/*=========================================================================

  Program:   Insight Segmentation & Registration Toolkit
  Module:    $RCSfile: itkPathSource.h,v $
  Language:  C++
  Date:      $Date: 2006/02/06 22:01:57 $
  Version:   $Revision: 1.3 $

  Copyright (c) Insight Software Consortium. All rights reserved.
  See ITKCopyright.txt or http://www.itk.org/HTML/Copyright.htm for details.

     This software is distributed WITHOUT ANY WARRANTY; without even 
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR 
     PURPOSE.  See the above copyright notices for more information.

=========================================================================*/
#ifndef __itkPathSource_h
#define __itkPathSource_h

#include "itkProcessObject.h"
#include "itkPath.h"

namespace itk
{
  
/** \class PathSource
 *  \brief Base class for all process objects that output path data.
 *
 * PathSource is the base class for all process objects that output
 * path data. Specifically, this class defines the GetOutput() method
 * that returns a pointer to the output path. The class also defines
 * some internal private data members that are used to manage streaming
 * of data.
 *
 * \ingroup DataSources
 * \ingroup Paths
 */

template <class TOutputPath>
class ITK_EXPORT PathSource : public ProcessObject
{
public:
  /** Standard class typedefs. */
  typedef PathSource                Self;
  typedef ProcessObject             Superclass;
  typedef SmartPointer<Self>        Pointer;
  typedef SmartPointer<const Self>  ConstPointer;
  
  /** Smart Pointer type to a DataObject. */
  typedef DataObject::Pointer DataObjectPointer;
  
  /** Method for creation through the object factory. */
  itkNewMacro(Self);
  
  /** Run-time type information (and related methods). */
  itkTypeMacro(PathSource,ProcessObject);
  
  /** Some convenient typedefs. */
  typedef TOutputPath                         OutputPathType;
  typedef typename OutputPathType::Pointer    OutputPathPointer;
  typedef typename OutputPathType::InputType  OutputPathInputType;
  typedef typename OutputPathType::OutputType OutputPathOutputType;
  typedef typename OutputPathType::IndexType  OutputPathIndexType;
  typedef typename OutputPathType::OffsetType OutputPathOffsetType;
  
  /** Get the output data of this process object.  The output of this
   * function is not valid until an appropriate Update() method has
   * been called, either explicitly or implicitly.  Both the filter
   * itself and the data object have Update() methods, and both
   * methods update the data.  Here are three ways to use
   * GetOutput() and make sure the data is valid.  In these
   * examples, \a image is a pointer to some Image object, and the
   * particular ProcessObjects involved are filters.  The same
   * examples apply to non-image (e.g. Mesh) data as well.
   *
   * \code
   *   anotherFilter->SetInput( someFilter->GetOutput() );
   *   anotherFilter->Update();
   * \endcode
   *
   * In this situation, \a someFilter and \a anotherFilter are said
   * to constitute a \b pipeline.  
   *
   * \code
   *   image = someFilter->GetOutput();
   *   image->Update();
   * \endcode
   *
   * \code
   *   someFilter->Update();
   *   image = someFilter->GetOutput();
   * \endcode
   * (In the above example, the two lines of code can be in
   * either order.)
   *
   * Note that Update() is not called automatically except within a
   * pipeline as in the first example.  When \b streaming (using a 
   * StreamingImageFilter) is activated, it may be more efficient to
   * use a pipeline than to call Update() once for each filter in
   * turn.
   *
   * For an image, the data generated is for the requested
   * Region, which can be set using ImageBase::SetRequestedRegion().
   * By default, the largest possible region is requested.
   */
  OutputPathType * GetOutput(void);
  OutputPathType * GetOutput(unsigned int idx);
  
  /** Graft the specified DataObject onto this ProcessObject's output.
   * This method grabs a handle to the specified DataObject's path
   * data to use as its output's own path data. It also copies the
   * region ivars (RequestedRegion, BufferedRegion,
   * LargestPossibleRegion) and meta-data (Spacing, Origin) from the
   * specified data object into this filter's output data object. Most
   * importantly, however, it leaves the Source ivar untouched so the
   * original pipeline routing is intact. This method is used when a
   * process object is implemented using a mini-pipeline which is
   * defined in its GenerateData() method.  The usage is:
   *
   * \code
   *    // setup the mini-pipeline to process the input to this filter
   *    firstFilterInMiniPipeline->SetInput( this->GetInput() );
   *
   *    // setup the mini-pipeline to calculate the correct regions
   *    // and write to the appropriate bulk data block
   *    lastFilterInMiniPipeline->GraftOutput( this->GetOutput() );
   *
   *    // execute the mini-pipeline
   *    lastFilterInMiniPipeline->Update();
   *
   *    // graft the mini-pipeline output back onto this filter's output.
   *    // this is needed to get the appropriate regions passed back.
   *    this->GraftOutput( lastFilterInMiniPipeline->GetOutput() );
   * \endcode
   *
   * For proper pipeline execution, a filter using a mini-pipeline
   * must implement the GeneratseInputRequestedRegion(),
   * GenerateOutputRequestedRegion(), GenerateOutputInformation() and
   * EnlargeOutputRequestedRegion() methods as necessary to reflect
   * how the mini-pipeline will execute (in other words, the outer
   * filter's pipeline mechanism must be consistent with what the
   * mini-pipeline will do). */
  // just calls GraftNthOutput()
  virtual void GraftOutput(OutputPathType *output);

  /** Graft the specified data object onto this ProcessObject's idx'th
   * output. This is the similar to GraftOutput method except is
   * allows you specify which output is affected. The specified index
   * must be a valid output number (less than
   * ProcessObject::GetNumberOfOutputs()). See the GraftOutput for
   * general usage information. */
  virtual void GraftNthOutput(unsigned int idx, OutputPathType *output);

  /** Make a DataObject of the correct type to used as the specified
   * output.  Every ProcessObject subclass must be able to create a
   * DataObject that can be used as a specified output. This method
   * is automatically called when DataObject::DisconnectPipeline() is
   * called.  DataObject::DisconnectPipeline, disconnects a data object
   * from being an output of its current source.  When the data object
   * is disconnected, the ProcessObject needs to construct a replacement
   * output data object so that the ProcessObject is in a valid state.
   * So DataObject::DisconnectPipeline eventually calls
   * ProcessObject::MakeOutput. Note that MakeOutput always returns a
   * SmartPointer to a DataObject. If a subclass of ImageSource has
   * multiple outputs of different types, then that class must provide
   * an implementation of MakeOutput(). */
  virtual DataObjectPointer MakeOutput(unsigned int idx);

protected:
  PathSource();
  virtual ~PathSource() {}
  void PrintSelf(std::ostream& os, Indent indent) const;
  
  // Inherit the empty ProcessObject::GenerateData()
  
  // Inherit ProcessObject::PrepareOutputs(), which calls Initialize()
  // (Image replaces w/ empty function)
  
private:
  PathSource(const Self&); //purposely not implemented
  void operator=(const Self&);   //purposely not implemented
};

} // end namespace itk

#ifndef ITK_MANUAL_INSTANTIATION
#include "itkPathSource.txx"
#endif

#endif
