var basic = {}

if (! ('window' in this)) {
  module.exports = basic
}

// Handle bases up to base 36
basic.abedecary = "0123456789abcdefghijklmnopqrstuvwxyz"

// Validate that a string s represents a number in base b
basic.validate = function (s, b) {
  return (basic.validate_base(b) && basic.validate_digits(s, b))
}

// Validate that a string does not contain numerals
// foreign to a particular base.
basic.validate_digits = function(s, b) {
  var A = basic.abedecary.substr(0, Math.abs(b))
	if (b > 0) {
	  A = "-" + A
  }
	var re = new RegExp ( "[^" + A + "]", "g" )
	return ! re.test(s)
}

// Validate that a base is valid.
basic.validate_base = function(b){
	return (
	   ! isNaN(b)
	&& b !== 0
	&& b !== 1
	&& b !== -1
	&& (Math.abs(b) % 1) === 0
	&& Math.abs(b) <= 36
	)
}

// Convert a string s representing a number in base b
// to an integer.  Assumes s is big-endian.
basic.toNumber = function (s, b) {
	if (! basic.validate(s, b)) {
	  return NaN
	}
  var n = 0, is_negative = false
	if (s.indexOf("-") == 0) {
	  is_negative = true
		s = s.substr(1)
	}
	for (var i = 0, len = s.length; i < len; i++) {
	  n += basic.abedecary.indexOf(s[len-1-i]) * Math.pow(b, i)
	}
	if (is_negative) {
	  n *= -1
	}
	return n
}

// Convert an integer n to a string representing that
// integer in base b, big-endian.
basic.toString = function (n, b) {
	if (! basic.validate_base(b)) {
	  throw new Error ("invalid base")
	}
	if (n === 0) {
	  return "0"
	}
	var is_negative = n < 0
	if (is_negative && b > 0) {
	  n = Math.abs(n)
	}
	var s = ""
	while (n) {
	  var remainder = n % b
    n = basic.floor(n / b)
		if (remainder < 0) {
		  n += 1
			remainder -= b
		}
		s = basic.abedecary[remainder] + s
	}
	if (is_negative && b > 0) {
	  s = "-" + s
	}
	return s
}

// Remove the mantissa from a number, handling negative numbers
basic.floor = function (n){
  if (n >= 0) {
	  return Math.floor(n)
  }
	return -1 * Math.floor(-n)
}