#include <GL/glew.h>
#include <GL/freeglut.h>
#include <iostream>
#include <sstream>
const unsigned int meshSize = 16;
GLuint posVertexBuffer;
GLuint indexVertexBuffer;

int mouseOldX, mouseOldY;
int mouseButtons = 0;
float rotateX = 20.0f, rotateY = 0.0f;
float translateX = 0.0f, translateY = 0.0f, translateZ = -2.0f;
void Init();
void Display();
void Resize(int w, int h);
void mouse(int button, int state, int x, int y);
void motion(int x, int y);
void CreateVBO(GLuint * vbo, int size)
{
    glGenBuffers(1, vbo);
    glBindBuffer(GL_ARRAY_BUFFER, *vbo);
    glBufferData(GL_ARRAY_BUFFER, size, 0, GL_DYNAMIC_DRAW);
    glBindBuffer(GL_ARRAY_BUFFER, 0);
}


void CreateMeshIndexBuffer(GLuint * id, int w, int h)
{
    int size = ((w * 2) + 2) * (h-1) * sizeof(GLuint);
    glGenBuffers(1, id);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, *id);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, size, 0, GL_STATIC_DRAW);
    GLuint * indices = (GLuint *)glMapBuffer(GL_ELEMENT_ARRAY_BUFFER, GL_WRITE_ONLY);
    if (!indices)
    {
        return;
    }
    //std::stringstream ss;
    for (int y = 0; y < h-1; ++y)
    {
        for (int x = 0; x < w; ++x)
        {
            *indices++ = y * w + x;
            //ss << y * w + x << ",";
            *indices++ = (y+1)*w + x;
            //ss << (y+1)*w + x << ",";
        }
        *indices++ = (y+1)*w+(w-1);
        //ss << (y+1)*w + (w-1) << ",";
        *indices++ = (y+1)*w;
        //ss << (y+1)*w << ",";
    }
    //std::cout << ss.str() << std::endl;
    glUnmapBuffer(GL_ELEMENT_ARRAY_BUFFER);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
}
void CreateMeshPositionVBO(GLuint * id, int w, int h)
{
    CreateVBO(id, w * h * 4 * sizeof(float));
    glBindBuffer(GL_ARRAY_BUFFER, *id);
    float * pos = (float *)glMapBuffer(GL_ARRAY_BUFFER, GL_WRITE_ONLY);
    if (!pos)
    {
        return;
    }
    for (int y = 0; y < h; ++y)
    {
        for (int x = 0; x < w; ++x)
        {
            float u = x / (float)(w-1);
            float v = y / (float)(h-1);
            *pos++ = u*2.0f-1.0f;
            *pos++ = 0.0f;
            *pos++ = v*2.0f-1.0f;
            *pos++ = 1.0f;
        }
    }
    glUnmapBuffer(GL_ARRAY_BUFFER);
    glBindBuffer(GL_ARRAY_BUFFER, 0);
}
int main(int argc, char ** argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA);
    glutInitWindowSize(1024, 800);
    glutCreateWindow("CUDA VBO");
    GLenum res = glewInit();
    if (res != GLEW_OK)
    {
        std::cout << glewGetErrorString(res) << std::endl;
    }
    Init();
    glutDisplayFunc(Display);
    glutReshapeFunc(Resize);
    glutMouseFunc(mouse);
    glutMotionFunc(motion);
    glutMainLoop();

    return EXIT_SUCCESS;
}


void Init()
{
    glClearColor(0.0, 0.0, 0.0, 1.0);    
    CreateMeshPositionVBO(&posVertexBuffer, meshSize, meshSize);
    CreateMeshIndexBuffer(&indexVertexBuffer, meshSize, meshSize);
}

void Display()
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    glTranslatef(translateX, translateY, translateZ);
    glRotatef(rotateX, 1.0, 0.0, 0.0);
    glRotatef(rotateY, 0.0, 1.0, 0.0);
    glBindBuffer(GL_ARRAY_BUFFER, posVertexBuffer);
    glVertexPointer(4, GL_FLOAT, 0, 0);
    glEnableClientState(GL_VERTEX_ARRAY);

    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, indexVertexBuffer);
    glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
    glDrawElements(GL_TRIANGLE_STRIP, ((meshSize * 2) + 2) * (meshSize - 1), GL_UNSIGNED_INT, 0);
    glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
    glDisableClientState(GL_VERTEX_ARRAY);
    glutSwapBuffers();
}

void mouse(int button, int state, int x, int y)
{
    if (state == GLUT_DOWN)
    {
        mouseButtons |= 1 << button;
    }
    else if (state == GLUT_UP)
    {
        mouseButtons = 0;
    }
    mouseOldX = x;
    mouseOldY = y;
    glutPostRedisplay();
}
void motion(int x, int y)
{
    float dx, dy;
    dx = (float)(x - mouseOldX);
    dy = (float)(y - mouseOldY);

    if (mouseButtons == 1)
    {
        rotateX += dy * 0.2f;
        rotateY += dx * 0.2f;
    }
    else if (mouseButtons == 2)
    {
        translateX += dx * 0.01f;
        translateY -= dy * 0.01f;
    }
    else if (mouseButtons == 4)
    {
        translateZ += dy * 0.01f;
    }
    mouseOldX = x;
    mouseOldY = y;
    glutPostRedisplay();
}
void Resize(int w, int h)
{
    if (0 == h)
        h = 1;
    glViewport(0, 0, w, h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(60.0, w/h, 0.1, 10.0);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
}