import gnu.jel.CompilationException;
import gnu.jel.CompiledExpression;
import gnu.jel.DVMap;
import gnu.jel.Evaluator;
import gnu.jel.Library;
import java.util.HashMap;

public class Vars {

    private static String PROPNAME = "cos";

    public static void main( String[] args ) throws CompilationException {

        Class<?>[] staClasses = new Class<?>[] { Math.class };
        Class<?>[] dynClasses = new Class<?>[] { Item1.class, Item2.class };
        Class<?>[] dotClasses = new Class<?>[ 0 ];
        DVMap resolver = new Resolver();
        HashMap<String,Class<?>> cnmap = null;

        Library lib = new Library( staClasses, dynClasses, dotClasses,
                                   resolver, cnmap );

        Item1 item1 = new Item1( 23 );
        Item2 item2 = new Item2( 5 );
        Object[] context = new Object[] { item1, item2 };

        String[] exprTxts = new String[] {
            "19+1",
            "sin",
            "sin(1)",
            "getDoubleProperty(\"" + PROPNAME + "\")",
            PROPNAME,
            "cos(1)",
        };
        for ( String txt : exprTxts ) {
            StringBuffer sbuf = new StringBuffer( "   " + txt );
            try {
                CompiledExpression expr = Evaluator.compile( txt, lib );
                sbuf.append( " = " + expr.evaluate( context ) );
            }
            catch ( Throwable e ) {
                sbuf.append( " FAIL [" + e + "]" );
            }
            System.out.println( sbuf.toString() );
        }
    }

    public static class Item1 {
        public final double value;
        Item1( double value ) {
            this.value = value;
        }
        public double sin() {
            return this.value;
        }
    }

    public static class Item2 {
        public final double value;
        Item2( double value ) {
            this.value = value;
        }
        public double getDoubleProperty( String name ) {
            if ( PROPNAME.equals( name ) ) {
                return value;
            }
            else {
                throw new IllegalArgumentException( "No value " + name );
            }
        }
    }

    public static class Resolver extends DVMap {
        public String getTypeName( String name ) {
            return PROPNAME.equals( name ) ? "Double" : null;
        }
    }
}