Application: gvSIG desktop

package org.gvsig.expressionevaluator.impl.function.numeric;

import org.apache.commons.lang3.Range;

import static org.gvsig.expressionevaluator.ExpressionBuilder.FUNCTION_DECR;

import org.gvsig.expressionevaluator.Interpreter;

import org.gvsig.expressionevaluator.MutableSymbolTable;

import org.gvsig.expressionevaluator.spi.AbstractFunction;

public class DecrFunction extends AbstractFunction {

    public DecrFunction() {

        super("Numeric", FUNCTION_DECR,Range.between(1,3),

            "Decrease the value of the indicated identifier and return its value.",

            FUNCTION_DECR+"('CONTADOR#1')",

            new String[]{

                "identifier name - the identifier used as counter.",

                "first value - Optional. The value with which the identifier must be initialized in its first use. By default zero",

                "step - Optional. The value used to decrease the identifier. By default one",

            },

            "Long",

            false

        );

    }

    @Override

    public boolean allowConstantFolding() {

        return false;

    }

    @Override

    public Object call(Interpreter interpreter, Object[] args) {

        String identifierName = this.getStr(args, 0);

        long firstValue = 0;

        long increment = 1; 

        long value;

        switch(args.length) {

            default:

            case 1:

                break;

            case 2:

                firstValue = this.getLong(args, 1);

                break;

            case 3:

                firstValue = this.getLong(args, 1);

                increment = this.getLong(args, 2);

                break;

        }

        MutableSymbolTable symbolTable = (MutableSymbolTable) interpreter.getSymbolTable();

        if( symbolTable.exists(identifierName) ) {

            value = ((Number) symbolTable.value(identifierName)).longValue();

        } else {

            value = firstValue;

        }

        value = value-increment;

        symbolTable.setVar(identifierName, value);

        return value;

    }

}