/*
 * Copyright 2003-2007 the original author or authors.
 *
 * Licensed 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 groovy.lang;

import java.util.*;

/**
 * Interceptor that registers the timestamp of each method call
 * before and after invocation. The timestamps are stored internally
 * and can be retrieved through the with the <pre>getCalls()</pre> 
 * and <pre>statistic()</pre> API. <br/><br/>
 * 
 * Example usage can be seen here: 
 * <pre>
 * def proxy = ProxyMetaClass.getInstance(ArrayList.class)
 * proxy.interceptor = new BenchmarkInterceptor()
 * proxy.use {
 *     def list = (0..10000).collect{ it }
 *     4.times { list.size() }
 *     4000.times { list.set(it, it+1) }
 * }
 * proxy.interceptor.statistic()
 * </pre>
 * Which produces the following output: 
 * <pre>
 * [[size, 4, 0], [set, 4000, 21]]
 * </pre>
 */
public class BenchmarkInterceptor implements Interceptor {

    protected Map calls = new LinkedHashMap(); // keys to list of invocation times and before and after

    /**
    * Returns the raw data associated with the current benchmark run. 
    */ 
    public Map getCalls() {
        return calls;
    }
    
    /**
    * Resets all the benchmark data on this object. 
    */
    public void reset() {
        calls = new HashMap();
    }

    public Object beforeInvoke(Object object, String methodName, Object[] arguments) {
        if (!calls.containsKey(methodName)) calls.put(methodName, new LinkedList());
        ((List) calls.get(methodName)).add(new Long(System.currentTimeMillis()));

        return null;
    }

    public Object afterInvoke(Object object, String methodName, Object[] arguments, Object result) {
        ((List) calls.get(methodName)).add(new Long(System.currentTimeMillis()));
        return result;
    }

    public boolean doInvoke() {
        return true;
    }

    /**
     * Returns benchmark statistics as a List<Object[]>. 
     * AccumulateTime is measured in milliseconds and is as accurate as
     * System.currentTimeMillis() allows it to be. 
     * @return a list of lines, each item is [methodname, numberOfCalls, accumulatedTime]
     */
    public List statistic() {
        List result = new LinkedList();
        for (Iterator iter = calls.keySet().iterator(); iter.hasNext();) {
            Object[] line = new Object[3];
            result.add(line);
            line[0] = iter.next();
            List times = (List) calls.get(line[0]);
            line[1] = new Integer(times.size() / 2);
            int accTime = 0;
            for (Iterator it = times.iterator(); it.hasNext();) {
                Long start = (Long) it.next();
                Long end = (Long) it.next();
                accTime += end.longValue() - start.longValue();
            }
            line[2] = new Long(accTime);
        }
        return result;
    }
}