/*
 * This GIF decoder is designed for use with Bert Tyler's FRACTINT
 * program. It should be noted that the "FRACTINT" program only decodes
 * GIF files FRACTINT creates, so this decoder code lacks full generality
 * in the following respects: supports single image, non-interlaced GIF
 * files with no local color maps and no extension blocks.
 *
 * GIF and 'Graphics Interchange Format' are trademarks (tm) of
 * Compuserve, Incorporated, an H&R Block Company.
 *
 *											Tim Wegner
 */

#include <stdio.h>
#include <string.h>
#include <dos.h>

#include "fractint.h"

#define MAXCOLORS	256

struct RGB
{
   unsigned char red, green, blue;
};

extern int decoder();
extern int rowcount;					/* row counter for screen */
extern char readname[]; 				/* file name		*/
static FILE *fpin = NULL;				/* FILE pointer 	    */
unsigned int height;

extern	FILE *dacfile;
extern	char MAP_name[];
extern	int	mapset;

extern int glassestype;
extern int display3d;
extern int dotmode;					/* so we can detect disk-video */
extern int calc_status;
extern long calctime;
extern long timer_interval;

int bad_code_count = 0; 				/* needed by decoder module */

get_byte()
{
   static int c;

   /* make sure fpin NULL if not open */
   if (!fpin)
   {
      char temp1[81];

      strcpy(temp1,readname);
      if (strchr(temp1,'.') == NULL) {
	 strcat(temp1,DEFAULTFRACTALTYPE);
	 if ((fpin = fopen(temp1,"rb")) != NULL) {
	    fclose(fpin);
	    }
	 else {
	    strcpy(temp1,readname);
	    strcat(temp1,ALTERNATEFRACTALTYPE);
	    }
	 }

      if ((fpin = fopen(temp1, "rb")) == NULL)
	 return (-1);
   }
   return (fgetc(fpin)); /* EOF is -1, as desired */
}

extern unsigned char dacbox[256][3];	/* Video-DAC (filled in by SETVIDEO) */
extern int reallyega;			/* "really-an-ega" flag */
extern int paletteVGA[16];		/* VGA Palette-to-DAC registers */
extern unsigned char decoderline[2049]; /* write-line routines use this */

/* Main entry decoder */
gifview()
{
   unsigned numcolors;
   unsigned char buffer[16];
   unsigned width, finished;

   int status;
   int i, j, k, planes;

   status = 0;

   /* initialize the row count for write-lines */
   rowcount = 0;

   /* zero out the full write-line */
   for (width = 0; width < 2049; width++) decoderline[width] = 0;

   /* Get the screen description */
   for (i = 0; i < 13; i++)
   {
      if ((buffer[i] = (unsigned char)get_byte ()) < 0)
      {
	 close_file();
	 return(-1);
      }
   }

   if(strncmp(buffer,"GIF87a",3) ||             /* use updated GIF specs */
      buffer[3] < '0' || buffer[3] > '9' ||
      buffer[4] < '0' || buffer[4] > '9' ||
      buffer[5] < 'A' || buffer[5] > 'z' )
   {
      close_file();
      return(-1);
   }

   planes = (buffer[10] & 0x0F) + 1;

   if((buffer[10] & 0x80)==0)	 /* color map (better be!) */
   {
      close_file();
      return(-1);
   }
   numcolors = 1 << planes;

   for (i = 0; i < numcolors; i++)
   {
      if (numcolors == 16 && !reallyega)	/* straight copy or indirect via palette? */
	 k = paletteVGA[i];
      else
	 k = i;
      for (j = 0; j < 3; j++) {
	 if ((buffer[j] = (unsigned char)get_byte()) < 0)
	    return(-1);
	 if (dacbox[0][0] != 255)	/* (only if we really have a DAC) */
	    if(!display3d || (glassestype != 1 && glassestype != 2))
	       dacbox[k][j] = buffer[j] >> 2;
      }
   }
   /* don't read if glasses */
   if (mapset && glassestype!=1 && glassestype != 2)
   {
       dacfile = fopen(MAP_name,"r");
       ValidateLuts(dacfile);  /* read the palette file */
       fclose(dacfile); /* close it */
       if (dotmode != 11)
	  spindac(0,1); /* load it, but don't spin */
   }
   if (dacbox[0][0] != 255 && dotmode != 11)
      spindac(0,1);	  /* update the DAC */

   if (dotmode == 11) /* disk-video */
   {
       movecursor(2,0);
       printf("...restoring...");
   }

   /* Now display one or more GIF objects */
   finished = 0;
   while (!finished)
   {
      switch (get_byte())
      {
      case ';':
	 /* End of the GIF dataset */

	 finished = 1;
	 status = 0;
	 break;

	case '!':                               /* GIF Extension Block */
		get_byte();			/* read (and ignore) the ID */
		while ((i = get_byte()) > 0)	/* get the data length */
			for (j = 0; j < i; j++)
				get_byte();	/* flush the data */
		break;
      case ',':
	 /*
	  * Start of an image object. Read the image description.
	  */

	  for (i = 0; i < 9; i++)
	  {
	     if ((buffer[i] = (unsigned char)get_byte ()) < 0)
	     {
		status = -1;
		break;
	     }
	  }
	  if(status < 0)
	  {
	     finished = 1;
	     break;
	  }

	  width  = buffer[4] | buffer[5] << 8;
	  height = buffer[6] | buffer[7] << 8;

	 /* Setup the color palette for the image */

	 if (calc_status == 1) /* should never be so, but make sure */
	    calc_status = 0;
	 status = timer(decoder,1,width);
	 if (calc_status == 1) /* e.g., set by line3d */
	 {
	    calctime = timer_interval; /* note how long it took */
	    if (keypressed() != 0)
	       calc_status = 3; /* interrupted, not resumable */
	    else
	       calc_status = 4; /* complete */
	 }
	 finished = 1;
	 break;
      default:
	 status = -1;
	 finished = 1;
	 break;
      }
   }
   close_file();
   if (dotmode == 11) /* disk-video */
   {
       home();
       printf("Restore completed        \n\n                    ");
   }

   /* if (status == 0)
      buzzer(0); */		/* audible signal - we done */
   return(status);
}
close_file()
{
   fclose(fpin);
   fpin = NULL;
}