#ifndef DBAPI_CONN_FACTORY_HPP
#define DBAPI_CONN_FACTORY_HPP

/*  $Id: dbapi_conn_factory.hpp 672706 2023-09-13 15:49:09Z ucko $
* ===========================================================================
*
*                            PUBLIC DOMAIN NOTICE
*               National Center for Biotechnology Information
*
*  This software/database is a "United States Government Work" under the
*  terms of the United States Copyright Act.  It was written as part of
*  the author's official duties as a United States Government employee and
*  thus cannot be copyrighted.  This software/database is freely available
*  to the public for use. The National Library of Medicine and the U.S.
*  Government have not placed any restriction on its use or reproduction.
*
*  Although all reasonable efforts have been taken to ensure the accuracy
*  and reliability of the software and data, the NLM and the U.S.
*  Government do not and cannot warrant the performance or results that
*  may be obtained by using this software or data. The NLM and the U.S.
*  Government disclaim all warranties, express or implied, including
*  warranties of performance, merchantability or fitness for any particular
*  purpose.
*
*  Please cite the author in any work or product based on this material.
*
* ===========================================================================
*
* Author: Sergey Sikorskiy
*
* File Description:
*
*============================================================================
*/

#include <corelib/ncbimtx.hpp>
#include <corelib/impl/ncbi_dbsvcmapper.hpp>
#include <dbapi/driver/dbapi_driver_conn_mgr.hpp>
#include <dbapi/driver/impl/handle_stack.hpp>
#include <dbapi/driver/impl/dbapi_pool_balancer.hpp>
#include <map>
#include <vector>
#include <memory>

BEGIN_NCBI_SCOPE

///////////////////////////////////////////////////////////////////////////////
/// CDBConnectionFactory
///

enum EDefaultMapping
{
    eUseDefaultMapper,
    eNoMapping
};

class NCBI_DBAPIDRIVER_EXPORT CDBConnectionFactory : public IDBConnectionFactory
{
public:
    /// CDBConnectionFactory won't take ownership of registry.
    CDBConnectionFactory(IDBServiceMapper::TFactory svc_mapper_factory,
                         const IRegistry* registry = NULL,
                         EDefaultMapping def_mapping = eUseDefaultMapper);

    //
    virtual void Configure(const IRegistry* registry = NULL);

    //
    unsigned int GetMaxNumOfConnAttempts(void) const;
    void SetMaxNumOfConnAttempts(unsigned int max_num);

    unsigned int GetMaxNumOfValidationAttempts(void) const;
    void SetMaxNumOfValidationAttempts(unsigned int max_num);

    unsigned int GetMaxNumOfServerAlternatives(void) const;
    void SetMaxNumOfServerAlternatives(unsigned int max_num);

    unsigned int GetMaxNumOfDispatches(void) const;
    void SetMaxNumOfDispatches(unsigned int max_num);

    unsigned int GetConnectionTimeout(void) const;
    void SetConnectionTimeout(unsigned int timeout);

    unsigned int GetLoginTimeout(void) const;
    void SetLoginTimeout(unsigned int timeout);

    void GetServersList(const string& validator_name,
                        const string& service_name,
                        list<string>* serv_list);
    void WorkWithSingleServer(const string& validator_name,
                              const string& service_name,
                              const string& server);

protected:
    class CServiceInfo : public IDBServiceInfo
    {
    public:
        CServiceInfo(const CDBConnectionFactory& factory,
                     IDBServiceMapper& mapper, const string& service_name)
            : m_Factory(factory), m_Mapper(&mapper),
              m_ServiceName(service_name), m_NumDispatches(0),
              m_NumValidationFailures(0)
            { }

        const string& GetServiceName(void) const override
            { return m_ServiceName; }
        const TOptions& GetOptions(void) override;
        void Lock(void) override
            { m_Mutex.Lock(); }
        void Unlock(void) override
            { m_Mutex.Unlock(); }

        void ClearOptions(void)
            { m_Options.clear(); }

        void SetDispatchedServer(const TSvrRef& server);
        TSvrRef GetDispatchedServer(void) const
            { return m_Dispatched; }
        TSvrRef GetMappedServer(void) override
            { return m_Mapper->GetServer(m_ServiceName); }

        unsigned int GetNumOfDispatches(void) const
            { return m_NumDispatches; }
        unsigned int GetNumOfValidationFailures(void) const
            { return m_NumValidationFailures; }
        void IncNumOfValidationFailures(const TSvrRef& dsp_srv);

        string GetMapperName(void) const
            { return m_Mapper->GetName(); }
        bool HasExclusions(void) const
            { return m_Mapper->HasExclusions(m_ServiceName); }
        string GetExcluded(void);
        void Exclude(const TSvrRef& server)
            {
                if (server.NotEmpty()) {
                    m_Mapper->Exclude(m_ServiceName, server);
                    if (m_Dispatched.NotEmpty()
                        &&  *server == *m_Dispatched) {
                        m_Dispatched.Reset();
                    }
                }
            }
        void CleanExcluded(void)
            { m_Mapper->CleanExcluded(m_ServiceName); }

    private:
        CFastMutex                  m_Mutex;
        const CDBConnectionFactory& m_Factory;
        CRef<IDBServiceMapper>      m_Mapper;
        string                      m_ServiceName;
        TOptions                    m_Options;
        TSvrRef                     m_Dispatched;
        unsigned int                m_NumDispatches;
        unsigned int                m_NumValidationFailures;
    };

    // Data
    class CRuntimeData
    {
    public:
        CRuntimeData(const CDBConnectionFactory& parent,
                     const CRef<IDBServiceMapper>& mapper);

        const IDBServiceMapper& GetDBServiceMapper(void) const
        {
            return *m_DBServiceMapper;
        }
        IDBServiceMapper& GetDBServiceMapper(void)
        {
            return *m_DBServiceMapper;
        }
        CServiceInfo& GetServiceInfo(const string& service_name);

    private:
        typedef map<string, CRef<CServiceInfo>> TServiceInfoMap;

        unique_ptr<CFastMutex>      m_Mutex;
        const CDBConnectionFactory* m_Parent;
        CRef<IDBServiceMapper>      m_DBServiceMapper;
        TServiceInfoMap             m_ServiceInfoMap;
    };

    friend class CServiceInfo;

    CRuntimeData& GetRuntimeData(const CRef<IConnValidator> validator);
    CRuntimeData& GetRuntimeData(const string& validator_name);

    void ConfigureFromRegistry(const IRegistry* registry = NULL);
    virtual CDB_Connection* MakeDBConnection(
        I_DriverContext& ctx,
        const CDBConnParams& params,
        CDB_UserHandler::TExceptions& exceptions);

private:
    struct SOpeningContext {
        SOpeningContext(I_DriverContext& driver_ctx_in,
                        CServiceInfo& service_info_in,
                        CDB_UserHandler::TExceptions& exceptions);

        I_DriverContext&            driver_ctx;
        CServiceInfo&               service_info;
        IConnValidator::EConnStatus conn_status;
        impl::CDBHandlerStack       handlers;
        CDB_UserHandler::TExceptions& errors;
        list<string>                tried;
        string                      excluded;
        TSvrRef                     last_tried;
        CStopWatch                  make_valid_connection_sw;
        CStopWatch                  dispatch_server_name_sw;
        // params deliberately left out (potentially call-specific)
    };

    struct CStopWatchScope {
        CStopWatchScope(CStopWatch&  sw_) : sw(sw_)
        { sw.Restart(); }
        ~CStopWatchScope()
        { sw.Stop(); }

        CStopWatch& sw;
    };

    // Methods
    CDB_Connection* DispatchServerName(SOpeningContext& ctx,
                                       const CDBConnParams& params);

    CDB_Connection* MakeValidConnection(SOpeningContext& ctx,
                                        const CDBConnParams& params,
                                        CDB_Connection* candidate = NULL);

    void x_LogConnection(const SOpeningContext& ctx,
                         const CDB_Connection* connection,
                         const CDBConnParams& params);

private:
    typedef map<string, CRuntimeData> TValidatorSet;

    class CMapperFactory
    {
    public:
        CMapperFactory(IDBServiceMapper::TFactory svc_mapper_factory,
                       const IRegistry* registry,
                       EDefaultMapping def_mapping);

    public:
        IDBServiceMapper* Make(void) const;

    private:
        const IDBServiceMapper::TFactory    m_SvcMapperFactory;
        const IRegistry*                    m_Registry;
        EDefaultMapping                     m_DefMapping;
    };

    mutable CRWLock m_Lock;

    const CMapperFactory        m_MapperFactory;
    TValidatorSet               m_ValidatorSet;
    CFastMutex                  m_ValidatorSetMutex;
    // 0 means *none* (even do not try to connect)
    unsigned int                m_MaxNumOfConnAttempts;
    // 0 means *unlimited*
    unsigned int                m_MaxNumOfValidationAttempts;
    // 0 means *none* (even do not try to connect)
    // 1 means *try only one server* (give up strategy)
    unsigned int                m_MaxNumOfServerAlternatives;
    // 0 means *unlimited*
    unsigned int                m_MaxNumOfDispatches;
    unsigned int                m_ConnectionTimeout;
    unsigned int                m_LoginTimeout;
    bool                        m_TryServerToo;
};

///////////////////////////////////////////////////////////////////////////////
/// CDBGiveUpFactory
///

/// Helper class
/// This policy will give up without trying to connect to alternative db servers.
class NCBI_DBAPIDRIVER_EXPORT CDBGiveUpFactory : public CDBConnectionFactory
{
public:
    CDBGiveUpFactory(IDBServiceMapper::TFactory svc_mapper_factory,
                     const IRegistry* registry = NULL,
                     EDefaultMapping def_mapping = eUseDefaultMapper);
    virtual ~CDBGiveUpFactory(void);
};

///////////////////////////////////////////////////////////////////////////////
/// CDBRedispatchFactory
///

/// Helper class
/// This policy will redispatch every time after a successful dispatch.
/// Servers will be kept in a list of available servers till they are
/// reported as IConnValidator::eInvalidConn by a validator.
class NCBI_DBAPIDRIVER_EXPORT CDBRedispatchFactory : public CDBConnectionFactory
{
public:
    CDBRedispatchFactory(IDBServiceMapper::TFactory svc_mapper_factory,
                         const IRegistry* registry = NULL,
                         EDefaultMapping def_mapping = eUseDefaultMapper);
    virtual ~CDBRedispatchFactory(void);
};


///////////////////////////////////////////////////////////////////////////////
/// CConnValidatorCoR
///
/// IConnValidator adaptor which implements the chain of responsibility
/// pattern
///

class NCBI_DBAPIDRIVER_EXPORT CConnValidatorCoR : public IConnValidator
{
public:
    CConnValidatorCoR(void);
    virtual ~CConnValidatorCoR(void);

    virtual EConnStatus Validate(CDB_Connection& conn);
    virtual string GetName(void) const;

    void Push(const CRef<IConnValidator>& validator);
    void Pop(void);
    CRef<IConnValidator> Top(void) const;
    bool Empty(void) const;

protected:
    typedef vector<CRef<IConnValidator> > TValidators;

    mutable CFastRWLock m_Lock;
    TValidators        m_Validators;
};

///////////////////////////////////////////////////////////////////////////////
class NCBI_DBAPIDRIVER_EXPORT CTrivialConnValidator : public IConnValidator
{
public:
    enum EValidateAttr {
        eKeepModifiedConnection = 0,
        eRestoreDefaultDB = 1,
        eCheckSysobjects = 2
    };
    enum {eDefaultValidateAttr = eRestoreDefaultDB | eCheckSysobjects};

    CTrivialConnValidator(const string& db_name,
                          int attr = eDefaultValidateAttr);
    virtual ~CTrivialConnValidator(void);

    virtual EConnStatus Validate(CDB_Connection& conn);
    virtual string GetName(void) const;

    const string& GetDBName(void) const
    {
        return m_DBName;
    }
    int GetAttr(void) const
    {
        return m_Attr;
    }

private:
    const string m_DBName;
    const int    m_Attr;
};


/////////////////////////////////////////////////////////////////////////////
class CDB_DBLB_Delegate : public CDBConnParamsDelegate
{
public:
    CDB_DBLB_Delegate(
            const string& srv_name,
            Uint4 host,
            Uint2 port,
            const CDBConnParams& other);
    virtual ~CDB_DBLB_Delegate(void);

public:
    virtual string GetServerName(void) const;
    virtual Uint4 GetHost(void) const;
    virtual Uint2  GetPort(void) const;
    virtual const impl::CDBHandlerStack& GetOpeningMsgHandlers(void) const;
    impl::CDBHandlerStack& SetOpeningMsgHandlers(void);

private:
    // Non-copyable.
    CDB_DBLB_Delegate(const CDB_DBLB_Delegate& other);
    CDB_DBLB_Delegate& operator =(const CDB_DBLB_Delegate& other);

private:
    const string m_ServerName;
    const Uint4  m_Host;
    const Uint2  m_Port;
    impl::CDBHandlerStack m_OpeningMsgHandlers;
};


/////////////////////////////////////////////////////////////////////////////
inline
unsigned int
CDBConnectionFactory::GetMaxNumOfConnAttempts(void) const
{
    CReadLockGuard guard(m_Lock);
    return m_MaxNumOfConnAttempts;
}

inline
unsigned int
CDBConnectionFactory::GetMaxNumOfValidationAttempts(void) const
{
    CReadLockGuard guard(m_Lock);
    return m_MaxNumOfValidationAttempts;
}

inline
unsigned int
CDBConnectionFactory::GetMaxNumOfServerAlternatives(void) const
{
    CReadLockGuard guard(m_Lock);
    return m_MaxNumOfServerAlternatives;
}

inline
unsigned int
CDBConnectionFactory::GetMaxNumOfDispatches(void) const
{
    CReadLockGuard guard(m_Lock);
    return m_MaxNumOfDispatches;
}

inline
unsigned int
CDBConnectionFactory::GetConnectionTimeout(void) const
{
    CReadLockGuard guard(m_Lock);
    return m_ConnectionTimeout;
}

inline
unsigned int
CDBConnectionFactory::GetLoginTimeout(void) const
{
    CReadLockGuard guard(m_Lock);
    return m_LoginTimeout;
}

END_NCBI_SCOPE

#endif // DBAPI_CONN_FACTORY_HPP
