/*******************************************************************************
 * Copyright (c) 2014, 2016 Association for Decentralized Information Management
 * in Industry THTH ry.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     VTT Technical Research Centre of Finland - initial API and implementation
 *******************************************************************************/
package org.simantics.r.scl;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Semaphore;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;

import org.rosuda.REngine.Rserve.RConnection;
import org.rosuda.REngine.Rserve.RserveException;
import org.simantics.r.scl.variable.RNodeManager;
import org.simantics.scl.runtime.SCLContext;
import org.simantics.scl.runtime.function.Function;
import org.simantics.scl.runtime.tuple.Tuple0;
import org.simantics.simulator.variable.NodeManager;
import org.simantics.simulator.variable.Realm;

public class RSession implements Realm {
    public static final String R = "r";
    
    RConnection connection;
    String id;
    Thread executorThread;
    ExecutorService executor = Executors.newSingleThreadExecutor(new ThreadFactory() {
        @Override
        public Thread newThread(Runnable r) {
            executorThread = new Thread(r);
            return executorThread;
        }
    });
    
    Semaphore beginSyncExec = new Semaphore(0);
    Semaphore endSyncExec = new Semaphore(0);
    
    RNodeManager nodeManager;
    
    Runnable scheduleSyncExec = new Runnable() {
        @Override
        public void run() {
            beginSyncExec.release();
            try {
                endSyncExec.acquire();
            } catch (InterruptedException e) {
            }
        }
    };
    
    RSession(RConnection connection, String id) {
        this.connection = connection;
        this.id = id;
        this.nodeManager = new RNodeManager(this);
    }

    public String getId() {
        return id;
    }
    
    public RConnection getConnection() {
        return connection;
    }
    
    public Thread getThread() {
        return executorThread;
    }
    
    @SuppressWarnings({ "rawtypes", "unchecked" })
    public Object syncExec(Function fun) throws RserveException, InterruptedException {
        executor.execute(scheduleSyncExec);
        
        SCLContext context = SCLContext.getCurrent();
        RConnection oldConnection = (RConnection)context.put(R, connection);
        
        try {
            beginSyncExec.acquire();
            Thread oldThread = executorThread;
            executorThread = Thread.currentThread();
            try {
                return fun.apply(Tuple0.INSTANCE);
            } finally {
                executorThread = oldThread;
                endSyncExec.release();
            }
        } finally {
            context.put(R, oldConnection);
        }
    }
    
    @SuppressWarnings("rawtypes")
    public void asyncExec(final Function fun) {
        executor.execute(new Runnable() {
            @SuppressWarnings("unchecked")
            @Override
            public void run() {
                SCLContext context = SCLContext.getCurrent();
                context.put(R, connection);
                fun.apply(Tuple0.INSTANCE);
            }
        });
    }

    @Override
    public void syncExec(Runnable runnable) throws InterruptedException {
        executor.execute(scheduleSyncExec);
        
        beginSyncExec.acquire();
        Thread oldThread = executorThread;
        executorThread = Thread.currentThread();
        try {
            runnable.run();
        } finally {
            executorThread = oldThread;
            endSyncExec.release();
        }
    }

    @Override
    public void asyncExec(Runnable runnable) {
        executor.execute(runnable);
    }
    
    public void refreshVariables() {
        nodeManager.refreshVariables();
    }
    
    public void refreshVariablesSync() {
        nodeManager.refreshVariablesSync();
    }

    public void close() {
        RSessionManager.CONNECTIONS.remove(id);
        executor.shutdown();
        try {
            executor.awaitTermination(500L, TimeUnit.MILLISECONDS);
        } catch (InterruptedException e) {
        }
        connection.close();
    }

    public NodeManager getNodeManager() {
        return nodeManager;
    }
}