/*
 * Copyright 2008, Yahoo! Inc.
 *
 * 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 com.yahoo.zookeeper.server;


public class ServerStats {
    private static ServerStats instance=null;
    private long packetsSent;
    private long packetsReceived;
    private long maxLatency;
    private long minLatency = Long.MAX_VALUE;
    private long totalLatency = 0;
    private long count = 0;
    
    public interface Provider{
        public long getOutstandingRequests();
        public long getLastProcessedZxid();
    }
    private Provider provider=null;
    private Object mutex=new Object();
    
    static public ServerStats getInstance(){
        return instance;
    }
    static public void registerAsConcrete() {
        setInstance(new ServerStats());
    }
    static synchronized public void unregister() {
        instance=null;
    }
    static synchronized protected void setInstance(ServerStats newInstance){
        assert instance==null;
        instance = newInstance;
    }
    protected ServerStats(){}
    
    // getters
    synchronized public long getMinLatency() {
        return (minLatency == Long.MAX_VALUE) ? 0 : minLatency;
    }

    synchronized public long getAvgLatency() {
        if(count!=0)
            return totalLatency / count;
        return 0;
    }

    synchronized public long getMaxLatency() {
        return maxLatency;
    }

    public long getOutstandingRequests() {
        synchronized(mutex){
            return (provider!=null)?provider.getOutstandingRequests():-1;
        }
    }
    public long getLastProcessedZxid(){
        synchronized(mutex){
            return (provider!=null)?provider.getLastProcessedZxid():-1;
        }
    }
    synchronized public long getPacketsReceived() {
        return packetsReceived;
    }

    synchronized public long getPacketsSent() {
        return packetsSent;
    }

    public String getServerState(){
        return "standalone";
    }
    
    public String toString(){
        StringBuilder sb = new StringBuilder();
        sb.append("Latency min/avg/max: " + getMinLatency() + "/"
                + getAvgLatency() + "/" + getMaxLatency() + "\n");
        sb.append("Received: " + getPacketsReceived() + "\n");
        sb.append("Sent: " + getPacketsSent() + "\n");
        if (provider != null) {
            sb.append("Outstanding: " + getOutstandingRequests() + "\n");
            sb.append("Zxid: 0x"+ Long.toHexString(getLastProcessedZxid())+ "\n");
        }
        sb.append("Mode: "+getServerState()+"\n");
        return sb.toString();
    }
    // mutators
    public void setStatsProvider(Provider zk){
        synchronized(mutex){
            provider=zk;
        }
    }
    synchronized void updateLatency(long requestCreateTime) {
        long latency = System.currentTimeMillis() - requestCreateTime;
        totalLatency += latency;
        count++;
        if (latency < minLatency) {
            minLatency = latency;
        }
        if (latency > maxLatency) {
            maxLatency = latency;
        }
    }
    synchronized public void resetLatency(){
        totalLatency=count=maxLatency=0;
        minLatency=Long.MAX_VALUE;
    }
    synchronized public void resetMaxLatency(){
        maxLatency=getMinLatency();
    }
    synchronized public void incrementPacketsReceived() {
        packetsReceived++;
    }
    synchronized public void incrementPacketsSent() {
        packetsSent++;
    }
    synchronized public void resetRequestCounters(){
        packetsReceived=packetsSent=0;
    }

}