/***************************************************************
   crc's _ _         __
        (_) | ___   / /_  __
        | | |/ _ \ / /\ \/ / a tiny virtual computer
        | | | (_) / /  >  <  64kw RAM, 32-bit, Dual Stack, MISC
        |_|_|\___/_/  /_/\_\ ilo-x.c (c) charles childers
 **************************************************************/

/* cc -o ilo-x vm/ilo-x.c `pkg-config --cflags x11 --libs`    */

/* Local Configuration */

#define BLOCKS  "ilo.blocks"
#define ROM     "ilo.rom"
#define FONT    "ilo.fnt"
#define FG      0xFFFFFF
#define BG      0x000000
#define CURSOR  0x00FFFF
#define FW      640
#define FH      384
#define FONT_H  16
#define FONT_W  8

#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <X11/Xlib.h>
#include <X11/Xutil.h>

#define T ds[sp]    /* Top of Data Stack    */
#define N ds[sp-1]  /* Next on Data Stack   */
#define R as[rp]    /* Top of Address Stack */
#define V void
#define I int
#define C char

I ip,        /* instruction pointer                   */
  sp,        /* data stack pointer                    */
  rp,        /* address stack pointer                 */
  ds[33],    /* data stack                            */
  as[257],   /* address stack                         */
  m[65536],  /* memory                                */
  ok;

C *blocks,   /* name of block file (ilo.blocks)       */
  *rom;      /* name of image (ilo.rom)               */

I a, b, f, s, d, l;       /* these others are used    */
C i[1];                   /* for misc. purposes       */

#define TERM_W (FW / FONT_W)
#define TERM_H (FH / FONT_H)

I frame[(FW * FH)/32];    /* frame buffer for display */
I font[4096];             /* font bitmap              */
I tx, ty;                 /* text cursor location     */

/* variables for Arland's DEC subset                  */
I acc[32], acc_i = 0, ground = 0, on = 0;

/* variables for X11 stuff                            */
Display *disp;
Window win;
GC gc;
XEvent event;
C text[255];

V dputc(I);
V redraw();
V iof();

V p(char *s) { while(*s) dputc(*s++); }
V e(char *s) { p("E:"); p(s); p("\n"); ok = 1; iof(); }
V dso() { if ((sp + 1) > 32)      { e("DSO"); } }
V dsu() { if ((sp - 1) < 0)       { e("DSU"); } }
V rso() { if ((rp + 1) > 256)     { e("RSO"); } }
V rsu() { if ((rp - 1) < 0)       { e("RSU"); } }
V dbz() { if (T == 0)             { e("DBZ"); } }
V mem() { if (T < 0 || T > 65535) { e("MEM"); } }
V uli() { if (f == -1)            { e("ULI"); } }
V ulf() { if (f == -1)            { e("ULF"); } }
V usi() { if (f == -1)            { e("URI"); } }
V urb() { if (f == -1)            { e("URB"); } }
V uwb() { if (f == -1)            { e("UWB"); } }
V push(I v) { dso(); ds[sp + 1] = v; sp += 1; }
I pop()     { dsu(); sp -= 1; return ds[sp + 1]; }

V cursor() {
  XSetForeground(disp, gc, CURSOR);
  XFillRectangle(disp, win, gc, tx, ty, FONT_W, FONT_H);
  XFlush(disp);
}

I wait_key() {
    while (1) {
        XNextEvent(disp, &event);
        if (event.type == KeyPress) {
            KeySym key = XLookupKeysym(&event.xkey, 0);
            XLookupString(&event.xkey, text, 255, &key, 0);
            if (text[0] == 13) text[0] = 10;
            if (text[0] != 0)  return (I) text[0];
        }
        if (event.type == Expose) { redraw(); }
    }
}

V load_font() {
  f = open(FONT, O_RDONLY, 0666);
  ulf();
  if (!f) { return; };
  read(f, &font, 4096);
  close(f);
}

V pixel(I x, I y, I c) {
  I index = y * FW + x;
  if (c == 0) {
    frame[(index / 32)] &= ~(1 << (31 - index % 32));
    XSetForeground(disp, gc, BG);
  } else {
    frame[(index / 32)] |= 1 << (31 - index % 32);
    XSetForeground(disp, gc, FG);
  }
  XDrawPoint(disp, win, gc, x, y);
}

I get_pixel(I x, I y) {
  I index = y * FW + x;
  I bit_pos = 31 - index % 32;
  I mask = 1 << bit_pos;
  return (frame[(index / 32)] & mask) >> bit_pos;
}

V redraw() {
  for (I x = 0; x < FW; x++) {
    for (I y = 0; y < FH; y++) {
      XSetForeground(disp, gc, get_pixel(x, y) ? FG : BG);
      XDrawPoint(disp, win, gc, x, y);
    }
  }
  cursor();
}

V scroll() {
  I memsize = (FH * FW) / 32;
  I last_row = (FW * FONT_H) / 32;
  for (I i = 0; i < memsize - last_row; i++) {
    frame[i] = frame[i + last_row];
  }
  for (I i = memsize - last_row; i < memsize; i++) {
    frame[i] = 0;
  }
  redraw();
}

unsigned C reverse(unsigned C b) {
   b = (b & 0xF0) >> 4 | (b & 0x0F) << 4;
   b = (b & 0xCC) >> 2 | (b & 0x33) << 2;
   b = (b & 0xAA) >> 1 | (b & 0x55) << 1;
   return b;
}

V handle_special_character(I c) {
  if (c == 8 || c == 127) { /* BACKSPACE/DELETE */
    if (tx - FONT_W >= 0) {
      tx -= FONT_W ;
      dputc(' ');
      tx -= FONT_W;
      redraw();
    }
  } else if (c == 9) { /* TAB */
    I ts = tx / FONT_W;
    for (I i = ts; i < ((ts + 7) / 8) * 8; i++) { dputc(' '); }
  } else if (c == 10 || c == 13) { /* CR or LF */
    ty += FONT_H;
    tx = 0;
    redraw();
  }
}

V handle_regular_character(C *bitmap) {
  I x, y, set;
  for (x = 0; x < FONT_H; x++) {
    for (y = 0; y < FONT_W; y++) {
      set = reverse(bitmap[x]) & 1 << y;
      pixel(tx + y, ty + x, set ? 1 : 0);
    }
  }
  tx += FONT_W;
}

V advance_cursor_and_scroll() {
  if (tx >= FW) { tx = 0; ty += FONT_H; }
  if (ty > (FH - FONT_H)) { ty -= FONT_H; scroll(); }
}

V dputc(I c) {
  C *bitmap = (C *)font + (c * ((FONT_H * FONT_W) / 8));

  handle_special_character(c);

  if (!(c == 8 || c == 127 || c == 9 || c == 10 || c == 13)) {
    handle_regular_character(bitmap);
  }

  advance_cursor_and_scroll();
  cursor();
}

I acc_pop() {
  I k = acc_i;
  if (acc_i > 0) {
    acc_i -= 1;
    if (acc_i == -1) {
      acc_i = 0;
    }
  }
  return acc[k];
}

V acc_reset() {
  for (I x = 0; x < 32; x++) { acc[x] = 0; }
  ground = on = 0;
}

V gt_up(I n)       { ty -= FONT_H; if (ty < 0) ty = 0;  }
V gt_down(I n)     { ty += FONT_H; if (ty > 24 * FONT_H) ty = 24 * FONT_H; }
V gt_left(I n)     { tx -= FONT_W; if (tx < 0) tx = 0; }
V gt_right(I n)    { tx += FONT_W; if (tx > 79 * FONT_W) ty = 79 * FONT_W; }
V gt_move_cursor() {
  if (acc_i >= 1) {
    I a = (acc_pop() - 1) * FONT_W;
    I b = (acc_pop() - 1) * FONT_H;
    ty = b; if (ty < 0) ty = 0; if (ty > FONT_H * 24) ty = FONT_H * 24;
    tx = a; if (tx < 0) tx = 0; if (tx > FONT_W * 79) tx = FONT_W * 79;
    acc_reset();
    return;
  }
  /* home */
  tx = 0; ty = 0;
  acc_reset();
}

V gt_reset()       { acc_reset(); }
V gt_next()        { acc_i += 1; acc[acc_i] = 0; }
V gt_clear() {
  acc_reset();
  for (I x = 0; x < (FW * FH) / 32; x++) frame[x] = 0;
  tx = ty = 0;
  redraw();
}
V gt_set_attr()    { acc_reset(); }

V term_putc(I c) {
  if (c == 27) {
    on = -2;
    return;
  }
  switch (on) {
    case 0:
      dputc(c);
      return;
    case -2:
      if (c == '[') {
        on = -1;
        return;
      }
      on = 0;
      dputc(c);
      return;
  }
  if (c >= '0' && c <= '9') {
    acc[acc_i] *= 10;
    acc[acc_i] += c - 48;
    if (c == '3') {
      ground = 0;
    }
    if (c == '4') {
      ground = 1;
    }
  } else {
    switch (c) {
      case 'A': gt_up(acc_pop());    break;
      case 'B': gt_down(acc_pop());  break;
      case 'C': gt_left(acc_pop());  break;
      case 'D': gt_right(acc_pop()); break;
      case 'm': gt_set_attr();       break;
      case ';': gt_next();           break;
      case 'H': gt_move_cursor();    break;
      case 'J': gt_clear();          break;
      default: on = 0;
               dputc(c);
    }
  }
}

V load_image() {
  f = open(rom, O_RDONLY, 0666);
  uli();
  if (!f) { return; };
  read(f, &m, 65536 * 4);
  close(f);
  ip = sp = rp = 0;
}

V save_image() {
  f = open(rom, O_WRONLY, 0666);
  usi();
  write(f, &m, 65536 * 4);
  close(f);
}

V block_common() {
  b = pop(); /* block buffer */
  a = pop(); /* block number */
  lseek(f, 4096 * a, SEEK_SET);
}

V read_block() {
  f = open(blocks, O_RDONLY, 0666);
  urb();
  block_common();
  read(f, m + b, 4096);
  close(f);
}

V write_block() {
  f = open(blocks, O_WRONLY, 0666);
  uwb();
  block_common();
  write(f, m + b, 4096);
  close(f);
}

V save_ip() { rso(); rp += 1; R = ip; }
V symmetric() { if (b >= 0 && N < 0) { T += 1; N -= b; } }

V li() { ip += 1; push(m[ip]); }
V du() { push(T); }
V dr() { pop(); }
V sw() { a = T; T = N; N = a; }
V pu() { rp += 1; R = pop(); }
V po() { push(R); rp -= 1; }
V ju() { ip = pop() - 1; }
V ca() { save_ip(); ip = pop() - 1; }
V cc() { a = pop(); if (pop()) { save_ip(); ip = a - 1; } }
V cj() { a = pop(); if (pop()) { ip = a - 1; } }
V re() { ip = R; rp -= 1; }
V eq() { N = (N == T) ? -1 : 0; sp -= 1; }
V ne() { N = (N != T) ? -1 : 0; sp -= 1; }
V lt() { N = (N <  T) ? -1 : 0; sp -= 1; }
V gt() { N = (N >  T) ? -1 : 0; sp -= 1; }
V fe() { mem(); T = m[T]; }
V st() { mem(); m[T] = N; sp -= 2; }
V ad() { N += T; sp -= 1; }
V su() { N -= T; sp -= 1; }
V mu() { N *= T; sp -= 1; }
V di() { dbz();
         a = T; b = N; T = b / a; N = b % a; symmetric(); }
V an() { N = T & N; sp -= 1; }
V or() { N = T | N; sp -= 1; }
V xo() { N = T ^ N; sp -= 1; }
V sl() { N = N << T; sp -= 1; }
V sr() { N = N >> T; sp -= 1; }
V cp() { l = pop(); d = pop(); s = T; T = -1;
         while (l) { if (m[d] != m[s]) { T = 0; }
                     l -= 1; s += 1; d += 1; } }
V cy() { l = pop(); d = pop(); s = pop();
         while (l) { m[d] = m[s]; l -= 1; s += 1; d += 1; } }
V ioa() { term_putc(pop()); }
V iob() { push(wait_key()); term_putc(T); }
V ioc() { read_block(); }
V iod() { write_block(); }
V ioe() { save_image(); }
V iof() { load_image(); ip = -1; }
V iog() { ip = 65536; }
V ioh() { push(sp); push(rp); }
V iox() { I c = pop();  I y = pop();  I x = pop();
          pixel(x, y, c); }
V ioy() { I y = pop(); I x = pop(); push(get_pixel(x, y)); }
V ioz() { I x, y, wx, wy, mask; Window w;
          XQueryPointer(disp, win, &w, &w, &x, &y, &wx, &wy, &mask);
          push(x); push(y); if (mask & Button1Mask) push(-1); else push(0); }
V io() {
  switch (pop()) {
    case 0: ioa(); break;  case 1: iob(); break;
    case 2: ioc(); break;  case 3: iod(); break;
    case 4: ioe(); break;  case 5: iof(); break;
    case 6: iog(); break;  case 7: ioh(); break;
    case 33: iox(); break; case 34: ioy(); break;
    case 35: ioz(); break;
    default: break;
  }
}

V process(I o) {
  switch (o) {
    case  0:       break;   case  1: li(); break;
    case  2: du(); break;   case  3: dr(); break;
    case  4: sw(); break;   case  5: pu(); break;
    case  6: po(); break;   case  7: ju(); break;
    case  8: ca(); break;   case  9: cc(); break;
    case 10: cj(); break;   case 11: re(); break;
    case 12: eq(); break;   case 13: ne(); break;
    case 14: lt(); break;   case 15: gt(); break;
    case 16: fe(); break;   case 17: st(); break;
    case 18: ad(); break;   case 19: su(); break;
    case 20: mu(); break;   case 21: di(); break;
    case 22: an(); break;   case 23: or(); break;
    case 24: xo(); break;   case 25: sl(); break;
    case 26: sr(); break;   case 27: cp(); break;
    case 28: cy(); break;   case 29: io(); break;
    default: break;
  }
}

#define VALID(n) (ok == 0) && ((opcode >> n) & 0xFF)

V execute() {
  I opcode;
  while (ip < 65536) {
    opcode = m[ip];
    ok = 0;
    if (VALID(0))   process(opcode & 0xFF);
    if (VALID(8))   process((opcode >> 8) & 0xFF);
    if (VALID(16))  process((opcode >> 16) & 0xFF);
    if (VALID(24))  process((opcode >> 24) & 0xFF);
    ip += 1;
  }
}

I main(I argc, C **argv) {
  blocks = (argc > 1) ? argv[1] : BLOCKS;
  rom    = (argc > 2) ? argv[2] : ROM;
  ok = 0;

/*
#ifdef __OpenBSD__
  pledge("stdio rpath wpath unix video", NULL);
#endif
*/

  load_image();

  load_font();

  disp = XOpenDisplay(NULL);
  win = XCreateSimpleWindow(disp, RootWindow(disp, 0),
                            0, 0, FW, FH, 0, 0x0, 0x0);
  XSelectInput(disp, win, ExposureMask | KeyPressMask | ButtonPressMask | ButtonReleaseMask);
  XStoreName(disp, win, "x/ilo");
  gc = DefaultGC(disp, DefaultScreen(disp));
  XMapWindow(disp, win);
  XFlush(disp);
  XMoveWindow(disp, win, (DisplayWidth(disp, DefaultScreen(disp)) - FW) / 2,
                         (DisplayHeight(disp, DefaultScreen(disp)) - FH) / 2);

  execute();

  XUnmapWindow(disp, win);
  XDestroyWindow(disp, win);
  XCloseDisplay(disp);

  return 0;
}