/* Demo exhibiting the use of a spotlight */

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

//allows user to change number of squares
int num = 4;

//variables for spotlight
GLfloat xVal = 5;
GLfloat yVal = 3;
GLfloat zVal = 5;

GLfloat light[4]={xVal,yVal,zVal,1}; /*spotlight location*/

GLfloat outline = true ;
GLfloat lightCutoff = 35;
GLfloat smooth = true;

GLfloat base;
/* =====================================================================
 1*1 unit square drawn with triangle_strips. In practice, we would
 probably just use twDrawUnitSquare(), but this allows us to draw the
 triangles if we choose.
*/

void drawUnitSquare(int w, int h ) {
    int i,j;
    GLfloat dw = 1.0/w;
    GLfloat dh = 1.0/h;
    glNormal3f(0,1,0);
    for( i=0; i<w; ++i) {
        glBegin( GL_TRIANGLE_STRIP );
        for( j=0; j<=h; ++j ) {
                   glVertex3f(dw*i,0,dh*j);
            glVertex3f(dw*(i+1),0,dh*j);
        }
        glEnd();
    }
    if (outline) {  //draw quads of unit square
        glPushMatrix();
        glTranslatef(0,0.03,0);
        twColorName(TW_BLACK);
        for( i=0; i<w; ++i) { 
            for( j=1; j<=h; ++j ) {
                glBegin( GL_LINE_LOOP );
                glVertex3f(dw*i,0,dh*(j-1));
                glVertex3f(dw*(i+1),0,dh*(j-1));
                glVertex3f(dw*(i+1),0,dh*(j));
                glVertex3f(dw*i,0, dh*(j));
                glEnd();
            }
        }
        glPopMatrix();
    } 
}

//sets up lighting
void lamp() {
    GLfloat ambient [] = {1,1,1,1};
    GLfloat diffuse [] = {1,1,1,1};
    GLfloat specular [] = {0.5,0.5,0.5,1};
    GLfloat direction [] = {0,-1,0}; /*spotlight direction*/
    GLfloat lightExponent = 5;

    twGraySpotlight(GL_LIGHT0, light, 1, 1, 0.5,
                    direction, lightCutoff, lightExponent);

    /* The following 8 lines are equivalent to the call to twGraySpotlight
    glLightfv(GL_LIGHT0, GL_POSITION, light);
    glLightfv(GL_LIGHT0, GL_AMBIENT, ambient);
    glLightfv(GL_LIGHT0, GL_DIFFUSE, diffuse);
    glLightfv(GL_LIGHT0, GL_SPECULAR, specular);
    glLightfv(GL_LIGHT0, GL_SPOT_DIRECTION, direction);
    glLightf(GL_LIGHT0, GL_SPOT_CUTOFF, lightCutoff);
    glLightf(GL_LIGHT0, GL_SPOT_EXPONENT, lightExponent);
    glEnable(GL_LIGHT0); 
    */
  
}

void display(void) {
    twDisplayInit();
    twCamera();

    glDisable(GL_LIGHTING);
    //draw cone at location of light.  Cone will be shown in RGB color, not with lighting.
    glPushMatrix();
    twColorName(TW_RED);
    const GLfloat coneHeight = 2;
    base = coneHeight*tan(lightCutoff*M_PI/180);
    glTranslatef(light[0],light[1],light[2]);
    glRotatef(90,1,0,0);
    twCylinder(0.01,base,coneHeight,20,1);
    glPopMatrix();
    
    glEnable(GL_LIGHTING);
    lamp();                     // turn on the light, and enable lighting
    twAmbient(0.1);
    if(smooth) glShadeModel(GL_SMOOTH);
    else glShadeModel(GL_FLAT);

    glLightModeli(GL_LIGHT_MODEL_LOCAL_VIEWER, GL_TRUE);

    // Draw a surface for the light to illuminate
    glPushMatrix();
    glTranslatef(-2.5,0,-3.0);
    glScalef(15,1,15);
    twColorName(TW_GREEN);
    twDrawUnitSquare(num,num);
    glPopMatrix();
    
    glFlush();
    glutSwapBuffers(); 
}

void modifySquare (unsigned char key, int x, int y) {
  switch(key) {
  case 'h': outline = false; glutPostRedisplay(); break;
  case 'd': outline = true;  glutPostRedisplay(); break;
  case '+': num++; glutPostRedisplay(); break;
  case '-': num--; glutPostRedisplay(); break;
  }
}

void modifyCutoff (unsigned char key, int x, int y) {
  switch(key) {
  case 'w': lightCutoff++; glutPostRedisplay(); break;
  case 'n': lightCutoff--; glutPostRedisplay(); break;
  }
}

void modifyShading (unsigned char key, int x, int y) {
 switch(key) {
 case 's': smooth = true;
           glutPostRedisplay(); break;
 case 'f': smooth = false;
           glutPostRedisplay(); break;
  }
}

void keyInit() {
  twKeyCallback('h', modifySquare, "hides the lines of the unit square");
  twKeyCallback('d', modifySquare, "draws the lines of the unit square");
  twKeyCallback('+', modifySquare, "increases the number of squares");
  twKeyCallback('-', modifySquare, "decreases the number of squares");
  twKeyCallback('w', modifyCutoff, "widens the cutoff angle");
  twKeyCallback('n', modifyCutoff, "narrows the cutoff angle");
  twKeyCallback('s', modifyShading, "smooth shading");
  twKeyCallback('f', modifyShading, "flat shading");
}


int main(int argc, char **argv) {
/* need both double buffering and z buffer */
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
    twInitWindowSize(800,500);
    twBoundingBox(-2,12,-2,10,-10,10);
    glutCreateWindow(argv[0]);
    glutDisplayFunc(display);
    twMainInit();
    keyInit();
    glutMainLoop();
    return 0;
}