NEDIT_require_macro_file("RSextensions.nm")
NEDIT_require_macro_file("RSselect.nm")
NEDIT_require_macro_file("centerline.nm")

# ------------------------------------------------------------------------------
# RangeSet_NavigateWhich([rs [, ask]]): if rangeset name rs is supplied, it is
#       checked for validity. If OK, it is returned. Otherwise, or if a second
#       argument is supplied, a new rangeset name is requested from the user
#       and returned. Whatever the result, $RS_Navigate["?"] is updated as
#       as appropriate.
# ------------------------------------------------------------------------------

define RangeSet_NavigateWhich
  {
  RSnavigation = "Navigation Range Set"
  none = !RangeSet_defined()

  $RS_Navigate[""] = ""
  error = ""

  blank = ""
  oldrs = ""
  current = ""
  if ("?" in $RS_Navigate)
    {
    oldrs = $RS_Navigate["?"]
    if (oldrs != "")
      current = "\n(Current " RSnavigation " name is \"" oldrs "\")"
    }

  rs = oldrs
  if ($n_args <= 1)
    {
    if ($n_args == 1)
      {
      if (RangeSet_defined($1))
        {
        $RS_Navigate["?"] = $1
        return $1
        }
      }

    # no args given
    if (RangeSet_defined(oldrs))
      return oldrs
    }

  # two arguments or more; or an error - ask
  if (none)
    error = RSnavigation " cannot be chosen: no range set defined" current
  else if (oldrs != "")
    {
    if (!RangeSet_defined(oldrs))
      error = RSnavigation " \"" oldrs "\" not defined in this document"
    else
      error = RSnavigation " was \"" oldrs "\""
    }


  # ask for a rangeset to navigate if any
  if (error != "")
    blank = "\n\n"
  if (!none)
    {
    rs = RangeSet_askExisting(error blank "Range set to navigate")
    if (RangeSet_defined(rs))
      {
      dialog(RSnavigation" "rs" has "$RangeSet_ranges" ranges")
      $RS_Navigate["?"] = rs
      return rs
      }
    }
  else if (error != "")
    dialog(error)

  return ""
  }

# ------------------------------------------------------------------------------
# RangeSet_Navigate(rs, direction, selectit, center): "navigates" the given
#       rangeset rs's ranges, asking for a valid rangeset if rs is empty or
#       invalid. Each time this is called, the cursor is moved in the current
#       window to the next or previous range in the set, if any.
#       If the operation cannot be completed, a beep is issued. Direction
#       should be a negative value for backward navigation; otherwise it is
#       forward. If selectit is non-zero, the range "navigated to" is selected;
#       if center is non-zero, the cursor line after cursor movement is centered
#       in the window.
# ------------------------------------------------------------------------------

define RangeSet_Navigate
  {
  rs = $1
  direction = $2
  selectit = 0
  center = 0
  if ($n_args > 2)
    {
    selectit = $3
    if ($n_args > 3)
      center = $4
    }

  if (rs == "")
    rs = RangeSet_NavigateWhich()
  else
    rs = RangeSet_NavigateWhich(rs)

  nrs = $RangeSet_ranges
  if (nrs == 0 || !("?" in $RS_Navigate))
    {
    return
    }

  # are we in a range of the set?
  prev = -1
  next = -1
  pos = $cursor
  r = -1

  if (RangeSet_includes_pos(rs, pos))
    {
    # we are in a range: if we're at its front, our prev is before it
    prev = $RangeSet_range_index - (pos == $RangeSet_range_start)
    next = $RangeSet_range_index + 1
    }
  else
    {
    # we are not in a range: find which gap we are in
    hi = nrs
    lo = 0
    for (mi = nrs / 2; lo < hi; mi = (lo + hi) / 2)
      {
      RangeSet_defined(rs, mi)
      if (pos < $RangeSet_range_start)
        hi = mi
      else
        lo = mi + 1
      }

    next = hi
    prev = next - 1
    }

  # right: move appropriately
  if (direction < 0 && prev >= 0)
    {
    # backward - use prev
    r = prev
    }
  else if (direction >= 0 && next < nrs)
    {
    # forward - use next
    r = next
    }
  else
    {
    # chosen direction has no more range motion possible
    beep()
    return
    }

  RangeSet_defined(rs, r)
  # try to maximise the visibility of the new range,
  # finishing with the cursor at the front of the range
  set_cursor_pos($RangeSet_range_end)
  if (center)
    centerline()
  set_cursor_pos($RangeSet_range_start)
  if (selectit)
    RangeSet_select(rs, r)
  }