#include "Wrapper.h"
#include <fstream>
#include <cstring>
#include <iostream>

using namespace std;

DummyClient DummyClient::dummy;

IClient* Engine::client = &DummyClient::dummy;
GLFWwindow* Engine::window = nullptr;

GLuint Engine::vShader = 0;
GLuint Engine::fShader = 0;
GLuint Engine::program = 0;

GLuint Engine::postVba = 0;
GLuint Engine::postVbo = 0;
GLuint Engine::postVShader = 0;
GLuint Engine::postFShader = 0;
GLuint Engine::postProgram = 0;

GLuint Engine::frameBuffer = 0;
GLuint Engine::frameTexture = 0;
GLuint Engine::renderBuffer = 0;
int Engine::scale = 1;
int Engine::width = 0;
int Engine::height = 0;

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);
    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;

    vShader = 0;
    fShader = 0;
    program = createProgram("shader/vertex.vs", "shader/fragment.fs", vShader, program);
    
    if(program == 0)
    {
        if(vShader != 0)
        {
            glDeleteShader(vShader);
        }
        if(fShader != 0)
        {
            glDeleteShader(fShader);
        }
        glfwDestroyWindow(window);
        glfwTerminate();
        return false;
    }
    
    postVShader = 0;
    postFShader = 0;
    postProgram = createProgram("shader/postVertex.vs", "shader/postFragment.fs", postVShader, postFShader);
    
    if(postProgram == 0)
    {
        if(postVShader != 0)
        {
            glDeleteShader(postVShader);
        }
        if(postFShader != 0)
        {
            glDeleteShader(postFShader);
        }
        glfwDestroyWindow(window);
        glfwTerminate();
        return false;
    }
    
    glfwSetKeyCallback(window, onKeyEvent);
    glfwSetMouseButtonCallback(window, onMouseClick);
    glfwSetFramebufferSizeCallback(window, onWindowResize); 
    //glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED);
    //glfwSetCursorPosCallback(window, onMouseMove);
    return true;
}

void Engine::start(IClient* client)
{
    if(client != nullptr)
    {
        Engine::client = client;
    }
    
    generateFramebuffer();
    generatePostData();

    glEnable(GL_CULL_FACE);
    glDepthFunc(GL_LEQUAL);
    
    uint64_t newTime = glfwGetTimerValue();
    uint64_t oldTime = newTime;
    uint64_t lag = 0;
    while(!glfwWindowShouldClose(window))
    {
        oldTime = newTime;
        newTime = glfwGetTimerValue();
        lag += newTime - oldTime;

        int ticksPerFrame = 0;
        while(lag >= NANOS_PER_TICK)
        {
            lag -= NANOS_PER_TICK;

            Engine::client->tick();
            ticksPerFrame++;

            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;
            }
        }

        // draw scene in framebuffer
        glUseProgram(program);
        glBindFramebuffer(GL_FRAMEBUFFER, frameBuffer);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        glEnable(GL_DEPTH_TEST);
        Engine::client->renderTick((float) lag / NANOS_PER_TICK);
        
        // draw textured framebuffer
        glUseProgram(postProgram);
        glBindFramebuffer(GL_FRAMEBUFFER, 0);
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        glDisable(GL_DEPTH_TEST);
        glBindTexture(GL_TEXTURE_2D, frameTexture);
        glBindVertexArray(postVba);
        glBindBuffer(GL_ARRAY_BUFFER, postVbo);
        glDrawArrays(GL_TRIANGLES, 0, 6);

        glfwSwapBuffers(window);
        glfwPollEvents();
    }
    
    destroyPostData();
    glDeleteFramebuffers(1, &frameBuffer);
    glDeleteShader(vShader);
    glDeleteShader(fShader);
    glDeleteProgram(program);
    glDeleteShader(postVShader);
    glDeleteShader(postFShader);
    glDeleteProgram(postProgram);
    glfwDestroyWindow(window);
    glfwTerminate();
}

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

GLchar* Engine::readFile(const char* name)
{
    ifstream in;
    in.open(name);
    if(!in.fail())
    {
        int size = 128;
        int index = 0;
        GLchar* content = new GLchar[size];
        
        while(true)
        {
            GLchar c = in.get();
            if(in.eof())
            {
                break;
            }
            if(index >= size - 1)
            {
                GLchar* newContent = new GLchar[size * 2];
                memcpy(newContent, content, size);
                size *= 2;
                delete[] content;
                content = newContent;
            }
            content[index] = c;
            index++;
        }
        
        content[index] = '\0';
        index++;
        
        in.close();
        return content;
    }
    return nullptr;
}

bool Engine::checkShaderErrors(const char* name, GLuint shader)
{
    bool returnValue = false;
    
    cout << "compiling " << name << " shader ..." << endl;
    GLenum error = glGetError();
    if(error)
    {
        cout << "error: " << glGetError() << endl;
        returnValue = true;
    }
    else
    {
        cout << "no error occured ..." << endl;
    }
    
    GLint compiled[1];
    glGetShaderiv(shader, GL_COMPILE_STATUS, compiled);
    if(compiled[0])
    {
        cout << name << " shader successfully compiled" << endl;
    }
    else
    {
        cout << name << "compiling of " << name << " failed:" << endl;
        GLchar buffer[512];
        GLsizei bufferSize = 512;
        GLsizei charsUsed = 0;
        glGetShaderInfoLog(shader, bufferSize, &charsUsed, buffer);
        // glGetProgramInfoLog should be null terminated ...
        buffer[bufferSize - 1] = '\0';
        cout << buffer << endl;
        returnValue = true;
    }
    return returnValue;
}

GLuint Engine::compileProgram(GLuint& vShader, GLuint& fShader, const GLchar* v, const GLchar* f)
{
    vShader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vShader, 1, &v, nullptr);
    glCompileShader(vShader);

    if(checkShaderErrors("vertex", vShader))
    {
        return 0;
    }    
    
    fShader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fShader, 1, &f, nullptr);
    glCompileShader(fShader);

    if(checkShaderErrors("fragment", fShader))
    {
        return 0;
    }    

    GLuint program = glCreateProgram();
    glAttachShader(program, vShader);
    glAttachShader(program, fShader);
    glLinkProgram(program);
    
    cout << "linking shaders to program ..." << endl;

    GLenum error = glGetError();
    if(error)
    {
        cout << "error: " << glGetError() << endl;
        return 0;
    }
    else
    {
        cout << "no error occured ..." << endl;
    }

    GLint compiled[1];
    glGetProgramiv(program, GL_LINK_STATUS, compiled);
    if(compiled[0])
    {
        cout << "shaders successfully linked" << endl;
    }
    else
    {
        cout << "linking of shaders failed:" << endl;
        GLchar buffer[512];
        GLsizei bufferSize = 512;
        GLsizei charsUsed = 0;
        glGetProgramInfoLog(program, bufferSize, &charsUsed, buffer);
        // glGetProgramInfoLog should be null terminated ...
        buffer[bufferSize - 1] = '\0';
        cout << buffer << endl;
        return 0;
    }
    return program;
}

GLuint Engine::createProgram(const char* v, const char* f, GLuint& vShader, GLuint& fShader)
{
    GLchar* vertex = readFile(v);
    if(vertex == nullptr)
    {
        cout << "cannot read " << v << endl;
        return 0;
    }
    GLchar* fragment = readFile(f);
    if(fragment == nullptr)
    {
        cout << "cannot read " << f << endl;
        delete[] vertex;
        return 0;
    }
    
    GLuint program = compileProgram(vShader, fShader, vertex, fragment);
    delete[] vertex;
    delete[] fragment;
    return program;
}

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

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)
{
    glViewport(0, 0, width, height);
    Engine::width = width;
    Engine::height = height;
    updateScale();
}

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;
}

GLint Engine::getUniformLocation(const GLchar* name)
{
    return glGetUniformLocation(program, name);
}

void Engine::setMatrix(GLint location, const GLfloat* m)
{
    glUniformMatrix4fv(location, 1, 0, m);
}

void Engine::setInt(GLint location, GLint i)
{
    glUniform1i(location, i);
}

void Engine::setFloat(GLint location, GLfloat f1, GLfloat f2, GLfloat f3, GLfloat f4)
{
    glUniform4f(location, f1, f2, f3, f4);
}

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::generateFramebuffer()
{
    glGenFramebuffers(1, &frameBuffer);
    glBindFramebuffer(GL_FRAMEBUFFER, frameBuffer); 
    
    glGenTextures(1, &frameTexture);
    glBindTexture(GL_TEXTURE_2D, frameTexture);
    
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glBindTexture(GL_TEXTURE_2D, 0);
    
    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, frameTexture, 0);  
    
    glGenRenderbuffers(1, &renderBuffer);
    glBindRenderbuffer(GL_RENDERBUFFER, renderBuffer); 
    glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT, width, height);  
    glBindRenderbuffer(GL_RENDERBUFFER, 0);
    
    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, renderBuffer);
    
    if(glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
    {
	cout << "ERROR::FRAMEBUFFER:: Framebuffer is not complete!" << endl;
    }
    else
    {
        cout << "WORKS" << endl;
    }
    glBindFramebuffer(GL_FRAMEBUFFER, 0);
}

void Engine::generatePostData()
{
    glGenVertexArrays(1, &postVba);
    glBindVertexArray(postVba);
    
    glGenBuffers(1, &postVbo);
    glBindBuffer(GL_ARRAY_BUFFER, postVbo);

    glVertexAttribPointer(0, 2, GL_FLOAT, 0, sizeof(float) * 4, (GLvoid*) 0);
    glEnableVertexAttribArray(0);

    glVertexAttribPointer(1, 2, GL_FLOAT, 0, sizeof(float) * 4, (GLvoid*) (sizeof(float) * 2));
    glEnableVertexAttribArray(1);
    
    float data[] = 
    {
        -1.0f, 1.0f, 0.0f, 1.0f, 
        -1.0f, -1.0f, 0.0f, 0.0f,
        1.0f, -1.0f, 1.0f, 0.0f,
        -1.0f, 1.0f, 0.0f, 1.0f,
        1.0f, -1.0f, 1.0f, 0.0f,
        1.0f, 1.0f, 1.0f, 1.0f
    };
    
    glBufferData(GL_ARRAY_BUFFER, sizeof(float) * 24, data, GL_STATIC_DRAW);
}

void Engine::destroyPostData()
{
    glDeleteVertexArrays(1, &postVba);
    glDeleteBuffers(1, &postVbo);
}