/*
 * Copyright (C) 2008-2012 TrinityCore <http://www.trinitycore.org/>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2 of the License, or (at your
 * option) any later version.
 *
 * 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 for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program. If not, see <http://www.gnu.org/licenses/>.
 */

#ifndef _DATABASEWORKERPOOL_H
#define _DATABASEWORKERPOOL_H

#include <ace/Thread_Mutex.h>

#include "Common.h"
#include "Callback.h"
#include "MySQLConnection.h"
#include "Transaction.h"
#include "DatabaseWorker.h"
#include "PreparedStatement.h"
#include "Log.h"
#include "QueryResult.h"
#include "QueryHolder.h"
#include "AdhocStatement.h"

class PingOperation : public SQLOperation
{
    /// Operation for idle delaythreads
    bool Execute()
    {
        if (m_conn->LockIfReady())
        {
            m_conn->Ping();
            m_conn->Unlock();
            return true;
        }

        return false;
    }
};

template <class T>
class DatabaseWorkerPool
{
    public:
        /* Activity state */
        DatabaseWorkerPool() :
        m_queue(new ACE_Activation_Queue(new ACE_Message_Queue<ACE_MT_SYNCH>))
        {
            memset(m_connectionCount, 0, sizeof(m_connectionCount));
            m_connections.resize(IDX_SIZE);

            WPFatal (mysql_thread_safe(), "Used MySQL library isn't thread-safe.");
        }

        ~DatabaseWorkerPool()
        {
        }

        bool Open(const std::string& infoString, uint8 async_threads, uint8 synch_threads)
        {
            bool res = true;
            m_connectionInfo = MySQLConnectionInfo(infoString);

            sLog->outSQLDriver("Opening databasepool '%s'. Async threads: %u, synch threads: %u", m_connectionInfo.database.c_str(), async_threads, synch_threads);

            /// Open asynchronous connections (delayed operations)
            m_connections[IDX_ASYNC].resize(async_threads);
            for (uint8 i = 0; i < async_threads; ++i)
            {
                T* t = new T(m_queue, m_connectionInfo);
                res &= t->Open();
                m_connections[IDX_ASYNC][i] = t;
                ++m_connectionCount[IDX_ASYNC];
            }

            /// Open synchronous connections (direct, blocking operations)
            m_connections[IDX_SYNCH].resize(synch_threads);
            for (uint8 i = 0; i < synch_threads; ++i)
            {
                T* t = new T(m_connectionInfo);
                res &= t->Open();
                m_connections[IDX_SYNCH][i] = t;
                ++m_connectionCount[IDX_SYNCH];
            }

            sLog->outSQLDriver("Databasepool opened successfully. %u total connections running.", (m_connectionCount[IDX_SYNCH] + m_connectionCount[IDX_ASYNC]));
            return res;
        }

        void Close()
        {
            sLog->outSQLDriver("Closing down databasepool '%s'.", m_connectionInfo.database.c_str());

            /// Shuts down delaythreads for this connection pool by underlying deactivate()
            m_queue->queue()->close();

            for (uint8 i = 0; i < m_connectionCount[IDX_ASYNC]; ++i)
            {
                /// TODO: Better way. probably should flip a boolean and check it on low level code before doing anything on the mysql ctx
                /// Now we just wait until m_queue gives the signal to the worker threads to stop
                T* t = m_connections[IDX_ASYNC][i];
                DatabaseWorker* worker = t->m_worker;
                worker->wait();
                delete worker;
                t->Close();
            }

            sLog->outSQLDriver("Asynchronous connections on databasepool '%s' terminated. Proceeding with synchronous connections.", m_connectionInfo.database.c_str());

            /// Shut down the synchronous connections
            for (uint8 i = 0; i < m_connectionCount[IDX_SYNCH]; ++i)
            {
                T* t = m_connections[IDX_SYNCH][i];
                //while (1)
                //    if (t->LockIfReady()) -- For some reason deadlocks us
                t->Close();
            }

            sLog->outSQLDriver("All connections on databasepool %s closed.", m_connectionInfo.database.c_str());
        }

        /**
            Delayed one-way statement methods.
        */

        //! Enqueues a one-way SQL operation in string format that will be executed asynchronously.
        void Execute(const char* sql)
        {
            if (!sql)
                return;

            BasicStatementTask* task = new BasicStatementTask(sql);
            Enqueue(task);
        }

        //! Enqueues a one-way SQL operation in string format -with variable args- that will be executed asynchronously.
        void PExecute(const char* sql, ...)
        {
            if (!sql)
                return;

            va_list ap;
            char szQuery[MAX_QUERY_LEN];
            va_start(ap, sql);
            vsnprintf(szQuery, MAX_QUERY_LEN, sql, ap);
            va_end(ap);

            Execute(szQuery);
        }

        //! Enqueues a one-way SQL operation in prepared statement format that will be executed asynchronously.
        //! Statement must be prepared with CONNECTION_ASYNC flag.
        void Execute(PreparedStatement* stmt)
        {
            PreparedStatementTask* task = new PreparedStatementTask(stmt);
            Enqueue(task);
        }

        /**
            Direct syncrhonous one-way statement methods.
        */

        //! Directly executes a one-way SQL operation in string format, that will block the calling thread until finished.
        void DirectExecute(const char* sql)
        {
            if (!sql)
                return;

            T* t = GetFreeConnection();
            t->Execute(sql);
            t->Unlock();
        }

        //! Directly executes a one-way SQL operation in string format -with variable args-, that will block the calling thread until finished.
        void DirectPExecute(const char* sql, ...)
        {
            if (!sql)
                return;

            va_list ap;
            char szQuery[MAX_QUERY_LEN];
            va_start(ap, sql);
            vsnprintf(szQuery, MAX_QUERY_LEN, sql, ap);
            va_end(ap);

            return DirectExecute(szQuery);
        }

        //! Directly executes a one-way SQL operation in prepared statement format, that will block the calling thread until finished.
        //! Statement must be prepared with the CONNECTION_SYNCH flag.
        void DirectExecute(PreparedStatement* stmt)
        {
            T* t = GetFreeConnection();
            t->Execute(stmt);
            t->Unlock();
        }

        /**
            Synchronous query (with resultset) methods.
        */

        //! Directly executes an SQL query in string format that will block the calling thread until finished.
        //! Returns reference counted auto pointer, no need for manual memory management in upper level code.
        QueryResult Query(const char* sql, MySQLConnection* conn = NULL)
        {
            if (!conn)
                conn = GetFreeConnection();

            ResultSet* result = conn->Query(sql);
            conn->Unlock();
            if (!result || !result->GetRowCount())
                return QueryResult(NULL);

            result->NextRow();
            return QueryResult(result);
        }

        //! Directly executes an SQL query in string format -with variable args- that will block the calling thread until finished.
        //! Returns reference counted auto pointer, no need for manual memory management in upper level code.
        QueryResult PQuery(const char* sql, MySQLConnection* conn, ...)
        {
            if (!sql)
                return QueryResult(NULL);

            va_list ap;
            char szQuery[MAX_QUERY_LEN];
            va_start(ap, sql);
            vsnprintf(szQuery, MAX_QUERY_LEN, sql, ap);
            va_end(ap);

            return Query(szQuery, conn);
        }

        //! Directly executes an SQL query in string format -with variable args- that will block the calling thread until finished.
        //! Returns reference counted auto pointer, no need for manual memory management in upper level code.
        QueryResult PQuery(const char* sql, ...)
        {
            if (!sql)
                return QueryResult(NULL);

            va_list ap;
            char szQuery[MAX_QUERY_LEN];
            va_start(ap, sql);
            vsnprintf(szQuery, MAX_QUERY_LEN, sql, ap);
            va_end(ap);

            return Query(szQuery);
        }

        //! Directly executes an SQL query in prepared format that will block the calling thread until finished.
        //! Returns reference counted auto pointer, no need for manual memory management in upper level code.
        //! Statement must be prepared with CONNECTION_SYNCH flag.
        PreparedQueryResult Query(PreparedStatement* stmt)
        {
            T* t = GetFreeConnection();
            PreparedResultSet* ret = t->Query(stmt);
            t->Unlock();

            if (!ret || !ret->GetRowCount())
                return PreparedQueryResult(NULL);

            return PreparedQueryResult(ret);
        }

        /**
            Asynchronous query (with resultset) methods.
        */

        //! Enqueues a query in string format that will set the value of the QueryResultFuture return object as soon as the query is executed.
        //! The return value is then processed in ProcessQueryCallback methods.
        QueryResultFuture AsyncQuery(const char* sql)
        {
            QueryResultFuture res;
            BasicStatementTask* task = new BasicStatementTask(sql, res);
            Enqueue(task);
            return res;         //! Actual return value has no use yet
        }

        //! Enqueues a query in string format -with variable args- that will set the value of the QueryResultFuture return object as soon as the query is executed.
        //! The return value is then processed in ProcessQueryCallback methods.
        QueryResultFuture AsyncPQuery(const char* sql, ...)
        {
            va_list ap;
            char szQuery[MAX_QUERY_LEN];
            va_start(ap, sql);
            vsnprintf(szQuery, MAX_QUERY_LEN, sql, ap);
            va_end(ap);

            return AsyncQuery(szQuery);
        }

        //! Enqueues a query in prepared format that will set the value of the PreparedQueryResultFuture return object as soon as the query is executed.
        //! The return value is then processed in ProcessQueryCallback methods.
        //! Statement must be prepared with CONNECTION_ASYNC flag.
        PreparedQueryResultFuture AsyncQuery(PreparedStatement* stmt)
        {
            PreparedQueryResultFuture res;
            PreparedStatementTask* task = new PreparedStatementTask(stmt, res);
            Enqueue(task);
            return res;
        }

        //! Enqueues a vector of SQL operations (can be both adhoc and prepared) that will set the value of the QueryResultHolderFuture
        //! return object as soon as the query is executed.
        //! The return value is then processed in ProcessQueryCallback methods.
        //! Any prepared statements added to this holder need to be prepared with the CONNECTION_ASYNC flag.
        QueryResultHolderFuture DelayQueryHolder(SQLQueryHolder* holder)
        {
            QueryResultHolderFuture res;
            SQLQueryHolderTask* task = new SQLQueryHolderTask(holder, res);
            Enqueue(task);
            return res;     //! Fool compiler, has no use yet
        }

        /**
            Transaction context methods.
        */

        //! Begins an automanaged transaction pointer that will automatically rollback if not commited. (Autocommit=0)
        SQLTransaction BeginTransaction()
        {
            return SQLTransaction(new Transaction);
        }

        //! Enqueues a collection of one-way SQL operations (can be both adhoc and prepared). The order in which these operations
        //! were appended to the transaction will be respected during execution.
        void CommitTransaction(SQLTransaction transaction)
        {
            if (sLog->GetSQLDriverQueryLogging())
            {
                switch (transaction->GetSize())
                {
                    case 0:
                        sLog->outSQLDriver("Transaction contains 0 queries. Not executing.");
                        return;
                    case 1:
                        sLog->outSQLDriver("Warning: Transaction only holds 1 query, consider removing Transaction context in code.");
                        break;
                    default:
                        break;
                }
            }

            Enqueue(new TransactionTask(transaction));
        }

        //! Directly executes a collection of one-way SQL operations (can be both adhoc and prepared). The order in which these operations
        //! were appended to the transaction will be respected during execution.
        void DirectCommitTransaction(SQLTransaction& transaction)
        {
            MySQLConnection* con = GetFreeConnection();
            if (con->ExecuteTransaction(transaction))
            {
                con->Unlock();      // OK, operation succesful
                return;
            }

            if (con->GetLastError() == 1213)
            {
                uint8 loopBreaker = 5;  // Handle MySQL Errno 1213 without extending deadlock to the core itself
                for (uint8 i = 0; i < loopBreaker; ++i)
                {
                    if (con->ExecuteTransaction(transaction))
                        break;
                }
            }

            // Clean up now.
            transaction->Cleanup();

            con->Unlock();
        }

        //! Method used to execute prepared statements in a diverse context.
        //! Will be wrapped in a transaction if valid object is present, otherwise executed standalone.
        void ExecuteOrAppend(SQLTransaction& trans, PreparedStatement* stmt)
        {
            if (trans.null())
                Execute(stmt);
            else
                trans->Append(stmt);
        }

        //! Method used to execute ad-hoc statements in a diverse context.
        //! Will be wrapped in a transaction if valid object is present, otherwise executed standalone.
        void ExecuteOrAppend(SQLTransaction& trans, const char* sql)
        {
            if (trans.null())
                Execute(sql);
            else
                trans->Append(sql);
        }

        /**
            Other
        */

        //! Automanaged (internally) pointer to a prepared statement object for usage in upper level code.
        //! This object is not tied to the prepared statement on the MySQL context yet until execution.
        PreparedStatement* GetPreparedStatement(uint32 index)
        {
            return new PreparedStatement(index);
        }

        //! Apply escape string'ing for current collation. (utf8)
        void EscapeString(std::string& str)
        {
            if (str.empty())
                return;

            char* buf = new char[str.size()*2+1];
            EscapeString(buf, str.c_str(), str.size());
            str = buf;
            delete[] buf;
        }

        //! Keeps all our MySQL connections alive, prevent the server from disconnecting us.
        void KeepAlive()
        {
            /// Ping synchronous connections
            for (uint8 i = 0; i < m_connectionCount[IDX_SYNCH]; ++i)
            {
                T* t = m_connections[IDX_SYNCH][i];
                if (t->LockIfReady())
                {
                    t->Ping();
                    t->Unlock();
                }
            }

            /// Assuming all worker threads are free, every worker thread will receive 1 ping operation request
            /// If one or more worker threads are busy, the ping operations will not be split evenly, but this doesn't matter
            /// as the sole purpose is to prevent connections from idling.
            for (size_t i = 0; i < m_connections[IDX_ASYNC].size(); ++i)
                Enqueue(new PingOperation);
        }

    private:
        unsigned long EscapeString(char *to, const char *from, unsigned long length)
        {
            if (!to || !from || !length)
                return 0;

            return mysql_real_escape_string(m_connections[IDX_SYNCH][0]->GetHandle(), to, from, length);
        }

        void Enqueue(SQLOperation* op)
        {
            m_queue->enqueue(op);
        }

        T* GetFreeConnection()
        {
            uint8 i = 0;
            size_t num_cons = m_connectionCount[IDX_SYNCH];
            for (;;)    /// Block forever until a connection is free
            {
                T* t = m_connections[IDX_SYNCH][++i % num_cons ];
                if (t->LockIfReady())   /// Must be matched with t->Unlock() or you will get deadlocks
                    return t;
            }

            // This will be called when Celine Dion learns to sing
            return NULL;
        }

    private:
        enum
        {
            IDX_ASYNC,
            IDX_SYNCH,
            IDX_SIZE,
        };

        ACE_Activation_Queue*           m_queue;             //! Queue shared by async worker threads.
        std::vector< std::vector<T*> >  m_connections;
        uint32                          m_connectionCount[2];       //! Counter of MySQL connections;
        MySQLConnectionInfo             m_connectionInfo;
};

#endif
