// Copyright (c) David Kabala 
// Fall 2009

#include <GL/glut.h>
#include <GL/gl.h>
#include <stdlib.h> 
#include <math.h>

class SceneManager
{
protected:
    enum DrawExample {SINGLE_POLYGON, MANY_POLYGONS, POLYGON_CIRCLE};
    DrawExample _Example;

public:
    SceneManager(void) : _Example(SINGLE_POLYGON)
    {
    }

    void init(void)
    {
    }

    void reshape(int w, int h)
    {
        glViewport(0,0,w,h);
        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        glOrtho(-w/2.0,w/2.0,-h/2.0,h/2.0,-1.0,1.0);
        glMatrixMode(GL_MODELVIEW);
        glutPostRedisplay();
    }

    void drawSinglePolygon(void) const
    {
        //Clear the Draw Buffer
        glClear(GL_COLOR_BUFFER_BIT);

        //Draw  a single polygon
        glBegin(GL_POLYGON);
            glColor3f(1.0, 1.0, 1.0);  /* white */
            glVertex2i(0, 0);
            glVertex2i(150, 0);
            glVertex2i(150, 150);
            glVertex2i(0, 150);
        glEnd();
        glFlush();  /* Single buffered, so needs a flush. */
    }


    void drawManyPolygons(void) const
    {
        //Clear the Draw Buffer
        glClear(GL_COLOR_BUFFER_BIT);

        //Draw  many polygon
        glBegin(GL_POLYGON);
            glColor3f(1.0, 1.0, 1.0);  /* white */
            glVertex2i(0, 0);
            glVertex2i(150, 0);
            glVertex2i(150, 150);
            glVertex2i(0, 150);
        glEnd();

        glBegin(GL_POLYGON);
            glColor3f(0.0, 1.0, 0.0);  /* green */
            glVertex2i(-100, 100);
            glVertex2i(0, 100);
            glVertex2i(-50, 50);
            glVertex2i(-150, 50);
        glEnd();

        glBegin(GL_POLYGON);
            glColor3f(1.0, 0.0, 0.0);  /* red */
            glVertex2i(50, 75);
            glVertex2i(100, 100);
            glVertex2i(75, 20);
            glVertex2i(0, 0);
        glEnd();
        glFlush();  /* Single buffered, so needs a flush. */
    }

    void drawPolygonCircle(void) const
    {
        //Clear the Draw Buffer
        glClear(GL_COLOR_BUFFER_BIT);

        const GLfloat PI = 3.14159;
        unsigned int steps = 60;
        GLfloat scale1 = 150.0;
        glBegin(GL_POLYGON);
            glColor3f(1.0, 1.0, 1.0);  /* white */
            //Draw a circle
            GLfloat theta;
            for(unsigned int i(0) ; i<steps ; ++i)
            {
                theta = (2.0*PI/steps)*i;
                glVertex2f(scale1*cos(theta), scale1*sin(theta));
            }
        glEnd();
        glFlush();  /* Single buffered, so needs a flush. */
    }

    void display(void) const
    {
        switch(_Example)
        {
        case POLYGON_CIRCLE:
            drawPolygonCircle();
            break;
        case MANY_POLYGONS:
            drawManyPolygons();
            break;
          
        case SINGLE_POLYGON:
        default:
            drawSinglePolygon();
            break;
        }
    }
    
    void keyboard(unsigned char key, int x, int y)
    {
        switch(key)
        {
        case 'q':
            exit(0);
            break;
        case '1':
            _Example = SINGLE_POLYGON;
            break;
        case '2':
            _Example = MANY_POLYGONS;
            break;
        case '3':
            _Example = POLYGON_CIRCLE;
            break;
        }
        glutPostRedisplay();
    }
};

SceneManager mgr;

void reshape(int w, int h)
{
    mgr.reshape(w,h);
}

void display(void)
{
    mgr.display();
}
void keyboard(unsigned char key, int x, int y)
{
    mgr.keyboard(key,x,y);
}

int main(int argc, char **argv)
{
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_RGBA | GLUT_SINGLE);
  glutCreateWindow("Polygons Examples");
  glutDisplayFunc(display);
  glutReshapeFunc(reshape);
  glutReshapeWindow(800,640);
  glutPositionWindow(50,50);
  glutKeyboardFunc(keyboard);
  mgr.init();
  glutMainLoop();
  return 0;             /* ANSI C requires main to return int. */
}