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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2013 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.Expression;
import net.sf.saxon.expr.StaticProperty;
import net.sf.saxon.expr.XPathContext;
import net.sf.saxon.expr.parser.ExpressionVisitor;
import net.sf.saxon.om.NodeInfo;
import net.sf.saxon.om.Sequence;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.tree.util.FastStringBuffer;
import net.sf.saxon.value.StringValue;

/**
* This class supports the generate-id() function
*/

public class GenerateId extends SystemFunctionCall {

    /**
    * Simplify and validate.
     * @param visitor an expression visitor
     */

     /*@NotNull*/
     public Expression simplify(/*@NotNull*/ ExpressionVisitor visitor) throws XPathException {
        useContextItemAsDefault(visitor);
        return simplifyArguments(visitor);
    }


    /**
     * Determine the special properties of this expression. The generate-id()
     * function is a special case: it is considered creative if its operand
     * is creative, so that generate-id(f()) is not taken out of a loop
     */

    public int computeSpecialProperties() {
        int p = super.computeSpecialProperties();
        return p & ~StaticProperty.NON_CREATIVE;
    }

    /**
    * Evaluate the function in a string context
    */

    public StringValue evaluateItem(XPathContext c) throws XPathException {
        NodeInfo node = (NodeInfo)argument[0].evaluateItem(c);
        return generateId(node);
    }

    public static StringValue generateId(NodeInfo node) {
        if (node==null) {
            return StringValue.EMPTY_STRING;
        }

        FastStringBuffer buffer = new FastStringBuffer(FastStringBuffer.TINY);
        node.generateId(buffer);
        buffer.condense();
        return new StringValue(buffer);

    }

    /**
     * Evaluate the expression
     *
     * @param context   the dynamic evaluation context
     * @param arguments the values of the arguments, supplied as Sequences
     * @return the result of the evaluation, in the form of a Sequence
     * @throws net.sf.saxon.trans.XPathException
     *          if a dynamic error occurs during the evaluation of the expression
     */
    public Sequence call(XPathContext context, Sequence[] arguments) throws XPathException {
        NodeInfo node = (arguments.length == 0 ? getContextNode(context) : (NodeInfo)arguments[0].head());
        return generateId(node);
    }

}