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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2018-2022 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.functions;

import net.sf.saxon.expr.XPathContext;
import net.sf.saxon.om.Item;
import net.sf.saxon.om.NodeInfo;
import net.sf.saxon.om.Sequence;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.value.SequenceExtent;
import net.sf.saxon.value.StringValue;

import java.util.ArrayList;
import java.util.List;

/**
 * This class implements the XPath 2.0 function fn:in-scope-prefixes()
 */

public class InScopePrefixes extends SystemFunction {

    /**
     * Call of in-scope-prefixes
     * @param context   the dynamic evaluation context
     * @param arguments the values of the arguments, supplied as Sequences.
     *                  Generally it is advisable, if calling iterate() to process a supplied sequence, to
     *                  call it only once; if the value is required more than once, it should first be converted
     *                  to a {@link net.sf.saxon.om.GroundedValue} by calling the utility methd
     *                  SequenceTool.toGroundedValue().
     *                  If the expected value is a single item, the item should be obtained by calling
     *                  Sequence.head(): it cannot be assumed that the item will be passed as an instance of
     *                  {@link net.sf.saxon.om.Item} or {@link net.sf.saxon.value.AtomicValue}.
     *                  It is the caller's responsibility to perform any type conversions required
     *                  to convert arguments to the type expected by the callee. An exception is where
     *                  this Callable is explicitly an argument-converting wrapper around the original
     *                  Callable.
     * @return the sequence of prefixes
     * @throws XPathException if a dynamic error occurs
     */

    @Override
    public Sequence call(final XPathContext context, Sequence[] arguments) throws XPathException {
        final NodeInfo element = (NodeInfo) arguments[0].head();
        String[] prefixes = element.getAllNamespaces().getPrefixArray();
        List result = new ArrayList<>();
        for (String s : prefixes) {
            result.add(new StringValue(s));
        }
        result.add(StringValue.bmp("xml"));
        return SequenceExtent.makeSequenceExtent(result);
    }

}