interface Target extends Element {
  _touchHandlers?: any;
}

type Handlers = {
  left: () => void;
  right: () => void;
  up: () => void;
  down: () => void;
  start: () => void;
  move: () => void;
  end: () => void;
};

// 处理手势
function handleGesture(wrapper) {
  const { touchstartX, touchendX, touchstartY, touchendY } = wrapper;

  // 用于判断方向边界
  const dirRatio = 0.5;
  // 用于判断滑动距离是否满足滑动
  const minDistance = 16;

  // 手指滑动距离
  wrapper.offsetX = touchendX - touchstartX;
  wrapper.offsetY = touchendY - touchstartY;

  // 判断左右滑动
  if (Math.abs(wrapper.offsetY) < dirRatio * Math.abs(wrapper.offsetX)) {
    wrapper.left &&
      touchendX < touchstartX - minDistance &&
      wrapper.left(wrapper);
    wrapper.right &&
      touchendX > touchstartX + minDistance &&
      wrapper.right(wrapper);
  }

  // 判断上下滑动
  if (Math.abs(wrapper.offsetX) < dirRatio * Math.abs(wrapper.offsetY)) {
    wrapper.up && touchendY < touchstartY - minDistance && wrapper.up(wrapper);
    wrapper.down &&
      touchendY > touchstartY + minDistance &&
      wrapper.down(wrapper);
  }
}

// 开始
function touchstart(event: TouchEvent, wrapper) {
  const touch = event.changedTouches[0];
  wrapper.touchstartX = touch.clientX;
  wrapper.touchstartY = touch.clientY;

  wrapper.start && wrapper.start(Object.assign(event, wrapper));
}

// 结束
function touchend(event: TouchEvent, wrapper) {
  const touch = event.changedTouches[0];
  wrapper.touchendX = touch.clientX;
  wrapper.touchendY = touch.clientY;

  wrapper.end && wrapper.end(Object.assign(event, wrapper));

  // 处理手势
  handleGesture(wrapper);
}

// 移动
function touchmove(event: TouchEvent, wrapper) {
  const touch = event.changedTouches[0];
  wrapper.touchmoveX = touch.clientX;
  wrapper.touchmoveY = touch.clientY;

  wrapper.move && wrapper.move(Object.assign(event, wrapper));
}

// 创建事件
function createHandlers(value: Handlers) {
  const wrapper = {
    touchstartX: 0,
    touchstartY: 0,
    touchendX: 0,
    touchendY: 0,
    touchmoveX: 0,
    touchmoveY: 0,
    offsetX: 0,
    offsetY: 0,
    left: value.left,
    right: value.right,
    up: value.up,
    down: value.down,
    start: value.start,
    move: value.move,
    end: value.end,
  };

  return {
    touchstart: (e: TouchEvent) => touchstart(e, wrapper),
    touchend: (e: TouchEvent) => touchend(e, wrapper),
    touchmove: (e: TouchEvent) => touchmove(e, wrapper),
  };
}

// 指令定义
function inserted(el: Element, binding: Record<string, any>) {
  const value = binding.value;

  const target: Target = value.parent ? el.parentElement : el;
  const options = value.options || { passive: true };

  if (!target) {
    return;
  }

  const handlers = createHandlers(value);
  target._touchHandlers = Object(target._touchHandlers);
  target._touchHandlers[binding.instance.$.uid] = handlers;

  // 添加事件
  Object.keys(handlers).forEach((eventName) => {
    target.addEventListener(eventName, handlers[eventName], options);
  });
}

// 指令与元素解绑时调用
function unbind(el: Element, binding: Record<string, any>) {
  const target: Target = binding.value.parent ? el.parentElement : el;

  if (!target || !target._touchHandlers) {
    return;
  }

  const handlers = target._touchHandlers[binding.instance.$.uid];
  Object.keys(handlers).forEach((eventName) => {
    target.removeEventListener(eventName, handlers[eventName]);
  });

  delete target._touchHandlers[binding.instance.$.uid];
}

export default {
  beforeMount: inserted,
  unmounted: unbind,
};