#pragma implementation
#include <virtpos.h>

virtpos::virtpos(const char *s) {
  pos = idx = 0; str = s ? s : "";
}

/* We don't handle CRs because this requires scanning the entire string
 * before being able to map position to index.  This would be workable
 * if the higher levels would keep virtpos objects around at least for
 * the current line.
 */

// map a screen position to a string index
// the screen position of the beginning of the string index is saved in pos
int virtpos::mappos(int offset) {
  if (offset < pos)
    pos = idx = 0;
#if 0
  /* this optimization doesn't seem to work!  The idea was to
     keep the pos & idx around to make small movements left and right
     cheap to compute. */
  while (idx > 0 && pos > offset) {
    switch (str[--idx]) {
    case '\t':
      pos = (pos - 1) & ~7;
      break;
    default:
      --pos;
    }
  }
#endif
  int inc;
  while (str[idx] && pos < offset) {
    switch (str[idx++]) {
    case '\f':
      inc = 10;
      break;
    case '\t':
      inc = 8 - (pos & 7);
      break;
    case '\b':
      if (pos)
	--pos;
      continue;
    default:
      ++pos;
      continue;
    }
    if (pos + inc > offset)
      return --idx;
    pos += inc;
  }
  return idx;
}

int virtpos::mapidx(int i) {
  // this is not actually correct when backspaces are present
  int offset;
  for (offset = i; mappos(offset) < i && str[idx]; ++offset)
    ;
  return offset;
}

// display string beginning at virtual line position offset
void virtpos::expand(int offset,CHTYPE *buf,int len) {
  mappos(offset);
  int i = 0;
  int max = 0;
  CHTYPE attr = A_NORMAL;
  pos = offset;
  while (str[idx]) {
    switch (str[idx++]) {
    case '\f': {
      const char *p = "[New Page]";
      while (*p && i < len) {
	buf[i++] = *p++ | A_REVERSE;
	++pos;
      }
      if (i > max) max = i;
      if (i >= len) break;
      continue;
    }
    case '\t':
      do {
	if (i < len)
	  buf[i++] = ' ' | attr;
      } while (++pos & 7);
      if (i > max) max = i;
      if (i >= len) break;
      continue;
    case '\b':
      if (pos) {
	--pos;
	--i;
      }
      continue;
    default:
      if (i >= len) break;
      unsigned char c = str[idx-1];
      if (i < 0)
	continue;
      if (i < max) {
	if ((char)buf[i] == '_')
	  buf[i] = c | attr | A_UNDERLINE;
	else if (c == '_')
	  buf[i] |= A_UNDERLINE;
	else if (c != ' ')
	  buf[i] |= A_STANDOUT;
      }
      else
	buf[i] = c | attr;
      if (++i > max) max = i;
      ++pos;
      continue;
    }
    break;
  }
  while (max < len)
    buf[max++] = ' ' | attr;
}