type CSSOMString = string
type FontFaceLoadStatus = 'unloaded' | 'loading' | 'loaded' | 'error'
type FontFaceSetStatus = 'loading' | 'loaded'

interface FontFace {
  family: CSSOMString
  style: CSSOMString
  weight: CSSOMString
  stretch: CSSOMString
  unicodeRange: CSSOMString
  variant: CSSOMString
  featureSettings: CSSOMString
  variationSettings: CSSOMString
  display: CSSOMString
  readonly status: FontFaceLoadStatus
  readonly loaded: Promise<FontFace>
  load(): Promise<FontFace>
}

interface FontFaceSet {
  readonly status: FontFaceSetStatus
  readonly ready: Promise<FontFaceSet>
  check(font: string, text?: string): Boolean
  load(font: string, text?: string): Promise<FontFace[]>
}

declare global {
  interface Document {
    fonts: FontFaceSet
  }
}