package lecteursRedacteurs;


/**
 * Database.java
 *
 * This class contains the methods the readers and writers will use
 * to coordinate access to the database. Access is coordinated using Java synchronization.
 *
 *
 */

public class DataBase {

    public DataBase() {
        this.lecteurCount = 0;
        this.dbLectures = false;
        this.dbEcritures = false;
        this.data = new Data(12,13 );
    }

    // readers and writers will call this to nap
    public static void napping() {
        int sleepTime = (int) (NAP_TIME * Math.random() );
        try { Thread.sleep(sleepTime*1000); }
        catch(InterruptedException e) {}
    }

    //
    public String effectiveLectures() {
        return "["+data.getElt1()+","+data.getElt2()+"]";
    }

    public void effectiveEcritures(int elt1, int elt2) {
        data.setElt1(elt1);
        Thread.yield(); // to force problems in case not well synchronized
        data.setElt2(elt2);
    }

    // reader will call this when they start reading
    public synchronized int startRead() {
        while (dbEcritures) {
            try { wait(); }
            catch(InterruptedException e) {}
        }

        ++lecteurCount;

        // if I am the first reader tell all others
        // that the database is being read
        if (lecteurCount == 1)
            dbLectures = true;

        return lecteurCount;
    }

    // reader will call this when they finish reading
    public synchronized int endRead() {
        --lecteurCount;

        // if I am the last reader tell all others
        // that the database is no longer being read
        if (lecteurCount == 0)
            dbLectures = false;

        notifyAll();

        System.out.println("Lecteur Count = " + lecteurCount);

        return lecteurCount;
    }

    // writer will call this when they start writing
    public synchronized void startWrite() {
        while (dbLectures  || dbEcritures ) {
            try { wait(); }
            catch(InterruptedException e) {}
        }

        // once there are either no readers or writers
        // indicate that the database is being written
        dbEcritures = true;
    }

    // writer will call this when they start writing
    public synchronized void endWrite() {
        dbEcritures = false;

        notifyAll();
    }

    // the number of active readers
    private int lecteurCount;

    // flags to indicate whether the database is
    // being read or written
    private boolean dbLectures;
    private boolean dbEcritures;
    private Data data;

    private static final int NAP_TIME = 5;

    class Data {
        int elt1, elt2;
        Data(int pairElt1, int pairElt2){
            elt1=pairElt1;
            elt2=pairElt2;
        }
        int getElt1() {
            return elt1;
        }
        int getElt2() {
            return elt2;
        }
        void setElt1(int elt1){
            this.elt1=elt1;
        }
        void setElt2(int elt2){
            this.elt2=elt2;
        }
    }
}