#include <cmath>
#include <chrono>
#include <thread>

#include "client/engine/Wrapper.h"

DummyClient DummyClient::dummy;

IClient* Engine::client = &DummyClient::dummy;

// window data
GLFWwindow* Engine::window = nullptr;
int Engine::scale = 1;
int Engine::width = 0;
int Engine::height = 0;
int Engine::resizeTicks = -1;

// projection data
float Engine::fovY = 60;
float Engine::nearClip = 0.1f;
float Engine::farClip = 1000.0f;
Matrix3D Engine::projMatrix;

// rectangle for framebuffer drawing
FramebufferRectangle Engine::rectangle;

int Engine::stage = 0;
// shader stage 1 - world
WorldShader Engine::worldShader;
// shader stage 2 - world ssao
SSAOShader Engine::ssaoShader;
// shader stage 3 - world ssao blur
SSAOBlurShader Engine::ssaoBlurShader;
// shader stage 4 - world post
WorldPostShader Engine::worldPostShader;
// shader stage 5 - 2D overlay
OverlayShader Engine::overlayShader;

bool Engine::init(int width, int height, const char* name)
{
    Engine::width = width;
    Engine::height = height;
    updateScale();
    
    if(!glfwInit())
    {
        cout << "could not initialize GLFW" << endl;
        return false;
    }

    glfwDefaultWindowHints();
    glfwWindowHint(GLFW_VISIBLE, 0);
    glfwWindowHint(GLFW_RESIZABLE, 1);
    
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 0);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
    
    window = glfwCreateWindow(width, height, name, nullptr, nullptr);
    if(!window)
    {
        cout << "could not create window" << endl;
        glfwTerminate();
        return false;
    }

    glfwMakeContextCurrent(window);
    glfwSwapInterval(1);

    glfwShowWindow(window);

    GLenum err = glewInit();
    if(GLEW_OK != err)
    {
        cout << "could not initialize GLEW: " << glewGetErrorString(err) << endl;
        return false;
    }
    cout << "Status: Using GLEW " << glewGetString(GLEW_VERSION) << endl;

    if(!worldShader.init() || !ssaoShader.init() || !ssaoBlurShader.init() || 
            !worldPostShader.init() || !overlayShader.init() || !rectangle.init())
    {
        glfwDestroyWindow(window);
        glfwTerminate();
        return false;
    }
    
    glfwSetKeyCallback(window, onKeyEvent);
    glfwSetMouseButtonCallback(window, onMouseClick);
    glfwSetFramebufferSizeCallback(window, onWindowResize); 
    glfwSetCursorPosCallback(window, onMouseMove);
    return true;
}

void Engine::sleep(uint64_t nanos)
{
    uint64_t end = glfwGetTimerValue() + nanos - 10000;
    // non busy wait until a close range
    while(end > glfwGetTimerValue() + 1000000)
    {
        this_thread::sleep_for(chrono::nanoseconds(1000000));
    }
    while(end > glfwGetTimerValue() + 100000)
    {
        this_thread::sleep_for(chrono::nanoseconds(100000));
    }
    // busy wait for higher accuracy at the end
    while(end > glfwGetTimerValue());
}

void Engine::start(IClient* client)
{
    if(client != nullptr)
    {
        Engine::client = client;
    }
    
    glEnable(GL_CULL_FACE);
    glDepthFunc(GL_LEQUAL);
    
    uint64_t newTime = glfwGetTimerValue();
    uint64_t oldTime = newTime;
    uint64_t lag = 0;
    uint64_t frameLag = 0;
    uint64_t lastFrame = 0;
    
    while(!glfwWindowShouldClose(window))
    {
        oldTime = newTime;
        newTime = glfwGetTimerValue();
        lag += newTime - oldTime;
        frameLag += newTime - oldTime;
        
        if(lag >= NANOS_PER_TICK || frameLag >= NANOS_PER_FRAME)
        {
            int ticksPerFrame = 0;
            while(lag >= NANOS_PER_TICK)
            {
                lag -= NANOS_PER_TICK;

                Engine::client->tick();           
                ticksPerFrame++;  
                
                resizeTicks -= (resizeTicks >= 0);
                if(resizeTicks == 0)
                {
                    glViewport(0, 0, width, height);
                    updateScale();
                    worldShader.resize();
                    ssaoShader.resize();
                    ssaoBlurShader.resize();
                    worldPostShader.resize();
                }

                if(ticksPerFrame >= MAX_TICKS_PER_FRAME)
                {
                    long skip = lag / NANOS_PER_TICK;
                    lag -= skip * NANOS_PER_TICK;
                    if(skip > 0)
                    {
                        cout << "skipped " << skip << " game ticks " << lag << endl;
                    }
                    break;
                }
            }

            if(frameLag >= NANOS_PER_FRAME)
            {
                frameLag -= NANOS_PER_FRAME;
                // make sure no frames are rendered immediately after each other
                // this happens if the game tick takes too long
                if(lastFrame + NANOS_PER_FRAME - 1000000 < glfwGetTimerValue())
                {
                    lastFrame = glfwGetTimerValue();
                    if(resizeTicks == -1)
                    {
                        onRenderTick((float) lag / NANOS_PER_TICK);
                        glfwSwapBuffers(window);
                    }
                }
            }

            glfwPollEvents();
        }
        else
        {
            // wait until next frame
            long waitingTime = min(NANOS_PER_FRAME - frameLag, NANOS_PER_TICK - lag);
            sleep(waitingTime);
        }
    }
    
    glfwDestroyWindow(window);
    glfwTerminate();
}

void Engine::stop()
{
    glfwSetWindowShouldClose(window, 1);
}

void Engine::onKeyEvent(GLFWwindow* w, int key, int scancode, int action, int mods)
{
    client->onKeyEvent(key, scancode, action, mods);
}

void Engine::onMouseMove(GLFWwindow* w, double x, double y)
{
    client->onMouseMove(x, y);
}

void Engine::onMouseClick(GLFWwindow* w, int button, int action, int mods)
{
    client->onMouseClick(button, action, mods);
}

void Engine::onWindowResize(GLFWwindow* w, int width, int height)
{
    Engine::width = width;
    Engine::height = height;
    resizeTicks = 10;
}

void Engine::updateScale()
{
    scale = 1;
    while(width / (scale + 1) >= 400 && height / (scale + 1) >= 300)
    {
        scale++;
    }
}

int Engine::getScale()
{
    return scale;
}

int Engine::getWidth()
{
    return width;
}

int Engine::getHeight()
{
    return height;
}

float Engine::getScaledWidth()
{
    return (float) width / scale;
}

float Engine::getScaledHeight()
{
    return (float) height / scale;
}

float Engine::getFieldOfView()
{
    return fovY;
}

float Engine::getNearClip()
{
    return nearClip;
}

float Engine::getFarClip()
{
    return farClip;
}

void Engine::printError()
{
    GLenum error = glGetError();
    switch(error)
    {
        case GL_NO_ERROR: 
            //cout << "> No error has been recorded." << endl;
            break;
        case GL_INVALID_ENUM: 
            cout << "> An unacceptable value is specified for an enumerated argument." << endl;
            break;
        case GL_INVALID_VALUE: 
            cout << "> A numeric argument is out of range." << endl;
            break;
        case GL_INVALID_OPERATION: 
            cout << "> The specified operation is not allowed in the current state." << endl;
            break;
        case GL_INVALID_FRAMEBUFFER_OPERATION: 
            cout << "> The framebuffer object is not complete." << endl;
            break;
        case GL_OUT_OF_MEMORY: 
            cout << "> There is not enough memory left to execute the command." << endl;
            break;
        case GL_STACK_UNDERFLOW: 
            cout << "> An attempt has been made to perform an operation that would cause an internal stack to underflow." << endl;
            break;
        case GL_STACK_OVERFLOW: 
            cout << "> An attempt has been made to perform an operation that would cause an internal stack to overflow." << endl;
            break;
        default:
            cout << "> Unknown OpenGL error: " << error << endl;
    }
}

void Engine::onRenderTick(float lag)
{
    // update projection matrix
    float tan = tanf((0.5f * fovY) * M_PI / 180.0f);
    float q = 1.0f / tan;
    float aspect = (float) width / height;

    projMatrix.set(0, 0, q / aspect);
    projMatrix.set(1, 1, q);
    projMatrix.set(2, 2, (nearClip + farClip) / (nearClip - farClip));
    projMatrix.set(3, 2, -1.0f);
    projMatrix.set(2, 3, (2.0f * nearClip * farClip) / (nearClip - farClip));
    projMatrix.set(3, 3, 0); 
    
    // -------------------------------------------------------------------------
    // shader stage 1 - world
    // -------------------------------------------------------------------------
    stage = 1;
    worldShader.preRender(projMatrix.getValues());
    // call render tick for further drawing
    client->render3DTick(lag);
    
    // -------------------------------------------------------------------------
    // shader stage 2 - world ssao
    // -------------------------------------------------------------------------
    stage = 2;
    ssaoShader.preRender(projMatrix.getValues());
 
    // bind previously generated texture data buffers
    worldShader.bindPositionTexture(1);
    worldShader.bindNormalTexture(2);
    worldShader.bindColorTexture(3);
    worldShader.bindDepthTexture(4);
    ssaoShader.bindNoiseTexture(5);
    
    rectangle.draw();
    
    // -------------------------------------------------------------------------
    // shader stage 3 - world ssao blur
    // -------------------------------------------------------------------------
    stage = 3;
    ssaoBlurShader.preRender();
    ssaoShader.bindTexture(6);
    rectangle.draw();
    
    // -------------------------------------------------------------------------
    // shader stage 4 - world post
    // -------------------------------------------------------------------------
    stage = 4;
    worldPostShader.preRender();
    ssaoBlurShader.bindTexture(7);
    rectangle.draw();
    
    // -------------------------------------------------------------------------
    // shader stage 5 - 2D overlay
    // -------------------------------------------------------------------------
    stage = 5;
    overlayShader.preRender();
    worldPostShader.bindTexture(0);
    rectangle.draw();
    overlayShader.setViewMatrix();
    
    setMixMode();
    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    glBlendEquation(GL_FUNC_ADD);
    client->render2DTick(lag);
    glDisable(GL_BLEND);
}

void Engine::setViewMatrix(const float* data)
{
    if(stage == 1)
    {
        worldShader.setViewMatrix(data);
    }
}

void Engine::setModelMatrix(const float* data)
{
    if(stage == 1)
    {
        worldShader.setModelMatrix(data);
    }
    else if(stage == 5)
    {
        overlayShader.setModelMatrix(data);
    }
}

void Engine::setMouseTrapped(bool mode)
{
    if(mode)
    {
        glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED);
    }
    else
    {
        glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_NORMAL);
    }
}

void Engine::setMixMode()
{
    if(stage == 5)
    {
        overlayShader.setUseColor(true);
        overlayShader.setUseTexture(true);
    }
}

void Engine::setColorMode()
{
    if(stage == 5)
    {
        overlayShader.setUseColor(true);
        overlayShader.setUseTexture(false);
    }
}

void Engine::setTextureMode()
{
    if(stage == 5)
    {
        overlayShader.setUseColor(false);
        overlayShader.setUseTexture(true);
    }
}