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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.functions;

import net.sf.saxon.expr.XPathContext;
import net.sf.saxon.expr.sort.CodepointCollator;
import net.sf.saxon.expr.sort.RuleBasedSubstringMatcher;
import net.sf.saxon.expr.sort.SimpleCollation;
import net.sf.saxon.lib.StringCollator;
import net.sf.saxon.lib.SubstringMatcher;
import net.sf.saxon.om.Sequence;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.value.BooleanValue;
import net.sf.saxon.value.StringValue;

import java.text.RuleBasedCollator;


/**
 * Implements the fn:starts-with() function, with the collation already known
 */
public class StartsWith extends CollatingFunctionFixed {

    public static boolean startsWith(StringValue arg0, StringValue arg1, StringCollator collator) throws XPathException {
        if (arg1 == null || arg1.isZeroLength()) {
            return true;
        }

        if (arg0 == null || arg0.isZeroLength()) {
            return false;
        }

        String s0 = arg0.getStringValue();
        String s1 = arg1.getStringValue();

        if (collator instanceof CodepointCollator) {
            // fast path for this common case
            return s0.startsWith(s1, 0);
        } else {
            if (collator instanceof SimpleCollation &&
                    ((SimpleCollation) collator).getComparator() instanceof RuleBasedCollator) {
                collator = new RuleBasedSubstringMatcher(collator.getCollationURI(), (RuleBasedCollator) ((SimpleCollation) collator).getComparator());
            }

            if (collator instanceof SubstringMatcher) {
                return ((SubstringMatcher) collator).startsWith(s0, s1);
            } else {
                throw new XPathException("The collation requested for starts-with() does not support substring matching", "FOCH0004");
            }
        }
    }

    /**
     * Evaluate the function
     */

    public BooleanValue call(XPathContext context, Sequence[] arguments) throws XPathException {
        StringValue s0 = (StringValue) arguments[0].head();
        StringValue s1 = (StringValue) arguments[1].head();
        return BooleanValue.get(startsWith(s0, s1, getStringCollator()));
    }


}