interface Window {
  ResizeObserver: ResizeObserver
}

/**
 * The ResizeObserver interface is used to observe changes to Element's content
 * rect.
 *
 * It is modeled after MutationObserver and IntersectionObserver.
 */
interface ResizeObserver {
  new (callback: ResizeObserverCallback)

  /**
   * Adds target to the list of observed elements.
   */
  observe: (target: Element) => void

  /**
   * Removes target from the list of observed elements.
   */
  unobserve: (target: Element) => void

  /**
   * Clears both the observationTargets and activeTargets lists.
   */
  disconnect: () => void
}

/**
 * This callback delivers ResizeObserver's notifications. It is invoked by a
 * broadcast active observations algorithm.
 */
interface ResizeObserverCallback {
  (entries: ResizeObserverEntry[], observer: ResizeObserver): void
}

interface ResizeObserverEntry {
  /**
   * @param target The Element whose size has changed.
   */
  new (target: Element)

  /**
   * The Element whose size has changed.
   */
  readonly target: Element

  /**
   * Element's content rect when ResizeObserverCallback is invoked.
   */
  readonly contentRect: DOMRectReadOnly
}

interface DOMRectReadOnly {
  fromRect(other: DOMRectInit | undefined): DOMRectReadOnly

  readonly x: number
  readonly y: number
  readonly width: number
  readonly height: number
  readonly top: number
  readonly right: number
  readonly bottom: number
  readonly left: number

  toJSON: () => any
}