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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2015 Saxonica Limited.
// This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
// If a copy of the MPL was not distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
// This Source Code Form is "Incompatible With Secondary Licenses", as defined by the Mozilla Public License, v. 2.0.
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

package net.sf.saxon.tree.iter;

import net.sf.saxon.expr.LastPositionFinder;
import net.sf.saxon.om.GroundedValue;
import net.sf.saxon.om.Item;
import net.sf.saxon.om.One;
import net.sf.saxon.om.SequenceIterator;
import net.sf.saxon.value.AtomicValue;
import net.sf.saxon.value.EmptySequence;
import net.sf.saxon.value.SequenceExtent;

import java.util.List;

/**
 * Class ListIterator, iterates over a sequence of items held in a Java List
 */

public class ListIterator
        implements UnfailingIterator, LastPositionFinder, LookaheadIterator, GroundedIterator, ReversibleIterator {

    int index = 0;
    int length;
    List list;

    /**
     * Create a ListIterator over a given List
     *
     * @param list the list: all objects in the list must be instances of {@link Item}
     */

    public ListIterator(/*@NotNull*/ List list) {
        index = 0;
        this.list = list;
        this.length = list.size();
    }

    /**
     * Create a ListIterator over the leading part of a given List
     *
     * @param list   the list: all objects in the list must be instances of {@link Item}
     * @param length the number of items to be included
     */

    public ListIterator(List list, int length) {
        index = 0;
        this.list = list;
        this.length = length;
    }

    public boolean hasNext() {
        return index < length;
    }

    /*@Nullable*/
    public Item next() {
        if (index >= length) {
            index = -1;
            length = -1;
            return null;
        }
        return list.get(index++);
    }

    public void close() {
    }

    public int getLength() {
        return length;
    }

    /*@NotNull*/
    public ListIterator getAnother() {
        return new ListIterator(list);
    }

    /**
     * Get properties of this iterator, as a bit-significant integer.
     *
     * @return the properties of this iterator. This will be some combination of
     *         properties such as {@link #GROUNDED}, {@link #LAST_POSITION_FINDER},
     *         and {@link #LOOKAHEAD}. It is always
     *         acceptable to return the value zero, indicating that there are no known special properties.
     *         It is acceptable for the properties of the iterator to change depending on its state.
     */

    public int getProperties() {
        return GROUNDED | LAST_POSITION_FINDER | LOOKAHEAD;
    }

    /**
     * Return a SequenceValue containing all the items in the sequence returned by this
     * SequenceIterator
     *
     * @return the corresponding SequenceValue
     */

    /*@Nullable*/
    public GroundedValue materialize() {
        if (length == 0) {
            return EmptySequence.getInstance();
        } else if (length == 1) {
            Item item = list.get(0);
            if (item instanceof GroundedValue) {
                return (GroundedValue) item;
            } else {
                return new One(item);
            }
        } else {
            return new SequenceExtent(list);
        }
    }

    public SequenceIterator getReverseIterator() {
        return new ReverseListIterator(list);
    }

    public static class Atomic extends ListIterator implements AtomicIterator {
        public Atomic (List list) {
            super(list);
        }
        public AtomicValue next() {
            return (AtomicValue)super.next();
        }

        @Override
        public Atomic getAnother() {
            return new Atomic((List)list);
        }
    }
}