//
// Pocket C ETA Compiler for the Palm Pilot
// (c) 2001 S.Sykes
// 
//  4 Apr 2001         SDS  Begun
//  5 Apr 2001   v1.0  SDS  First working version
//  8 Apr 2001   v1.1  SDS  Fixed some optimisations, improved recognition of null sequences

//
// Constants
//
#define VERSION "1.1"
#define MAXSTACK 100
#define MAXSTACKINDEX 99
#define MAXLINES 256
#define PROGNAME "ETA2C"
#define OUTMEMO "// etaout"
// #define PROFILE

//
// Meta data
//
@cid "SSYk";
@name "ETA->C";
@dbname "ETA->C";
@ver VERSION;
@licon1 "eta-large-c.bmp";
@sicon1 "eta-small-c.bmp";

//
// Globals
//
int currentline=0;

//
// Error handling
//
barf(string s) {
  mmclose();
  if (currentline) alert(s+" at line "+(currentline-1));
  else alert(s);
//  while (true) event(1);
  exit();
}

//
// ETA program storage and read function
//
int readlines=1;
string theprog[MAXLINES];
int linelens[MAXLINES];

readprogram() {
  if (!mmfind(PROGNAME)) barf("Program not found - your program must be in a memo titled ETA2C");
  mmgetl();  // dispose of the title line
  while(!mmeof()) {
    linelens[readlines]=strlen(theprog[readlines]=strupr(mmgetl()));
    if (++readlines==MAXLINES) barf("Program too long, max lines="+MAXLINES);
  }
  mmclose();
}

//
// Preprocessor
//
preprocess(pointer nflags) {
  string tprog[MAXLINES],ts,cline;
  int tl,cl,clinepos,a,inanumber=0,numstart,numend;
  char ch;

  while(currentline<readlines) {  // line level loop
    puts(".");
    cline=theprog[currentline];
    cl=linelens[currentline];
    clinepos=numstart=numend=0;
    while(cl--) {  // char level loop
      ch=cline@[clinepos];
      clinepos++;
      if (nflags[ch]) {
        tprog[currentline]=tprog[currentline]+ch;
        tl=strlen(tprog[currentline]);
        if (ch=='N' && !inanumber) {
          inanumber=1;
          numstart=tl;
        }
        if (ch=='E') {
          inanumber=0;
          numend=tl;
        }
        if (!inanumber) {
          if (tl>2 && ((numstart>=tl-2 && numend>tl-2) || (numstart<tl-2 && numend<tl-2))) {
            ts=strright(tprog[currentline],3);
            if (ts=="AAT") {  // ignore rest of line
              tprog[currentline]=strleft(tprog[currentline],tl-3);
              break;
            }
            if (ts=="NES") {  // this is a no-op
              tprog[currentline]=strleft(tprog[currentline],tl-3);
              continue;
		    }
		  }
		  if (ch=='T') {
  		    if (tl>3 && numstart==tl-3 && numend==tl-2) {
              ts=strright(tprog[currentline],4);
              if (ts=="NEAT") {  // this is a no-op
                tprog[currentline]=strleft(tprog[currentline],tl-4);
                continue;
              }
            }
            if (tl>4 && numend==tl-2) {
              ts=strright(tprog[currentline],2);
              if (ts=="AT") {   // any number followed by AT means ignore rest of line
                tprog[currentline]=strleft(tprog[currentline],numstart-1);
                break;
              }
            }
            if (numend==tl-1 && numstart>2) {  // testing for NENsomethingET which is a no-op
              if (substr(tprog[currentline],numstart-2,2)=="NE") {
                tprog[currentline]=strleft(tprog[currentline],numstart-3);
                continue;
              }
            }
          }
        }
      }
    }
//    if (theprog[currentline]!=tprog[currentline]) puts("tx: "+theprog[currentline]+" to:"+tprog[currentline]+"\n");
    theprog[currentline]=tprog[currentline];
    linelens[currentline]=strlen(tprog[currentline]);
    currentline++;
  }
}

//
// main program - read program from memo then interpret it
//

main() {
  int clinepos,accum,numberstate=1,cl,s1,s2,a,lastwaspush,lastwaspop,noverline,caserequired;
  char ch;
  string cline;
  pointer nums,nflags;
  
  if (!(nflags=malloc(a=276))) barf("Yikes, malloc failed");  // this section is efficient but ugly
  while (a--) nflags[a]=0;           // may be quicker to unroll this a bit, but it's run once only
  nflags['E']=nflags['T']=nflags['A']=nflags['O']=nflags['I']=nflags['N']=nflags['S']=nflags['H']=1;
  nums=nflags+191;                   // ha, cunning re-use of space
  nums['T']=1;
  nums['A']=2;
  nums['O']=3;
  nums['I']=4;
  nums['N']=5;
  nums['S']=6;  
  clear();
  puts("ETA compiler for Palm OS v"+VERSION+"\n");
  readprogram();
  puts("Preprocessing");
  preprocess(nflags);
  
  currentline=1; noverline=0; caserequired=0;
  if (mmfind(OUTMEMO)) mmdelete();
  mmnew();
  mmputs(OUTMEMO+'\n');  // preamble
  mmputs("#define oc if (stacktop<0) barf(\"Stack underflow\")\n");
  mmputs("#define ot if (stacktop<=0) barf(\"Stack underflow\")\n");
  mmputs("#define po stack[stacktop--]\n");
  mmputs("#define ppo stack[stacktop]\n");
  mmputs("#define uc if (stacktop=="+MAXSTACKINDEX+") barf(\"Stack overflow\")\n");
  mmputs("#define pu stack[++stacktop]=\n");
  mmputs("#define ppu stack[stacktop]=\n");
  mmputs("#define TXR \"Transfer out of range\"\n");
  mmputs("#define TRM \"Program terminated nicely (transfer to zero)\"\n");
  mmputs("#define DIV \"Divide by zero\"\n");
  mmputs("int stack["+MAXSTACK+"],stacktop=-1,tx=1,a,b;\n");
#ifdef PROFILE
  mmputs("int tik;");
#endif
  mmputs("barf(string s) {");
#ifdef PROFILE
  mmputs("puts(\"\nTicks taken = \"+(ticks()-tik));");
#endif
  mmputs("alert(s);while (1) event(1);}\n");
  mmputs("halibut(int n) {int i,m,smn;\n");
  mmputs("if (n>0) {if (n>stacktop) barf(\"Stack underflow - positive halibut\");");
  mmputs("m=stack[i=stacktop-n];while (i<stacktop) stack[i]=stack[++i];stack[i]=m;");
  mmputs("} else {if (-n>stacktop) barf(\"Stack underflow - negative halibut\");");
  mmputs("stack[stacktop+1]=stack[n+stacktop++];}}\n");
  mmputs("main() {\n");
#ifdef PROFILE
  mmputs("tik=ticks();");
#endif
  mmputs("clear();while (tx) {\n");
  mmputs("switch(tx) {\n");
  puts("\nCompiling");
  while(currentline<readlines) {  // line level loop
    puts(".");
    if (!numberstate) {if (!noverline) noverline=currentline;}
    else {
      if (noverline) {currentline=noverline; noverline=0; caserequired=1;}
      mmputs("case "+currentline+": {\n");  // transfers are done with case statements
    }
    cline=theprog[currentline];
    cl=linelens[currentline++];
    clinepos=0;
    lastwaspush=0;
    lastwaspop=0;
    while(cl--) {  // char level loop
      ch=cline@[clinepos++];
      if (nflags[ch]) if (numberstate) {  // it's just a two state state machine
        switch(ch) {
        case 'E': {
            mmputs("ot;if (!(a=po)) barf(DIV);ppu (b=ppo)/a;pu b%a;");
            if (caserequired) {mmputs("}\ncase 50"+currentline+": {\n"); lastwaspush=caserequired=0;}
            else lastwaspush=1;
            lastwaspop=0;
            break;
          }
        case 'T': {
            mmputs("ot;a=po;");
            mmputs("if (po) {if (a<"+readlines+" && a>=0) tx=a;");
            mmputs("else barf(TXR);\n");
            mmputs("if (!tx) barf(TRM);");
            mmputs("break;}\n");
            lastwaspush=0;
            lastwaspop=1;
            break;
          }
        case 'A': {
            if (!lastwaspop) mmputs("uc;");
            mmputs("pu "+currentline+";\n");
            lastwaspush=1;
            lastwaspop=0;
            break;
          }
        case 'O': {
            if (!lastwaspush) mmputs("oc;");
            mmputs("puts((char)po);");
            lastwaspush=0;
            lastwaspop=1;
            break;
          }
        case 'I': {
            if (!lastwaspop) mmputs("uc;");
            mmputs("puts((char)(pu getc()));\n");
            lastwaspush=1;
            lastwaspop=0;
            break;
          }
        case 'N': {
            numberstate=accum=0;
            break;
          }
        case 'S': {
            mmputs("ot;a=po;ppu (ppo-a);");
            lastwaspush=1;
            lastwaspop=1;
            break;
          }
        case 'H': {
            if (!lastwaspush) mmputs("oc;");
            mmputs("halibut(po);");
            lastwaspush=1;
            lastwaspop=0;
            break;
          }
        }
      } else { // in numberstate
        if (ch=='E') {
          if (!lastwaspop) mmputs("uc;");
          mmputs("pu "+accum+";\n"); 
          numberstate=1;
          if (noverline) {
            mmputs("tx=50"+currentline+";break;");
            break;
          }
          if (caserequired) {mmputs("}\ncase 50"+currentline+": {\n"); lastwaspush=caserequired=0;}
          else lastwaspush=1;
          lastwaspop=0;
        } else accum=accum*7+nums[ch];
      }
    }  // ends char level loop
    if (numberstate) mmputs("}\n");  // ends case for this line
  }
  if (!numberstate) mmputs("}\n");
  mmputs("tx=0;}}\nbarf(\"Program terminated normally\");}\n");
  puts("done");
  barf("Finished");
}