epam/miew

import settings from '../settings'
import { Quaternion, Vector3 } from 'three'

class View {
  constructor() {
    this.position = new Vector3(0, 0, 0)
    this.scale = 1
    this.orientation = new Quaternion(0, 0, 0, 1)
  }

  set(position, scale, orientation) {
    this.position = position
    this.scale = scale
    this.orientation = orientation
  }
}

const _transitionTime = 1.5 // in seconds

export default class ViewInterpolator {
  setup(startView, endView) {
    this._startTime = undefined
    this._endTime = undefined
    this._isPaused = false

    this._srcView = startView
    this._dstView = endView
    this._isMoving = false
  }

  isMoving() {
    return this._isMoving
  }

  wasStarted() {
    return (
      typeof this._startTime !== 'undefined' &&
      typeof this._endTime !== 'undefined'
    )
  }

  start() {
    this._startTime = Date.now()
    const transTime = settings.now.interpolateViews ? _transitionTime * 1000 : 0
    this._endTime = this._startTime + transTime
    this._isMoving = true
  }

  getCurrentView() {
    if (
      typeof this._srcView === 'undefined' ||
      typeof this._dstView === 'undefined' ||
      !this._isMoving ||
      !this.wasStarted()
    ) {
      return { success: false }
    }

    let view = this.createView()
    const time = Date.now()
    if (time > this._endTime) {
      view = this._dstView
      this.reset()
      return { success: true, view }
    }

    const factor = (time - this._startTime) / (this._endTime - this._startTime)
    view.position.copy(this._srcView.position)
    view.position.lerp(this._dstView.position, factor)
    view.scale =
      (1 - factor) * this._srcView.scale + factor * this._dstView.scale
    view.orientation.copy(this._srcView.orientation)
    view.orientation.slerp(this._dstView.orientation, factor)
    return { success: true, view }
  }

  reset() {
    this._startTime = this._endTime = 0
    this._isMoving = false
  }

  pause() {
    if (!this._isPaused) {
      this.setup(this.getCurrentView().view, this._dstView)
      this._isPaused = true
    }
  }

  resume() {
    this._isPaused = false
  }

  createView() {
    return new View()
  }
}