/* 
 *  HISTORY.C - command line history.
 *
 *
 *
 *  Comments:
 *
 *  14/01/95 (Tim Norman) ---------------------------------------------------
 *    started.
 *
 *  08/08/95 (Matt Rains) ---------------------------------------------------
 *    i have cleaned up the source code. changes now bring this source into
 *    guidelines for recommended programming practice.
 */

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

#define MAXLINES 128

unsigned history_size = 256; /* make this configurable later */

void history(int dir, char *commandline)
{
   static char *history = NULL; 
   static char *lines[MAXLINES];
   static unsigned int curline = 0;
   static unsigned int numlines = 0;
   static unsigned int maxpos = 0;
   int count; 
   int length;

   if(!history)
   {
      history = malloc(history_size * sizeof(char));
      lines[0] = history;
      history[0] = 0;
   }

   if(dir > 0) /* next command */
   {
      if(curline < numlines)
      {
         curline++;
      }

      if(curline == numlines)
      {
         commandline[0] = 0;
      }
      else
      {
         strcpy(commandline, lines[curline]);
      }
   }
   else if(dir < 0) /* prev command */
   {
      if(curline > 0)
      {
         curline--;
      }

      strcpy(commandline, lines[curline]);
   }
   else /* add to history */
   {
      /* remove oldest string until there's enough room for next one */
      /* strlen (commandline) must be less than history_size! */
      while(maxpos + strlen (commandline) + 1 > history_size || numlines >= MAXLINES)
      {
         length = strlen(lines[0]) + 1;

         for(count = 0; count < maxpos && count + (lines[1] - lines[0]) < history_size; count++)
         {
            history[count] = history[count + length];
         }

         maxpos -= length;

         for(count = 0; count <= numlines && count < MAXLINES; count++)
         {
            lines[count] = lines[count + 1] - length;
         }

         numlines--;
#ifdef DEBUG         
         printf("Reduced size:  %ld lines\n", numlines);

         for(count = 0; count < numlines; count++)
         {
            printf("%d: %s\n", count, lines[count]);
         }
#endif
      }

      strcpy(lines[numlines], commandline);
      numlines++;
      lines[numlines] = lines[numlines - 1] + strlen (commandline) + 1;
      maxpos += strlen(commandline) + 1;
      curline = numlines; /* last line, empty */
   }

   return;
}