/**********************************************************************

   Audacity - A Digital Audio Editor
   Copyright 1999-2009 Audacity Team
   File License: wxWidgets

   Dan Horgan

******************************************************************//**

\file Command.h
\brief Contains declaration of Command base class.

\class CommandExecutionContext
\brief Represents a context to which a command may be applied.

\class Command
\brief Abstract base class for command interface.  It implements 
Command::SetParameter() and defers all other operations to derived classes.

That process may depend on certain parameters (determined by the command's
signature) and may produce output on various channels. Any process which is to
be controlled by a script should be separated out into its own Command class.
(And that class should be registered with the CommandDirectory).

\class ApplyAndSendResponse
\brief Decorator command that performs the given command and then 
outputs a status message according to the result.

\class CommandImplementation,
\brief is derived from Command.  It validates and 
applies the command.  CommandImplementation::Apply() is overloaded in 
classes derived from it.

*//*******************************************************************/

#ifndef __COMMAND__
#define __COMMAND__

#include <wx/app.h>

#include "../Project.h"

#include "CommandMisc.h"
#include "CommandSignature.h"

class AudacityApp;
class CommandOutputTarget;

class CommandExecutionContext
{
public:
   CommandExecutionContext(AudacityApp *WXUNUSED(app), AudacityProject *WXUNUSED(proj))
   {
   };
   AudacityApp *GetApp() const
   {
      return (AudacityApp *) wxTheApp;
   };
   AudacityProject *GetProject() const
   {
      // TODO:  Presumably, this would be different if running in a command context.
      // So, if this command system is ever actually enabled, then this will need to
      // be reviewed.
      return GetActiveProject();
   };
};

// Abstract base class for command interface.  
class Command /* not final */
{
public:
   virtual void Progress(double completed) = 0;
   virtual void Status(const wxString &message) = 0;
   virtual void Error(const wxString &message) = 0;
   virtual ~Command() { }
   virtual wxString GetName() = 0;
   virtual CommandSignature &GetSignature() = 0;
   virtual bool SetParameter(const wxString &paramName, const wxVariant &paramValue);
   virtual bool Apply(CommandExecutionContext context) = 0;
};

using CommandHolder = std::shared_ptr<Command>;

/// Command which wraps another command
class DecoratedCommand /* not final */ : public Command
{
protected:
   CommandHolder mCommand;
public:
   void Progress(double completed) override;
   void Status(const wxString &message) override;
   void Error(const wxString &message) override;

   DecoratedCommand(const CommandHolder &cmd)
      : mCommand(cmd)
   {
      wxASSERT(cmd != NULL);
   }
   virtual ~DecoratedCommand();
   wxString GetName() override;
   CommandSignature &GetSignature() override;
   bool SetParameter(const wxString &paramName, const wxVariant &paramValue) override;
};

// Decorator command that performs the given command and then outputs a status
// message according to the result
class ApplyAndSendResponse final : public DecoratedCommand
{
public:
   ApplyAndSendResponse(const CommandHolder &cmd)
      : DecoratedCommand(cmd)
   { }

   bool Apply(CommandExecutionContext context) override;
};

class CommandImplementation /* not final */ : public Command
{
private:
   CommandType &mType;
   ParamValueMap mParams;

   /// Using the command signature, looks up a possible parameter value and
   /// checks whether it passes the validator.
   bool Valid(const wxString &paramName, const wxVariant &paramValue);

protected:
   std::unique_ptr<CommandOutputTarget> mOutput;

   // Convenience methods for allowing subclasses to access parameters
   void TypeCheck(const wxString &typeName,
                  const wxString &paramName,
                  const wxVariant &param);
   void CheckParam(const wxString &paramName);
   bool GetBool(const wxString &paramName);
   long GetLong(const wxString &paramName);
   double GetDouble(const wxString &paramName);
   wxString GetString(const wxString &paramName);

public:
   // Convenience methods for passing messages to the output target
   void Progress(double completed);
   void Status(const wxString &status) override;
   void Error(const wxString &message) override;

   /// Constructor should not be called directly; only by a factory which
   /// ensures name and params are set appropriately for the command.
   CommandImplementation(CommandType &type,
                         std::unique_ptr<CommandOutputTarget> &&output);

   virtual ~CommandImplementation();

   /// An instance method for getting the command name (for consistency)
   wxString GetName();

   /// Get the signature of the command
   CommandSignature &GetSignature();

   /// Attempt to one of the command's parameters to a particular value.
   /// (Note: wxVariant is reference counted)
   bool SetParameter(const wxString &paramName, const wxVariant &paramValue);

   // Subclasses should override the following:
   // =========================================

   /// Actually carry out the command. Return true if successful and false
   /// otherwise.
   bool Apply(CommandExecutionContext context) override;
};

#endif /* End of include guard: __COMMAND__ */