import Vue from 'vue';

/**
 * 1. 在调用的时候必须写v-
 * 2. 在使用的组件上或者div的位置必须是绝对的，在需要拖拽的最外层样式上加上 position: absolute;
 * 3. 在所需要的样式上使用 v-drag
 * 4. 激活之后的样式名为 v-drag-active 没有激活的样式名为 v-drag-inactive
 */
const drag = Vue.directive('drag', {
    // 指令绑定到元素上回立刻执行bind函数，只执行一次
    bind: function (el) {

    },
    //inserted表示一个元素，插入到DOM中会执行inserted函数，只触发一次
    inserted: function (el) {


        let wMax = document.documentElement.clientWidth - el.offsetWidth;
        let hMax = document.documentElement.clientHeight - el.offsetHeight;

        if ("ontouchstart" in window) { // 移动端
            el.ontouchstart = function (e) {
                let time1 = new Date().getTime();
                let x = e.touches[0].pageX - el.offsetLeft;
                let y = e.touches[0].pageY - el.offsetTop;
                // 抑制浏览器端默认拖拽行为，移动端是拖拽屏幕，pc端无
                // e.preventDefault(); 开启后点击 子集点击事件事件会无效
                document.ontouchmove = function (e) {
                    let time2 = new Date().getTime();
                    if (time2 - time1 > 300) {
                        el.classList.remove('v-drag-inactive')
                        el.classList.add('v-drag-active')
                    }
                    let left = e.touches[0].pageX - x;
                    let top = e.touches[0].pageY - y;

                    if (left < 0) left = 0;
                    else if (left > wMax) left = wMax;

                    if (top < 0) top = 0;
                    else if (top > hMax) top = hMax;

                    el.style.left = left + 'px';
                    el.style.top = top + 'px';
                }
                document.ontouchend = function () {
                    let time2 = new Date().getTime();
                    if (time2 - time1 > 300) {
                        el.classList.remove('v-drag-active')
                        el.classList.add('v-drag-inactive')
                    }

                    document.ontouchmove = document.ontouchend = null;
                }
            }
        } else { // pc端
            el.onmousedown = function (e) {
                let time1 = new Date().getTime();
                let x = e.pageX - el.offsetLeft;
                let y = e.pageY - el.offsetTop;
                document.onmousemove = function (e) {
                    let time2 = new Date().getTime();
                    if (time2 - time1 > 300) {
                        el.classList.remove('v-drag-inactive')
                        el.classList.add('v-drag-active')
                    }
                    el.style.left = e.pageX - x + 'px';
                    el.style.top = e.pageY - y + 'px';
                }
                document.onmouseup = function () {
                    let time2 = new Date().getTime();
                    if (time2 - time1 > 300) {
                        el.classList.remove('v-drag-active')
                        el.classList.add('v-drag-inactive')
                    }
                    document.onmousemove = document.onmouseup = null;
                }
            }
        }


    },
    updated: function (el) {
    }
})
export default drag;