keyframeInterplation function using binary search

keyframeInterpolateBinary.js

function keyframeInterpolate(keyframes, time, timing, lib) {
  const first = 0
  const last = keyframes.length - 1

  // Clamp time to [0, 1]
  time = Math.max(Math.min(time, 1), 0)

  if (!Array.isArray(keyframes) || !keyframes.length) {
    return lib.zero()
  }

  if (keyframes.length === 1) {
    return keyframes[first].value
  }

  if (time < keyframes[first].stop) {
    return keyframes[first].value
  }

  if (time > keyframes[last].stop) {
    return keyframes[last].value
  }

  const pairs = []
  keyframes.reduce((a, b) => {
    pairs.push([a, b])
    return b
  })

  const pair = search.binary(pairs, time, pair => {
    const [a, b] = pair

    if (time < a.stop) { return -1 }
    else if (time > b.stop) { return 1 }
    return 0
  })

  if (pair != null) {
    const [a, b] = pair
    const t_segment = (time - a.stop) / (b.stop - a.stop)
    const interpolate = timingToInterpFn(timing, lib)
    return interpolate(a.value, b.value, t_segment)
  }

  return lib.zero()
}