/**
 * mu808: an ultralight numeric-only VM
 * ANSI C99 reference implementation
 * Compile with: cc -std=c99 -O2 -s -lm -o mu808 mu808.c 
 * See the README.md file for all documentation
 * Created by Luxferre in 2025, released into public domain
 */

#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#include <math.h>

/* POSIX-specific terminal stuff for unbuffered input for I/O port 2 */
#if defined (__unix__) || (defined (__APPLE__) && defined (__MACH__))
#define NLC "\n"
#include <unistd.h>
#include <termios.h>
struct termios orig_termios;
void disable_raw_mode() {
  tcsetattr(STDIN_FILENO, TCSAFLUSH, &orig_termios);
}
void enable_raw_mode() {
  tcgetattr(STDIN_FILENO, &orig_termios);
  atexit(disable_raw_mode);
  struct termios raw = orig_termios;
  raw.c_iflag &= ~(BRKINT | ICRNL | INPCK | ISTRIP | IXON);
  raw.c_oflag &= ~(OPOST);
  raw.c_cflag |= (CS8);
  raw.c_lflag &= ~(ECHO | ICANON | IEXTEN | ISIG);
  tcsetattr(STDIN_FILENO, TCSAFLUSH, &raw);
}
#else
#define NLC "\r\n"
void disable_raw_mode() {}
void enable_raw_mode() {}
#endif

/* core memory */
#ifndef MEMLIMIT
#define MEMLIMIT 16384
#endif
#define ushort unsigned short
ushort PMEM[MEMLIMIT*4] = {0}; /* program memory */
double DMEM[MEMLIMIT] = {0.0};         /* data memory */
static unsigned int runlimit = MEMLIMIT;
static unsigned char traceflag = 0;
static unsigned int runcount = 0;

/* port output function */
void portout(ushort port, double data) {
  if(port == 0) /* standard numeric output port */
    printf("%f" NLC, data);
  else if(port == 1) /* character output port */
    fputc(((int)floor(data)) & 255, stdout);
}

/* port input function */
double portin(ushort port) {
  double val = 0.0;
  if(port == 0) /* standard numeric input port */
    scanf("%lf", &val);
  else if(port == 2) { /* character input port */
    enable_raw_mode();
    val = (double) (fgetc(stdin) & 255);
    disable_raw_mode();
  }
  return val;
}

/* instruction line execution function (the main mu808 logic is defined here) */
void ilexec(ushort lno, ushort cmd, ushort x, ushort y, ushort z) {
  unsigned char halt = 0, data_override = 0, bcheck;
  ushort i;
  double v1, v2, v3;
  while(halt == 0) {
    if(traceflag) printf("PC: %hu INSTR: %hu %hu %hu %hu" NLC, lno, cmd, x, y, z);
    DMEM[0] = data_override = 0; /* force the value at 0 to be always 0 */
    DMEM[127] = 1; /* force the value at 127 to always be 1 */
    bcheck = (x < MEMLIMIT) && (y < MEMLIMIT) && (z < MEMLIMIT);
    if(bcheck) {
      v1 = DMEM[x]; v2 = DMEM[y]; v3 = DMEM[z]; /* prefetch the memory values */
      if(cmd == 1) {                                                     /* JMP */
        if((v2 == 0 && x == 0) || (v2 > 0 && x == 1) || (v2 < 0 && x == 2) \
          || (v2 >= 0 && x == 3) || (v2 <= 0 && x == 4) || (v2 != 0 && x == 5) \
          || x == 6) { halt = 0; lno = z - 1; }
        else if((v2 == 0 && x == 7) || (v2 > 0 && x == 8) || (v2 < 0 && x == 9) \
          || (v2 >= 0 && x == 10) || (v2 <= 0 && x == 11) || (v2 != 0 && x == 12) \
          || x == 13) { halt = 0; lno = (int)floor(v3) - 1; }
      } else if(cmd == 2) data_override = 1;                             /* IAT */
      else if(cmd == 3) for(i=x;i<=y;i++) portout(z, DMEM[i]);           /* OUT */
      else if(cmd == 4) for(i=x;i<=y;i++) DMEM[i] = portin(z);           /* INP */
      else if(cmd == 5) DMEM[z] = (x % 10000) + (y % 10000) / 10000.0;   /* SET */
      else if(cmd == 6) {                                                /* CPY */
        if(x == 0) DMEM[z] = y;
        else if(x == 1) DMEM[z] = v2;
        else if(v2 < MEMLIMIT && v3 < MEMLIMIT) 
          DMEM[(int)floor(v3)] = DMEM[(int)floor(v2)]; 
      } else if(cmd == 7) DMEM[z] = fma(v3, v2, v1);                     /* FMA */
      else if(cmd == 8) DMEM[z] = v1 - v2;                               /* SUB */
      else if(cmd == 9) DMEM[z] = (v2 == 0) ? 0 : (v1 / v2);             /* DIV */
      else if(cmd == 10) DMEM[z] = (v2 == 0) ? floor(v1) : fmod(v1, v2); /* MDF */
      else if(cmd == 11) DMEM[z] = fabs(v2);                             /* ABS */
      else if(cmd == 12) DMEM[z] = sqrt(fabs(v2));                       /* SQR */
      else if(cmd == 13) {                                               /* NEL */  
        if(x == 0) DMEM[z] = exp(v2);
        else DMEM[z] = (v2 == 0) ? 0 : log(fabs(v2));
      } else if(cmd == 14) {                                             /* TRI */
        if(x == 0) DMEM[z] = sin(v2);
        else if(x == 1) DMEM[z] = cos(v2);
        else DMEM[z] = atan(v2);
      } else if(cmd == 15) {                                             /* RND */
        v1 = floor(v1);
        DMEM[z] = v1 + (rand() % (int)(floor(v2) + 1 - v1));
      } 
    }
    lno++; /* increment the program counter */
    if(lno >= MEMLIMIT || lno < 1 || (runlimit > 0 && runcount > runlimit)) {
      halt = 1;
      if(traceflag) puts("Memory limit or runlimit hit, halting...");
    } else { /* fetch the next instruction */
      runcount++;
      if(data_override && bcheck) {
        cmd = PMEM[lno << 2];
        x = ((int) floor(v1)) % MEMLIMIT;
        y = ((int) floor(v2)) % MEMLIMIT;
        z = ((int) floor(v3)) % MEMLIMIT;
      } else {
        cmd = PMEM[lno << 2];
        x = PMEM[(lno << 2) + 1];
        y = PMEM[(lno << 2) + 2];
        z = PMEM[(lno << 2) + 3];
      }
    }
  }
}

/* instruction line entry function */
void ilenter(int lno, ushort cmd, ushort x, ushort y, ushort z) {
  if(lno > 0) { /* record the instruction in memory */
    PMEM[lno << 2] = cmd;
    PMEM[(lno << 2) + 1] = x;
    PMEM[(lno << 2) + 2] = y;
    PMEM[(lno << 2) + 3] = z;
  } else if(lno == 0) { /* immediate execution */
    runcount = 0;
    ilexec(lno, cmd, x, y, z);
  } else if(lno == -1) { /* display a range of instructions from cmd to x */
    if(cmd < MEMLIMIT && x < MEMLIMIT) for(y=cmd;y<=x;y++) {
      z = y << 2;
      printf("@%hu:\t%hu %hu %hu %hu" NLC,
        y, PMEM[z], PMEM[z+1], PMEM[z+2], PMEM[z+3]);
    }
  } else if(lno == -2) { /* clear a range of data or instructions from x to y */
    if(cmd < MEMLIMIT && x < MEMLIMIT) for(z=x;z<=y;z++) {
      if(cmd == 0)
        PMEM[z<<2] = PMEM[(z<<2)+1] = PMEM[(z<<2)+2] = PMEM[(z<<2)+3] = 0;
      else DMEM[z] = 0.0;
    }
  } else if(lno == -3) { /* tracing on/off */
    if(cmd == 0) {traceflag = 0; puts("Tracing off");}
    else {traceflag = 1; puts("Tracing on");}
  } else if(lno == -4) {
    printf("Runlimit set to %u" NLC, runlimit = cmd);
  } else if(lno == -5) {puts("Bye!"); exit(0);}
}

/* entry point to the VM REPL */
void main(int argc, char* argv[]) {
  srand(time(NULL));
  printf("mu808 v1 by Luxferre" NLC "PROGMEM: %u steps" NLC "DATAMEM: %u floats" NLC,
    MEMLIMIT, MEMLIMIT);
  int lno; /* line number can be negative at this point */
  ushort cmd, x, y, z; /* commands and their parameters */
  if(argc > 1) { /* preload the file from a command line parameter */
    FILE *fd = fopen(argv[1], "r");
    if(fd != NULL) { /* opened successfully */
      while(!feof(fd)) {
        fscanf(fd, "%d %hu %hu %hu %hu", &lno, &cmd, &x, &y, &z); /* read the five numbers */
        ilenter(lno, cmd, x, y, z); /* run the entry routine */
      }
      fclose(fd);
    } else puts("Warning: no file could be preloaded!");
  }
  while(1) { /* main interactive loop */
    printf("> ");
    lno = cmd = x = y = z = 0;
    scanf("%d %hu %hu %hu %hu", &lno, &cmd, &x, &y, &z); /* read the five numbers */
    while(getchar() != '\n'); /* ignore the rest of the line */
    ilenter(lno, cmd, x, y, z); /* run the entry routine */
  }
}