// ifdef.e
//
// Mon, 11/19/1992 18:00:00
//
// Purpose:
//
//    This extension searches your current buffer for #ifdef-relevant
//    C-preprocessor lines, and displays the ones that would be in effect
//    for the current line in a popup window.
//
// Usage:
//
//    Load this module and save your state file.
//
//
// Notes:
//
//    The extension searches backwards from the current position
//    backwards looking for:
//
//    <start-of-line>[white-space(s)]#[white-space(s)]if|el|end
//
//    This is the MS C/C++ 7.00 definition of preprocessor command syntax.
//
//    This search string assumes that
//         #if, #ifdef, #ifndef, and alike start with "if",
//         #else, #elif, and alike start with "el",
//         #end, #endif, and alike start with "end", and
//         no other preprocessor command uses these prefixes.
//
//    The whole command is bound to the A-i key.
//
// Example:
//
//    If you have the following text:
//
//       text #0
//       #ifdef COMPILE
//       text #1;
//       #elif FOO
//       text #2;
//       #else
//       #ifndef DEBUG
//       text #3;
//       #else
//       text #4;
//       #endif
//       text #5;
//       #endif
//       text #6;
//
//    and hit A-i while the cursor is on text:
//
//       TEXT #        OUTPUT
//       ------        ------
//       0             Not in a #if/#else/#endif block.
//
//       1             #ifdef COMPILE
//
//       2             #ifdef COMPILE
//                     #elif FOO
//
//       3             #ifdef COMPILE
//                     #elif FOO
//                     #else
//                     #ifndef DEBUG
//
//       4             #ifdef COMPILE
//                     #elif FOO
//                     #else
//                     #ifndef DEBUG
//                     #else
//
//       5             #ifdef COMPILE
//                     #elif FOO
//                     #else
//
//       6             Not in a #if/#else/#endif block.
//
//
// The modifications to this code are dedicated to the public domain
// with the caveat that Lugaru is welcome to use this within their
// distribution source code which is supplied with Epsilon.  Use it
// any way you want for whatever purposes. The catch is that this header
// has to be included in any file using this extension, and any changes
// made to this extension should be sent to me as well.
//
//
// Tuna Ertemalp
//
// INTERNET: tunae@microsoft.com
//           ertem@cs.stanford.edu
//
//
// Modification History:
//
//    Mon, 11/19/1992 18:00:00 V1.0 initial release.
//
// Thanks to:
//
//    John Kercheval, since I based most of these comments on his
//                    standard comment header. Couldn't have done
//                    a better job myself... :-)
//


#include <eel.h>

#define bool  int
#define true  1
#define false 0

#define IFELSEENDIFBUFFER "*#if/#else/#endif*"
#define SEARCHIFELSEENDIF "^([ \t]*#[ \t]*(if|el|end))"

command
show_preprocessor_if_then_else_structure()
on reg_tab[ALT('i')]
{
   int  oldPoint      = point;
   int  origbufnum    = bufnum;
   int  origbeginline = give_begin_line();
   int  bNum          = zap(IFELSEENDIFBUFFER);
   int  nest          = 0;
   bool found         = false;

   iter = 0;

   say("Searching...");

   nl_forward();

   while (re_search(-1,SEARCHIFELSEENDIF)) {

      if (character(matchstart-1) == 'd' &&
          point < origbeginline) {                // #end

         nest++;

      } else if (nest == 0) {

         found = true;

         buf_xfer(bNum,give_begin_line(),give_end_line()+1);

         bufnum = bNum;
         point = 0;
         bufnum = origbufnum;

      } else if (character(matchstart-1) == 'f') { // #if

         nest--;

      }
   }

   point = oldPoint;

   if (found) {

      say("Search completed.");
      view_buf(bNum,0);

   } else {

      say("Not in a #if/#else/#endif block.");
   }

   buf_delete(bNum);
}