package com.icl.saxon.functions;
import com.icl.saxon.*;
import com.icl.saxon.expr.*;

import java.util.*;
import java.text.*;



public class StartsWith extends Function {

    /**
    * Function name (for diagnostics)
    */

    public String getName() {
        return "starts-with";
    };

    /**
    * Determine the data type of the expression
    * @return Value.BOOLEAN
    */

    public int getDataType() {
        return Value.BOOLEAN;
    }

    /**
    * Simplify and validate.
    * This is a pure function so it can be simplified in advance if the arguments are known
    */

    public Expression simplify() throws XPathException {
        checkArgumentCount(2, 2);
        argument[0] = argument[0].simplify();
        argument[1] = argument[1].simplify();

        if (argument[0] instanceof Value && argument[1] instanceof Value) {
            return evaluate(null);
        }
        
        if (argument[1] instanceof Value &&
                 ((Value)argument[1]).asString().equals("")) {
            return new BooleanValue(true);
        }

        return this;
    }

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

    public boolean evaluateAsBoolean(Context c) throws XPathException {
        String arg0 = argument[0].evaluateAsString(c);
        String arg1 = argument[1].evaluateAsString(c);        
        return arg0.startsWith(arg1);
    }

    /**
    * Evaluate in a general context
    */

    public Value evaluate(Context c) throws XPathException {
        return new BooleanValue(evaluateAsBoolean(c));
    }

    /**
    * Determine the dependencies
    */

    public int getDependencies() {
        return argument[0].getDependencies() | argument[1].getDependencies();
    }

    /**
    * Reduce the dependencies
    */

    public Expression reduce(int dep, Context c) throws XPathException {
        StartsWith f = new StartsWith();
        f.addArgument(argument[0].reduce(dep, c));
        f.addArgument(argument[1].reduce(dep, c));
        f.setStaticContext(getStaticContext());
        return f.simplify();
    }

}



//
// The contents of this file are subject to the Mozilla Public License Version 1.0 (the "License");
// you may not use this file except in compliance with the License. You may obtain a copy of the
// License at http://www.mozilla.org/MPL/ 
//
// Software distributed under the License is distributed on an "AS IS" basis,
// WITHOUT WARRANTY OF ANY KIND, either express or implied.
// See the License for the specific language governing rights and limitations under the License. 
//
// The Original Code is: all this file. 
//
// The Initial Developer of the Original Code is
// Michael Kay of International Computers Limited (mhkay@iclway.co.uk).
//
// Portions created by (your name) are Copyright (C) (your legal entity). All Rights Reserved. 
//
// Contributor(s): none. 
//