/********************************************************************************
* ReactPhysics3D physics library, http://www.reactphysics3d.com                 *
* Copyright (c) 2010-2015 Daniel Chappuis                                       *
*********************************************************************************
*                                                                               *
* This software is provided 'as-is', without any express or implied warranty.   *
* In no event will the authors be held liable for any damages arising from the  *
* use of this software.                                                         *
*                                                                               *
* Permission is granted to anyone to use this software for any purpose,         *
* including commercial applications, and to alter it and redistribute it        *
* freely, subject to the following restrictions:                                *
*                                                                               *
* 1. The origin of this software must not be misrepresented; you must not claim *
*    that you wrote the original software. If you use this software in a        *
*    product, an acknowledgment in the product documentation would be           *
*    appreciated but is not required.                                           *
*                                                                               *
* 2. Altered source versions must be plainly marked as such, and must not be    *
*    misrepresented as being the original software.                             *
*                                                                               *
* 3. This notice may not be removed or altered from any source distribution.    *
*                                                                               *
********************************************************************************/

// Libraries
#include "Gui.h"
#include <GLFW/glfw3.h>
#include "TestbedApplication.h"

GLFWwindow* Gui::mWindow = NULL;
double Gui::g_Time = 0.0f;
bool Gui::g_MousePressed[3] = {false, false, false};
float Gui::g_MouseWheel = 0.0f;
GLuint Gui::g_FontTexture = 0;
size_t Gui::g_VboSize = 0;
int Gui::g_AttribLocationTex = 0, Gui::g_AttribLocationProjMtx = 0;
int Gui::g_AttribLocationPosition = 0, Gui::g_AttribLocationUV = 0, Gui::g_AttribLocationColor = 0;
Shader Gui::mShader;
openglframework::VertexBufferObject Gui::mVBO(GL_ARRAY_BUFFER);
openglframework::VertexArrayObject Gui::mVAO;
Gui::LeftPane Gui::mLeftPane = SCENES;

// Constructor
Gui::Gui() {

    g_Time = 0.0f;
    g_MousePressed[0] = false;
    g_MousePressed[1] = false;
    g_MousePressed[2] = false;
    g_MouseWheel = 0.0f;
    g_FontTexture = 0;
    g_VboSize = 0;
}

// Destructor
Gui::~Gui() {

    mVAO.destroy();
    mVBO.destroy();

    mShader.destroy();

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

// Create and return the singleton instance of this class
Gui& Gui::getInstance() {
    static Gui instance;
    return instance;
}

/// Initialize the GUI
void Gui::init() {

    ImGuiIO& io = ImGui::GetIO();
    io.KeyMap[ImGuiKey_Tab] = GLFW_KEY_TAB;
    io.KeyMap[ImGuiKey_LeftArrow] = GLFW_KEY_LEFT;
    io.KeyMap[ImGuiKey_RightArrow] = GLFW_KEY_RIGHT;
    io.KeyMap[ImGuiKey_UpArrow] = GLFW_KEY_UP;
    io.KeyMap[ImGuiKey_DownArrow] = GLFW_KEY_DOWN;
    io.KeyMap[ImGuiKey_Home] = GLFW_KEY_HOME;
    io.KeyMap[ImGuiKey_End] = GLFW_KEY_END;
    io.KeyMap[ImGuiKey_Delete] = GLFW_KEY_DELETE;
    io.KeyMap[ImGuiKey_Backspace] = GLFW_KEY_BACKSPACE;
    io.KeyMap[ImGuiKey_Enter] = GLFW_KEY_ENTER;
    io.KeyMap[ImGuiKey_Escape] = GLFW_KEY_ESCAPE;
    io.KeyMap[ImGuiKey_A] = GLFW_KEY_A;
    io.KeyMap[ImGuiKey_C] = GLFW_KEY_C;
    io.KeyMap[ImGuiKey_V] = GLFW_KEY_V;
    io.KeyMap[ImGuiKey_X] = GLFW_KEY_X;
    io.KeyMap[ImGuiKey_Y] = GLFW_KEY_Y;
    io.KeyMap[ImGuiKey_Z] = GLFW_KEY_Z;

    io.RenderDrawListsFn = renderDrawLists;
    io.SetClipboardTextFn = setClipboardText;
    io.GetClipboardTextFn = getClipboardText;

    io.FontGlobalScale = GUI_SCALING;
}

void Gui::displayHeader() {

    ImVec2 buttonSize(120, 40);

    int display_w, display_h;
    glfwGetFramebufferSize(mWindow, &display_w, &display_h);

    ImGuiWindowFlags window_flags = 0;
    window_flags |= ImGuiWindowFlags_NoTitleBar;
    window_flags |= ImGuiWindowFlags_NoResize;
    window_flags |= ImGuiWindowFlags_NoMove;

    ImGui::PushID("Header");
    ImGui::PushStyleColor(ImGuiCol_WindowBg, BACKGROUND_COLOR);

        ImGui::Begin("Header", NULL, ImVec2(display_w, HEADER_HEIGHT), 1.0f, window_flags);
        ImGui::SetWindowPos(ImVec2(0, 0));
        ImGui::Button("Play", buttonSize); ImGui::SameLine();
        ImGui::Button("Pause", buttonSize); ImGui::SameLine();
        ImGui::Button("Step", buttonSize); ImGui::SameLine();
        ImGui::Button("Restart", buttonSize); ImGui::SameLine();
        ImGui::End();

    ImGui::PopStyleColor(1);
    ImGui::PopID();
}

void Gui::displayLeftPane() {

    const int nbButtonsHeader = 4;
    ImVec2 buttonSize(LEFT_PANE_WIDTH / nbButtonsHeader - 9, LEFT_PANE_HEADER_HEIGHT);

    int display_w, display_h;
    glfwGetFramebufferSize(mWindow, &display_w, &display_h);

    ImGuiWindowFlags window_flags = 0;
    window_flags |= ImGuiWindowFlags_NoTitleBar;
    window_flags |= ImGuiWindowFlags_NoResize;
    window_flags |= ImGuiWindowFlags_NoMove;

    ImGui::PushID("LeftPane");
    ImGui::PushStyleColor(ImGuiCol_WindowBg, BACKGROUND_COLOR);

        ImGui::Begin("LeftPane", NULL, ImVec2(LEFT_PANE_WIDTH, display_h - HEADER_HEIGHT), 1.0f, window_flags);
        ImGui::SetWindowPos(ImVec2(0, HEADER_HEIGHT));

        // ----- Left Pane Header ----- //
        ImGui::Button("Scenes", buttonSize); ImGui::SameLine();
        ImGui::Button("Physics", buttonSize); ImGui::SameLine();
        ImGui::Button("Rendering", buttonSize); ImGui::SameLine();
        ImGui::Button("Profiling", buttonSize);

        // Display the left pane content
        switch(mLeftPane) {
            case SCENES: displayScenesPane(); break;
            case PHYSICS: displayPhysicsPane(); break;
            case RENDERING: displayRenderingPane(); break;
            case PROFILING: displayProfilingPane(); break;
        }

        ImGui::End();

    ImGui::PopStyleColor(1);
    ImGui::PopID();
}

// Display the list of scenes
void Gui::displayScenesPane() {

    static int choice = 0;
    int startChoice = choice;
    TestbedApplication& app = TestbedApplication::getInstance();
    std::vector<Scene*> scenes = app.getScenes();

    // For each scene
    for (int i=0; i<scenes.size(); i++) {

        // Display a radio button
        ImGui::RadioButton(scenes[i]->getName().c_str(), &choice, i);
    }

    // If the user changed scene
    if (choice != startChoice) {
        app.switchScene(scenes[choice]);
    }
}

void Gui::displayPhysicsPane() {

}

void Gui::displayRenderingPane() {

}

void Gui::displayProfilingPane() {

}

void Gui::createDeviceObjects() {

    mShader.create("shaders/gui.vert", "shaders/gui.frag");

    GLuint shaderID = mShader.getProgramObjectId();
    g_AttribLocationTex = glGetUniformLocation(shaderID, "Texture");
    g_AttribLocationProjMtx = glGetUniformLocation(shaderID, "ProjMtx");
    g_AttribLocationPosition = glGetAttribLocation(shaderID, "Position");
    g_AttribLocationUV = glGetAttribLocation(shaderID, "UV");
    g_AttribLocationColor = glGetAttribLocation(shaderID, "Color");

    mVBO.create();

    mVAO.create();
    mVAO.bind();
    mVBO.bind();
    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
    mVAO.unbind();
    mVBO.unbind();

    createFontTextures();
}

// Display the GUI
void Gui::render() {

    ImGuiIO& io = ImGui::GetIO();
    //glfwPollEvents();
    beginNewFrame();

    bool show_test_window = true;
    bool show_another_window = false;
    ImVec4 clear_color = ImColor(255, 255, 255);

    displayHeader();
    displayLeftPane();

    ImGui::ShowTestWindow();

    // Render the GUI
    ImGui::Render();
}

void Gui::beginNewFrame() {

    if (!g_FontTexture)
        createDeviceObjects();

    ImGuiIO& io = ImGui::GetIO();

    // Setup display size (every frame to accommodate for window resizing)
    int w, h;
    int display_w, display_h;
    glfwGetWindowSize(mWindow, &w, &h);
    glfwGetFramebufferSize(mWindow, &display_w, &display_h);
    io.DisplaySize = ImVec2((float)display_w, (float)display_h);

    // Setup time step
    double current_time =  glfwGetTime();
    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 glfw callbacks polled in glfwPollEvents())
    if (glfwGetWindowAttrib(mWindow, GLFW_FOCUSED))
    {
        double mouse_x, mouse_y;
        glfwGetCursorPos(mWindow, &mouse_x, &mouse_y);
        mouse_x *= (float)display_w / w;                        // Convert mouse coordinates to pixels
        mouse_y *= (float)display_h / h;
        io.MousePos = ImVec2((float)mouse_x, (float)mouse_y);   // Mouse position, in pixels (set to -1,-1 if no mouse / on another screen, etc.)
    }
    else
    {
        io.MousePos = ImVec2(-1,-1);
    }

    for (int i = 0; i < 3; i++)
    {
        io.MouseDown[i] = g_MousePressed[i] || glfwGetMouseButton(mWindow, i) != 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.
        g_MousePressed[i] = false;
    }

    io.MouseWheel = g_MouseWheel;
    g_MouseWheel = 0.0f;

    // Hide/show hardware mouse cursor
    glfwSetInputMode(mWindow, GLFW_CURSOR, io.MouseDrawCursor ? GLFW_CURSOR_HIDDEN : GLFW_CURSOR_NORMAL);

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

void Gui::createFontTextures()
{
    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.

    glGenTextures(1, &g_FontTexture);
    glBindTexture(GL_TEXTURE_2D, g_FontTexture);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, pixels);

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

// 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)
void Gui::renderDrawLists(ImDrawList** const cmd_lists, int cmd_lists_count)
{
    if (cmd_lists_count == 0)
        return;

    // Setup render state: alpha-blending enabled, no face culling, no depth testing, scissor enabled
    GLint last_program, last_texture;
    glGetIntegerv(GL_CURRENT_PROGRAM, &last_program);
    glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
    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);
    glActiveTexture(GL_TEXTURE0);


    // Setup orthographic projection matrix
    const float width = ImGui::GetIO().DisplaySize.x;
    const float height = ImGui::GetIO().DisplaySize.y;
    Matrix4 orthoProj(2.0f / width, 0.0f, 0.0f, 0.0f,
                      0.0f, 2.0/-height, 0.0f, 0.0f,
                      0.0f, 0.0f, -1.0f, 0.0f,
                      -1.0f, 1.0f, 0.0f, 1.0f);
    const float ortho_projection[4][4] =
    {
        { 2.0f/width,	0.0f,			0.0f,		0.0f },
        { 0.0f,			2.0f/-height,	0.0f,		0.0f },
        { 0.0f,			0.0f,			-1.0f,		0.0f },
        { -1.0f,		1.0f,			0.0f,		1.0f },
    };

    mShader.bind();
    //mShader.setIntUniform("Texture", 0);
    //mShader.setMatrix4x4Uniform("ProjMtx", orthoProj);
    ///glUseProgram(g_ShaderHandle);
    glUniform1i(g_AttribLocationTex, 0);
    glUniformMatrix4fv(g_AttribLocationProjMtx, 1, GL_FALSE, &ortho_projection[0][0]);

    // Grow our buffer according to what we need
    size_t total_vtx_count = 0;
    for (int n = 0; n < cmd_lists_count; n++)
        total_vtx_count += cmd_lists[n]->vtx_buffer.size();
    mVBO.bind();
    size_t needed_vtx_size = total_vtx_count * sizeof(ImDrawVert);
    if (g_VboSize < needed_vtx_size)
    {
        g_VboSize = needed_vtx_size + 5000 * sizeof(ImDrawVert);  // Grow buffer
        mVBO.copyDataIntoVBO(g_VboSize, NULL, GL_STREAM_DRAW);
        //glBufferData(GL_ARRAY_BUFFER, g_VboSize, NULL, GL_STREAM_DRAW);
    }

    // Copy and convert all vertices into a single contiguous buffer
    unsigned char* buffer_data = (unsigned char*)glMapBuffer(GL_ARRAY_BUFFER, GL_WRITE_ONLY);
    if (!buffer_data)
        return;
    for (int n = 0; n < cmd_lists_count; n++)
    {
        const ImDrawList* cmd_list = cmd_lists[n];
        memcpy(buffer_data, &cmd_list->vtx_buffer[0], cmd_list->vtx_buffer.size() * sizeof(ImDrawVert));
        buffer_data += cmd_list->vtx_buffer.size() * sizeof(ImDrawVert);
    }
    glUnmapBuffer(GL_ARRAY_BUFFER);
    mVBO.unbind();
    mVAO.bind();

    int cmd_offset = 0;
    for (int n = 0; n < cmd_lists_count; n++)
    {
        const ImDrawList* cmd_list = cmd_lists[n];
        int vtx_offset = cmd_offset;
        const ImDrawCmd* pcmd_end = cmd_list->commands.end();
        for (const ImDrawCmd* pcmd = cmd_list->commands.begin(); pcmd != pcmd_end; pcmd++)
        {
            if (pcmd->user_callback)
            {
                pcmd->user_callback(cmd_list, pcmd);
            }
            else
            {
                glBindTexture(GL_TEXTURE_2D, (GLuint)(intptr_t)pcmd->texture_id);
                glScissor((int)pcmd->clip_rect.x, (int)(height - pcmd->clip_rect.w), (int)(pcmd->clip_rect.z - pcmd->clip_rect.x), (int)(pcmd->clip_rect.w - pcmd->clip_rect.y));
                glDrawArrays(GL_TRIANGLES, vtx_offset, pcmd->vtx_count);
            }
            vtx_offset += pcmd->vtx_count;
        }
        cmd_offset = vtx_offset;
    }

    // Restore modified state
    mVAO.unbind();
    glUseProgram(last_program);
    glDisable(GL_SCISSOR_TEST);
    glBindTexture(GL_TEXTURE_2D, last_texture);
}

const char* Gui::getClipboardText() {
    return glfwGetClipboardString(mWindow);
}

void Gui::setClipboardText(const char* text) {
    glfwSetClipboardString(mWindow, text);
}