//  crm_expr_window.c  - Controllable Regex Mutilator,  version v1.0
//  Copyright 2001-2004  William S. Yerazunis, all rights reserved.
//  
//  This software is licensed to the public under the Free Software
//  Foundation's GNU GPL, version 2.  You may obtain a copy of the
//  GPL by visiting the Free Software Foundations web site at
//  www.fsf.org, and a copy is included in this distribution.  
//
//  Other licenses may be negotiated; contact the 
//  author for details.  
//
//  include some standard files
#include "crm114_sysincludes.h"

//  include any local crm114 configuration file
#include "crm114_config.h"

//  include the crm114 data structures file
#include "crm114_structs.h"

//  and include the routine declarations file
#include "crm114.h"

//    the command line argc, argv
extern int prog_argc;
extern char **prog_argv;

//    the auxilliary input buffer (for WINDOW input)
extern char *newinputbuf;

//    the globals used when we need a big buffer  - allocated once, used 
//    wherever needed.  These are sized to the same size as the data window.
extern char *inbuf;
extern char *outbuf;
extern char *tempbuf;

//    a helper function that should be in the C runtime lib but isn't.
//
char *my_strnchr (const char *str, long len, int c)
{
  long i;
  i = 0;
  for (i = 0; i < len; i++)
    {
      if (str[i] == (char) c)
	return ((char *) &(str[i]));
    };
  return (NULL);
}

  
int crm_expr_window (CSL_CELL *csl, ARGPARSE_BLOCK *apb)
{
  //       a window operation - two steps...first is to discard
  //       everything up till the first regex match, and second
  //       is to add more data until the second regex is
  //       satisfied by the incoming data.  We just add the
  //       incoming data onto the back of the window buffer, and
  //       when we get a read completes.
  //
  //       Yes, there are more efficient, less memory-intensive ways
  //       to do this, but this is simple and unlikely to be broken in 
  //       subtle ways.
  
  static long newbuflen = 0;
  char pch [MAX_PATTERN];

  long i;
  long srcidx;
  int inputsrc;
  char inputsrcname[MAX_VARNAME];
  long inputsrclen;
  char *savedinputtxt;
  long savedinputtxtlen;
  char wvname [MAX_VARNAME];
  long wvnamelen;
  CSL_CELL* mdw;
  long flen;
  int regexflags;
  regex_t preg;
  //  int inputmode;
  int inputsize;         //  can be by char or by EOF  < bychar byeof >
  int inputretryEOF;     //  do we retry an EOF?       < eoffails eofretry >
  int inputEOFaccept;    //  accept an EOF as pat-end  < acceptEOF >
  int saweof;
  int failout;
  long vmidx;
  regmatch_t matches [2];  //  we're only interested in the first match.
  int done;
  int firsttime;


  inputsrcname[0] = '\000';
  inputsrclen = 0;
  
  //	wvname[0] = '\000';
  //wvnamelen = 0;
  
  srcidx = 0;
  savedinputtxt = NULL;
  savedinputtxtlen = 0;
  failout = 0;

  if (user_trace) 
    fprintf (stderr, "Executing a 'window' operation\n");

  //       there's the choice of input from a 
  //       variable, or input from stdin.  This is controlled strictly
  //       by whether there's a [] in the statement (someday it may 
  //       allow other files than stdin, but not yet.)  So right now, it's-
  //          1) read from the variable [:foo:] if supplied, else
  //          2) read from STDIN (default)
  //                these are inputsrc=FROM_VAR vs FROM_STDIN
#define FROM_STDIN 0
#define FROM_VAR 1
#define FROM_VAR_DONE 2
  //      
  //       Second, there's how much to read "preemptively", that is,
  //       to read ahead, but with the possibility of reading ahead too
  //       much (and thereby messing up a script or other typeahead that
  //       another program sharing stdin was meant to actually read.  
  //       The three choices we support are:
  //          1) read everything available (BYEOF), else
  //          3) read one character at a time (BYCHAR) (default)
  //                 these are inputsize = bychar, byeof
#define BYCHAR 0
#define BYEOF 1
#define BYLINE 999   //  DANGER - BYLINE IS NOT SUPPORTED ANY MORE!!!
  //
  //       Third, there's the question of what to do if the read doesn't
  //       have enough material to satisfy the second regex (i.e. we hit 
  //       end of variable or EOF first). 
  //  
  //       Our options are 
  //  
  //       1) just fail.  (the default)
  //       2) just accept what we got, even though it doesn't fulfill
  //          the paste regex (accepteof).
  //      these are expressed as inputEOFaccept= ...
#define EOFFAILS 0
#define EOFACCEPTS 1
  //

  //       As to other behavior, we can also clear the eof, wait a
  //       bit, and try again, so we have:
  //
  //          1) leave EOF's alone.
  //          2) try to reset the EOF before reading
  //              these are denoted by inputretryEOF = ...
#define EOFSTAYS 0
#define EOFRETRY 1
  
  //      check for the flags
  //
  //   default is BYCHAR
  inputsrc = 0;
  inputEOFaccept = EOFFAILS;
  inputsize = BYCHAR;
  inputretryEOF = EOFSTAYS;
  if (apb->sflags & CRM_BYCHAR)
    {
      if (user_trace)
	fprintf (stderr, "  window input by character\n");
      inputsize = BYCHAR;
    };
  if (apb->sflags & CRM_BYEOF)
    {
      if (user_trace)
	fprintf (stderr, "  window input by EOFs\n");
      inputsize = BYEOF;
    };
  inputEOFaccept = EOFFAILS;
  if (apb->sflags & CRM_EOFACCEPTS)
    {
      if (user_trace)
	fprintf (stderr, "  window input EOF is always accepted\n");
      inputEOFaccept = EOFACCEPTS;
    };
  inputretryEOF = EOFSTAYS;
  if (apb->sflags & CRM_EOFRETRY)
    {
      if (user_trace)
	fprintf (stderr, "  window input EOF is retried\n");
      inputretryEOF = EOFRETRY;
    };
  regexflags = REG_EXTENDED;
  if (apb->sflags & CRM_NOCASE)
    {
      if (user_trace)
	fprintf (stderr, "  no case matching turned on\n ");
      regexflags = regexflags | REG_ICASE;
    };
  if (apb->sflags & CRM_NOCASE)
    {
      if (user_trace)
	fprintf (stderr, "  no case matching turned on\n ");
      regexflags = regexflags | REG_ICASE;
    };
  if (apb->sflags & CRM_LITERAL)
    {
      if (user_trace)
	fprintf (stderr, "  no case matching turned on\n ");
      regexflags = regexflags | REG_LITERAL;
    };
  
  //    part 1: dispose of old window worth of data.  If no match,
  //    dispose of all of the old window.
  //  
  //     get the disposal pattern	
  //
  crm_get_pgm_arg (pch, MAX_PATTERN, apb->s1start, apb->s1len);
  
  //     null window check - if no cut or paste patterns, then we
  //     just skip to the end of the WINDOW statement code
  //     which is how a WINDOW statement can be used to have a
  //     program "come out running" before reading stdin.
  if (apb->s1len == 0 && apb->s2len == 0)
    goto crm_window_no_changes_made;
  
  //     We have the first pattern in pch.  We ought to look for the
  //     appropriate flags here (common code, anyone?) but for now,
  //     we'll just do a brutally straightforward expansion and then
  //     matching.
  
  if (internal_trace)
    fprintf (stderr, " window cut pattern ---%s---\n", pch);
  flen = apb->s1len;
  
  //       expand the match pattern
  flen = crm_nexpandvar (pch, apb->s1len, MAX_PATTERN);
  //
  //       compile the regex
  i = crm_regcomp (&preg, pch, flen, regexflags);
  if ( i > 0)
    {
      crm_regerror ( i, &preg, tempbuf, data_window_size);
      nonfatalerror ("Regular Expression Compilation Problem:", tempbuf);
      goto invoke_bailout;
    };
  
  //    Get the variable we're windowing.  If there's no such
  //    variable, we default to :_dw:
  
  crm_get_pgm_arg (wvname, MAX_PATTERN, apb->p1start, apb->p1len);
  wvnamelen = crm_nexpandvar (wvname, apb->p1len, MAX_PATTERN);
  //    if no svname, then we're defaulted to :_dw:
  if (strlen (wvname) == 0)
    {
      strcat (wvname, ":_dw:");
      wvnamelen = strlen (":_dw:");
    };
  
  vmidx = crm_vht_lookup (vht, wvname, 
			  strlen (wvname));
  if (vht[vmidx] == NULL)
    {
      nonfatalerror ("We seem to be windowing a nonexistent variable.",
		     "How very bizarre.");
      goto invoke_bailout;
    }
  
  mdw = NULL;
  if (vht[vmidx]->valtxt == cdw->filetext) mdw = cdw;
  if (vht[vmidx]->valtxt == tdw->filetext) mdw = tdw;
  if (mdw == NULL)
    {
      nonfatalerror ("We seem to have lost the windowed var buffer",
		     "This is just plain sick.");
      goto invoke_bailout;
    }

  //
  //
  //       OK, we've got the arguments for part 1 - the cutting out
  //       of the old data.  So, let's do the cut.
  //     
  //       execute the regex.
  i = crm_regexec ( &preg, 
		    &(vht[vmidx]->valtxt[vht[vmidx]->vstart]),
		    vht[vmidx]->vlen, 
		    1, matches, 0, NULL);
  crm_regfree (&preg);
  
  //       starting offset of the "keep section" is at matches[0].rm.eo
  //       so we use crm_slice_and_splice_window to get rid of it.
  //
  if (i == 0)
    {
      //     delete everything up to and including the delimiter
      crm_slice_and_splice_window (mdw,
				   vht[vmidx]->vstart, 
				   -matches[0].rm_eo);
    }
  else
    {
      //  didn't find the terminator pattern at all, which means we
      //  flush the input window completely.

      crm_slice_and_splice_window (mdw,
				   vht[vmidx]->vstart, 
				   -vht[vmidx]->vlen);
    };
  
  if (user_trace) 
    fprintf (stderr, "  cut completed, variable length after cut is %ld\n", 
	     vht[vmidx]->vlen);

  //**************************************************************  
  //       OK, part one is done- we've windowed off the first
  //       part of the input.  
  //
  //       Now we put the new 
  //
  //        Now we get the "put" half of the regex.

  if (user_trace)
    fprintf (stderr, " now finding new section to add to end.\n");

  crm_get_pgm_arg (pch, MAX_PATTERN, apb->s2start, apb->s2len);
  flen = apb->s2len;
  if (user_trace)
    fprintf (stderr, "adding input with terminator of --%s--,", pch);
  
  //       expand the match pattern
  flen = crm_nexpandvar (pch, flen, MAX_PATTERN);
  
  if (user_trace)
    fprintf (stderr, " which expands to --%s--", pch);
  
  //
  //       compile the paste match regex 
  i = crm_regcomp (&preg, pch, flen, regexflags);
  if ( i > 0)
    {
      crm_regerror ( i, &preg, tempbuf, data_window_size);
	    nonfatalerror ("Regular Expression Compilation Problem:", tempbuf);
	    goto invoke_bailout;
    };
  
  //    decide - do we suck input from stdin, or from
  //    a variable that's already here?
  //
  //     Get the input source, if one is supplied (2nd set of parens is
  //     the var to use as input source, if it exists)
  crm_get_pgm_arg (inputsrcname, MAX_PATTERN, apb->p2start, apb->p2len);
  inputsrclen = apb->p2len;

  if (apb->p2start)
    {
      //     NonZero input source variable, so we're gonna take our input
      //     from this input variable.
      inputsrc = FROM_VAR;
      if (user_trace)
	fprintf (stderr, "  getting input from var %s\n", inputsrcname);
    };
  
  //
  //    Now, depending on inputmode, we set up the final pasting
  //    to do the right thing (the final pasting params are in 
  //     matches[0] ).  
  //
  //     we'll set up dummy limits for now though...
  //
  matches[0].rm_so = 0;
  matches[0].rm_eo = 0;
  
  //   Now, the WHILE loop to find satisfaction for the second
  //   regex, within the boundaries of from_var vs from_stdin, and
  //   byline vs bychar vs byeof.  So it's really a read/test/maybe_loop
  //   loop.

  done = 0;
  saweof = 0;
  firsttime = 1;

  while (! done)
    {
      //
      //     Switch on whether we're reading from a var or from
      //     standard input.  (either way, we use the newinputbuf)
      //
      switch (inputsrc)
	{
	case FROM_VAR:
	  {
	    //    we're supposed to grab our input from an input variable.
	    //     so we fake it as though it came from a file.
	    //
	    //    Later on, we have to undo the faking, and also modify
	    //    the length of the input variable (cutting out the stuff 
	    //    that went into the WINDOW).
	
	    //   diagnostic - what was in the newinputbuf before this stmt?
	    if (user_trace)
	      {
		fprintf (stderr, " Using input source from variable %s\n",
			 inputsrcname);
		fprintf (stderr, "   prior newinput buf --%s--\n", 
			 newinputbuf);
	      }
	    
	    //  Get the source input stuff
	    // 
	    srcidx = crm_vht_lookup (vht, inputsrcname, inputsrclen);
	    if (vht[srcidx] == NULL) 
	      {
		nonfatalerror ("Trying to take WINDOW input from"
			       "nonexistent variables doesn't work,"
			       "in this case, from :", inputsrcname);
		goto invoke_bailout;
	      };
	    //
	    //
	    //    malloc up some temporary space to keep the static input
	    //   buffer's stored text
	    savedinputtxt = (char *) 
	      malloc (sizeof (char) * (32 + newbuflen ));
	    if (savedinputtxt == NULL)
	      {
		fatalerror ("Malloc in WINDOW failed.  Aw, crud.", 
			    "Can't WINDOW this way");
		goto invoke_bailout;
	      };
	    
	    //
	    //    save our newinputbuf txt
	    strncpy (savedinputtxt,
		     newinputbuf,
		     newbuflen);
	    savedinputtxtlen = newbuflen;
	    //
	    //     and push the contents of the variable into newinputbuf
	    //     (we know it's no bigger than data_window_len)
	    strncpy (newinputbuf, 
		     &vht[srcidx]->valtxt[vht[srcidx]->vstart], 
		     vht[srcidx]->vlen );
	    newinputbuf[vht[srcidx]->vlen] = '\000';
	    newbuflen = vht[srcidx]->vlen;
	    //
	    //    and there we have it - newintputbuf has all we will
	    //    get from this variable.  
	    //  
	    //    Mark the fact that we're done with this variable by
	    //    setting inputsrc to FROM_VAR_DONE;
	    inputsrc = FROM_VAR_DONE;
	    saweof = 1;
	  };
	  break;
	case FROM_VAR_DONE:
	  {
	    if (user_trace)
	      fprintf (stderr, "  got to FROM_VAR_DONE - this should"
		       " NEVER happen.  You've ound a bug.");
	    saweof = 1;
	  }
	  break;
	case FROM_STDIN:
	  {
	    int icount;
	    icount = 0;
	    if (!firsttime )
	      {
		//  If we're reading from stdin, then we have three options:
		//   read a character, read up to (and including) the newline,
		//   or read till EOF.  After each one, we set 
		if (feof(stdin)) 
		  saweof = 1;
		if (inputretryEOF == EOFRETRY 
		    && (feof (stdin) || ferror (stdin) ) )
		    {
		      if (user_trace)
		      fprintf (stderr, "  resetting the stdin stream\n");
		      clearerr (stdin);
		    };
		if (user_trace)
		  fprintf (stderr, "  getting window input from STDIN\n");
		switch (inputsize)
		  {
		  case BYLINE:
		    {
		      fatalerror (" Sorry, but BYLINE input is not supported;",
				  " we recommend using '\\n' in your match "
				  "pattern");
		    }
		    break;
		  case BYEOF:
		    {
		      //    if BYEOF, we read as big a hunk as will fit.
		      //    If that's less than the full buffer, we declare
		      //    that we got an EOF as well.
		      if (user_trace)
			fprintf (stderr, "  bigchunk BYEOF read starting \n");
		      icount = fread (&(newinputbuf[newbuflen]), 1, 
				      data_window_size - (newbuflen + 256),
				      stdin);
		      if (feof (stdin)) saweof = 1;
		    }
		    break;
		  case BYCHAR:
		  default:
		    {
		      //   if BYCHAR, read one character and we're done
		      //	  icount = read (0, &(newinputbuf[newbuflen]), 1); 
		      //
		      if (user_trace)
			fprintf (stderr, "   single character BYCHAR read \n");
		      icount = fread (&(newinputbuf[newbuflen]), 1, 1, stdin);
		    };
		    break;
		  };
	      }
	    //      
	    //     end of major part of BYCHAR / BYEOF specialized code.
	    //
	    if (icount > 0)
	      {
		newbuflen = newbuflen + icount;
		newinputbuf[newbuflen] = '\000'; // put on the terminator
	      };
	    //              icount < 0 means an error occurred
	    if (icount < 0)
	      {
		nonfatalerror (" Something went wrong in WINDOW "
			       "while trying to read",
			       "I will keep trying. ");
	      };
	    if (feof (stdin))
	      saweof = 1;
	  };
	};      // END OF SWITCH ON INPUTSRC

      //     mark that this is not the first time through the loop
      //
      firsttime = 0;

      //      now have an newinputbuf with something worth examining
      //     in it, of length newbuflen (i.e. using chars [0...newbuflen-1])
      //
      //     So, we run the paste regex on it, and depending on the outcome,
      //     set "done" or not.
	  
      i = crm_regexec ( &preg, 
			newinputbuf, 
			newbuflen, 
			1, matches, 0, NULL);
      
      //
      //        Now we deal with the result of the regex matching (or not
      //        matching.  i== 0 for success, i > 0 for failure.
      //
      if (i == 0) 
	{
	  //   we found the regex; do the cut/paste 
	  //   
	  done = 1;
	  if (user_trace)
	    fprintf (stderr, "  Found the paste pattern\n");
	  //   (and the cut/paste is already set up correctly in
	  //   matches[0]; we don't have to do anything.
	}
      else
	{
	  //    Nope, the regex was not found.  But if we had inputEOFaccept=
	  //    EOFACCEPTS, then we accept it anyway.
	  if (saweof)
	    {	
	      done = 1;
	      failout = 1;
	      if (user_trace)
		fprintf (stderr, " saw EOF, EOFAccept= %d\n", inputEOFaccept);
	      switch (inputEOFaccept)
		{
		case EOFACCEPTS:
		  {
		    //         In EOFENDS and EOFAIL, we take the available
		    //     input, shove it in, and go onward.  We do this
		    //     by "faking" the matches[0] variable.
		    matches[0].rm_so = 0;
		    matches[0].rm_eo = newbuflen;
		    if (matches[0].rm_eo < 0) matches[0].rm_eo = 0;
		    failout = 0;
		  }
		  break;
		case EOFFAILS:
		default:
		  {
		    //      Nope - got an EOF, and we aren't supposed to
		    //      accept it.  So we MIGHT be done.  Or maybe not... 
		    //      if we have EOFRETRY set then we clear it and
		    //      try again.
		    if (inputretryEOF == EOFRETRY)
		      {
			clearerr (stdin);
			done = 0;
			failout = 0;
		      }
		    //     But, if we are reading from a var, there will never
		    //     be any more, so we are -always- done.
		    if (inputsrc == FROM_VAR ||
			inputsrc == FROM_VAR_DONE)
		      {
			done = 1 ;
		      };
		  };
		  break;
		};
	    };
	};        
    };  // end of the (!done) loop... 
  //    
  //    It's just use the computed values from here on.

  crm_regfree (&preg);
  
  if (internal_trace)
    fprintf (stderr, "   now newinput buf --%s--\n", newinputbuf);

  //     Once we get to here, we have the new input in newinputbuf, and
  //     matches[0].rm_eo is the length.  So, we copy the new data onto
  //     the end of the cdw window, and slide the new input up.
  //     
  //     start by making some space at the end of the input buffer
  
  crm_slice_and_splice_window (mdw,
			       vht[vmidx]->vstart+vht[vmidx]->vlen,
			       matches[0].rm_eo);
  
  //     copy the pertinent part of newinputbuf into the space
  //     we just made.
  memmove (&(vht[vmidx]->valtxt[vht[vmidx]->vstart 
				+ vht[vmidx]->vlen
				- matches[0].rm_eo]),
	   newinputbuf, 
	   matches[0].rm_eo);
  
  //     and get rid of the same characters out of newinputbuf
  if (newbuflen > 0 )
    memmove (newinputbuf, 
	     &(newinputbuf[matches[0].rm_eo]), 
	     newbuflen - matches[0].rm_eo + 1);
  newbuflen = newbuflen - matches[0].rm_eo;
  newinputbuf[newbuflen] = '\000';


  //       Now, if we had EOFFAILS, and we hit the fail condition,
  //       we have to set up the CSL so that it will continue execution
  //       in the "right" place.

  if (failout == 1) 
    {
      if (user_trace)
	fprintf (stderr, "  CUT match failed so we're going to fail.\n");
      csl->cstmt = csl->mct[csl->cstmt]->fail_index - 1;
      csl->aliusstk [ csl->mct[csl->cstmt]->nest_level ] = -1;
    };

  //       and, if we got a nonfatal error, we skip all the stuff above;
  //       this is cleanup that we have to do eiher way.  Failure here
  //       is Really Bad.
 invoke_bailout:
  //

  //
  //    Last little bit of cleanup is that IF we fetched from a 
  //    variable (not a file) we have to undo our fakery of stuffing
  //    the var's contents into newinputbuf.
  //   
  //    This cleanup is two parts - stuffing the remains of inputsrcname
  //    back into inputsrcname, and then restoring the old stdin buffer
  //    contents from savedinputtxt and freeing the temporary
  //    space,
  if (inputsrc == FROM_VAR || inputsrc == FROM_VAR_DONE)
    {
      //     stuff the remaining characters back into the src var

      if (user_trace)
	fprintf (stderr, " restoring remains of input src variable.\n");

      crm_destructive_alter_nvariable (inputsrcname, inputsrclen,
				       newinputbuf,
				       newbuflen);

      //      and restore the old stdin buffer
      strncpy (newinputbuf,
	       savedinputtxt,
	       savedinputtxtlen + 1);
      newbuflen = savedinputtxtlen;
      //

    };

  //      and free the temporary space
  if (savedinputtxt) free (savedinputtxt);

 crm_window_no_changes_made:

  return (0);

}