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

  Program:   Visualization Toolkit
  Module:    vtkPNMReader.cxx

  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
  All rights reserved.
  See Copyright.txt or http://www.kitware.com/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 notice for more information.

=========================================================================*/
#include "vtkPNMReader.h"

#include "vtkImageData.h"
#include "vtkObjectFactory.h"

vtkStandardNewMacro(vtkPNMReader);

char vtkPNMReaderGetChar(FILE *fp)
{
  char c;
  int result;

  if ((result = getc(fp)) == EOF )
    {
    return '\0';
    }
  
  c = (char)result;
  if (c == '#')
    {
    do
      {
      if ((result = getc(fp)) == EOF )
        {
        return '\0';
        }
      c = (char)result;
      }
    while (c != '\n');
    }
  
  return c;
}

int vtkPNMReaderGetInt(FILE *fp)
{
  char c;
  int result = 0;
  
  do
    {
    c = vtkPNMReaderGetChar(fp);
    }
  while ((c < '1')||(c > '9'));
  do
    {
    result = result * 10 + (c - '0');
    c = vtkPNMReaderGetChar(fp);
    }
  while ((c >= '0')&&(c <= '9'));

  // put the CR/LF or whitespace back.....
  ungetc(c, fp);
  return result;
}
  

void vtkPNMReader::ExecuteInformation()
{
  int xsize, ysize, comp;
  char magic[80];
  char c;
  FILE *fp;

  // if the user has not set the extent, but has set the VOI
  // set the zaxis extent to the VOI z axis
  if (this->DataExtent[4]==0 && this->DataExtent[5] == 0 &&
      (this->DataVOI[4] || this->DataVOI[5]))
    {
    this->DataExtent[4] = this->DataVOI[4];
    this->DataExtent[5] = this->DataVOI[5];
    }

  if (!this->FileName && !this->FilePattern)
    {
    vtkErrorMacro(<<"Either a FileName or FilePattern must be specified.");
    return;
    }

  // Allocate the space for the filename
  this->ComputeInternalFileName(this->DataExtent[4]);
  
  // get the magic number by reading in a file
  fp = fopen(this->InternalFileName,"rb");
  if (!fp)
    {
    vtkErrorMacro("Unable to open file " << this->InternalFileName);
    return;
    }

  do
    {
    c = vtkPNMReaderGetChar(fp);
    if (c == '\0')
      { // Bad file.
      this->GetOutput()->SetWholeExtent(0, -1, 0, -1, 0, -1);
      fclose(fp);
      return;
      }
    }
  while (c != 'P');
  magic[0] = c;
  magic[1] = vtkPNMReaderGetChar(fp);
  magic[2] = '\0';

  // now get the dimensions
  xsize = vtkPNMReaderGetInt(fp);
  ysize = vtkPNMReaderGetInt(fp);

  // read max pixel value into comp for now
  vtkPNMReaderGetInt(fp);
  // if file is ascii, any amount of whitespace may follow.
  // if file is binary, a single whitespace character will follow.
  // We only support binary ppm and pgm files right now.  So the next
  // character IS always ignored.
  c = getc(fp);

  // if this file was "written" on the PC, then a CR will have been
  // written as a CR/LF combination.  So, if this single whitespace
  // character is a CR and it is followed by a LF, then swallow the
  // linefeed character as well. (Not part of the PPM standard, but a
  // a hard fact of life. 
  if ( c == 0x0d )
     {
     c = getc(fp);
     if ( c != 0x0a )
        {
        ungetc( c, fp );
        }
     }
     
  // Set the header size now that we have parsed it
  this->SetHeaderSize(ftell(fp));

  fclose(fp);

  // compare magic number to determine file type
  if ( ! strcmp(magic,"P5") ) 
    {
    comp = 1;
    }
  else if ( ! strcmp(magic,"P6") ) 
    {
    comp = 3;
    }
  else
    {
    vtkErrorMacro(<<"Unknown file type! " << this->InternalFileName 
                  <<" is not a binary PGM or PPM!");
    return;
    }

  // if the user has set the VOI, just make sure its valid
  if (this->DataVOI[0] || this->DataVOI[1] || 
      this->DataVOI[2] || this->DataVOI[3] ||
      this->DataVOI[4] || this->DataVOI[5])
    { 
    if ((this->DataVOI[0] < 0) ||
        (this->DataVOI[1] >= xsize) ||
        (this->DataVOI[2] < 0) ||
        (this->DataVOI[3] >= ysize))
      {
      vtkWarningMacro("The requested VOI is larger than the file's (" << this->InternalFileName << ") extent ");
      this->DataVOI[0] = 0;
      this->DataVOI[1] = xsize - 1;
      this->DataVOI[2] = 0;
      this->DataVOI[3] = ysize - 1;
      }
    }

  this->DataExtent[0] = 0;
  this->DataExtent[1] = xsize - 1;
  this->DataExtent[2] = 0;
  this->DataExtent[3] = ysize - 1;
  
  this->SetDataScalarTypeToUnsignedChar();
  this->SetNumberOfScalarComponents(comp);

  this->vtkImageReader::ExecuteInformation();
}


inline int iseol(int c)
{
  return c == 10 || c == 13;
}



int vtkPNMReader::CanReadFile(const char* fname)
{
  FILE *fp = fopen(fname, "rb");
  if(!fp)
    {
    return 0;
    } 
  unsigned char magic[3];
  if(fread(magic, 1, 3, fp) != 3)
    {
    fclose(fp);
    return 0;
    }
  int ok = ((magic[0] == 'P') &&
            iseol(magic[2]) &&
            (magic[1] >= '1' && magic[1] <= '6'));
  fclose(fp);
  if (ok)
    {
    return 3;
    }
  return 0;
}

//----------------------------------------------------------------------------
void vtkPNMReader::PrintSelf(ostream& os, vtkIndent indent)
{
  this->Superclass::PrintSelf(os,indent);
}