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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2018-2023 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.expr;

import net.sf.saxon.om.AtomicSequence;
import net.sf.saxon.om.AtomizedValueIterator;
import net.sf.saxon.om.SequenceIterator;
import net.sf.saxon.trans.UncheckedXPathException;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.value.AtomicValue;

/**
 * This iterator returns a sequence of atomic values, the result of atomizing the sequence
 * of nodes returned by an underlying SequenceIterator.
 */

public final class AxisAtomizingIterator implements SequenceIterator {

    private final AtomizedValueIterator base;
    private AtomicSequence results = null;
    private int atomicPosition = 0;

    /**
     * Construct an atomizing iterator
     *
     * @param base the base iterator (whose nodes are to be atomized)
     */

    public AxisAtomizingIterator(AtomizedValueIterator base) {
        this.base = base;
    }

    @Override
    public AtomicValue next() {
        while (true) {
            if (results != null) {
                if (atomicPosition < results.getLength()) {
                    return results.itemAt(atomicPosition++);
                } else {
                    results = null;
                    continue;
                }
            }

            try {
                AtomicSequence atomized = base.nextAtomizedValue();
                if (atomized == null) {
                    results = null;
                    return null;
                }
                if (atomized instanceof AtomicValue) {
                    // common case (the atomized value of the node is a single atomic value)
                    results = null;
                    return (AtomicValue) atomized;
                } else {
                    results = atomized;
                    atomicPosition = 0;
                    // continue
                }
            } catch (XPathException e) {
                throw new UncheckedXPathException(e);
            }
        }
    }

    @Override
    public void close() {
        base.close();
    }


}