import { toNumber } from './tool'

interface Position {
  x: number
  y: number
}

interface RegisterMoveablePanelOptions {
  wrapEl?: HTMLElement
  onmousedown?(position: Position, event: MouseEvent): void
  onmousemove?(position: Position, event: MouseEvent): void
  onmouseup?(position: Position, event: MouseEvent): void
}

export const registerMoveableElement = (el: HTMLElement, { onmousedown, onmousemove, onmouseup }: RegisterMoveablePanelOptions = {}) => {
  let elRect = el.getBoundingClientRect()
  const position = { x: 0, y: 0 }

  const update = (event: MouseEvent) => {
    let dx = event.pageX - elRect.x
    let dy = event.pageY - elRect.y

    if (dx < 0) dx = 0
    if (dx > elRect.width) dx = elRect.width
    if (dy < 0) dy = 0
    if (dy > elRect.height) dy = elRect.height

    position.x = toNumber(dx / elRect.width, { decimal: 2 })
    position.y = toNumber(dy / elRect.height, { decimal: 2 })
  }

  const _onmousemove = (event: MouseEvent) => {
    update(event)

    if (onmousemove) {
      onmousemove(position, event)
    }
  }

  const _onmouseup = (event: MouseEvent) => {
    document.removeEventListener('mousemove', _onmousemove)
    document.removeEventListener('mouseup', _onmouseup)

    if (onmouseup) {
      onmouseup(position, event)
    }
  }

  const _onmousedown = (event: MouseEvent) => {
    // elRect 可能不准确，这里更新一下
    elRect = el.getBoundingClientRect()

    update(event)

    document.addEventListener('mousemove', _onmousemove)
    document.addEventListener('mouseup', _onmouseup)

    if (onmousedown) {
      onmousedown(position, event)
    }
  }

  el.addEventListener('mousedown', _onmousedown)

  return {
    destroy() {
      el.removeEventListener('mousedown', _onmousedown)
    },
  }
}