/*
  COMMAND.hpp  -  Key abstraction for proc/edit operations and UNDO management
 
  Copyright (C)         Lumiera.org
    2009,               Hermann Vosseler <Ichthyostega@web.de>
 
  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, write to the Free Software
  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 
*/


/** @file command.hpp
 ** Proc-Layer command frontend.
 ** A \b command is a functor, which can be invoked according to a pre-defined HandlingPattern.
 ** Most notably, command invocation can be scheduled and logged with the serialiser, and the effect
 ** of any command invocation can be \em undone later on by invoking the "undo operation" defined
 ** alongside with the command's operation. The command operation is defined through a C/C++ function
 ** and may receive an arbitrary number and type of arguments. After setting up such a CommandDef ,
 ** it can be referred for use through a symbolic ID. Before being able to invoke the command, concrete
 ** function arguments need to be provided (this is called "binding" or "closing the function arguments").
 ** These function arguments are stored within the command definition and remain opaque to the client code
 ** actually invoking the command. Behind the scenes, there is a CommandRegistry, holding an index of the
 ** registered commands and managing the storage for command definitions and arguments. The actual 
 ** Command object used by client code is a small, copyable and ref-counting handle to this 
 ** stored definition backend.
 ** 
 ** //TODO maybe summarise how UNDO works?  
 ** 
 ** @see command-def.hpp
 ** @see command-use1-test.cpp
 ** @see command-use2-test.cpp
 ** @see command-use3-test.cpp
 ** @see ProcDispatcher
 ** @see Session
 **
 */



#ifndef CONTROL_COMMAND_H
#define CONTROL_COMMAND_H

#include "pre.hpp"
#include "lib/error.hpp"
#include "include/symbol.hpp"
#include "proc/control/command-binding.hpp"
#include "proc/control/argument-erasure.hpp"
#include "proc/control/handling-pattern.hpp"
#include "lib/bool-checkable.hpp"
#include "lib/meta/tuple.hpp"
#include "lib/handle.hpp"

#include <string>

///////////////////////////////////////////TODO: define an C-API representation here, make the header multilingual!



namespace control {
  
  using std::string;
  using lumiera::Symbol;
  using std::tr1::shared_ptr;
  using lumiera::typelist::Tuple;
  
  
  LUMIERA_ERROR_DECLARE (UNBOUND_ARGUMENTS);  ///< Command functor not yet usable, because arguments aren't bound
  LUMIERA_ERROR_DECLARE (INVALID_COMMAND);    ///< Unknown or insufficiently defined command
  LUMIERA_ERROR_DECLARE (DUPLICATE_COMMAND);  ///< Attempt to redefine an already existing command definition
  LUMIERA_ERROR_DECLARE (INVALID_ARGUMENTS);  ///< Arguments provided for binding doesn't match stored command function parameters
  
  
  
  typedef void* FuncPtr;
  
  class CommandDef;
  class CommandImpl;
  
  
  /**
   *  Handle object representing a single Command instance to be used by client code.
   *  Commands are accessed \link #get through a symbolic ID \endlink; there need to be
   *  a CommandDef somewhere to specify the actual operation and to define, how the
   *  effect of the command can be undone. Moreover, the command's definition 
   *  refers to a HandlingPattern, which describes how the command is actually
   *  to be executed (the default is to schedule it within the ProcDispatcher)
   *  
   *  Client code usually just
   *  - creates a command instance by referring to a command ID
   *  - maybe binds to concrete arguments (e.g. a target object)
   *  - triggers command execution through operator()
   *  - maybe checks the return value for errors
   */
  class Command
    : public com::ArgumentBinder<Command    // accepts arbitrary bind(..) calls (with runtime check)
           , lib::Handle<CommandImpl>      //  actually implemented as ref counting Handle
           >                              //
    {
      typedef lib::Handle<CommandImpl> _Handle;
      
    public:
      /* === command registry === */
      static Command get (Symbol cmdID);
      static Command get (FuncPtr func);
      static bool remove (Symbol cmdID); 
      
      Command storeDef (Symbol newCmdID);
      
      Command() { } ///< undefined command
     ~Command();
      
      ExecResult operator() () ;
      ExecResult undo () ;
      
      
      /** core operation: invoke the command
       *  @param execPattern describes the individual steps
       *         necessary to get this command invoked properly
       */
      ExecResult exec (HandlingPattern const& execPattern);
      ExecResult exec (HandlingPattern::ID);
      
      ExecResult execSync ();
      
      /** @return ID of the execution pattern used by operator() */
      HandlingPattern::ID getDefaultHandlingPattern()  const;
      
      /** define a handling pattern to be used by default
       *  @return ID of the currently defined default pattern */
      HandlingPattern::ID setHandlingPattern (HandlingPattern::ID);
      
      
      
      /* === command lifecycle === */
      
      Command& activate (shared_ptr<CommandImpl> const&);
      
      template<typename TYPES>
      Command& bindArg (Tuple<TYPES> const&);
      
      
      /* === diagnostics === */
      
      static size_t definition_count();
      static size_t instance_count();
      
      bool canExec()  const;
      bool canUndo()  const;
      
      operator string() const;
      friend bool operator== (Command const&, Command const&);
      
      
    protected:
      static Command fetchDef (Symbol cmdID);
      
      friend class CommandDef;
      
      
    private:
      void setArguments (Arguments&);
    };
  
  
  
  
  
  inline ExecResult
  Command::operator() ()
  {
    return exec (getDefaultHandlingPattern());
  }
  
  
  template<typename TYPES>
  inline Command&
  Command::bindArg (Tuple<TYPES> const& tuple)
    {
      TypedArguments<Tuple<TYPES> > args(tuple);
      this->setArguments (args);
      return *this;
    }
  
  
  
  inline bool
  operator== (Command const& c1, Command const& c2)
    {
      return (!c1 && !c2)
          || ( c1 &&  c2  && (&c1.impl() == &c2.impl())); 
    }
  
  inline bool
  operator!= (Command const& c1, Command const& c2)
    {
      return ! (c1 == c2); 
    }
  
  
  
  
} // namespace control
#endif