/***********************************************************************************
 * @author  John Miller
 * @version 1.0
 * @date    Sat Aug 23 13:21:52 EDT 2014
 */

package transj;

import java.util.List;

import static java.lang.System.out;
import static java.util.Arrays.asList;

import static transj.Database.data;
import static transj.Database.ltab;

/***********************************************************************************
 * Abstract representation of a database as a collection of data objects and a
 * lock table.
 */
class Database
{
    /** the lock table to control concurrent access to the database
     */
    final static LockTable ltab = new LockTable ();

    /** the abstract database representation (an array of double objects)
     */
    final static double [] data = new double [100];

} // Database class


/***********************************************************************************
 * This class models database transactions.
 */
class Transaction extends Thread implements ReadWrite
{
    private final int      tid;       // the transaction identifier
    private final Schedule s;         // the schedule of read/write operations making up the transaction

    /*******************************************************************************
     * Construct a transaction object.
     * @param tid  the transaction identifier
     * @param s    the schedule of read/write operations making up the transaction
     */
    public Transaction (int tid_, Schedule s_)
    {
        tid = tid_;
        s   = s_;
    } // constructor

    /*******************************************************************************
     * Run the transaction: begin, reads/writes, commit.
     */
    public void run ()
    {
        double value = 0.0;
        begin ();
        for (Op op : s.get ()) {
            if (op.typ == r) {
                ltab.rl (tid, op.oid); value = read (op.oid);
            } else {
                ltab.wl (tid, op.oid); write (op.oid, value + 1.0);
            } // if
        } // for
        for (Op op : s.get ()) ltab.ul (op.tid, op.oid);
        commit ();
    } // run

    /*******************************************************************************
     * Begin this transaction.
     */
    public void begin ()
    {
        try { Thread.sleep (5); } catch (InterruptedException ex) {}
        out.println ("begin transaction " + tid);
    } // begin

    /*******************************************************************************
     * Read data object oid.
     * @param oid  the database object
     */
    public double read (int oid)
    {
        try { Thread.sleep (10); } catch (InterruptedException ex) {}
        double value = data[oid];
        out.println ("read " + tid + " ( " + oid + " ) value = " + value);
        return value;
    } // read

    /*******************************************************************************
     * Write data object oid.
     * @param oid  the database object
     */
    public void write (int oid, double value)
    {
        try { Thread.sleep (15); } catch (InterruptedException ex) {}
        out.println ("write " + tid + " ( " + oid + " ) value = " + value);
        data[oid] = value;
    } // write

    /*******************************************************************************
     * Commit this transaction.
     */
    public void commit ()
    {
        try { Thread.sleep (20); } catch (InterruptedException ex) {}
        out.println ("commit transaction " + tid);
    } // commit

    /*******************************************************************************
     * Test the Transaction class by running several concurrent transactions/threads.
     */
    public static void main (String [] args)
    {
        out.println ("Test Transactions");
        List <Op> list1 = asList (new Op (w, 1, 0), new Op (w, 1, 1));
        Transaction t1  = new Transaction (1, new Schedule (list1));
        List <Op> list2 = asList (new Op (w, 2, 0), new Op (w, 2, 1));
        Transaction t2  = new Transaction (2, new Schedule (list2));

        t1.start ();
        t2.start ();
    } // main

} // Transaction class