#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>

#define SERVERNAME "smtp.rewrite.proxy"

FILE*fout;
char tempfilename[256]="/tmp/smtpreid.XXXXXX";
long dataoffset=0;
long maildataoffset=0;
char mailfrom[256]="";
char mailenvelopefrom[256]="";
int resentfrom=0;
char*pineaddrbook=NULL;
char configfile[]="/etc/smtpreident.conf";
char configuserfile[]="/etc/smtpreident.conf.%s";

/*
 * silly implementation for the strcasestr funcion, from somewhere on the Net
 * 
 */
char *strcasestr(char *hailstack, char *needle)
{
   register int lneed = strlen(needle);
   register int lhail = strlen(hailstack);
   register int i;
   for (i = 0; i < lhail; i++) 
      if (!strncasecmp(hailstack + i, needle, lneed))
         return hailstack + i;
   return NULL;
}

char*xstrncpy(char*s,char*s1,int n)
{ strncpy(s,s1,n);s[n-1]=0;return s;}




int stripcrlf(char*s)
{ char*sp;
  int t=0;
  sp=strrchr(s,'\n');if(sp)if(!sp[1]){sp[0]=0;t=1;}
  sp=strrchr(s,'\r');if(sp)if(!sp[1]){sp[0]=0;t=1;}
  return t;
}

void stripparentheses(char*s)
{ char*sp;
  sp=strchr(s,'>');if(sp)sp[0]=0;
  if(s[0]=='<'){memmove(s,s+1,strlen(s));}
}

void handlemailfrom(char*s)
{
  stripcrlf(s);
  stripparentheses(s);
//syslog(LOG_WARNING,"FROM:%s",s);
  fprintf(fout,"FROM:%s\n",s);
  xstrncpy(mailfrom,s,256);
}

void handlercptto(char*s)
{
  stripcrlf(s);
  stripparentheses(s);
//syslog(LOG_WARNING,"TO:%s",s);
  fprintf(fout,"TO:%s\n",s);
}

void handledata(FILE*f)
{ char s[256];
  int isheader=1;
  dataoffset=ftell(fout);
  while(!feof(f))
  {s[0]=0;fgets(s,256,f);
   if(!strcmp(s,".\r\n"))break;
   if(!strcmp(s,".\n"))break;
   if(stripcrlf(s))fprintf(fout,"%s\n",s);   
              else fprintf(fout,"%s",s);
   if(!strcmp(s,""))if(isheader){maildataoffset=ftell(fout);isheader=0;}
   if(!strncasecmp(s,"ReSent-From:",12))resentfrom=1;
  }
}



// read pine addressbook, retrieve the alias
int getaliasformail(char*alias,char*addr)
{ FILE*f;
  char s[512],*sp,*sp1,*sp2;
  alias[0]=0;
  if(!pineaddrbook)return 0;
//  f=fopen("./addressbook","r");if(!f)return 0;
  f=fopen(pineaddrbook,"r");if(!f)return 0;
  while(!feof(f))
  {s[0]=0;fgets(s,256,f);
     sp=strrchr(s,'\t');if(sp)if(sp[1]=='\n'){fgets(sp+1,256,f);}//for two-lined records
   sp=strchr(s,'\t');if(!sp)continue;sp[0]=0;sp++;
   sp2=strcasestr(sp,addr);if(!sp2)continue;
   sp1=sp;while(sp1[0]){if(!isalnum(sp1[0]))if(sp1[0]!='@')sp1[0]=' ';sp1++;}
   sp1--;if(sp1[0]!=' ')continue;sp1++;
   xstrncpy(alias,s,256);fclose(f);return 1;
  }
  fclose(f);return 0;
}




char configline[256]="";
char rewrite_from[256]="";
char rewrite_to[256]="";
int remove_headers=0;
int remove_resent_headers=0;
int remove_received_headers=0;
int remove_deliveredto_headers=0;
int remove_xshad_headers=0;
int remove_xspam_headers=0;
char variables[1024]="";
#define FILTER_MAX 1024
char filter[FILTER_MAX]="";

void replacegrepvar(char*s)
{ char s1[256];
  snprintf(s1,255,"\n%s=",s);
  
}

void addvar(char*s1)
{ strcat(variables,"\n");
  strcat(variables,s1);
}

void addfilter(char*s1)
{ strcat(filter,s1);
  strcat(filter,"|");
}

int compareto(char*s,char*to,char*toalias)
{ int n=0;
  char*sp;
  if(!strncmp(s,"*",1))n=1;
  if(toalias)if(toalias[0])if(!strncasecmp(s,toalias,strlen(toalias)))n=strlen(toalias);
  if(to)if(to[0])if(!strncasecmp(s,to,strlen(to)))n=strlen(to);
  if(s[0]=='@'){sp=strchr(to,'@');if(sp)if(!strncasecmp(s,sp,strlen(sp)))n=strlen(sp);}
//syslog(LOG_WARNING,"%s - %s - %s - %d - %s",s,to,toalias,n,s+n);
  if(!n)return 0;
  if(s[n]==':')return n+1;
  return 0;
}  

void readconfigfile_file(char*conffile,char*from,char*to)
{ char s1[256],s2[256];
  char s[256];
  char alias[256];
  char*sp,*sp2;
  int n,n1,n2;
  FILE*f;
  f=fopen(conffile,"r");
  if(!f)
  {//syslog(LOG_WARNING,"Cannot open config file %s",conffile);
   return;}
  if(getaliasformail(alias,to))syslog(LOG_WARNING,"alias:%s",alias);
  while(!feof(f))
  {s[0]=0;fgets(s,256,f);stripcrlf(s);
   if(s[0]=='#')continue;
   if(s[0]=='$'){if(s[1]=='=')xstrncpy(configline,s+2,256);else addvar(s);continue;}
   if(!strncasecmp(s,"to:",3))
    {if(strchr(s,':'))if(strchr(s,':')==strrchr(s,':'))strcat(s,":"); // add trailing : if no : present, to simplify syntax
     n=compareto(s+3,to,alias);if(!n)continue;
     sp=s+3+n;
    if((!sp[0])||(!strcmp(sp,"$")))xstrncpy(sp,configline,255-(sp-s));
    while(sp)
    {sp2=strchr(sp,';');if(sp2){sp2[0]=0;sp2++;}
     if(!strncasecmp(sp,"from:",5))xstrncpy(rewrite_from,sp+5,256);
     else if(!strncasecmp(sp,"to:",3))xstrncpy(rewrite_to,sp+3,256);
     else if(!strncasecmp(sp,"fromenv:",8))xstrncpy(mailenvelopefrom,sp+8,256);
     else if(!strncasecmp(sp,"filter:",7))addfilter(sp+7);
     else if(!strcasecmp(sp,"noresent"))remove_resent_headers=1;
     else if(!strcasecmp(sp,"noreceived"))remove_received_headers=1;
     else if(!strcasecmp(sp,"noxshad"))remove_xshad_headers=1;
     else if(!strcasecmp(sp,"noxspam"))remove_xspam_headers=1;
     else if(!strcasecmp(sp,"nodeliveredto"))remove_deliveredto_headers=1;
     sp=sp2;}
   }
  }
  if(resentfrom)rewrite_from[0]=0; // FIXME: Probably obsolete because of the acct-specific config files
syslog(LOG_WARNING,"rewrite_from:%s %i",rewrite_from,resentfrom);
}

void readconfigfile(char*from,char*to)
{ char s[256];
  configline[0]=0;
  rewrite_from[0]=0;
  rewrite_to[0]=0;
  mailenvelopefrom[0]=0;
  filter[0]=0;
  remove_headers=0;
  remove_resent_headers=0;
  remove_received_headers=0;
  remove_xshad_headers=0;
  remove_xspam_headers=0;
  remove_deliveredto_headers=0;
  //
  readconfigfile_file(configfile,from,to);
  snprintf(s,256,configuserfile,from);
syslog(LOG_WARNING,"userfile:%s",s);
  readconfigfile_file(s,from,to);
}

int remove_next_header=0;
void rewriteheaderline(char*s)
{ if((s[0]==' ')||(s[0]=='\t')){if(remove_next_header){s[0]=0;return;}}else remove_next_header=0;
  if(rewrite_from[0])if(!strncasecmp(s,"From:",5)){if(!strstr(s,"MAILER-DAEMON"))sprintf(s,"From: %s\n",rewrite_from);remove_next_header=1;return;}
  if(remove_resent_headers)if(!strncasecmp(s,"ReSent-",7)){s[0]=0;remove_next_header=1;return;}
  if(remove_deliveredto_headers)if(!strncasecmp(s,"Delivered-To:",13)){s[0]=0;remove_next_header=1;return;}
  if(remove_received_headers)if(!strncasecmp(s,"Received:",9)){s[0]=0;remove_next_header=1;return;}
  if(remove_received_headers)if(!strncasecmp(s,"X-Received:",11)){s[0]=0;remove_next_header=1;return;}
  if(remove_xshad_headers)if(!strncasecmp(s,"X-Shad-",7)){s[0]=0;remove_next_header=1;return;}
  if(remove_xspam_headers)if(!strncasecmp(s,"X-Spam-",7)){s[0]=0;remove_next_header=1;return;}
}


void sendmail(char*to)
{ FILE*f;
  char s[256];
  int isheader=1;
  readconfigfile(mailfrom,to);
  if(!mailenvelopefrom[0])xstrncpy(mailenvelopefrom,mailfrom,256);
  if(rewrite_to[0])xstrncpy(to,rewrite_to,256);
  sprintf(s,"%s/usr/sbin/sendmail -f '%s' '%s'",filter,mailenvelopefrom,to);
  // inhibit sending mails, for test purposes
  f=fopen("./nosend","r");
  if(f){syslog(LOG_WARNING,"Mail send inhibited by configuration.",s);
        syslog(LOG_WARNING,"From rewrite set to %s.",rewrite_from);
        fclose(f);return;}
  //
  if(!strcasecmp(to,"nobody"))
   {syslog(LOG_WARNING,"Mail thrown away.");
    return;}
  syslog(LOG_WARNING,"%s",s);
  f=popen(s,"w");if(!f)return;
  fseek(fout,dataoffset,SEEK_SET);
  while(!feof(fout))
   {s[0]=0;
    fgets(s,256,fout);
    if(!strcmp(s,"\n"))isheader=0;else if(!strcmp(s,""))isheader=0;
    if(isheader)rewriteheaderline(s);
    fputs(s,f);}
  pclose(f);
}

void dumpdatatosendmail()
{ FILE*f;
  char s[256];
  char sfrom[256]="";
  long pos;
  fseek(fout,0,SEEK_SET);
  fgets(s,256,fout);//ignore the FROM: line
  pos=ftell(fout);
  while(pos<dataoffset)
  {fseek(fout,pos,SEEK_SET);
   fgets(s,256,fout);stripcrlf(s);
   pos=ftell(fout);
   if(!strncmp(s,"TO:",3))sendmail(s+3);
  }
}



int main(int argc,char*argv[])
{ char s[256],*sp;
  FILE*f,*fo;
  f=stdin;
  fo=stdout;
  xstrncpy(s,argv[0],256);
  sp=strrchr(s,'/');if(sp){sp[0]=0;chdir(s);}
  pineaddrbook=argv[1];//first parameter is the pine addressbook path - implement real parameter processing!
  fout=fdopen(mkstemp(tempfilename),"w+");
//  fout=fopen(mktemp(tempfilename),"w+");
  if(!fout){printf("400 Error creating temporary file.\r\n");return 1;}
  printf("220 " SERVERNAME " SMTP\r\n");fflush(fo);
// FIXME: Stateless state machine.
  while(!feof(f)) // command loop
  {s[0]=0;fgets(s,256,f);
   if(!strncmp(s,"HELO ",5)){printf("250 " SERVERNAME "\r\n");fflush(fo);}
   else if(!strncmp(s,"EHLO ",5)){printf("250 " SERVERNAME "\r\n");fflush(fo);}
   else if(!strncmp(s,"RSET",4)){printf("250 flushed\r\n");fflush(fo);}
   else if(!strncmp(s,"MAIL FROM:",10)){handlemailfrom(s+10);printf("250 ok\r\n");fflush(fo);}
   else if(!strncmp(s,"RCPT TO:",8)){handlercptto(s+8);printf("250 ok\r\n");fflush(fo);}
   else if(!strncmp(s,"DATA",4)){printf("354 go ahead\r\n");fflush(fo);handledata(f);printf("250 ok 1077959499 qp 1183\r\n");fflush(fo);}
   else if(!strncmp(s,"QUIT",4)){printf("221 " SERVERNAME "\r\n");fflush(fo);break;}
   else {printf("502 unimplemented\r\n");fflush(fo);}
  }
  dumpdatatosendmail();
  fclose(fout);
  unlink(tempfilename);
  return 0;
}