
/*
 * Janino - An embedded Java[TM] compiler
 *
 * Copyright (c) 2001-2010 Arno Unkrig. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification, are permitted provided that the
 * following conditions are met:
 *
 *    1. Redistributions of source code must retain the above copyright notice, this list of conditions and the
 *       following disclaimer.
 *    2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the
 *       following disclaimer in the documentation and/or other materials provided with the distribution.
 *    3. Neither the name of the copyright holder nor the names of its contributors may be used to endorse or promote
 *       products derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.codehaus.commons.compiler.util.iterator;

import java.util.Arrays;
import java.util.Collection;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.NoSuchElementException;

/**
 * An {@link java.util.Iterator} that iterates over a delegate, which produces arrays, {@link java.util.Collection}s,
 * {@link java.util.Enumeration}s or {@link java.util.Iterator}s. This {@link java.util.Iterator} returns the elements
 * of these objects.
 * <p>
 *   The count of dimensions is declared at construction. Count "1" produces an {@link java.util.Iterator} that adds no
 *   functionality to its delegate, count "2" produces an {@link Iterator} that behaves as explained above, and so
 *   forth.
 * </p>
 *
 * @param <T> The type of the objects that the returned iterator produces
 */
public
class MultiDimensionalIterator<T> implements Iterator<T> {
    private final Iterator<?>[]           nest;
    private static final Iterator<Object> EMPTY_ITERATOR = new Iterator<Object>() {
        @Override public boolean hasNext() { return false;                                      }
        @Override public Object  next()    { throw new NoSuchElementException();                }
        @Override public void    remove()  { throw new UnsupportedOperationException("remove"); }
    };

    public
    MultiDimensionalIterator(Iterator<?> delegate, int dimensionCount) {
        this.nest    = new Iterator[dimensionCount];
        this.nest[0] = delegate;
        for (int i = 1; i < dimensionCount; ++i) this.nest[i] = MultiDimensionalIterator.EMPTY_ITERATOR;
    }

    /**
     * @throws UniterableElementException
     */
    @Override public boolean
    hasNext() {

        // Unroll this check because it is so performance critical:
        if (this.nest[this.nest.length - 1].hasNext()) return true;

        int i = this.nest.length - 2;
        if (i < 0) return false;

        for (;;) {
            if (!this.nest[i].hasNext()) {
                if (i == 0) return false;
                --i;
            } else {
                if (i == this.nest.length - 1) return true;
                Object o = this.nest[i].next();
                if (o instanceof Iterator) {
                    this.nest[++i] = (Iterator<?>) o;
                } else
                if (o instanceof Object[]) {
                    this.nest[++i] = Arrays.asList((Object[]) o).iterator();
                } else
                if (o instanceof Collection) {
                    this.nest[++i] = ((Collection<?>) o).iterator();
                } else
                if (o instanceof Enumeration) {
                    this.nest[++i] = new EnumerationIterator<>((Enumeration<?>) o);
                } else
                {
                    throw new UniterableElementException();
                }
            }
        }
    }

    @Override public T
    next() {

        if (!this.hasNext()) throw new NoSuchElementException();

        @SuppressWarnings("unchecked") T result = (T) this.nest[this.nest.length - 1].next();

        return result;
    }

    @Override public void remove() { throw new UnsupportedOperationException("remove"); }
}
