/*
 * Copyright 2017 Red Hat, Inc. and/or its affiliates.
 *
 * 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 org.jbpm.process.core.timer.impl;

import java.io.Serializable;
import java.util.Date;
import java.util.concurrent.Callable;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;

import org.drools.core.time.InternalSchedulerService;
import org.drools.core.time.Job;
import org.drools.core.time.JobContext;
import org.drools.core.time.JobHandle;
import org.drools.core.time.SelfRemovalJobContext;
import org.drools.core.time.TimerService;
import org.drools.core.time.Trigger;
import org.drools.core.time.impl.TimerJobInstance;
import org.jbpm.process.core.timer.GlobalSchedulerService;
import org.jbpm.process.core.timer.JobNameHelper;
import org.jbpm.process.core.timer.NamedJobContext;
import org.jbpm.process.core.timer.SchedulerServiceInterceptor;
import org.jbpm.process.core.timer.impl.GlobalTimerService.GlobalJobHandle;
import org.jbpm.process.instance.timer.TimerManager.ProcessJobContext;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * ThreadPool based scheduler service backed by <code>ThreadPoolSchedulerService</code>
 *
 */
public class ThreadPoolSchedulerService implements GlobalSchedulerService {
    
    private static final Logger logger = LoggerFactory.getLogger(ThreadPoolSchedulerService.class);
    
    private static final Integer FAILED_JOB_RETRIES = Integer.parseInt(System.getProperty("org.jbpm.timer.thread.retries", "5"));
    private static final Integer FAILED_JOB_DELAY = Integer.parseInt(System.getProperty("org.jbpm.timer.thread.delay", "1000"));
    
    private AtomicLong idCounter = new AtomicLong();
    private ScheduledThreadPoolExecutor scheduler;
    private TimerService globalTimerService;
    private SchedulerServiceInterceptor interceptor = new DelegateSchedulerServiceInterceptor(this);
    
    private int poolSize;
    
    private ConcurrentHashMap<String, JobHandle> activeTimer = new ConcurrentHashMap<String, JobHandle>();
    
    public ThreadPoolSchedulerService(int poolSize) {
        this.poolSize = poolSize;        
    }
    

    @Override
    public void initScheduler(TimerService globalTimerService) {
        this.globalTimerService = globalTimerService;
        
        this.scheduler = new ScheduledThreadPoolExecutor(poolSize);
    }

    @Override
    public void shutdown() {
        
        try {
        	this.scheduler.shutdown();
            if ( !this.scheduler.awaitTermination( 10, TimeUnit.SECONDS ) ) {
            	this.scheduler.shutdownNow();
            }
        } catch ( InterruptedException e ) {
        	this.scheduler.shutdownNow();
            Thread.currentThread().interrupt();
        }
        this.activeTimer.clear();
    }

    @Override
    public JobHandle scheduleJob(Job job, JobContext ctx, Trigger trigger) {

        long id = idCounter.getAndIncrement(); 
        Date date = trigger.hasNextFireTime();
        if ( date != null ) {
            String jobname = JobNameHelper.getJobName(ctx, id);
            if (activeTimer.containsKey(jobname)) {
                return activeTimer.get(jobname);
            }
            
            GlobalJDKJobHandle jobHandle = new GlobalJDKJobHandle( id);
            
            TimerJobInstance jobInstance = globalTimerService.
                                 getTimerJobFactoryManager().createTimerJobInstance( job,
                                                                                     ctx,
                                                                                     trigger,
                                                                                     jobHandle,
                                                                                     (InternalSchedulerService) globalTimerService );
            jobHandle.setTimerJobInstance( (TimerJobInstance) jobInstance );
            interceptor.internalSchedule( (TimerJobInstance) jobInstance );
            activeTimer.put(jobname, jobHandle);
            return jobHandle;
        } else {
            return null;
        }

    }

    @Override
    public boolean removeJob(JobHandle jobHandle) {
        if (jobHandle == null) {
            return false;
        }
        jobHandle.setCancel( true );
        JobContext jobContext = ((GlobalJDKJobHandle) jobHandle).getTimerJobInstance().getJobContext();
        try {
            ProcessJobContext processCtx = null;
            if (jobContext instanceof SelfRemovalJobContext) {
                processCtx = (ProcessJobContext) ((SelfRemovalJobContext) jobContext).getJobContext();
            } else {
                processCtx = (ProcessJobContext) jobContext;
            }
            String jobname = JobNameHelper.getJobName(processCtx, jobContext.getJobHandle().getId());
            activeTimer.remove(jobname);
            globalTimerService.getTimerJobFactoryManager().removeTimerJobInstance( ((GlobalJDKJobHandle) jobHandle).getTimerJobInstance() );
        } catch (ClassCastException e) {
            // do nothing in case ProcessJobContext was not given
        }
        boolean removed =  this.scheduler.remove( (Runnable) ((GlobalJDKJobHandle) jobHandle).getFuture() );
        return removed;       
    }
    
    @Override
    public void internalSchedule(TimerJobInstance timerJobInstance) {
        if (scheduler.isShutdown()) {
            return;
        }
        Date date = timerJobInstance.getTrigger().hasNextFireTime();
        Callable<Void> item = (Callable<Void>) timerJobInstance;

        GlobalJDKJobHandle jobHandle = (GlobalJDKJobHandle) timerJobInstance.getJobHandle();
        long then = date.getTime();
        long now = System.currentTimeMillis();
        ScheduledFuture<Void> future = null;
        if ( then >= now ) {
            future = scheduler.schedule( new RetriggerCallable(scheduler, item),
                                         then - now,
                                         TimeUnit.MILLISECONDS );
        } else {
            future = scheduler.schedule( new RetriggerCallable(scheduler, item),
                                         0,
                                         TimeUnit.MILLISECONDS );
        }

        jobHandle.setFuture( future );
        globalTimerService.getTimerJobFactoryManager().addTimerJobInstance( timerJobInstance );
    }
    
    public static class GlobalJDKJobHandle extends GlobalJobHandle implements Serializable {
    
        private static final long     serialVersionUID = 510l;
    
        private transient ScheduledFuture<Void> future;       
    
        public GlobalJDKJobHandle(long id) {
            super(id);
        }
    
        public ScheduledFuture<Void> getFuture() {
            return future;
        }
    
        public void setFuture(ScheduledFuture<Void> future) {
            this.future = future;
        }    
    
    }

    @Override
    public JobHandle buildJobHandleForContext(NamedJobContext ctx) {
        // this is in memory scheduler and the building of context is required for permanent ScueduleService only
        return null;
    }


    @Override
    public boolean isTransactional() {
        return false;
    }


    @Override
    public void setInterceptor(SchedulerServiceInterceptor interceptor) {
        this.interceptor = interceptor;        
    }

	@Override
	public boolean retryEnabled() {
		return false;
	}


	@Override
	public boolean isValid(GlobalJobHandle jobHandle) {
		
		return true;
	}
	
	private static class RetriggerCallable implements Callable<Void> {

	    private Callable<Void> delegate;
	    private ScheduledThreadPoolExecutor scheduler;
	    
	    private int retries = 0;
	    
	    RetriggerCallable(ScheduledThreadPoolExecutor scheduler, Callable<Void> delegate) {
	        this.scheduler = scheduler;
	        this.delegate = delegate;	        
	    }
        @Override
        public Void call() throws Exception {
            try {
                this.delegate.call();
                return null;
            } catch (Exception e) {
                GlobalJDKJobHandle jobHandle = (GlobalJDKJobHandle) ((TimerJobInstance)this.delegate).getJobHandle();
                if (retries < FAILED_JOB_RETRIES) {                                                       
                    ScheduledFuture<Void> future = this.scheduler.schedule( this,
                                                     FAILED_JOB_DELAY,
                                                     TimeUnit.MILLISECONDS );
                    jobHandle.setFuture( future );
                    retries++;
                } else {
                    logger.error("Timer execution failed {} times in a roll, unscheduling ({})", FAILED_JOB_RETRIES, jobHandle);                    
                }
                throw e;
            }
        }
	    
	}
}
