/*
 * $Id: CartesianProductInfinite.java 3297 2010-08-26 19:09:03Z kredel $
 */

package edu.jas.util;


import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Collections;
import java.util.NoSuchElementException;


/**
 * Cartesian product of infinite components with iterator.
 * Works also for finite iterables.
 * @author Heinz Kredel
 */
public class CartesianProductInfinite<E> implements Iterable<List<E>> {


    /**
     * data structure.
     */
    public final List<Iterable<E>> comps; 


    /**
     * CartesianProduct constructor.
     * @param comps components of the cartesian product.
     */
    public CartesianProductInfinite(List<Iterable<E>> comps) {
        if (comps == null || comps.size() == 0) {
            throw new IllegalArgumentException("null components not allowed");
        }
        this.comps = comps;
    }


    /**
     * Get an iterator over subsets.
     * @return an iterator.
     */
    public Iterator<List<E>> iterator() {
        if ( comps.size() == 1 ) {
            return new CartesianOneProductInfiniteIterator<E>(comps.get(0));
        } 
//         if ( comps.size() == 2 ) { // this part is not realy required
//             return new CartesianTwoProductInfiniteIterator<E>(comps.get(0),comps.get(1));
//         }
        int n = comps.size();
        int k = n / 2 + n % 2; // ceiling
        Iterable<List<E>> c0 = new CartesianProductInfinite<E>( comps.subList(0,k) );
        Iterable<List<E>> c1 = new CartesianProductInfinite<E>( comps.subList(k,n) );
        return new CartesianTwoProductInfiniteIteratorList<E>(c0,c1);
    }

}


/**
 * Cartesian product infinite iterator, one factor.
 * @author Heinz Kredel
 */
class CartesianOneProductInfiniteIterator<E> implements Iterator<List<E>> {


    /**
     * data structure.
     */
    final Iterator<E> compit;


    /**
     * CartesianProduct iterator constructor.
     * @param comps components of the cartesian product.
     */
    public CartesianOneProductInfiniteIterator(Iterable<E> comps) {
        if (comps == null) {
            throw new IllegalArgumentException("null comps not allowed");
        }
        compit = comps.iterator();
    }


    /**
     * Test for availability of a next tuple.
     * @return true if the iteration has more tuples, else false.
     */
    public synchronized boolean hasNext() {
        return compit.hasNext();
    }


    /**
     * Get next tuple.
     * @return next tuple.
     */
    public synchronized List<E> next() {
        List<E> res = new ArrayList<E>(1);
        res.add( compit.next() );
        return res;
    }


    /**
     * Remove a tuple if allowed.
     */
    public void remove() {
        throw new UnsupportedOperationException("cannnot remove tuples");
    }

}


/**
 * Cartesian product infinite iterator, two factors.
 * @author Heinz Kredel
 */
class CartesianTwoProductInfiniteIterator<E> implements Iterator<List<E>> {


    /**
     * data structure.
     */
    final Iterator<E> compit0;
    final Iterator<E> compit1;


    final List<E> fincomps0;
    final List<E> fincomps1;


    Iterator<E> fincompit0;
    Iterator<E> fincompit1;


    List<E> current;


    boolean empty;


    long level;


    /**
     * CartesianProduct iterator constructor.
     * @param comps components of the cartesian product.
     */
    public CartesianTwoProductInfiniteIterator(Iterable<E> comps0, Iterable<E> comps1) {
        if (comps0 == null || comps1 == null) {
            throw new IllegalArgumentException("null comps not allowed");
        }
        empty = false;
        level = 0;
        current = new ArrayList<E>(2);

        compit0 = comps0.iterator();
        E e = compit0.next();
        current.add(e);
        fincomps0 = new ArrayList<E>();
        fincomps0.add(e); 
        fincompit0 = fincomps0.iterator();
        E d = fincompit0.next(); // remove current

        compit1 = comps1.iterator();
        e = compit1.next();
        current.add(e);
        fincomps1 = new ArrayList<E>();
        fincomps1.add(e); 
        fincompit1 = fincomps1.iterator();
        d = fincompit1.next(); // remove current
        //System.out.println("current   = " + current);
    }


    /**
     * Test for availability of a next tuple.
     * @return true if the iteration has more tuples, else false.
     */
    public synchronized boolean hasNext() {
        return !empty;
    }


    /**
     * Get next tuple.
     * @return next tuple.
     */
    public synchronized List<E> next() {
        if (empty) {
            throw new NoSuchElementException("invalid call of next()");
        }
        List<E> res = current; // new ArrayList<E>(current); // copy
        if ( fincompit0.hasNext() && fincompit1.hasNext() ) {
            E e0 = fincompit0.next();
            E e1 = fincompit1.next();
            current = new ArrayList<E>();
            current.add(e0);
            current.add(e1);
            return res;
        }
        level++;
        if ( level % 2 == 1 ) {
            Collections.reverse(fincomps0);
        } else {
            Collections.reverse(fincomps1);
        }
        if ( compit0.hasNext() && compit1.hasNext() ) {
            fincomps0.add( compit0.next() );
            fincomps1.add( compit1.next() );
        } else { 
            empty = true;
            return res;
        }
        if ( level % 2 == 0 ) {
            Collections.reverse(fincomps0);
        } else {
            Collections.reverse(fincomps1);
        }
        //System.out.println("list(0) = " + fincomps0);
        //System.out.println("list(1) = " + fincomps1);
        fincompit0 = fincomps0.iterator();
        fincompit1 = fincomps1.iterator();
        E e0 = fincompit0.next();
        E e1 = fincompit1.next();
        current = new ArrayList<E>();
        current.add(e0);
        current.add(e1);
        return res;
    }


    /**
     * Remove a tuple if allowed.
     */
    public void remove() {
        throw new UnsupportedOperationException("cannnot remove tuples");
    }

}


/**
 * Cartesian product infinite iterator, two factors list version.
 * @author Heinz Kredel
 */
class CartesianTwoProductInfiniteIteratorList<E> implements Iterator<List<E>> {


    /**
     * data structure.
     */
    final Iterator<List<E>> compit0;
    final Iterator<List<E>> compit1;


    final List<List<E>> fincomps0;
    final List<List<E>> fincomps1;


    Iterator<List<E>> fincompit0;
    Iterator<List<E>> fincompit1;


    List<E> current;


    boolean empty;


    long level;


    /**
     * CartesianProduct iterator constructor.
     * @param comps components of the cartesian product.
     */
    public CartesianTwoProductInfiniteIteratorList(Iterable<List<E>> comps0, Iterable<List<E>> comps1) {
        if (comps0 == null || comps1 == null) {
            throw new IllegalArgumentException("null comps not allowed");
        }
        current = new ArrayList<E>();
        empty = false;
        level = 0;

        compit0 = comps0.iterator();
        List<E> e = compit0.next();
        current.addAll(e);
        fincomps0 = new ArrayList<List<E>>();
        fincomps0.add(e); 
        fincompit0 = fincomps0.iterator();
        List<E> d = fincompit0.next(); // remove current

        compit1 = comps1.iterator();
        e = compit1.next();
        current.addAll(e);
        fincomps1 = new ArrayList<List<E>>();
        fincomps1.add(e); 
        fincompit1 = fincomps1.iterator();
        d = fincompit1.next(); // remove current
        //System.out.println("current   = " + current);
    }


    /**
     * Test for availability of a next tuple.
     * @return true if the iteration has more tuples, else false.
     */
    public synchronized boolean hasNext() {
        return !empty;
    }


    /**
     * Get next tuple.
     * @return next tuple.
     */
    public synchronized List<E> next() {
        if (empty) {
            throw new NoSuchElementException("invalid call of next()");
        }
        List<E> res = current; // new ArrayList<E>(current);
        if ( fincompit0.hasNext() && fincompit1.hasNext() ) {
            List<E> e0 = fincompit0.next();
            List<E> e1 = fincompit1.next();
            current = new ArrayList<E>();
            current.addAll(e0);
            current.addAll(e1);
            return res;
        }
        level++;
        if ( level % 2 == 1 ) {
            Collections.reverse(fincomps0);
        } else {
            Collections.reverse(fincomps1);
        }
        if ( compit0.hasNext() && compit1.hasNext() ) {
            fincomps0.add( compit0.next() );
            fincomps1.add( compit1.next() );
        } else { 
            empty = true;
            return res;
        }
        if ( level % 2 == 0 ) {
            Collections.reverse(fincomps0);
        } else {
            Collections.reverse(fincomps1);
        }
        //System.out.println("list(0) = " + fincomps0);
        //System.out.println("list(1) = " + fincomps1);
        fincompit0 = fincomps0.iterator();
        fincompit1 = fincomps1.iterator();
        List<E> e0 = fincompit0.next();
        List<E> e1 = fincompit1.next();
        current = new ArrayList<E>();
        current.addAll(e0);
        current.addAll(e1);
        return res;
    }


    /**
     * Remove a tuple if allowed.
     */
    public void remove() {
        throw new UnsupportedOperationException("cannnot remove tuples");
    }

}
