module.exports = balanced;
  function balanced(a, b, str) {
    if (a instanceof RegExp) a = maybeMatch(a, str);
    if (b instanceof RegExp) b = maybeMatch(b, str);
  
    var r = range(a, b, str);
  
    return r && {
      start: r[0],
      end: r[1],
      pre: str.slice(0, r[0]),
      body: str.slice(r[0] + a.length, r[1]),
      post: str.slice(r[1] + b.length)
    };
  }
  
  function maybeMatch(reg, str) {
    var m = str.match(reg);
    return m ? m[0] : null;
  }
  
  balanced.range = range;
  function range(a, b, str) {
    var begs, beg, left, right, result;
    var ai = str.indexOf(a);
    var bi = str.indexOf(b, ai + 1);
    var i = ai;
  
    if (ai >= 0 && bi > 0) {
      begs = [];
      left = str.length;
  
      while (i >= 0 && !result) {
        if (i == ai) {
          begs.push(i);
          ai = str.indexOf(a, i + 1);
        } else if (begs.length == 1) {
          result = [ begs.pop(), bi ];
        } else {
          beg = begs.pop();
          if (beg < left) {
            left = beg;
            right = bi;
          }
  
          bi = str.indexOf(b, i + 1);
        }
  
        i = ai < bi && ai >= 0 ? ai : bi;
      }
  
      if (begs.length) {
        result = [ left, right ];
      }
    }
  
    return result;
  }