/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.    
 */
package calculator.dosgi;

import org.osgi.framework.BundleContext;
import org.osgi.framework.Constants;
import org.osgi.framework.Filter;
import org.osgi.framework.InvalidSyntaxException;
import org.osgi.util.tracker.ServiceTracker;

import calculator.dosgi.operations.AddService;
import calculator.dosgi.operations.DivideService;
import calculator.dosgi.operations.MultiplyService;
import calculator.dosgi.operations.SubtractService;

/**
 * An implementation of the Calculator service.
 */
public class CalculatorServiceImpl implements CalculatorService {
//    private AddService addService;
//    private SubtractService subtractService;
//    private MultiplyService multiplyService;
//    private DivideService divideService;

    private ServiceTracker tracker;

    public CalculatorServiceImpl() {
        super();
    }

    public CalculatorServiceImpl(BundleContext context) {
        super();
        Filter filter = null;
        try {
            filter = context.createFilter("(" + Constants.OBJECTCLASS + "=calculator.dosgi.operations.*)");
        } catch (InvalidSyntaxException e) {
            e.printStackTrace();
        }
        this.tracker = new ServiceTracker(context, filter, null);
        tracker.open();
    }

    /*
     * The following setters can be used for DS injection
     */
    /*
    public void setAddService(AddService addService) {
        this.addService = addService;
    }

    public void setSubtractService(SubtractService subtractService) {
        this.subtractService = subtractService;
    }

    public void setDivideService(DivideService divideService) {
        this.divideService = divideService;
    }

    public void setMultiplyService(MultiplyService multiplyService) {
        this.multiplyService = multiplyService;
    }
    */

    private <T> T getService(Class<T> cls) {
        for (Object s : tracker.getServices()) {
            if (cls.isInstance(s)) {
                return cls.cast(s);
            }
        }
        throw new IllegalStateException(cls.getSimpleName() + " is not available");
    }

    public double add(double n1, double n2) {
        return getService(AddService.class).add(n1, n2);
    }

    public double subtract(double n1, double n2) {
        return getService(SubtractService.class).subtract(n1, n2);
    }

    public double multiply(double n1, double n2) {
        return getService(MultiplyService.class).multiply(n1, n2);
    }

    public double divide(double n1, double n2) {
        return getService(DivideService.class).divide(n1, n2);
    }
}