// 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
//
// Permission to use, copy, modify, and distribute this software and its
// documentation for any purpose, without fee, and without a written
// agreement is hereby granted, provided that the above copyright notice
// and this paragraph and the following two paragraphs appear in all copies.
// 
// IN NO EVENT SHALL THE NPGSQL DEVELOPMENT TEAM BE LIABLE TO ANY PARTY
// FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES,
// INCLUDING LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
// DOCUMENTATION, EVEN IF THE NPGSQL DEVELOPMENT TEAM HAS BEEN ADVISED OF
// THE POSSIBILITY OF SUCH DAMAGE.
// 
// THE NPGSQL DEVELOPMENT TEAM SPECIFICALLY DISCLAIMS ANY WARRANTIES,
// INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
// AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
// ON AN "AS IS" BASIS, AND THE NPGSQL DEVELOPMENT TEAM HAS NO OBLIGATIONS
// TO PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.


using System;
using System.Data;
using System.Data.Common;
using System.Reflection;
using System.Resources;
using System.Text;
using System.Threading;

namespace Npgsql
{
    /// <summary>
    /// Represents a transaction to be made in a PostgreSQL database. This class cannot be inherited.
    /// </summary>
    public sealed class NpgsqlTransaction : DbTransaction
    {
        private static readonly String CLASSNAME = MethodBase.GetCurrentMethod().DeclaringType.Name;
        private static readonly ResourceManager resman = new ResourceManager(MethodBase.GetCurrentMethod().DeclaringType);

        private NpgsqlConnection _conn = null;
        private readonly IsolationLevel _isolation = IsolationLevel.ReadCommitted;
        private bool _disposed = false;

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

        internal NpgsqlTransaction(NpgsqlConnection conn, IsolationLevel isolation)
        {
            NpgsqlEventLog.LogMethodEnter(LogLevel.Debug, CLASSNAME, CLASSNAME);

            _conn = conn;
            _isolation = isolation;

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

            if (isolation == IsolationLevel.RepeatableRead)
            {
            	commandText.Append("REPEATABLE READ");
            }
            else if ((isolation == IsolationLevel.Serializable) ||
                (isolation == IsolationLevel.Snapshot))
            {
                commandText.Append("SERIALIZABLE");
            }
            else
            {
                // Set isolation level default to read committed.
                _isolation = IsolationLevel.ReadCommitted;
                commandText.Append("READ COMMITTED");
            }

            commandText.Append(";");

            NpgsqlCommand command = new NpgsqlCommand(commandText.ToString(), conn.Connector);
            command.ExecuteBlind();
            _conn.Connector.Transaction = this;
        }

        /// <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 new NpgsqlConnection Connection
        {
            get { return _conn; }
        }

        protected override DbConnection DbConnection
        {
            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 override IsolationLevel IsolationLevel
        {
            get
            {
                if (_conn == null)
                {
                    throw new InvalidOperationException(resman.GetString("Exception_NoTransaction"));
                }

                return _isolation;
            }
        }

        protected override void Dispose(bool disposing)
        {
            if (disposing && this._conn != null)
            {
                if (_conn.Connector.Transaction != null)
                {
                    if ((Thread.CurrentThread.ThreadState & (ThreadState.Aborted | ThreadState.AbortRequested)) != 0)
                    {
                        // can't count on Rollback working if the thread has been aborted
                        // need to copy since Cancel will set it to null
                        NpgsqlConnection conn = _conn;
                        Cancel();
                        // must close connection since transaction hasn't been rolled back
                        conn.Close();
                    }
                    else
                    {
                        this.Rollback();
                    }
                }

                this._disposed = true;
            }
            base.Dispose(disposing);
        }

        /// <summary>
        /// Commits the database transaction.
        /// </summary>
        public override void Commit()
        {
            CheckDisposed();

            if (_conn == null)
            {
                throw new InvalidOperationException(resman.GetString("Exception_NoTransaction"));
            }

            NpgsqlEventLog.LogMethodEnter(LogLevel.Debug, CLASSNAME, "Commit");

            NpgsqlCommand command = new NpgsqlCommand("COMMIT", _conn.Connector);
            command.ExecuteBlind();
            _conn.Connector.Transaction = null;
            _conn = null;
        }

        /// <summary>
        /// Rolls back a transaction from a pending state.
        /// </summary>
        public override void Rollback()
        {
            CheckDisposed();

            if (_conn == null)
            {
                throw new InvalidOperationException(resman.GetString("Exception_NoTransaction"));
            }

            NpgsqlEventLog.LogMethodEnter(LogLevel.Debug, CLASSNAME, "Rollback");

            NpgsqlCommand command = new NpgsqlCommand("ROLLBACK", _conn.Connector);
            command.ExecuteBlind();
            _conn.Connector.Transaction = null;
            _conn = null;
        }
        
        /// <summary>
        /// Rolls back a transaction from a pending savepoint state.
        /// </summary>
        public void Rollback(String savePointName)
        {
            
            CheckDisposed();

            if (_conn == null)
            {
                throw new InvalidOperationException(resman.GetString("Exception_NoTransaction"));
            }
            
            if (!_conn.Connector.SupportsSavepoint)
            {
                throw new InvalidOperationException(resman.GetString("Exception_SavePointNotSupported"));
            }
                
            
            
            if (savePointName.Contains(";"))
            {
                throw new InvalidOperationException(resman.GetString("Exception_SavePointWithSemicolon"));
                      
            }
            
            
            NpgsqlCommand command = new NpgsqlCommand("ROLLBACK TO SAVEPOINT " + savePointName, _conn.Connector);
            command.ExecuteBlind();
            
        }
        
        /// <summary>
        /// Creates a transaction save point.
        /// </summary>

        public void Save(String savePointName)
        {
            
            CheckDisposed();

            if (_conn == null)
            {
                throw new InvalidOperationException(resman.GetString("Exception_NoTransaction"));
            }
            
            if (!_conn.Connector.SupportsSavepoint)
            {
                throw new InvalidOperationException(resman.GetString("Exception_SavePointNotSupported"));
            }
                
            
            if (savePointName.Contains(";"))
            {
                throw new InvalidOperationException(resman.GetString("Exception_SavePointWithSemicolon"));
                      
            }
            
            
            NpgsqlCommand command = new NpgsqlCommand("SAVEPOINT " + savePointName, _conn.Connector);
            command.ExecuteBlind();
            
        }
        /// <summary>
        /// Cancel the transaction without telling the backend about it.  This is
        /// used to make the transaction go away when closing a connection.
        /// </summary>
        internal void Cancel()
        {
            CheckDisposed();

            if (_conn != null)
            {
                _conn.Connector.Transaction = null;
                _conn = null;
            }
        }

        internal bool Disposed
        {
            get { return _disposed; }
        }


        internal void CheckDisposed()
        {
            if (_disposed)
            {
                throw new ObjectDisposedException(CLASSNAME);
            }
        }
    }
}