var common = typeof window !== 'undefined' ? window : exports

common.startTime = new Date('2015-08-05').getTime()

var colors20 = [
  [255, 106, 152], [255, 98, 188], [250, 98, 219], [231, 107, 243],
  [199, 124, 255], [149, 144, 255], [53, 162, 255], [0, 176, 246],
  [0, 186, 224], [0, 191, 196], [0, 193, 163], [0, 191, 125],
  [0, 187, 78], [57, 182, 0], [124, 174, 0], [163, 165, 0],
  [192, 155, 0], [216, 144, 0], [234, 131, 49], [248, 118, 109],
  [255, 106, 152]
]

common.interpolate = function (a, b, n) {
  if (!a) a = [0, 0, 0, 0]
  if (!b) b = [0, 0, 0, 0]
  var m = 1 - n
  return [
    a[0] * m + b[0] * n,
    a[1] * m + b[1] * n,
    a[2] * m + b[2] * n,
    a[3] * m + b[3] * n,
  ]
}

common.computeIdColors = function (ids, flat) {
  var idColors = {}
  var colorsUsed = {}
  var ensureUniqueness = !flat
  for (var i = 0; i < ids.length; i++) {
    var id = ids[i]
    var x = i / ids.length
    var colorI = Math.floor(x*20)
    var inbetweenAmount = x*20 - colorI
    var color = common.interpolate(colors20[colorI], colors20[colorI+1], inbetweenAmount)
    color[0] = Math.floor(color[0])
    color[1] = Math.floor(color[1])
    color[2] = Math.floor(color[2])
    color[3] = 255
    if (ensureUniqueness) {
      while (colorsUsed[color]) {
        color[3]--
      }
      if (color[3] < 0) throw new Error('Too many ids for color')
      colorsUsed[color] = true
    }
    idColors[id] = color
  }
  return idColors
}