/*
  需求：给整个页面添加背景水印。

  思路：
    1、使用 canvas 特性生成 base64 格式的图片文件，设置其字体大小，颜色等。
    2、将其设置为背景图片，从而实现页面或组件水印效果
  
  使用：设置水印文案，颜色，字体大小即可
  <div v-waterMarker="{text:'版权所有',textColor:'rgba(180, 180, 180, 0.4)'}"></div>
*/
// watermark 样式
let style = `
	display: block;
	overflow: hidden;
	position: absolute;
	left: 0;
	top: 0;
	width: 100%;
	height: 100%;
	background-repeat: repeat;
	pointer-events: none;
`;
import type { Directive, DirectiveBinding } from "vue";
const addWaterMarker = (parentNode: any, binding: any = {}) => {
	console.log(binding);
	// 水印文字，父元素，字体，文字颜色
	let can: HTMLCanvasElement = document.createElement("canvas");
	parentNode.appendChild(can);
	can.width = 205;
	can.height = 140;
	can.style.display = "none";
	let cans = can.getContext("2d") as CanvasRenderingContext2D;
	cans.rotate((-20 * Math.PI) / 180);
	cans.font = binding.font || "16px Microsoft JhengHei";
	cans.fillStyle = binding.textColor || "rgba(180, 180, 180, 0.3)";
	cans.textAlign = "left";
	cans.textBaseline = "Middle" as CanvasTextBaseline;
	cans.fillText(binding.text, can.width / 10, can.height / 2);

	// 创建waterMark父元素
	const waterMark = document.createElement("div");
	waterMark.className = `water-mark`; // 方便自定义展示结果
	style = `${style}background-image: url(${can.toDataURL("image/png")})`;
	waterMark.setAttribute("style", style);
	// 将对应图片的父容器作为定位元素
	parentNode.setAttribute("style", "position:relative;");
	// 将图片元素移动到waterMark中
	parentNode.appendChild(waterMark);
	// parentNode.style.backgroundImage = "url(" + can.toDataURL("image/png") + ")";
};

const waterMarker = {
	mounted(el: HTMLElement, binding: any) {
		console.log(666);
		// addWaterMarker(binding.value.text, el, binding.value.font, binding.value.textColor);
		el.onload = init(el, binding);
	}
};

// 监听DOM变化
const createObserver = (el: HTMLElement, binding: any) => {
	const waterMarkEl = el.parentElement?.querySelector(".water-mark");
	const observer = new MutationObserver(mutationsList => {
		if (mutationsList.length) {
			const { removedNodes, type, target } = mutationsList[0];
			const currStyle = waterMarkEl?.getAttribute("style");

			// 证明被删除了
			if (removedNodes[0] === waterMarkEl) {
				observer.disconnect();
				init(el, binding);
			} else if (type === "attributes" && target === waterMarkEl && currStyle !== style) {
				waterMarkEl.setAttribute("style", style);
			}
		}
	});
	observer.observe(el.parentElement, {
		childList: true,
		attributes: true,
		subtree: true
	});
};
const init = (el: HTMLElement, binding: any = {}) => {
	console.log(666);
	// 设置水印
	addWaterMarker(el, binding.value);
	// 启动监控
	createObserver(el, binding.value);
};
export default waterMarker;