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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.lib.StringCollator;
import net.sf.saxon.om.Sequence;
import net.sf.saxon.str.UnicodeString;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.value.AtomicValue;
import net.sf.saxon.value.Base64BinaryValue;
import net.sf.saxon.value.StringValue;

/**
 * Implements the collation-key function defined in the XSLT 3.0 and XPath 3.1 specifications
 */
public class CollationKeyFn extends CollatingFunctionFixed {


    public static Base64BinaryValue getCollationKey(UnicodeString s, StringCollator collator) {
        AtomicValue val = collator.getCollationKey(s).asAtomic();
        if (val instanceof Base64BinaryValue) {
            return (Base64BinaryValue) val;
        } else if (val instanceof StringValue) {
            return ((StringValue) val).getCodepointCollationKey();
        } else {
            throw new IllegalStateException("Collation key must be Base64Binary");
        }
    }

    /**
     * Call the Callable.
     *
     * @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 result of the evaluation, in the form of a Sequence. It is the responsibility
     *         of the callee to ensure that the type of result conforms to the expected result type.
     * @throws net.sf.saxon.trans.XPathException
     *          if a dynamic error occurs during the evaluation of the expression
     */
    @Override
    public Base64BinaryValue call(XPathContext context, Sequence[] arguments) throws XPathException {
        StringValue in = (StringValue)arguments[0].head();
        StringCollator collator = getStringCollator();
        return getCollationKey(in.getUnicodeStringValue(), collator);
    }
}