% Here is a new version of isearch.sl reworked by John Burnell <johnb@whio.grace.cri.nz>.
% This one is said to be more emacs-like.
%% isearch.sl
%% Routines here perform incremental forward/backward searches
%% 
%% ESCAPE key aborts the search
%% ENTER key finds next match
%% DELETE key deletes last character entered and returns to previous point
%%
%%  "isearch_forward"	"^FIf"   setkey  %(sample bindings)
%%  "isearch_backward"	"^FIb"   setkey

variable Isearch_Last_Search = Null_String;

%% This code fragment checks to see what the isearch keys are bound to
variable Isearch_Forward_Char = 19;   %^S
variable Isearch_Backward_Char = 18;  %^R

static define get_bound_key (search_func, default)
{
   variable n, key;
   if (n = which_key (search_func), n)  
     {
	key = (); n--;
	if (strlen (key) == 2) 
	  {
	     if (key [0] == '^') 
	       return (key [1] - '@');
	  }
     }
   return default;
}

Isearch_Forward_Char = get_bound_key ("isearch_forward", 19);
Isearch_Backward_Char = get_bound_key ("isearch_backward", 18);

static define isearch_simple_search (dir)
{
#iffalse
   variable fun, prompt;
   
   prompt = "Search:";
   fun = &fsearch;
   
   if (dir < 0)
     {
	prompt = "Search Backwards:";
	fun = &bsearch;
     }
   
   Isearch_Last_Search = read_mini (prompt, Isearch_Last_Search, Null_String);
   
   !if (@fun (Isearch_Last_Search))
     error ("Not Found.");
#else
   if (dir < 0)
     search_backward ();
   else
     search_forward ();
   Isearch_Last_Search = LAST_SEARCH;
#endif
}

static define perform_search (str, dir)
{
   variable cs = CASE_SEARCH;
   if (strlow (str) != str)
     CASE_SEARCH = 1;
   
   if (dir == 1) 
     dir = fsearch (str);
   else
     dir = bsearch (str);
   
   cs = CASE_SEARCH;
   return dir;
}


static define isearch_del (str)
{
   variable n = strlen (str);
   if (n) str = substr (str, 1, n - 1);
   str;
}


define isearch_dir (dir)
{
   variable prompt, str = Null_String;
   variable c, m, first = 1;
   variable len = 0;
   
  % This is tricky.  I am leaving a 1 or a 0 on the stack which indicates
  % whether or not a character is attached to a mark.  The number of ones
  % and zeros on the stack should match the value of m.
  % These 0s and 1s are used when unwinding the search stack
  % Since a mark was pushed and not attached to a character, push 0
  
   push_mark ();
   0;
   m = 1;
   ERROR_BLOCK { loop (m) { pop (); pop_mark (0);}} %make sure we pop marks
  
   forever {
      if (dir == 1)
      	prompt = "Isearch forward: ";
      else
      	prompt = "Isearch Backward: ";
      message (prompt + str);
      push_spot ();
      if ((dir > 0) and looking_at (str))
	{
	   go_right (strlen (str));
	}
      update_sans_update_hook (0);
      pop_spot ();
            
      c = getkey();
      switch (c)
	{ case 27 and first : isearch_simple_search (dir); break;}
        { case Isearch_Forward_Char :       % ^S
	   push_mark (); ++m; 0;             % mark not attached to char!
	   if (dir < 0) {
	      dir = 1;
	   } else {
	      go_right_1 ();
	      !if (strlen (str)) 
		{
		   str = Isearch_Last_Search;
		   len = strlen (str);
		}
	   }
        }  
        { case Isearch_Backward_Char :  %^R
	   push_mark (); 0; ++m;         % mark not attached to char!
	   if (dir > 0) {   
	      dir = -1;
	      c = ' ';                      % use this to fool test (*) below
	   } else  {
	      !if (strlen (str)) str = Isearch_Last_Search;
	   }
        }
        { case 127 : 
		  
	  if (m) {
	    if (()) { 
	      if (strlen (str)) str = isearch_del (str); % delete char
	    }
	    --m; pop_mark (1);     % top of stack already popped
	  }
	  continue;
        }
        { case 7 : % ^G go back to start
	   loop (m - 1) {pop (); pop_mark (0);}  % pop marks
	   pop ();
	   pop_mark (1);                      % go to start of search
	   beep ();
	   return;
	}
	{
	 case '\r' and first:
	   loop (m)
	     {
		pop ();
		pop_mark (0);
	     }
	   m = 0;
	   if (dir > 0) return search_forward ();
	   else return search_backward ();
	}
	{
	 case '\e':
	   if (input_pending (3))
	     ungetkey (c);
	   break;
	}
#ifdef IBMPC_SYSTEM
	{
	 case 0xE0:
	   ungetkey (c);
	   break;
	}
#endif
        { c < 32 :
	   if (c != '\r') ungetkey (c);
	   break; 	       % terminate search
	}

	{ str += char (c);             % any other char  
	   1; push_mark(); ++m;	       % push 1 and mark  
	}

      first = 0;

% test (*), see ^R switch above
      if ((dir < 0) and (m > 1) and looking_at (str) and (c >= ' ')) 
	continue;
      
      if (perform_search (str, dir))
	len = strlen (str);
      else
	{
 	   if (c == Isearch_Forward_Char) go_left_1();
	   flush (str + " not found.");
	   beep ();
	   () = input_pending (10); 
	   if (() == 1) str = isearch_del (str);
	   --m; pop_mark (0);     % top of stack already popped in test
	   if (EXECUTING_MACRO)
	     error ("not found.");
	}
   }
  
   EXECUTE_ERROR_BLOCK;
   if (strlen (str)) 
     Isearch_Last_Search = str;
   if (dir == 1) 
     go_right (strlen (str) - len);
   message ("Done.");

   %flush_input ();
}

static variable save_abort;
 
define isearch_forward()
{
   save_abort = IGNORE_USER_ABORT;
   IGNORE_USER_ABORT = 1;
   isearch_dir (1);
   IGNORE_USER_ABORT = save_abort;
}

define isearch_backward()
{
   save_abort = IGNORE_USER_ABORT;
   IGNORE_USER_ABORT = 1;
   isearch_dir (-1);
   IGNORE_USER_ABORT = save_abort;
}