LRESULT ImGui_ImplDX9_WndProcHandler(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    ImGuiIO& io = ImGui::GetIO();
    switch (msg)
    {
    case WM_LBUTTONDOWN:
        io.MouseDown[0] = true;
        return true;
    case WM_LBUTTONUP:
        io.MouseDown[0] = false; 
        return true;
    case WM_RBUTTONDOWN:
        io.MouseDown[1] = true; 
        return true;
    case WM_RBUTTONUP:
        io.MouseDown[1] = false; 
        return true;
    case WM_MOUSEWHEEL:
        io.MouseWheel += GET_WHEEL_DELTA_WPARAM(wParam) > 0 ? +1.0f : -1.0f;
        return true;
    case WM_MOUSEMOVE:
        io.MousePos.x = (signed short)(lParam);
        io.MousePos.y = (signed short)(lParam >> 16); 
        return true;
    case WM_KEYDOWN:
        if (wParam >= 0 && wParam < 256)
            io.KeysDown[wParam] = 1;
        return true;
    case WM_KEYUP:
        if (wParam >= 0 && wParam < 256)
            io.KeysDown[wParam] = 0;
        return true;
    case WM_CHAR:
        // You can also use ToAscii()+GetKeyboardState() to retrieve characters.
        if (wParam > 0 && wParam < 0x10000)
            io.AddInputCharacter((unsigned short)wParam);
        return true;
    }
    return 0;
}

bool    ImGui_ImplDX9_Init(void* hwnd, IDirect3DDevice9* device)
{
    g_hWnd = (HWND)hwnd;
    g_pd3dDevice = device;

    if (!QueryPerformanceFrequency((LARGE_INTEGER *)&g_TicksPerSecond)) 
        return false;
    if (!QueryPerformanceCounter((LARGE_INTEGER *)&g_Time))
        return false;

    ImGuiIO& io = ImGui::GetIO();
    io.KeyMap[ImGuiKey_Tab] = VK_TAB;                              // Keyboard mapping. ImGui will use those indices to peek into the io.KeyDown[] array that we will update during the application lifetime.
    io.KeyMap[ImGuiKey_LeftArrow] = VK_LEFT;
    io.KeyMap[ImGuiKey_RightArrow] = VK_RIGHT;
    io.KeyMap[ImGuiKey_UpArrow] = VK_UP;
    io.KeyMap[ImGuiKey_DownArrow] = VK_UP;
    io.KeyMap[ImGuiKey_Home] = VK_HOME;
    io.KeyMap[ImGuiKey_End] = VK_END;
    io.KeyMap[ImGuiKey_Delete] = VK_DELETE;
    io.KeyMap[ImGuiKey_Backspace] = VK_BACK;
    io.KeyMap[ImGuiKey_Enter] = VK_RETURN;
    io.KeyMap[ImGuiKey_Escape] = VK_ESCAPE;
    io.KeyMap[ImGuiKey_A] = 'A';
    io.KeyMap[ImGuiKey_C] = 'C';
    io.KeyMap[ImGuiKey_V] = 'V';
    io.KeyMap[ImGuiKey_X] = 'X';
    io.KeyMap[ImGuiKey_Y] = 'Y';
    io.KeyMap[ImGuiKey_Z] = 'Z';

    io.RenderDrawListsFn = ImGui_ImplDX9_RenderDrawLists;
    io.ImeWindowHandle = g_hWnd;

    if (g_pd3dDevice->CreateVertexBuffer(10000 * sizeof(CUSTOMVERTEX), D3DUSAGE_DYNAMIC | D3DUSAGE_WRITEONLY, D3DFVF_CUSTOMVERTEX, D3DPOOL_DEFAULT, &g_pVB, NULL) < 0)
        return false;

    return true;
}

void ImGui_ImplDX9_Shutdown()
{
    ImGui_ImplDX9_InvalidateDeviceObjects();
    ImGui::Shutdown();
    g_pd3dDevice = NULL;
    g_hWnd = 0;
}

static void ImGui_ImplDX9_CreateFontsTexture()
{
    ImGuiIO& io = ImGui::GetIO();

    // Build
    unsigned char* pixels;
    int width, height, bytes_per_pixel;
    io.Fonts->GetTexDataAsAlpha8(&pixels, &width, &height, &bytes_per_pixel);

    // Create DX9 texture
    LPDIRECT3DTEXTURE9 pTexture = NULL;
    if (D3DXCreateTexture(g_pd3dDevice, width, height, 1, D3DUSAGE_DYNAMIC, D3DFMT_A8, D3DPOOL_DEFAULT, &pTexture) < 0)
    {
        IM_ASSERT(0);
        return;
    }
    D3DLOCKED_RECT tex_locked_rect;
    if (pTexture->LockRect(0, &tex_locked_rect, NULL, 0) != D3D_OK) 
    {	
        IM_ASSERT(0); 
        return; 
    }
    for (int y = 0; y < height; y++)
        memcpy((unsigned char *)tex_locked_rect.pBits + tex_locked_rect.Pitch * y, pixels + (width * bytes_per_pixel) * y, (width * bytes_per_pixel));
    pTexture->UnlockRect(0);

    // Store our identifier
    io.Fonts->TexID = (void *)pTexture;
}

bool ImGui_ImplDX9_CreateDeviceObjects()
{
    if (!g_pd3dDevice)
        return false;

    if (g_pd3dDevice->CreateVertexBuffer(10000 * sizeof(CUSTOMVERTEX), D3DUSAGE_DYNAMIC | D3DUSAGE_WRITEONLY, D3DFVF_CUSTOMVERTEX, D3DPOOL_DEFAULT, &g_pVB, NULL) < 0)
        return false;

    ImGui_ImplDX9_CreateFontsTexture();
    return true;
}

void ImGui_ImplDX9_InvalidateDeviceObjects()
{
    if (!g_pd3dDevice)
        return;
    if (g_pVB)
    {
        g_pVB->Release();
        g_pVB = NULL;
    }
    if (LPDIRECT3DTEXTURE9 tex = (LPDIRECT3DTEXTURE9)ImGui::GetIO().Fonts->TexID)
    {
        tex->Release();
        ImGui::GetIO().Fonts->TexID = 0;
    }
}

void ImGui_ImplDX9_NewFrame()
{
    if (!g_pVB)
        ImGui_ImplDX9_CreateDeviceObjects();

    ImGuiIO& io = ImGui::GetIO();

    // Setup display size (every frame to accommodate for window resizing)
    RECT rect;
    GetClientRect(g_hWnd, &rect);
    io.DisplaySize = ImVec2((float)(rect.right - rect.left), (float)(rect.bottom - rect.top));

    // Setup time step
    INT64 current_time;
    QueryPerformanceCounter((LARGE_INTEGER *)&current_time); 
    io.DeltaTime = (float)(current_time - g_Time) / g_TicksPerSecond;
    g_Time = current_time;

    // Read keyboard modifiers inputs
    io.KeyCtrl = (GetKeyState(VK_CONTROL) & 0x8000) != 0;
    io.KeyShift = (GetKeyState(VK_SHIFT) & 0x8000) != 0;
    // io.KeysDown : filled by WM_KEYDOWN/WM_KEYUP events
    // io.MousePos : filled by WM_MOUSEMOVE events
    // io.MouseDown : filled by WM_*BUTTON* events
    // io.MouseWheel : filled by WM_MOUSEWHEEL events

    // Start the frame
    ImGui::NewFrame();
}