#include <stdlib.h>
#include <stdio.h>

// for mac osx
#ifdef __APPLE__
#include <OpenGL/gl.h>
#include <OpenGL/glu.h>
#include <GLUT/glut.h>
#else
// only for windows
#ifdef _WIN32
#include <windows.h>
#endif
// for windows and linux
#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/freeglut.h>
#endif

#include <math.h>

// Global variables to animate the robotic arm
int Angle1 = 45;
int Angle2 = 45;

// Global variables to rotate the arm as a whole
int RobotAngleX = 0;
int RobotAngleY = -20;

float pincer = 0.5;

//*************************************************************************
// Function that draws a reference system
//*************************************************************************
void DrawReferenceSystem()
{
    //**********************************
    // set the line width to 3.0
    //**********************************

    glLineWidth(3);

    //**********************************
    // Draw three lines along the x, y, z axis to represent the reference system
    // Use red for the x-axis, green for the y-axis and blue for the z-axis
    //**********************************

    glBegin(GL_LINES);

    glColor3f(1, 0, 0);
    glVertex3f(0, 0, 0);
    glVertex3f(1, 0, 0);

    glColor3f(0, 1, 0);
    glVertex3f(0, 0, 0);
    glVertex3f(0, 1, 0);

    glColor3f(0, 0, 1);
    glVertex3f(0, 0, 0);
    glVertex3f(0, 0, 1);

    glEnd();

    //**********************************
    // reset the drawing color to white
    //**********************************

    glColor3f(1, 1, 1);

    //**********************************
    // reset the line width to 1.0
    //**********************************

    glLineWidth(1);
}

//*************************************************************************
// Function that draws a single joint of the robotic arm
//*************************************************************************
void DrawJoint()
{
    // first draw the reference system
    DrawReferenceSystem();

    // Draw the joint as a parallelepiped (a cube scaled on the y-axis)
    // the bottom face of the cube must be on the xz plane

    //**********************************
    // draw the parallelepiped
    //**********************************
    glPushMatrix();
    glTranslatef(0, 1, 0);
    glScalef(1, 2, 1);
    glutWireCube(1);
    glPopMatrix();
}

// Function that draws the robot as three parallelepipeds
void DrawRobot()
{
    //**********************************
    // It's better to work on a local reference system...
    //**********************************
    glPushMatrix();

    // draw the first joint
    DrawJoint();

    // Draw the other joints
    // every joint must be placed on top of the previous one
    // and rotated according to the relevant Angle
    //**********************************
    // the second joint
    //**********************************
    glTranslatef(0, 2, 0);
    glRotatef(Angle1, 0, 0, 1);
    DrawJoint();

    //**********************************
    // the third joint
    //**********************************
    glTranslatef(0, 2, 0);
    glRotatef(Angle2, 0, 0, 1);
    DrawJoint();

    //**********************************
    // the pincer's base
    //**********************************
    glTranslatef(0, 2, 0);
    DrawReferenceSystem();

    glPushMatrix();
    glTranslatef(0, 0.125, 0);
    glScalef(1, 0.25, 0.25);
    glutWireCube(1);
    glPopMatrix();

    glTranslatef(0, 0.25, 0);
    DrawReferenceSystem();

    // pincer left
    glPushMatrix();
    glTranslatef(pincer, 0.5, 0);
    glScalef(0.25, 1, 0.25);
    glutWireCube(1);
    glPopMatrix();

    // picer right
    glPushMatrix();
    glTranslatef(-pincer, 0.5, 0);
    glScalef(0.25, 1, 0.25);
    glutWireCube(1);
    glPopMatrix();

    //**********************************
    // "Release" the copy of the current MODELVIEW matrix
    //**********************************
    glPopMatrix();
}

//*************************************************************************
// display callback
//*************************************************************************
void display(void)
{
    // clear the window
    glClear(GL_COLOR_BUFFER_BIT);

    // working with the GL_MODELVIEW Matrix
    glMatrixMode(GL_MODELVIEW);

    //**********************************
    // we work on a copy of the current MODELVIEW matrix, hence we need to...
    //**********************************
    glPushMatrix();

    //**********************************
    // Rotate the robot around the x-axis and y-axis according to the relevant angles
    //**********************************
    glRotatef(RobotAngleX, 1, 0, 0);
    glRotatef(RobotAngleY, 0, 1, 0);

    // draw the robot
    DrawRobot();

    //**********************************
    // not anymore on a local reference system
    //**********************************
    glPopMatrix();

    // flush drawing routines to the window
    glutSwapBuffers();
}

//*************************************************************************
// Special keys callback
//*************************************************************************
void arrows(int key, int x, int y)
{
    //**********************************
    // Manage the update of RobotAngleX and RobotAngleY with the arrow keys
    //**********************************
    switch (key)
    {
    case GLUT_KEY_LEFT:
        RobotAngleY += 5;
        break;
    case GLUT_KEY_RIGHT:
        RobotAngleY -= 5;
        break;
    case GLUT_KEY_UP:
        RobotAngleX += 5;
        break;
    case GLUT_KEY_DOWN:
        RobotAngleX -= 5;
        break;
    default:
        break;
    }
    glutPostRedisplay();
}

//*************************************************************************
// Keyboard callback
//*************************************************************************
void keyboard(unsigned char key, int x, int y)
{
    switch (key)
    {
    case 'q':
    case 27:
        exit(0);
        break;

    //**********************************
    // Manage the update of Angle1 with the key 'a' and 'z'
    //**********************************
    case 'a':
        Angle1 += 5;
        break;
    case 'z':
        Angle1 -= 5;
        break;

    //**********************************
    // Manage the update of Angle2 with the key 'e' and 'r'
    //**********************************
    case 'e':
        Angle2 += 5;
        break;
    case 'r':
        Angle2 -= 5;
        break;

    //**********************************
    // Manage the pincer
    //**********************************
    case 'o':
        pincer += 0.01;
        break;
    case 'l':
        pincer -= 0.01;
        break;

    default:
        break;
    }

    if (pincer >= 0.5)
    {
        pincer = 0.5;
    }
    else if (pincer <= 0.125)
    {
        pincer = 0.125;
    }

    glutPostRedisplay();
}

void init(void)
{
    glClearColor(0.0, 0.0, 0.0, 0.0);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(65.0, 1.0, 1.0, 100.0);

    glShadeModel(GL_FLAT);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    // Place the camera
    gluLookAt(-6, 5, -6, 0, 0, 2, 0, 1, 0);
}

//*************************************************************************
// Function called every time the main window is resized
//*************************************************************************
void reshape(int width, int height)
{

    // define the viewport transformation;
    glViewport(0, 0, width, height);
    if (width < height)
        glViewport(0, (height - width) / 2, width, width);
    else
        glViewport((width - height) / 2, 0, height, height);
}

//*************************************************************************
// Prints out how to use the keyboard
//*************************************************************************
void usage()
{
    printf("\n*******\n");
    printf("Arrows key: rotate the whole robot\n");
    printf("[a][z] : move the second joint of the arm\n");
    printf("[e][r] : move the third joint of the arm\n");
    printf("[esc]  : terminate\n");
    printf("*******\n");
}

//////////////////////////////////////////////////////////////
int main(int argc, char **argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
    glutInitWindowSize(500, 500);
    glutInitWindowPosition(100, 100);
    glutCreateWindow(argv[0]);
    init();
    glutDisplayFunc(display);

    glutReshapeFunc(reshape);

    //**********************************
    // Register the keyboard function
    //**********************************
    glutKeyboardFunc(keyboard);

    //**********************************
    // Register the special key function
    //**********************************
    glutSpecialFunc(arrows);

    // just print the help
    usage();

    glutMainLoop();

    return EXIT_SUCCESS;
}

//////////////////////////////////////////////////////////////