/*
Copyright (c) 2012, Roman Muentener, fmnssun _at_ gmail [dot] com

Permission to use, copy, modify, and/or distribute this software for any 
purpose with or without fee is hereby granted, provided that the above 
copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 
WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY 
AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, 
INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM 
LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE 
OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR 
PERFORMANCE OF THIS SOFTWARE.
*/

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <assert.h>
#include <limits.h>

int valid_bf(char* program);
char* next_bf(char* program, int pos);
void interpret(char* program, int* solutions, unsigned long int boundl, unsigned long int boundh);
inline int mod(int a, int b);

#define PROG_MAX_LEN 40
#define PROG_MAX_STEPS 5000

int main(int argc, char* argv[])
{
  printf("  _                        \n");
  printf(" / `_   _  _  /__/|   _  /_\n");
  printf("/_,//_// //_ / // /_//_ /\\ \n");
  printf("\n");


  char* program;
  int* solutions;

  if(argc != 5) {
    printf("Usage: %s prog boundl boundh n\n", argv[0]);
    printf("\tprog - A start program (example: ++++++++)\n");
    printf("\tn - How many (next) programs you want to check\n");
    exit(1);
  }

  fflush(stdout);

  program = calloc(PROG_MAX_LEN, sizeof(char));
  assert(program != NULL);

  solutions = calloc(265, sizeof(int));
  assert(solutions != NULL);

  strncpy(program, argv[1], PROG_MAX_LEN - 1);
  
  unsigned long int limit = strtoul(argv[2], NULL, 10), i = 0;
  unsigned long int boundl = strtoul(argv[3], NULL, 10);
  unsigned long int boundh = strtoul(argv[4], NULL, 10);
  assert(limit > 0);
  

  //printf("Reading a list of already known solutions for...\n");
  /*while(1) {
    int d;
    if(scanf("%d",&d) == 1) {
      solutions[d] = 1;
    }
    else break;
  }*/
  //printf("Done reading...\n");
  

  for(;i < limit;i++) {
    if(valid_bf(program))
      interpret(program, solutions, boundl, boundh);
    program = next_bf(program, 0);
  }

  printf("Last program: %s\n", program);
}

inline int mod(int a, int b) {
  if(a > b)
    return a - b;
  if(a < 0)
    return a + b;
  return a;
}

void interpret(char* program, int* solutions, unsigned long int boundl, unsigned long int boundh)
{
  unsigned char memory[256] = {0};
  short iptr = 0;
  unsigned char cptr = 0;
  short steps = 0;
  short len = strlen(program);

  while(iptr < len) {
    if(steps > PROG_MAX_STEPS) return;
    steps++;

    //printf("%d %c (iptr := %d, cptr := %d)\n",steps, program[iptr], iptr, cptr); 

    switch(program[iptr]) {
      case '+':
        memory[cptr]++;
        break;
      case '-':
        memory[cptr]--;
        break;
      case '>':
        cptr++;
        break;
      case '<':
        cptr--;
        break;
      case '[':
        if(memory[cptr] == 0) {
          int lvl = 0;
          iptr++;
          while(iptr < len) {
            if(program[iptr] == ']')
              if(lvl < 1) break;
              else lvl--;
            if(program[iptr] == '[')
              lvl++;
            iptr++;
          }
        }
        break;
      case ']':
        if(memory[cptr] != 0) {
          int lvl = 0;
          iptr--;
          while(iptr >= 0) {
            if(program[iptr] == '[')
              if(lvl < 1) break;
              else lvl--;
            if(program[iptr] == ']')
              lvl++;
            iptr--;
          }
        }
        break;
    }

    iptr++;
  }

  if(!solutions[memory[cptr]]) {
    if(memory[cptr] > boundl && memory[cptr] < boundh)
      printf("Result: %u -> %s\n", memory[cptr], program);
    fflush(stdout);
    solutions[memory[cptr]] = 1;
  }
}

char* next_bf(char* program, int pos)
{
  if(pos >= PROG_MAX_LEN) {
    fputs("Presumed maximum length exceeded!\n", stderr);
    exit(1);
  }

  /* Next instruction */
  switch(program[pos]) {
    case '\0':
      program[pos] = '+';
      break;
    case '+':
      program[pos] = '-';
      break;
    case '-':
      program[pos] = '>';
      break;
    case '>':
      program[pos] = '<';
      break;
    case '<':
      program[pos] = '[';
      break;
    case '[':
      program[pos] = ']';
      break;
    case ']':
      program[pos] = '+';
      return next_bf(program, pos+1);
  }

  return program;
}

int valid_bf(char* program)
{
  int level = 0;
  while(*program) {
    char c = *program;
    switch(c) {
      case '[':
        level++;
        break;
      case ']':
        level--;
        break;
      default: break;
    }

    if(level < 0)
      return 0;

    program++;
  }

  if(level != 0)
    return 0;

  return 1;
}