/**
 *  Generic example of master/worker program.
 *
 *  "Tasks" just consist of sleeping for a specified time; times to wait are
 *  generatedly randomly from 1 to a specified maximum.
 *
 *  Command-line arguments:  total tasks, maximum task time, seed
 *  (optional) "--verbose" for verbose output
 *
 *  Master process for client/server version using RMI.
 *
 *  This version does not try to measure total execution time; it's not clear 
 *  that would be meaningful.
 *
 *  RMI specifics in this example are loosely based on an example from 
 *  Sun's online tutorial.
 */
package csci3366.sample.masterworker.rmi;

import java.net.MalformedURLException;
import java.rmi.Naming;
import java.rmi.NotBoundException;
import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.server.UnicastRemoteObject;
import java.util.List;

import csci3366.sample.masterworker.FakeTasks;

public class Master implements MasterInterface {

    /* variables */

    private int numTasks;
    private int maxTaskTime;
    private int seed;
    private boolean verbose = false;

    private FakeTasks.SynchTaskQueue taskQueue;

    private int nextWorker = 0;
    private int activeWorkers = 0;

    private int totalTaskTime = 0;
    private int maxWorkerTotalTaskTime;
    private int minWorkerTotalTaskTime;

    /* MasterInterface methods */

    /** Register new worker (returns worker ID, or -1 if no more tasks). */
    public int registerNewWorker(WorkerInterface w)
        throws RemoteException
    {
        int workerID = addWorker();
        if (verbose) {
            System.out.printf("connection from %s, worker %d\n", 
                    w.getHostName(), workerID);
        }
        return workerID;
    }

    /** Get task from queue (null if none).  */
    public FakeTasks.Task getTask(WorkerInterface w) 
        throws RemoteException
    {
        if (verbose) {
            System.out.printf("(worker %d) requested task\n", w.getID());
        }
        return taskQueue.get();
    }

    /** Accept result for single task from worker. */
    public void reportResult(WorkerInterface w, 
            FakeTasks.Task t, FakeTasks.TaskResult tr) 
        throws RemoteException
    {
        if (verbose) {
            System.out.printf("(worker %d) sent result:  %s\n",
                w.getID(), FakeTasks.toString(t, tr));
        }
    }

    /** Accept summary result for worker. */
    public void reportSummaryResults(WorkerInterface w,
        int numTasks, int totalTaskTime) 
        throws RemoteException
    {
        System.out.printf(
                "worker %d number of tasks = %d, total task time = %d\n", 
                w.getID(), numTasks, totalTaskTime);
        updateGlobals(totalTaskTime);
        removeWorker();
    }

    /* other methods */

    /**
     * Main method.
     */
    public static void main(String[] args) {

        String usageMessage = 
            "parameters:  numTasks maxTaskTime seed [--verbose]";

        int numTasks = 0;
        int maxTaskTime = 0;
        int seed = 0;
        boolean verbose = false;

        /* process command-line arguments */
        if (args.length < 3) {
            System.err.println(usageMessage); System.exit(1);
        }
        try {
            numTasks = Integer.parseInt(args[0]);
            maxTaskTime = Integer.parseInt(args[1]);
            seed = Integer.parseInt(args[2]);
        }
        catch (NumberFormatException e) {
            System.err.println(usageMessage); System.exit(1);
        }
        if (args.length > 3) {
            if (args[3].equals("--verbose"))
                verbose = true;
            else {
                System.err.println(usageMessage); System.exit(1);
            }
        }

        /* do processing */
        Master m = null;
        try {
            m = new Master(numTasks, maxTaskTime, seed, verbose);
            m.go();
        }
        /* FIXME?:  improve error handling? */
        catch (Exception e) {
            System.err.println("error in master:\n\t" + e);
        }

        /* 
         * shut down:  be sure there are no remaining references to
         * remote objects, since otherwise RMI keeps process(es) running
         */
        if (m != null) { m.cleanupRMI(); }
        m = null;
    }

    /** Constructor. */
    public Master(int numTasks_, int maxTaskTime_, int seed_, boolean verbose_) 
    {
        numTasks = numTasks_;
        maxTaskTime = maxTaskTime_;
        seed = seed_;
        verbose = verbose_;

        /* initialize variables */
        maxWorkerTotalTaskTime = 0;
        minWorkerTotalTaskTime = maxTaskTime * numTasks;

        taskQueue = new FakeTasks.SynchTaskQueue(
                FakeTasks.randomTasks(numTasks, maxTaskTime, seed));
    }

    /** Perform processing. */
    public void go() 
        throws MalformedURLException, NotBoundException, RemoteException
    {
        /* create registry (so no need to start separately) */
        LocateRegistry.createRegistry(REGISTRY_PORT);
        /* register self as ready for remote calls */
        MasterInterface stub = 
            (MasterInterface) UnicastRemoteObject.exportObject(this, 0);
        LocateRegistry.getRegistry(REGISTRY_PORT).rebind(BINDING_NAME, stub);
        if (verbose) {
            System.out.println("waiting for workers");
        }

        /* wait for all tasks to be assigned */
        synchronized (taskQueue) {
            while (!taskQueue.isEmpty()) {
                try {
                    taskQueue.wait();
                }
                catch (InterruptedException e) {
                    System.err.println("this should not happen");
                    e.printStackTrace();
                }
            }
        }
        if (verbose) {
            System.out.println("all tasks assigned");
        }

        /* wait for all workers to report results */
        synchronized (this) {
            while (activeWorkers > 0) {
                try {
                    wait();
                }
                catch (InterruptedException e) {
                    System.err.println("this should not happen");
                    e.printStackTrace();
                }
            }
        }

        /* print summary information */
        System.out.printf("\nRMI client/server version\n");
        System.out.printf("number of workers = %d\n", nextWorker);
        System.out.printf("number of tasks = %d\n", numTasks);
        System.out.printf("max task time = %d\n", maxTaskTime);
        System.out.printf("total task time = %d\n", totalTaskTime);
        System.out.printf("total task time in workers ranges from %d to %d\n",
                minWorkerTotalTaskTime, maxWorkerTotalTaskTime);
    }

    /** 
     * Clean up all RMI-related resources.
     * (If references still exist to remote objects, RMI keeps process(es)
     * running.)
     */
    public void cleanupRMI() {
        /* FIXME?:  improve error handling? */

        /* unregister self */
        try {
            UnicastRemoteObject.unexportObject(this, false);
        }
        catch (Exception e) {
            System.err.println("error shutting down master:\n\t" + e);
        }
        try {
            LocateRegistry.getRegistry(REGISTRY_PORT).unbind(BINDING_NAME);
        }
        catch (Exception e) {
            System.err.println("error shutting down master:\n\t" + e);
        }
    }

    /**
     * Add worker and return ID (thread-safe).
     */
    private synchronized int addWorker() {
        int workerID = nextWorker++;
        ++activeWorkers;
        return workerID;
    }

    /**
     * Update globals when worker finishes (thread-safe).
     */
    private synchronized void updateGlobals(int workerTotalTaskTime) {
        maxWorkerTotalTaskTime =
            Math.max(maxWorkerTotalTaskTime, workerTotalTaskTime);
        minWorkerTotalTaskTime =
            Math.min(minWorkerTotalTaskTime, workerTotalTaskTime);
        totalTaskTime += workerTotalTaskTime;
    }

    /**
     * Remove worker (thread-safe).
     */
    private synchronized void removeWorker() {
        if (--activeWorkers == 0) {
            notifyAll();
        }
    }

}