export class ImgManager {
  imgCache: {
    [index: string]: HTMLImageElement
  } = {}

  constructor(private getImageBlob: (imageId: string) => Promise<Blob>) {}

  getImg = (imageId: string): Promise<HTMLImageElement> => {
    if (imageId in this.imgCache) {
      return Promise.resolve(this.imgCache[imageId])
    }
    return new Promise(r => {
      this.getImageBlob(imageId).then(blob => {
        const img = document.createElement("img")
        img.addEventListener("load", () => {
          this.imgCache[imageId] = img
          r(img)
        })
        img.src = URL.createObjectURL(blob)
      })
    })
  }
}