decoupling article - main no generators

main.js

function main(state) {
  for(;;) {
    switch(state.control) {
    case "init":
      state.action = "read"
      state.control = "loop1"
      return
    case "loop1":
      const i = state.value 
      if (i.type === "pointerdown") {
        const element = state.element = i.target.closest(".draggable")
        if (element) {
          const box = element.getBoundingClientRect()
          state.x = box.x + window.pageXOffset - i.x
          state.y = box.y + + window.pageYOffset - i.y
          state.control = "loop2"
          state.action = "read"
          return
        }
      }
      state.control = "loop1"
      state.action = "yield"
      state.value = i
      return
    case "loop2":
      const j = state.value
      if (j.type === "pointerup") {
        state.control = "loop1"
        break
      }
      if (j.type === "pointermove") {
        state.element.style.left = `${j.x + state.x}px`
        state.element.style.top = `${j.y + state.y}px`
      }
      state.action = "yield"
      state.control = "loop1"
      state.value = j
      return
    }
  }
}