//----------------------------------------
// document onload
//----------------------------------------
let isready = false
const readycbs = []
addEventListener("load", () => {
  isready = true
  while(readycbs.length > 0) {
    readycbs.shift()()
  }
})

export const ready = (callback: () => void) => {
  if(isready) {
    callback()
  } else {
    readycbs.push(callback)
  }
}
//----------------------------------------
// render loop
//----------------------------------------
const loopcbs = []
const step = () => {
  requestAnimationFrame(() => {
    loopcbs.forEach(callback => callback())
  })
}
export const loop = (callback: () => void) => {
  loopcbs.push(callback)
}

//----------------------------------------
// image loader
//----------------------------------------
export const load = (uri: string) => new Promise<ImageData>((resolve, reject) => {
  const image = new Image()
  image.onload = () => {
    const canvas  = document.createElement("canvas")
    canvas.width  = image.width
    canvas.height = image.height
    const context = canvas.getContext("2d")
    context.drawImage(image, 0, 0)
    const data = context.getImageData(0, 0, image.width, image.height)
    resolve(data)
  }; image.src = uri
})