unfuck/src/steps/prepare.js

A brainfuck to Javascript compiler with optimizations.

var valid = [
  '+','-','>','<','[',']','.',','
]

function prepare ( settings, bf ) {
  var program = bf.split('').filter(x => valid.indexOf(x) > -1).join('');
  if (program[0] === "[") {
    var i = 0;
    var length = 0;
    var prev = 0;
    var open = 1;
    while (open > 0) {
      for (let j = (i + 1); program[j] !== ']' && j < program.length; j++) {
        if (program[j] == "[") open++;
        length++;
      }
      i += (length - prev) + 1
      prev = ((length - prev) + 1) + prev
      open--;
      length++;
    }
    if (length >= program.length) {
      throw new BrainfuckError(program, {start: 0, end: 1}, 'Comment loop is never closed!')
    }
    program = program.slice(length+1);
  }
  return program;
}

module.exports = prepare;