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 //------------------------------------------------------------------------------
 // Copyright (c) 2011-2017 by European Organization for Nuclear Research (CERN)
 // Author: Krzysztof Jamrog <krzysztof.piotr.jamrog@cern.ch>,
 //         Michal Simon <michal.simon@cern.ch>
 //------------------------------------------------------------------------------
 // This file is part of the XRootD software suite.
 //
 // XRootD 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 3 of the License, or
 // (at your option) any later version.
 //
 // XRootD 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 Lesser General Public License
 // along with XRootD.  If not, see <http://www.gnu.org/licenses/>.
 //
 // In applying this licence, CERN does not waive the privileges and immunities
 // granted to it by virtue of its status as an Intergovernmental Organization
 // or submit itself to any jurisdiction.
 //------------------------------------------------------------------------------
 
 #ifndef __XRD_CL_OPERATIONS_HH__
 #define __XRD_CL_OPERATIONS_HH__
 
 #include <memory>
 #include <stdexcept>
 #include <sstream>
 #include <tuple>
 #include <future>
 #include "XrdCl/XrdClXRootDResponses.hh"
 #include "XrdCl/XrdClOperationHandlers.hh"
 #include "XrdCl/XrdClArg.hh"
 #include "XrdCl/XrdClOperationTimeout.hh"
 #include "XrdCl/XrdClFinalOperation.hh"
 #include "XrdSys/XrdSysPthread.hh"
 
 #include "XrdCl/XrdClResponseJob.hh"
 #include "XrdCl/XrdClJobManager.hh"
 #include "XrdCl/XrdClPostMaster.hh"
 #include "XrdCl/XrdClDefaultEnv.hh"
 
 namespace XrdCl
 {
 
   template<bool HasHndl> class Operation;
 
   class Pipeline;
 
 
   //----------------------------------------------------------------------------
   //! Type of the recovery function to be provided by the user
   //----------------------------------------------------------------------------
   typedef std::function<Operation<true>*(const XRootDStatus&)>  rcvry_func;
 
   //----------------------------------------------------------------------------
   //! Wrapper for ResponseHandler, used only internally to run next operation
   //! after previous one is finished
   //----------------------------------------------------------------------------
   class PipelineHandler: public ResponseHandler
   {
       template<bool> friend class Operation;
 
     public:
 
       //------------------------------------------------------------------------
       //! Constructor.
       //!
       //! @param handler  : the handler of our operation
       //------------------------------------------------------------------------
       PipelineHandler( ResponseHandler   *handler );
 
       //------------------------------------------------------------------------
       //! Default Constructor.
       //------------------------------------------------------------------------
       PipelineHandler()
       {
       }
 
       //------------------------------------------------------------------------
       //! Callback function.
       //------------------------------------------------------------------------
       void HandleResponseWithHosts( XRootDStatus *status, AnyObject *response,
           HostList *hostList );
 
       //------------------------------------------------------------------------
       //! Callback function.
       //------------------------------------------------------------------------
       void HandleResponse( XRootDStatus *status, AnyObject *response );
 
       //------------------------------------------------------------------------
       //! Destructor.
       //------------------------------------------------------------------------
       ~PipelineHandler()
       {
       }
 
       //------------------------------------------------------------------------
       //! Add new operation to the pipeline
       //!
       //! @param operation  :  operation to add
       //------------------------------------------------------------------------
       void AddOperation( Operation<true> *operation );
 
       //------------------------------------------------------------------------
       //! Set workflow to this and all next handlers. In the last handler
       //! it is used to finish workflow execution
       //!
       //! @param  prms         :  a promis that the pipeline will have a result
       //! @param  final        :  a callable that should be called at the end of
       //!                         pipeline
       //------------------------------------------------------------------------
       void Assign( const Timeout                            &timeout,
                    std::promise<XRootDStatus>                prms,
                    std::function<void(const XRootDStatus&)>  final,
                    Operation<true>                          *opr );
 
       //------------------------------------------------------------------------
       //! Assign the finalization routine
       //------------------------------------------------------------------------
       void Assign( std::function<void(const XRootDStatus&)>  final );
 
       //------------------------------------------------------------------------
       //! Called by a pipeline on the handler of its first operation before Run
       //------------------------------------------------------------------------
       void PreparePipelineStart();
 
     private:
 
       //------------------------------------------------------------------------
       //! Callback function implementation;
       //------------------------------------------------------------------------
       void HandleResponseImpl( XRootDStatus *status, AnyObject *response,
           HostList *hostList = nullptr );
 
       inline void dealloc( XRootDStatus *status, AnyObject *response,
           HostList *hostList )
       {
         delete status;
         delete response;
         delete hostList;
       }
 
       //------------------------------------------------------------------------
       //! The handler of our operation
       //------------------------------------------------------------------------
       std::unique_ptr<ResponseHandler> responseHandler;
 
       //------------------------------------------------------------------------
       //! The operation the handler is assigned to
       //------------------------------------------------------------------------
       std::unique_ptr<Operation<true>> currentOperation;
 
       //------------------------------------------------------------------------
       //! Next operation in the pipeline
       //------------------------------------------------------------------------
       std::unique_ptr<Operation<true>> nextOperation;
 
       //------------------------------------------------------------------------
       //! Pipeline timeout
       //------------------------------------------------------------------------
       Timeout timeout;
 
       //------------------------------------------------------------------------
       //! The promise that there will be a result (traveling along the pipeline)
       //------------------------------------------------------------------------
       std::promise<XRootDStatus> prms;
 
       //------------------------------------------------------------------------
       //! The lambda/function/functor that should be called at the end of the
       //! pipeline (traveling along the pipeline)
       //------------------------------------------------------------------------
       std::function<void(const XRootDStatus&)> final;
   };
 
   //----------------------------------------------------------------------------
   //! Operation template. An Operation is a once-use-only object - once executed
   //! by a Workflow engine it is invalidated. Also if used as an argument for
   //! >> or | the original object gets invalidated.
   //!
   //! @arg HasHndl : true if operation has a handler, false otherwise
   //----------------------------------------------------------------------------
   template<bool HasHndl>
   class Operation
   {
       // Declare friendship between templates
       template<bool>
       friend class Operation;
 
       friend std::future<XRootDStatus> Async( Pipeline, uint16_t );
 
       friend class Pipeline;
       friend class PipelineHandler;
 
     public:
 
       //------------------------------------------------------------------------
       //! Constructor
       //------------------------------------------------------------------------
       Operation() : valid( true )
       {
       }
 
       //------------------------------------------------------------------------
       //! Move constructor between template instances.
       //------------------------------------------------------------------------
       template<bool from>
       Operation( Operation<from> && op ) :
           handler( std::move( op.handler ) ), valid( true )
       {
         if( !op.valid ) throw std::invalid_argument( "Cannot construct "
             "Operation from an invalid Operation!" );
         op.valid = false;
       }
 
       //------------------------------------------------------------------------
       //! Destructor
       //------------------------------------------------------------------------
       virtual ~Operation()
       {
       }
 
       //------------------------------------------------------------------------
       //! Name of the operation.
       //------------------------------------------------------------------------
       virtual std::string ToString() = 0;
 
       //------------------------------------------------------------------------
       //! Move current object into newly allocated instance
       //!
       //! @return : the new instance
       //------------------------------------------------------------------------
       virtual Operation<HasHndl>* Move() = 0;
 
       //------------------------------------------------------------------------
       //! Move current object into newly allocated instance, and convert
       //! it into 'handled' operation.
       //!
       //! @return : the new instance
       //------------------------------------------------------------------------
       virtual Operation<true>* ToHandled() = 0;
 
     protected:
 
       //------------------------------------------------------------------------
       //! Run operation
       //!
       //! @param prms   : the promise that we will have a result
       //! @param final  : the object to call at the end of pipeline
       //------------------------------------------------------------------------
       void Run( Timeout                                   timeout,
                 std::promise<XRootDStatus>                prms,
                 std::function<void(const XRootDStatus&)>  final )
       {
         static_assert(HasHndl, "Only an operation that has a handler can be assigned to workflow");
         handler->Assign( timeout, std::move( prms ), std::move( final ), this );
 
         PipelineHandler *h = handler.release();
         XRootDStatus st;
         try
         {
           st = RunImpl( h, timeout );
         }
         catch( const operation_expired& ex )
         {
           st = XRootDStatus( stError, errOperationExpired );
         }
         catch( const PipelineException& ex ) // probably not needed
         {
           st = ex.GetError();
         }
         catch( const std::exception& ex )
         {
           st = XRootDStatus( stError, errInternal, 0, ex.what() );
         }
 
         if( !st.IsOK() ){
           ResponseJob *job = new ResponseJob(h, new XRootDStatus(st), 0, nullptr);
           DefaultEnv::GetPostMaster()->GetJobManager()->QueueJob(job);
         }
       }
 
       //------------------------------------------------------------------------
       //! Run the actual operation
       //!
       //! @param params :  container with parameters forwarded from
       //!                  previous operation
       //! @return       :  status of the operation
       //------------------------------------------------------------------------
       virtual XRootDStatus RunImpl( PipelineHandler *handler, uint16_t timeout ) = 0;
 
       //------------------------------------------------------------------------
       //! Add next operation in the pipeline
       //!
       //! @param op : operation to add
       //------------------------------------------------------------------------
       void AddOperation( Operation<true> *op )
       {
         if( handler )
           handler->AddOperation( op );
       }
 
       //------------------------------------------------------------------------
       //! Operation handler
       //------------------------------------------------------------------------
       std::unique_ptr<PipelineHandler> handler;
 
       //------------------------------------------------------------------------
       //! Flag indicating if it is a valid object
       //------------------------------------------------------------------------
       bool valid;
   };
 
   //----------------------------------------------------------------------------
   //! A wrapper around operation pipeline. A Pipeline is a once-use-only
   //! object - once executed by a Workflow engine it is invalidated.
   //!
   //! Takes ownership of given operation pipeline (which is in most would
   //! be a temporary object)
   //----------------------------------------------------------------------------
   class Pipeline
   {
       template<bool> friend class ParallelOperation;
       friend std::future<XRootDStatus> Async( Pipeline, uint16_t );
       friend class PipelineHandler;
 
     public:
 
       //------------------------------------------------------------------------
       //! Default constructor
       //------------------------------------------------------------------------
       Pipeline()
       {
       }
 
       //------------------------------------------------------------------------
       //! Constructor
       //------------------------------------------------------------------------
       Pipeline( Operation<true> *op ) :
           operation( op->Move() )
       {
       }
 
       //------------------------------------------------------------------------
       //! Constructor
       //------------------------------------------------------------------------
       Pipeline( Operation<true> &op ) :
           operation( op.Move() )
       {
       }
 
       //------------------------------------------------------------------------
       //! Constructor
       //------------------------------------------------------------------------
       Pipeline( Operation<true> &&op ) :
           operation( op.Move() )
       {
       }
 
       Pipeline( Operation<false> *op ) :
           operation( op->ToHandled() )
       {
       }
 
       //------------------------------------------------------------------------
       //! Constructor
       //------------------------------------------------------------------------
       Pipeline( Operation<false> &op ) :
           operation( op.ToHandled() )
       {
       }
 
       //------------------------------------------------------------------------
       //! Constructor
       //------------------------------------------------------------------------
       Pipeline( Operation<false> &&op ) :
           operation( op.ToHandled() )
       {
       }
 
       Pipeline( Pipeline &&pipe ) :
           operation( std::move( pipe.operation ) )
       {
       }
 
       //------------------------------------------------------------------------
       //! Constructor
       //------------------------------------------------------------------------
       Pipeline& operator=( Pipeline &&pipe )
       {
         operation = std::move( pipe.operation );
         return *this;
       }
 
       //------------------------------------------------------------------------
       //! Extend pipeline
       //------------------------------------------------------------------------
       Pipeline& operator|=( Operation<true>&& op )
       {
         operation->AddOperation( op.Move() );
         return *this;
       }
 
       //------------------------------------------------------------------------
       //! Extend pipeline
       //------------------------------------------------------------------------
       Pipeline& operator|=( Operation<false>&& op )
       {
         operation->AddOperation( op.ToHandled() );
         return *this;
       }
 
       //------------------------------------------------------------------------
       //! Conversion to Operation<true>
       //!
       //! @throws : std::logic_error if pipeline is invalid
       //------------------------------------------------------------------------
       operator Operation<true>&()
       {
         if( !bool( operation ) ) throw std::logic_error( "Invalid pipeline." );
         return *operation.get();
       }
 
       //------------------------------------------------------------------------
       //! Conversion to boolean
       //!
       //! @return : true if it's a valid pipeline, false otherwise
       //------------------------------------------------------------------------
       operator bool()
       {
         return bool( operation );
       }
 
       //------------------------------------------------------------------------
       //! Stop the current pipeline
       //!
       //! @param status : the final status for the pipeline
       //------------------------------------------------------------------------
       static void Stop( const XRootDStatus &status = XrdCl::XRootDStatus() );
 
       //------------------------------------------------------------------------
       //! Repeat current operation
       //------------------------------------------------------------------------
       static void Repeat();
 
       //------------------------------------------------------------------------
       //! Replace current operation
       //------------------------------------------------------------------------
       static void Replace( Operation<false> &&opr );
 
       //------------------------------------------------------------------------
       //! Replace with pipeline
       //------------------------------------------------------------------------
       static void Replace( Pipeline p );
 
       //------------------------------------------------------------------------
       //! Ignore error and proceed with the pipeline
       //------------------------------------------------------------------------
       static void Ignore();
 
     private:
 
       //------------------------------------------------------------------------
       //! Member access declaration, provides access to the underlying
       //! operation.
       //!
       //! @return : pointer to the underlying
       //------------------------------------------------------------------------
       Operation<true>* operator->()
       {
         return operation.get();
       }
 
       //------------------------------------------------------------------------
       //! Schedules the underlying pipeline for execution.
       //!
       //! @param timeout : pipeline timeout value
       //! @param final   : to be called at the end of the pipeline
       //------------------------------------------------------------------------
       void Run( Timeout timeout, std::function<void(const XRootDStatus&)> final = nullptr )
       {
         if( ftr.valid() )
           throw std::logic_error( "Pipeline is already running!" );
 
         // a promise that the pipe will have a result
         std::promise<XRootDStatus> prms;
         ftr = prms.get_future();
 
         if( !operation ) std::logic_error( "Empty pipeline!" );
 
         Operation<true> *opr = operation.release();
         PipelineHandler *h = opr->handler.get();
         if( h )
           h->PreparePipelineStart();
 
         opr->Run( timeout, std::move( prms ), std::move( final ) );
       }
 
       //------------------------------------------------------------------------
       //! First operation in the pipeline
       //------------------------------------------------------------------------
       std::unique_ptr<Operation<true>> operation;
 
       //------------------------------------------------------------------------
       //! The future result of the pipeline
       //------------------------------------------------------------------------
       std::future<XRootDStatus> ftr;
 
   };
 
   //----------------------------------------------------------------------------
   //! Helper function, schedules execution of given pipeline
   //!
   //! @param pipeline : the pipeline to be executed
   //! @param timeout  : the pipeline timeout
   //!
   //! @return         : future status of the operation
   //----------------------------------------------------------------------------
   inline std::future<XRootDStatus> Async( Pipeline pipeline, uint16_t timeout = 0 )
   {
     pipeline.Run( timeout );
     return std::move( pipeline.ftr );
   }
 
   //----------------------------------------------------------------------------
   //! Helper function, schedules execution of given pipeline and waits for
   //! the status
   //!
   //! @param pipeline : the pipeline to be executed
   //! @param timeout  : the pipeline timeout
   //!
   //! @return         : status of the operation
   //----------------------------------------------------------------------------
   inline XRootDStatus WaitFor( Pipeline pipeline, uint16_t timeout = 0 )
   {
     return Async( std::move( pipeline ), timeout ).get();
   }
 
   //----------------------------------------------------------------------------
   //! Concrete Operation template
   //! Defines | and >> operator as well as operation arguments.
   //!
   //! @arg Derived : the class that derives from this template (CRTP)
   //! @arg HasHndl : true if operation has a handler, false otherwise
   //! @arg Args    : operation arguments
   //----------------------------------------------------------------------------
   template<template<bool> class Derived, bool HasHndl, typename HdlrFactory, typename ... Args>
   class ConcreteOperation: public Operation<HasHndl>
   {
       template<template<bool> class, bool, typename, typename ...>
       friend class ConcreteOperation;
 
     public:
 
       //------------------------------------------------------------------------
       //! Constructor
       //!
       //! @param args : operation arguments
       //------------------------------------------------------------------------
       ConcreteOperation( Args&&... args ) : args( std::tuple<Args...>( std::move( args )... ) ),
                                             timeout( 0 )
       {
         static_assert( !HasHndl, "It is only possible to construct operation without handler" );
       }
 
       //------------------------------------------------------------------------
       //! Move constructor from other states
       //!
       //! @arg from : state from which the object is being converted
       //!
       //! @param op : the object that is being converted
       //------------------------------------------------------------------------
       template<bool from>
       ConcreteOperation( ConcreteOperation<Derived, from, HdlrFactory, Args...> && op ) :
         Operation<HasHndl>( std::move( op ) ), args( std::move( op.args ) ), timeout( 0 )
       {
       }
 
       //------------------------------------------------------------------------
       //! Adds ResponseHandler/function/functor/lambda/future handler for
       //! the operation.
       //!
       //! Note: due to reference collapsing this covers both l-value and
       //!       r-value references.
       //!
       //! @param hdlr : function/functor/lambda
       //------------------------------------------------------------------------
       template<typename Hdlr>
       Derived<true> operator>>( Hdlr &&hdlr )
       {
         return this->StreamImpl( HdlrFactory::Create( hdlr ) );
       }
 
       //------------------------------------------------------------------------
       //! Creates a pipeline of 2 or more operations
       //!
       //! @param op  : operation to add
       //!
       //! @return    : handled operation
       //------------------------------------------------------------------------
       Derived<true> operator|( Operation<true> &op )
       {
         return PipeImpl( *this, op );
       }
 
       //------------------------------------------------------------------------
       //! Creates a pipeline of 2 or more operations
       //!
       //! @param op :  operation to add
       //!
       //! @return   :  handled operation
       //------------------------------------------------------------------------
       Derived<true> operator|( Operation<true> &&op )
       {
         return PipeImpl( *this, op );
       }
 
       //------------------------------------------------------------------------
       //! Creates a pipeline of 2 or more operations
       //!
       //! @param op   operation to add
       //!
       //! @return     handled operation
       //------------------------------------------------------------------------
       Derived<true> operator|( Operation<false> &op )
       {
         return PipeImpl( *this, op );
       }
 
       //------------------------------------------------------------------------
       //! Creates a pipeline of 2 or more operations
       //!
       //! @param op  : operation to add
       //!
       //! @return    : handled operation
       //------------------------------------------------------------------------
       Derived<true> operator|( Operation<false> &&op )
       {
         return PipeImpl( *this, op );
       }
 
       //------------------------------------------------------------------------
       //! Adds a final operation to the pipeline
       //------------------------------------------------------------------------
       Derived<true> operator|( FinalOperation &&fo )
       {
         AllocHandler( *this );
         this->handler->Assign( fo.final );
         return this->template Transform<true>();
       }
 
       //------------------------------------------------------------------------
       //! Move current object into newly allocated instance
       //!
       //! @return : the new instance
       //------------------------------------------------------------------------
       inline Operation<HasHndl>* Move()
       {
         Derived<HasHndl> *me = static_cast<Derived<HasHndl>*>( this );
         return new Derived<HasHndl>( std::move( *me ) );
       }
 
       //------------------------------------------------------------------------
       //! Transform operation to handled
       //!
       //! @return Operation<true>&
       //------------------------------------------------------------------------
       inline Operation<true>* ToHandled()
       {
         this->handler.reset( new PipelineHandler() );
         Derived<HasHndl> *me = static_cast<Derived<HasHndl>*>( this );
         return new Derived<true>( std::move( *me ) );
       }
 
       //------------------------------------------------------------------------
       //! Set operation timeout
       //------------------------------------------------------------------------
       Derived<HasHndl> Timeout( uint16_t timeout )
       {
         this->timeout = timeout;
         Derived<HasHndl> *me = static_cast<Derived<HasHndl>*>( this );
         return std::move( *me );
       }
 
     protected:
 
       //------------------------------------------------------------------------
       //! Transform into a new instance with desired state
       //!
       //! @return : new instance in the desired state
       //------------------------------------------------------------------------
       template<bool to>
       inline Derived<to> Transform()
       {
         Derived<HasHndl> *me = static_cast<Derived<HasHndl>*>( this );
         return Derived<to>( std::move( *me ) );
       }
 
       //------------------------------------------------------------------------
       //! Implements operator>> functionality
       //!
       //! @param handler :  handler to be added
       //!
       //! @return   :  return an instance of Derived<true>
       //------------------------------------------------------------------------
       inline Derived<true> StreamImpl( ResponseHandler *handler )
       {
         static_assert( !HasHndl, "Operator >> is available only for operation without handler" );
         this->handler.reset( new PipelineHandler( handler ) );
         return Transform<true>();
       }
 
       //------------------------------------------------------------------------
       // Allocate handler if necessary
       //------------------------------------------------------------------------
       inline static
       void AllocHandler( ConcreteOperation<Derived, true, HdlrFactory, Args...> &me )
       {
         // nothing to do
       }
 
       //------------------------------------------------------------------------
       // Allocate handler if necessary
       //------------------------------------------------------------------------
       inline static
       void AllocHandler( ConcreteOperation<Derived, false, HdlrFactory, Args...> &me )
       {
         me.handler.reset( new PipelineHandler() );
       }
 
       //------------------------------------------------------------------------
       //! Implements operator| functionality
       //!
       //! @param me  :  reference to myself (*this)
       //! @param op  :  reference to the other operation
       //!
       //! @return    :  move-copy of myself
       //------------------------------------------------------------------------
       inline static
       Derived<true> PipeImpl( ConcreteOperation<Derived, HasHndl, HdlrFactory,
           Args...> &me, Operation<true> &op )
       {
         AllocHandler( me ); // if HasHndl is false allocate handler
         me.AddOperation( op.Move() );
         return me.template Transform<true>();
       }
 
       //------------------------------------------------------------------------
       //! Implements operator| functionality
       //!
       //! @param me  :  reference to myself (*this)
       //! @param op  :  reference to the other operation
       //!
       //! @return    :  move-copy of myself
       //------------------------------------------------------------------------
       inline static
       Derived<true> PipeImpl( ConcreteOperation<Derived, HasHndl, HdlrFactory,
           Args...> &me, Operation<false> &op )
       {
         AllocHandler( me ); // if HasHndl is false allocate handler
         me.AddOperation( op.ToHandled() );
         return me.template Transform<true>();
       }
 
       //------------------------------------------------------------------------
       //! Operation arguments
       //------------------------------------------------------------------------
       std::tuple<Args...> args;
 
       //------------------------------------------------------------------------
       //! Operation timeout
       //------------------------------------------------------------------------
       uint16_t timeout;
     };
 }
 
 #endif // __XRD_CL_OPERATIONS_HH__

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