// Java version of Food Visitors Program.  Designed for AOP assignment

interface visitor
{
    Object visit(fruit x);
    Object visit(vegetable x);
    Object visit(meat x);
    Object visit(nofood x);
}

interface visitee
{
    int calories();
    Object accept(visitor v);
}

//// concrete visitees

// common superclass
class foodbase
{
    public String name;
    public int cals;
    public visitee next;  // implements linked list
    public int calories() { return cals; }
    public foodbase(String n, int c, visitee t)
    { name=n; cals=c; next=t;}
}//foodbase

class fruit extends foodbase implements visitee
{
    public fruit(String n, visitee t)
    { super(n,100,t); }  // all fruits have 100 calories
    public Object accept(visitor v) {return v.visit(this);}
}

class vegetable extends foodbase implements visitee
{
    public String color;  // vegetable has additional attribute
    public vegetable(String n, String c, visitee t)
    { super(n, 0, t);  color = c; }  // chew your food!
    public int calories() { return (int)(Math.random()*500); } 
    public Object accept(visitor v) {return v.visit(this);}
}

class meat extends foodbase implements visitee
{
    public boolean red;  // true if red meat, else white meat
    public meat(String n, boolean m, visitee t)
    { super(n,0,t); red=m;}
    public int calories() { if (red) return 2000; else return 1000; }
    public Object accept(visitor v) {return v.visit(this);}
}

class nofood implements visitee
{
    public int calories() { return 0; }
    public Object accept(visitor v) {return v.visit(this);}
}


////////////////// Visitor classes

class eater implements visitor  // eats and return sum calories ate
{
    private int ax = 0;  // calories accumulator
    public Object visit(fruit x)
    { ax += x.calories(); return x.next.accept(this); }
    public Object visit(meat x)
    { ax += x.calories(); return x.next.accept(this); }
    public Object visit(vegetable x)
    {
	if (x.color.equals("green"))
	    System.out.println("I won't eat green vegetables!");
	else ax += x.calories();
	return x.next.accept(this);
    }
    public Object visit(nofood x)
    {
	return new Integer(ax);  // older style, but some systems prefer
    }
}//eater visitor


// how would you implement a vegetarian eater?

class printer implements visitor // prints list
{
    public Object visit(fruit x)
    { System.out.println("fruit " +x.name); return x.next.accept(this); }
    public Object visit(vegetable x)
    { System.out.println(x.color+" vegetable "+x.name); 
      return x.next.accept(this);
    }
    public Object visit(meat x)
    {   String r = "white meat ";
	if (x.red) r = "red meat ";
	System.out.println(r+x.name);
	return x.next.accept(this);	
    }
    public Object visit(nofood x)
    { return null; }
}// printer


////////////////// main for testing  (recommend move to different file)

public class food
{
    public static void main(String[] argv) throws Exception
    {
      visitee a = new fruit("apple",new nofood());
      visitee b = new fruit("watermellon",a);
      visitee c = new vegetable("cabbage soup","white",b);
      visitee d = new vegetable("spinach","green",c);
      visitee e = new meat("chicken",false,d);
      visitee f = new meat("beef",true,e);  // f is start of list
      visitee thefood = f; // start of list;
    
      thefood.accept(new printer());  // prints list
      Integer ate = (Integer)thefood.accept(new eater());    // bon appetite
      System.out.println("just ate "+ate+" calories, yum!");
    }// main
}