// ImGui SDL2 binding with OpenGL3
// In this binding, ImTextureID is used to store an OpenGL 'GLuint' texture identifier. Read the FAQ about ImTextureID in imgui.cpp.
// (SDL is a cross-platform general purpose library for handling windows, inputs, OpenGL/Vulkan graphics context creation, etc.)
// (GL3W is a helper library to access OpenGL functions since there is no standard header to access modern OpenGL functions easily. Alternatives are GLEW, Glad, etc.)

// You can copy and use unmodified imgui_impl_* files in your project. See main.cpp for an example of using this.
// If you use this binding you'll need to call 4 functions: ImGui_ImplXXXX_Init(), ImGui_ImplXXXX_NewFrame(), ImGui::Render() and ImGui_ImplXXXX_Shutdown().
// If you are new to ImGui, see examples/README.txt and documentation at the top of imgui.cpp.
// https://github.com/ocornut/imgui

#include "../libs/ImGui/imgui.h"
#include "ImGuiHelper.h"

#include "GLHelper.h"
#include "GLSLProgram.h"
#include "InputHandler.h"
#include "Options.h"
// SDL,GL3W
#include <SDL.h>
#include <SDL_syswm.h>


// This is the main rendering function that you have to implement and provide to ImGui (via setting up 'RenderDrawListsFn' in the ImGuiIO structure)
// Note that this implementation is little overcomplicated because we are saving/setting up/restoring every OpenGL state explicitly, in order to be able to run within any OpenGL engine that doesn't do so. 
// 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)
void ImGuiHelper::RenderDrawLists()
{
    ImGui::Render();
    ImDrawData* draw_data = ImGui::GetDrawData();
    // Avoid rendering when minimized, scale coordinates for retina displays (screen coordinates != framebuffer coordinates)
    ImGuiIO& io = ImGui::GetIO();
    int fb_width = (int)(io.DisplaySize.x * io.DisplayFramebufferScale.x);
    int fb_height = (int)(io.DisplaySize.y * io.DisplayFramebufferScale.y);
    if (fb_width == 0 || fb_height == 0)
        return;
    draw_data->ScaleClipRects(io.DisplayFramebufferScale);

    // Backup GL state
    GLenum last_active_texture; glGetIntegerv(GL_ACTIVE_TEXTURE, (GLint*)&last_active_texture);
    glActiveTexture(GL_TEXTURE0);
    GLint last_program; glGetIntegerv(GL_CURRENT_PROGRAM, &last_program);
    GLint last_texture; glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
    GLint last_sampler; glGetIntegerv(GL_SAMPLER_BINDING, &last_sampler);
    GLint last_array_buffer; glGetIntegerv(GL_ARRAY_BUFFER_BINDING, &last_array_buffer);
    GLint last_element_array_buffer; glGetIntegerv(GL_ELEMENT_ARRAY_BUFFER_BINDING, &last_element_array_buffer);
    GLint last_vertex_array; glGetIntegerv(GL_VERTEX_ARRAY_BINDING, &last_vertex_array);
    GLint last_polygon_mode[2]; glGetIntegerv(GL_POLYGON_MODE, last_polygon_mode);
    GLint last_viewport[4]; glGetIntegerv(GL_VIEWPORT, last_viewport);
    GLint last_scissor_box[4]; glGetIntegerv(GL_SCISSOR_BOX, last_scissor_box);
    GLenum last_blend_src_rgb; glGetIntegerv(GL_BLEND_SRC_RGB, (GLint*)&last_blend_src_rgb);
    GLenum last_blend_dst_rgb; glGetIntegerv(GL_BLEND_DST_RGB, (GLint*)&last_blend_dst_rgb);
    GLenum last_blend_src_alpha; glGetIntegerv(GL_BLEND_SRC_ALPHA, (GLint*)&last_blend_src_alpha);
    GLenum last_blend_dst_alpha; glGetIntegerv(GL_BLEND_DST_ALPHA, (GLint*)&last_blend_dst_alpha);
    GLenum last_blend_equation_rgb; glGetIntegerv(GL_BLEND_EQUATION_RGB, (GLint*)&last_blend_equation_rgb);
    GLenum last_blend_equation_alpha; glGetIntegerv(GL_BLEND_EQUATION_ALPHA, (GLint*)&last_blend_equation_alpha);
    GLboolean last_enable_blend = glIsEnabled(GL_BLEND);
    GLboolean last_enable_cull_face = glIsEnabled(GL_CULL_FACE);
    GLboolean last_enable_depth_test = glIsEnabled(GL_DEPTH_TEST);
    GLboolean last_enable_scissor_test = glIsEnabled(GL_SCISSOR_TEST);

    // Setup render state: alpha-blending enabled, no face culling, no depth testing, scissor enabled, polygon fill
    glEnable(GL_BLEND);
    glBlendEquation(GL_FUNC_ADD);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    glDisable(GL_CULL_FACE);
    glDisable(GL_DEPTH_TEST);
    glEnable(GL_SCISSOR_TEST);
    glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);

    // Setup viewport, orthographic projection matrix
    glViewport(0, 0, (GLsizei)fb_width, (GLsizei)fb_height);
    glm::mat4 ortho_projection =
    {
        { 2.0f/io.DisplaySize.x, 0.0f,                   0.0f, 0.0f },
        { 0.0f,                  2.0f/-io.DisplaySize.y, 0.0f, 0.0f },
        { 0.0f,                  0.0f,                  -1.0f, 0.0f },
        {-1.0f,                  1.0f,                   0.0f, 1.0f },
    };

    glUseProgram(program->getID());
    program->setUniform("Texture", 0);
    program->setUniform("ProjMtx",ortho_projection);
    glBindVertexArray(g_VaoHandle);
    glBindSampler(0, 0); // Rely on combined texture/sampler state.

    for (int n = 0; n < draw_data->CmdListsCount; n++)
    {
        const ImDrawList* cmd_list = draw_data->CmdLists[n];
        const ImDrawIdx* idx_buffer_offset = 0;

        glBindBuffer(GL_ARRAY_BUFFER, g_VboHandle);
        glBufferData(GL_ARRAY_BUFFER, (GLsizeiptr)cmd_list->VtxBuffer.Size * sizeof(ImDrawVert), (const GLvoid*)cmd_list->VtxBuffer.Data, GL_STREAM_DRAW);

        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, g_ElementsHandle);
        glBufferData(GL_ELEMENT_ARRAY_BUFFER, (GLsizeiptr)cmd_list->IdxBuffer.Size * sizeof(ImDrawIdx), (const GLvoid*)cmd_list->IdxBuffer.Data, GL_STREAM_DRAW);

        for (int cmd_i = 0; cmd_i < cmd_list->CmdBuffer.Size; cmd_i++)
        {
            const ImDrawCmd* pcmd = &cmd_list->CmdBuffer[cmd_i];
            if (pcmd->UserCallback)
            {
                pcmd->UserCallback(cmd_list, pcmd);
            }
            else
            {
                glBindTexture(GL_TEXTURE_2D, (GLuint)(intptr_t)pcmd->TextureId);
                glScissor((int)pcmd->ClipRect.x, (int)(fb_height - pcmd->ClipRect.w), (int)(pcmd->ClipRect.z - pcmd->ClipRect.x), (int)(pcmd->ClipRect.w - pcmd->ClipRect.y));
                glDrawElements(GL_TRIANGLES, (GLsizei)pcmd->ElemCount, sizeof(ImDrawIdx) == 2 ? GL_UNSIGNED_SHORT : GL_UNSIGNED_INT, idx_buffer_offset);
            }
            idx_buffer_offset += pcmd->ElemCount;
        }
    }

    // Restore modified GL state
    glUseProgram(last_program);
    glBindTexture(GL_TEXTURE_2D, last_texture);
    glBindSampler(0, last_sampler);
    glActiveTexture(last_active_texture);
    glBindVertexArray(last_vertex_array);
    glBindBuffer(GL_ARRAY_BUFFER, last_array_buffer);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, last_element_array_buffer);
    glBlendEquationSeparate(last_blend_equation_rgb, last_blend_equation_alpha);
    glBlendFuncSeparate(last_blend_src_rgb, last_blend_dst_rgb, last_blend_src_alpha, last_blend_dst_alpha);
    if (last_enable_blend) glEnable(GL_BLEND); else glDisable(GL_BLEND);
    if (last_enable_cull_face) glEnable(GL_CULL_FACE); else glDisable(GL_CULL_FACE);
    if (last_enable_depth_test) glEnable(GL_DEPTH_TEST); else glDisable(GL_DEPTH_TEST);
    if (last_enable_scissor_test) glEnable(GL_SCISSOR_TEST); else glDisable(GL_SCISSOR_TEST);
    glPolygonMode(GL_FRONT_AND_BACK, last_polygon_mode[0]);
    glViewport(last_viewport[0], last_viewport[1], (GLsizei)last_viewport[2], (GLsizei)last_viewport[3]);
    glScissor(last_scissor_box[0], last_scissor_box[1], (GLsizei)last_scissor_box[2], (GLsizei)last_scissor_box[3]);
}

const char* ImGuiHelper::GetClipboardText(void*)
{
    return SDL_GetClipboardText();
}

void ImGuiHelper::SetClipboardText(void*, const char* text)
{
    SDL_SetClipboardText(text);
}

// 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.
// - When io.WantCaptureKeyboard is true, do not dispatch keyboard input data to your main application.
// Generally you may always pass all inputs to dear imgui, and hide them from your application based on those two flags.
/**
 * Returns if we processed the input. False means we didn't so game should work as no ImGui
 * @param inputHandler
 * @return
 */
bool ImGuiHelper::ProcessEvent(const InputHandler& inputHandler) {
    ImGuiIO& io = ImGui::GetIO();
    if(io.WantCaptureKeyboard || io.WantCaptureMouse) {
        if(inputHandler.getInputEvents(InputHandler::MOUSE_WHEEL_UP)) {
            g_MouseWheel = 1;
        }
        if(inputHandler.getInputEvents(InputHandler::MOUSE_WHEEL_DOWN)) {
            g_MouseWheel = -1;
        }

        if(inputHandler.getInputStatus(InputHandler::MOUSE_BUTTON_LEFT)) {
            g_MousePressed[0] = true;
        } else {
            g_MousePressed[0] = false;
        }
        if(inputHandler.getInputStatus(InputHandler::MOUSE_BUTTON_RIGHT)) {
            g_MousePressed[1] = true;
        } else {
            g_MousePressed[1] = false;
        }
        if(inputHandler.getInputStatus(InputHandler::MOUSE_BUTTON_MIDDLE)) {
            g_MousePressed[2] = true;
        } else {
            g_MousePressed[2] = false;
        }

        if(inputHandler.getInputEvents(InputHandler::TEXT_INPUT)) {
            io.AddInputCharactersUTF8(inputHandler.getText());
        }

        if(inputHandler.getInputEvents(InputHandler::KEY_SHIFT)) {
            io.KeyShift = ((SDL_GetModState() & KMOD_SHIFT) != 0);
        }
        if(inputHandler.getInputEvents(InputHandler::KEY_SUPER)) {
            io.KeySuper = ((SDL_GetModState() & KMOD_GUI) != 0);
        }
        if(inputHandler.getInputEvents(InputHandler::KEY_CTRL)) {
            io.KeyCtrl = ((SDL_GetModState() & KMOD_CTRL) != 0);
        }
        if(inputHandler.getInputEvents(InputHandler::KEY_ALT)) {
            io.KeyAlt = ((SDL_GetModState() & KMOD_ALT) != 0);
        }


        if(inputHandler.keyBufferSize > sizeof(io.KeysDown)) {
            memcpy(io.KeysDown, inputHandler.getAllKeyStates(), inputHandler.keyBufferSize);
        } else {
            memcpy(io.KeysDown, inputHandler.getAllKeyStates(), sizeof(io.KeysDown));
        }
        return true;
    } else {
        return false;
    }
}

void ImGuiHelper::CreateFontsTexture()
{
    // Build texture atlas
    ImGuiIO& io = ImGui::GetIO();
    unsigned char* pixels;
    int width, height;
    io.Fonts->GetTexDataAsRGBA32(&pixels, &width, &height);   // Load as RGBA 32-bits for OpenGL3 demo because it is more likely to be compatible with user's existing shader.

    g_FontTexture = glHelper->loadTexture(height, width, GL_RGBA, pixels);

    /* this method used to do these too, but they are not done now:
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
     */

    io.Fonts->TexID = (void *)(intptr_t)g_FontTexture;
}

/**
 * creates Program using shaders
 * sets up a vao with ->
 *   glEnableVertexAttribArray(g_AttribLocationPosition);
 *   glEnableVertexAttribArray(g_AttribLocationUV);
 *   glEnableVertexAttribArray(g_AttribLocationColor);
 *
 *   glVertexAttribPointer magic
 * @return
 */
bool ImGuiHelper::CreateDeviceObjects()
{
    // Backup GL state
    GLint last_texture, last_array_buffer, last_vertex_array;
    glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
    glGetIntegerv(GL_ARRAY_BUFFER_BINDING, &last_array_buffer);
    glGetIntegerv(GL_VERTEX_ARRAY_BINDING, &last_vertex_array);

    program = new GLSLProgram(glHelper, "./Engine/Shaders/ImGui/vertex.glsl",
                              "./Engine/Shaders/ImGui/fragment.glsl", true);

    g_AttribLocationPosition = glGetAttribLocation(program->getID(), "Position");
    g_AttribLocationUV = glGetAttribLocation(program->getID(), "UV");
    g_AttribLocationColor = glGetAttribLocation(program->getID(), "Color");

    glGenBuffers(1, &g_VboHandle);
    glGenBuffers(1, &g_ElementsHandle);

    glGenVertexArrays(1, &g_VaoHandle);
    glBindVertexArray(g_VaoHandle);
    glBindBuffer(GL_ARRAY_BUFFER, g_VboHandle);
    glEnableVertexAttribArray(g_AttribLocationPosition);
    glEnableVertexAttribArray(g_AttribLocationUV);
    glEnableVertexAttribArray(g_AttribLocationColor);

#define OFFSETOF(TYPE, ELEMENT) ((size_t)&(((TYPE *)0)->ELEMENT))
    glVertexAttribPointer(g_AttribLocationPosition, 2, GL_FLOAT, GL_FALSE, sizeof(ImDrawVert), (GLvoid*)OFFSETOF(ImDrawVert, pos));
    glVertexAttribPointer(g_AttribLocationUV, 2, GL_FLOAT, GL_FALSE, sizeof(ImDrawVert), (GLvoid*)OFFSETOF(ImDrawVert, uv));
    glVertexAttribPointer(g_AttribLocationColor, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof(ImDrawVert), (GLvoid*)OFFSETOF(ImDrawVert, col));
#undef OFFSETOF

    CreateFontsTexture();

    // Restore modified GL state
    glBindTexture(GL_TEXTURE_2D, last_texture);
    glBindBuffer(GL_ARRAY_BUFFER, last_array_buffer);
    glBindVertexArray(last_vertex_array);

    return true;
}

/*
 * GLHELPER ->
 * delete vao
 * delete vbo
 * delete element buffer
 * delete shader
 * delete shader
 * delete program
 * delete texture (For font)
 */
void    ImGuiHelper::InvalidateDeviceObjects()
{
    if (g_VaoHandle) glDeleteVertexArrays(1, &g_VaoHandle);
    if (g_VboHandle) glDeleteBuffers(1, &g_VboHandle);
    if (g_ElementsHandle) glDeleteBuffers(1, &g_ElementsHandle);
    g_VaoHandle = g_VboHandle = g_ElementsHandle = 0;

    //if (g_ShaderHandle && g_VertHandle) glDetachShader(g_ShaderHandle, g_VertHandle);
    if (g_VertHandle) glDeleteShader(g_VertHandle);
    g_VertHandle = 0;

    //if (g_ShaderHandle && g_FragHandle) glDetachShader(g_ShaderHandle, g_FragHandle);
    if (g_FragHandle) glDeleteShader(g_FragHandle);
    g_FragHandle = 0;

    //if (g_ShaderHandle) glDeleteProgram(g_ShaderHandle);
    //g_ShaderHandle = 0;
    delete program;
    program = nullptr;

    if (g_FontTexture)
    {
        glDeleteTextures(1, &g_FontTexture);
        ImGui::GetIO().Fonts->TexID = 0;
        g_FontTexture = 0;
    }


}

ImGuiHelper::ImGuiHelper(GLHelper* glHelper, Options* options) : options(options) {
    this->glHelper = glHelper;
    context = ImGui::CreateContext();
    ImGuiIO& io = ImGui::GetIO();
    io.KeyMap[ImGuiKey_Tab] = SDLK_TAB;                     // Keyboard mapping. ImGui will use those indices to peek into the io.KeyDown[] array.
    io.KeyMap[ImGuiKey_LeftArrow] = SDL_SCANCODE_LEFT;
    io.KeyMap[ImGuiKey_RightArrow] = SDL_SCANCODE_RIGHT;
    io.KeyMap[ImGuiKey_UpArrow] = SDL_SCANCODE_UP;
    io.KeyMap[ImGuiKey_DownArrow] = SDL_SCANCODE_DOWN;
    io.KeyMap[ImGuiKey_PageUp] = SDL_SCANCODE_PAGEUP;
    io.KeyMap[ImGuiKey_PageDown] = SDL_SCANCODE_PAGEDOWN;
    io.KeyMap[ImGuiKey_Home] = SDL_SCANCODE_HOME;
    io.KeyMap[ImGuiKey_End] = SDL_SCANCODE_END;
    io.KeyMap[ImGuiKey_Delete] = SDLK_DELETE;
    io.KeyMap[ImGuiKey_Backspace] = SDLK_BACKSPACE;
    io.KeyMap[ImGuiKey_Enter] = SDLK_RETURN;
    io.KeyMap[ImGuiKey_Escape] = SDLK_ESCAPE;
    io.KeyMap[ImGuiKey_A] = SDLK_a;
    io.KeyMap[ImGuiKey_C] = SDLK_c;
    io.KeyMap[ImGuiKey_V] = SDLK_v;
    io.KeyMap[ImGuiKey_X] = SDLK_x;
    io.KeyMap[ImGuiKey_Y] = SDLK_y;
    io.KeyMap[ImGuiKey_Z] = SDLK_z;

    //io.RenderDrawListsFn = RenderDrawLists;   // Alternatively you can set this to NULL and call ImGui::GetDrawData() after ImGui::Render() to get the same ImDrawData pointer.
    io.SetClipboardTextFn = SetClipboardText;
    io.GetClipboardTextFn = GetClipboardText;
    io.ClipboardUserData = NULL;

#ifdef _WIN32
    io.ImeWindowHandle = options->getImeWindowHandle();
#endif

    // Setup style
    ImGui::StyleColorsClassic();
}

ImGuiHelper::~ImGuiHelper()
{
    InvalidateDeviceObjects();
    ImGui::DestroyContext(context);
}

void ImGuiHelper::NewFrame() {
    if (!g_FontTexture) {
        CreateDeviceObjects();
    }

    ImGuiIO& io = ImGui::GetIO();

    // Setup display size (every frame to accommodate for window resizing)
    io.DisplaySize = ImVec2((float)options->getWindowWidth(), (float)options->getWindowHeight());
    io.DisplayFramebufferScale = ImVec2(options->getWindowWidth() > 0 ? ((float)options->getDrawableWidth() / options->getWindowWidth()) : 0,
                                        options->getWindowHeight() > 0 ? ((float)options->getWindowHeight() / options->getWindowHeight()) : 0);

    // Setup time step
    Uint32	time = SDL_GetTicks();
    double current_time = time / 1000.0;
    io.DeltaTime = g_Time > 0.0 ? (float)(current_time - g_Time) : (float)(1.0f / 60.0f);
    g_Time = current_time;

    // Setup inputs
    // (we already got mouse wheel, keyboard keys & characters from SDL_PollEvent())
    int mx, my;
    Uint32 mouseMask = SDL_GetMouseState(&mx, &my);
    if (options->isIsWindowInFocus())
        io.MousePos = ImVec2((float)mx, (float)my);   // Mouse position, in pixels (set to -1,-1 if no mouse / on another screen, etc.)
    else
        io.MousePos = ImVec2(-FLT_MAX, -FLT_MAX);

    io.MouseDown[0] = g_MousePressed[0] || (mouseMask & SDL_BUTTON(SDL_BUTTON_LEFT)) != 0;		// If a mouse press event came, always pass it as "mouse held this frame", so we don't miss click-release events that are shorter than 1 frame.
    io.MouseDown[1] = g_MousePressed[1] || (mouseMask & SDL_BUTTON(SDL_BUTTON_RIGHT)) != 0;
    io.MouseDown[2] = g_MousePressed[2] || (mouseMask & SDL_BUTTON(SDL_BUTTON_MIDDLE)) != 0;
    g_MousePressed[0] = g_MousePressed[1] = g_MousePressed[2] = false;

    io.MouseWheel = g_MouseWheel;
    g_MouseWheel = 0.0f;

    // Hide OS mouse cursor if ImGui is drawing it
    SDL_ShowCursor(io.MouseDrawCursor ? 0 : 1);

    // Start the frame. This call will update the io.WantCaptureMouse, io.WantCaptureKeyboard flag that you can use to dispatch inputs (or not) to your application.
    ImGui::NewFrame();
}
