function updateTable(pairs) {
  pairs.forEach(function(pair) {
    var hash = pair[0]
    var mult = pair[1]
    var color = 'gray'
    if (mult == 3) color = 'green'
    if (mult == 5) color = 'purple'
    if (mult == 50) color = 'orange'
    var tableBody = document.getElementById("tbody");
    tableBody.innerHTML += "<tr><td>" + hash + "</td><td style='background:" + color + "'>" + mult + "</td></tr>";
  })
}

var maxHex = 13
var maxInt = Math.pow(2, maxHex * 4)
var clientSeed = '000000000000000007a9a31ff7f07463d91af6b5454241d5faf282e5e0fe1b3a'
var pocketTypes = [{
  count: 1,
  multiplier: 50
}, {
  count: 10,
  multiplier: 5
}, {
  count: 17,
  multiplier: 3
}, {
  count: 26,
  multiplier: 2
}, ]

function previousHash(hash) {
  return CryptoJS.SHA256(hash).toString()
};

function hmac(key, v) {
  var hmacHasher = CryptoJS.algo.HMAC.create(CryptoJS.algo.SHA256, key);
  return hmacHasher.finalize(v).toString();
}

function toInt(hash) {
  return parseInt(hash.slice(0, maxHex), 16)
}

function randomInt(hash, max) {
  hash = hmac(hash, clientSeed)
  var integer = toInt(hash)
  return Math.floor(max * (integer / maxInt))
}

function createPockets(pocketTypes) {
  return pocketTypes.reduce(function(result, next) {
    return result.concat(Array(next.count).fill(next.multiplier))
  }, [])
}

function pickRandom(hash, pockets) {
  var index = randomInt(hash, pockets.length)
  return pockets[index]
}

function nPrevious(hash, n, result) {
  if(result == null) result = []
  if(n == 0) return result
  var previous = previousHash(hash)
  result.push(previous)
  return nPrevious(previous,--n,result)
}

function getParams(name, url) {
  if (!url) url = window.location.href;
  name = name.replace(/[\[\]]/g, "\\$&");
  var regex = new RegExp("[?&]" + name + "(=([^&#]*)|&|#|$)"),
    results = regex.exec(url);
  if (!results) return null;
  if (!results[2]) return '';
  return decodeURIComponent(results[2].replace(/\+/g, " "));
}

function run() {
  var currentHash = getParams('hash')
  if (currentHash == null) {
    return console.log('must supply hash as url parameter')
  }
  var previousHashes = nPrevious(currentHash, 20)
  var hashes = [currentHash].concat(previousHashes)

  var pockets = createPockets(pocketTypes)
  var results = hashes.map(function(hash) {
    return [hash, pickRandom(hash, pockets)]
  })
  updateTable(results)
}
run()