// Copyright (c) 2004, 2020, Oracle and/or its affiliates. All rights reserved.
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License, version 2.0, as
// published by the Free Software Foundation.
//
// This program is also distributed with certain software (including
// but not limited to OpenSSL) that is licensed under separate terms,
// as designated in a particular file or component or in included license
// documentation.  The authors of MySQL hereby grant you an
// additional permission to link the program and your derivative works
// with the separately licensed software that they have included with
// MySQL.
//
// Without limiting anything contained in the foregoing, this file,
// which is part of MySQL Connector/NET, is also subject to the
// Universal FOSS Exception, version 1.0, a copy of which can be found at
// http://oss.oracle.com/licenses/universal-foss-exception.
//
// This program 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 General Public License, version 2.0, for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software Foundation, Inc.,
// 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA

using System;
using System.Transactions;
using System.Collections;
using System.Collections.Generic;
using System.Data;
using System.Data.Common;
using System.Threading;

namespace MySql.Data.MySqlClient
{
    /// <summary>
    /// Represents a single(not nested) TransactionScope
    /// </summary>
    internal class MySqlTransactionScope
    {
        public MySqlConnection connection;
        public Transaction baseTransaction;
        public MySqlTransaction simpleTransaction;
        public int rollbackThreadId;

        public MySqlTransactionScope(MySqlConnection con, Transaction trans,
            MySqlTransaction simpleTransaction)
        {
            this.connection = con;
            this.baseTransaction = trans;
            this.simpleTransaction = simpleTransaction;
        }

        public void Rollback(SinglePhaseEnlistment singlePhaseEnlistment)
        {
            // prevent commands in main thread to run concurrently
            Driver driver = this.connection.driver;
            lock (driver)
            {
                this.rollbackThreadId = Thread.CurrentThread.ManagedThreadId;
                while (this.connection.Reader != null)
                {
                    // wait for reader to finish. Maybe we should not wait 
                    // forever and cancel it after some time?
                    System.Threading.Thread.Sleep(100);
                }

                this.simpleTransaction.Rollback();
                singlePhaseEnlistment.Aborted();
                DriverTransactionManager.RemoveDriverInTransaction(this.baseTransaction);

                driver.currentTransaction = null;

                if (this.connection.State == ConnectionState.Closed)
                {
                    this.connection.CloseFully();
                }

                this.rollbackThreadId = 0;
            }
        }

        public void SinglePhaseCommit(SinglePhaseEnlistment singlePhaseEnlistment)
        {
            this.simpleTransaction.Commit();
            singlePhaseEnlistment.Committed();
            DriverTransactionManager.RemoveDriverInTransaction(this.baseTransaction);
            this.connection.driver.currentTransaction = null;

            if (this.connection.State == ConnectionState.Closed)
            {
                this.connection.CloseFully();
            }
        }
    }

    internal sealed class MySqlPromotableTransaction : IPromotableSinglePhaseNotification, ITransactionPromoter
    {
        // Per-thread stack to manage nested transaction scopes
        [ThreadStatic]
        static Stack<MySqlTransactionScope> globalScopeStack;

        MySqlConnection connection;
        Transaction baseTransaction;
        Stack<MySqlTransactionScope> scopeStack;


        public MySqlPromotableTransaction(MySqlConnection connection, Transaction baseTransaction)
        {
            this.connection = connection;
            this.baseTransaction = baseTransaction;
        }

        public Transaction BaseTransaction
        {
            get
            {
                if (this.scopeStack.Count > 0)
                {
                    return this.scopeStack.Peek().baseTransaction;
                }
                else
                {
                    return null;
                }
            }
        }

        public bool InRollback
        {
            get
            {
                if (this.scopeStack.Count > 0)
                {
                    MySqlTransactionScope currentScope = this.scopeStack.Peek();
                    if (currentScope.rollbackThreadId == Thread.CurrentThread.ManagedThreadId)
                    {
                        return true;
                    }
                }

                return false;
            }
        }

        void IPromotableSinglePhaseNotification.Initialize()
        {
            string valueName = Enum.GetName(
            typeof(System.Transactions.IsolationLevel), this.baseTransaction.IsolationLevel);
            System.Data.IsolationLevel dataLevel = (System.Data.IsolationLevel)Enum.Parse(
                 typeof(System.Data.IsolationLevel), valueName);
            MySqlTransaction simpleTransaction = this.connection.BeginTransaction(dataLevel, "SESSION");

            // We need to save the per-thread scope stack locally.
            // We cannot always use thread static variable in rollback: when scope
            // times out, rollback is issued by another thread.
            if (globalScopeStack == null)
            {
                globalScopeStack = new Stack<MySqlTransactionScope>();
            }

            this.scopeStack = globalScopeStack;
            this.scopeStack.Push(new MySqlTransactionScope(this.connection, this.baseTransaction,
               simpleTransaction));
        }

        void IPromotableSinglePhaseNotification.Rollback(SinglePhaseEnlistment singlePhaseEnlistment)
        {

            MySqlTransactionScope current = this.scopeStack.Peek();
            current.Rollback(singlePhaseEnlistment);
            this.scopeStack.Pop();
        }

        void IPromotableSinglePhaseNotification.SinglePhaseCommit(SinglePhaseEnlistment singlePhaseEnlistment)
        {
            this.scopeStack.Pop().SinglePhaseCommit(singlePhaseEnlistment);
        }

        byte[] ITransactionPromoter.Promote()
        {
            throw new NotSupportedException();
        }
    }

    internal class DriverTransactionManager
    {
        private static Hashtable driversInUse = new Hashtable();

        public static Driver GetDriverInTransaction(Transaction transaction)
        {
            lock (driversInUse.SyncRoot)
            {
                Driver d = (Driver)driversInUse[transaction.GetHashCode()];
                return d;
            }
        }

        public static void SetDriverInTransaction(Driver driver)
        {
            lock (driversInUse.SyncRoot)
            {
                driversInUse[driver.currentTransaction.BaseTransaction.GetHashCode()] = driver;
            }
        }

        public static void RemoveDriverInTransaction(Transaction transaction)
        {
            lock (driversInUse.SyncRoot)
            {
                driversInUse.Remove(transaction.GetHashCode());
            }
        }
    }
}