// opcodes

static final int
  op_return = 0,
  op_nop    = 1,
  op_jump   = 2,
  op_jump_rel = 16,
  op_branchif = 3,
  op_branchifnot = 4,
  op_less = 5,
  op_less_im = 17, // highest
  op_equal = 6,
  op_more = 7,
  op_set = 8,
  op_set_ind = 9,
  op_copy = 10,
  op_copy_ind = 11,
  op_add = 12,
  op_add_im = 13,
  op_not = 14,
  op_neg = 15,
  op_illegal = 999;
  
static int runProgram_maxSteps = 1000*1000;

static void runProgram(Grid g, int pc) {
  new Runner(g, pc, runProgram_maxSteps);
}

sclass Runner {
  Grid g;
  int pc;
  
  *(Grid *g, int startAddress, int steps) {
    pc = startAddress;
    bool flag = false;
    for (int step = 0; step < steps; step++) {
      int opcode = g.get(pc++);
      int a, b;
      switch (opcode) {
               case op_return: ret;
               case op_nop:
        break; case op_jump: pc = g.get(pc);
        break; case op_jump_rel: pc += g.get(pc)-1;
        break; case op_branchif: if (flag) pc = g.get(pc); else ++pc;
        break; case op_branchifnot: if (!flag) pc = g.get(pc); else ++pc;
        break; case op_less: a = y(); b = y(); flag = a < b;
        break; case op_less_im: a = y(); b = x(); flag = a < b;
        break; case op_equal: a = y(); b = y(); flag = a == b;
        break; case op_more: a = y(); b = y(); flag = a > b;
        break; case op_set: a = x(); set(x(), a);
        break; case op_set_ind: a = x(); set(y(), a);
        break; case op_copy: a = y(); set(x(), a);
        break; case op_copy_ind: a = y(); set(y(), a);
        break; case op_add: a = x(); b = x(); set(a, get(a)+get(b));
        break; case op_add_im: a = x(); b = x(); set(a, get(a)+b);
        break; case op_not: a = x(); set(a, ~get(a));
        break; case op_neg: a = x(); set(a, -get(a));
        default: fail("Illegal opcode " + opcode + " at " + (pc-1));
      }
    }
  }
  
  int x() { ret get(pc++); }
  int y() { ret get(get(pc++)); }
  int get(int addr) { ret g.get(addr); }
  void set(int addr, int x) { g.set(addr, x); }
}

static void testProgram(Grid g, int startAddress, int... values) {
  runProgram(g, startAddress);
  for (int i = 0; i < l(values); i += 2)
    assertEquals(values[i+1], g.get(values[i]));
  //print("Program OK (" + n(l(program), "int") + ", " + n(l(values)/2, "value") + ")");
  print("Program OK (" + n(l(values)/2, "value") + ")");
}

static void disassemble(Grid g, int pc) {
  print(new Disassembler(g, pc).buf);
}

sclass Disassembler {
  Grid g;
  int pc;
  new StringBuffer buf;
  
  *(Grid *g, int startAddress) {
    pc = startAddress;
    int end = g.lastNonZero();
    while (pc < end) {
      int opcode = g.get(pc++);
      int a, b;
      S s = "?";
      switch (opcode) {
               case op_return: s = "return";
        break; case op_nop: s = "nop";
        break; case op_jump: s = "jump " + x();
        break; case op_jump_rel: s = "jump rel " + x();
        break; case op_branchif: s = "branch if " + x();
        break; case op_branchifnot: s = "branch if not " + x();
        break; case op_less: a = x(); b = x(); s = "less " + a + " " + b;
        break; case op_less_im: a = x(); b = x(); s = "less im " + a + " " + b;
        break; case op_equal: a = x(); b = x(); s = "equal " + a + " " + b;
        break; case op_more: a = x(); b = x(); s = "more " + a + " " + b;
        break; case op_set: a = x(); b = x(); s = "set " + a + " " + b;
        break; case op_set_ind: a = x(); b = x(); s = "set ind " + a + " " + b;
        break; case op_copy: a = x(); b = x(); s = "copy " + a + " " + b;
        break; case op_copy_ind: a = x(); b = x(); s = "copy ind " + a + " " + b;
        break; case op_add: a = x(); b = x(); s = "add " + a + " " + b;
        break; case op_add_im: a = x(); b = x(); s = "add im " + a + " " + b;
        break; case op_not: s = "not " + x();
        break; case op_neg: s = "neg " + x();
        default: s = "Unknown opcode " + opcode;
      }
      buf.append(s).append("\n");
    }
  }
  
  int x() { ret g.get(pc++); }
}