// created on 17/11/2002 at 19:04

// Npgsql.NpgsqlTransaction.cs
//
// Author:
//	Francisco Jr. (fxjrlists@yahoo.com.br)
//
//	Copyright (C) 2002 The Npgsql Development Team
//	npgsql-general@gborg.postgresql.org
//	http://gborg.postgresql.org/project/npgsql/projdisplay.php
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA


using System;
using System.Text;
using System.Data;


namespace Npgsql
{
    /// <summary>

    /// Represents a transaction to be made in a PostgreSQL database. This class cannot be inherited.

    /// </summary>
    public sealed class NpgsqlTransaction : MarshalByRefObject, IDbTransaction
    {

        private static readonly String CLASSNAME = "NpgsqlTransaction";

        private NpgsqlConnection	_conn				= null;
        private IsolationLevel		_isolation	= IsolationLevel.ReadCommitted;
        private bool _disposing = false;
        private System.Resources.ResourceManager resman;




        internal NpgsqlTransaction(NpgsqlConnection conn) : this(conn, IsolationLevel.ReadCommitted)
        {
        }

        internal NpgsqlTransaction(NpgsqlConnection conn, IsolationLevel isolation)
        {
            resman = new System.Resources.ResourceManager(this.GetType());

            NpgsqlEventLog.LogMethodEnter(LogLevel.Debug, CLASSNAME, CLASSNAME);
            if ((isolation != IsolationLevel.ReadCommitted) &&
                    (isolation != IsolationLevel.Serializable))
                throw new ArgumentException(resman.GetString("Exception_UnsopportedIsolationLevel"), "isolation");

            _conn = conn;
            _isolation = isolation;

            StringBuilder commandText = new StringBuilder("SET TRANSACTION ISOLATION LEVEL ");

            if (isolation == IsolationLevel.ReadCommitted)
                commandText.Append("READ COMMITTED");
            else
                commandText.Append("SERIALIZABLE");

            commandText.Append("; BEGIN");


            NpgsqlCommand command = new NpgsqlCommand(commandText.ToString(), conn);
            command.ExecuteNonQuery();
            _conn.InTransaction = true;

        }

        /// <summary>
        /// Gets the <see cref="Npgsql.NpgsqlConnection">NpgsqlConnection</see>
        /// object associated with the transaction, or a null reference if the
        /// transaction is no longer valid.
        /// </summary>
        /// <value>The <see cref="Npgsql.NpgsqlConnection">NpgsqlConnection</see>
        /// object associated with the transaction.</value>
        public NpgsqlConnection Connection
        {
            get
            {
                return _conn;
            }

        }


        IDbConnection IDbTransaction.Connection
        {
            get
            {
                return Connection;
            }
        }

        /// <summary>
        /// Specifies the <see cref="System.Data.IsolationLevel">IsolationLevel</see> for this transaction.
        /// </summary>
        /// <value>The <see cref="System.Data.IsolationLevel">IsolationLevel</see> for this transaction.
        /// The default is <b>ReadCommitted</b>.</value>
        public IsolationLevel IsolationLevel
        {
            get
            {
                return _isolation;
            }
        }

        /// <summary>
        /// Releases the unmanaged resources used by the
        /// <see cref="Npgsql.NpgsqlTransaction">NpgsqlTransaction</see>
        /// and optionally releases the managed resources.
        /// </summary>
        public void Dispose()
        {
            this.Dispose(true);
        }

        private void Dispose(bool disposing)
        {
            if(disposing && this._conn != null)
            {
                this._disposing = true;
                if (_conn.InTransaction)
                    this.Rollback();
            }
        }

        /// <summary>
        /// Commits the database transaction.
        /// </summary>
        public void Commit()
        {
            NpgsqlEventLog.LogMethodEnter(LogLevel.Debug, CLASSNAME, "Commit");
            NpgsqlCommand command = new NpgsqlCommand("COMMIT", _conn);
            command.ExecuteNonQuery();
            _conn.InTransaction = false;
        }

        /// <summary>
        /// Rolls back a transaction from a pending state.
        /// </summary>
        public void Rollback()
        {
            NpgsqlEventLog.LogMethodEnter(LogLevel.Debug, CLASSNAME, "Rollback");
            NpgsqlCommand command = new NpgsqlCommand("ROLLBACK", _conn);
            command.ExecuteNonQuery();
            _conn.InTransaction = false;
        }

        internal bool Disposing{
            get
            {
                return _disposing;
            }
        }
    }
}