import { marked } from "marked";
import { gfmHeadingId } from "marked-gfm-heading-id";
import { markedHighlight } from "marked-highlight";
import { mangle } from "marked-mangle";
import Prism from "prismjs";
import "prismjs/themes/prism.css";
import { Toolkit } from "~/index";

export default class Markdown {

	private static instance: Markdown;

	renderer = new marked.Renderer();

	private constructor() {
		marked.use(mangle());
		marked.use(gfmHeadingId());
		marked.use(markedHighlight({
			highlight(code: string, lang: string) {
				if (Prism.languages[lang]) {
					return Prism.highlight(code, Prism.languages[lang], lang);
				} else {
					return code;
				}
			}
		}));
		// Markdown 解析器配置
		marked.setOptions({
			renderer: this.renderer,
			pedantic: false,
			gfm: true,
			breaks: true
		});

		Prism.hooks.add("complete", (env: any) => {
			if (!env.code) return;

			// 行号渲染调整
			const el = env.element;

			const lineNumber = el.querySelector(".line-numbers-rows") as HTMLDivElement;
			if (lineNumber) {
				const clone = lineNumber.cloneNode(true);
				el.removeChild(lineNumber);
				// 加容器做滚动
				el.innerHTML = `<span class="codes">${el.innerHTML}</span>`;
				el.insertBefore(clone, el.firstChild);

				if (el.parentNode) {
					const markdownRoot = el.parentNode.parentNode;
					if (markdownRoot) {
						const maxHeight = markdownRoot.dataset.maxHeight;
						if (maxHeight === "auto") {
							return;
						}
						// 注册双击事件
						const lines = lineNumber.children.length;
						if (lines < 18) {
							return;
						}
						const parent = el.parentNode;
						parent.addEventListener("dblclick", (): void => {
							const isExpand = parent.classList.contains("expand");
							if (isExpand) {
								parent.style.maxHeight = maxHeight;
								parent.classList.remove("expand");
							} else {
								parent.style.maxHeight = lines * 22 + "px";
								parent.classList.add("expand");
							}
							const selection = window.getSelection();
							if (selection) {
								selection.removeAllRanges();
							}
						});
					}
				}
			}
		});

		/**
		 * ### 超链渲染方式
		 *
		 * 1. 链接前加 ~ 符号会被渲染为新标签打开。例：`[文本](~链接)`
		 * 3. 没有标题的链接将使用文本作为标题
		 * 4. 没有链接的会被渲染为 span 标签
		 */
		this.renderer.link = function ({ href, title, text }) {
			title = title ?? text;

			if (!href) {
				return `<span>${text}</span>`;
			}
			// 新标签打开
			let target = "_self";
			if (href.startsWith("~")) {
				target = "_blank";
				href = href.substring(1);
			}
			// 内部资源链接
			if (href.indexOf("@") !== -1) {
				href = Toolkit.toResURL(href);
			}
			{
				// 处理嵌套 markdown，这可能不是最优解
				const tokens = (marked.lexer(text, { inline: true } as any) as any)[0].tokens;
				text = this.parser.parseInline(tokens);
			}
			return `<a href="${href}" target="${target}" title="${title}">${text}</a>`;
		};

		/**
		 * ### 重点内容扩展
		 *
		 * ```md
		 * 默认 `文本` 表现为红色
		 * 使用 `[red bold]文本` 可以自定义类
		 * ```
		 */
		this.renderer.codespan = ({ text }) => {
			const clazz = text.match(/\[(.+?)]/);
			if (clazz) {
				return `<span class="${clazz[1]}">${text.substring(text.indexOf("]") + 1)}</span>`;
			} else {
				return `<span class="red">${text}</span>`;
			}
		};

		/**
		 * ### 组件渲染方式（原为图像渲染方式）
		 *
		 * ```md
		 * [] 内文本以 # 开始时，该组件带边框
		 * ```
		 *
		 * 1. 渲染为网页：`![]($/html/index.html)`
		 * 2. 渲染为视频：`![](#/media/video.mp4)`
		 * 3. 渲染为音频：`![](~/media/music.mp3)`
		 * 4. 渲染为图片：`![](/image/photo.png)`
		 * 6. 带边框图片：`![#图片Alt](/image/photo.png)`
		 */
		this.renderer.image = ({ href, title, text }) => {
			const clazz = ["media"];

			const hasBorder = text[0] === "#";
			if (hasBorder) {
				clazz.push("border");
			}
			title = title ?? text;

			const extendTags = ["~", "#", "$"];
			let extendTag;
			if (extendTags.indexOf(href.charAt(0)) !== -1) {
				extendTag = href.charAt(0);
			}

			// 内部资源链接
			if (href.indexOf("@") !== -1) {
				if (extendTag) {
					href = href.substring(1);
				}
				href = Toolkit.toResURL(href);
			}

			const clazzStr = clazz.join(" ");
			let elStr;
			switch (extendTag) {
				case "~":
					elStr = `<audio class="${clazzStr}" controls><source type="audio/mp3" src="${href}" title="${title}" /></audio>`;
					break;
				case "#":
					elStr = `<video class="${clazzStr}" controls><source type="video/mp4" src="${href}" title="${title}" /></video>`;
					break;
				case "$":
					elStr = `<iframe class="${clazzStr}" src="${href}" allowfullscreen title="${title}"></iframe>`;
					break;
				default:
					elStr = `<img class="${clazzStr}" src="${href}" alt="${title}" />`;
					break;
			}
			return elStr + `<span class="media-tips">${title}</span>`;
		};
	}

	/**
	 * ### 解析 Markdown 文本为 HTML 节点
	 *
	 * ```js
	 * const html = toHTML('# Markdown Content');
	 * ```
	 *
	 * @param mkData Markdown 文本
	 * @returns HTML 节点
	 */
	public toHTML(mkData: string | undefined): string | Promise<string> {
		if (mkData) {
			return marked(mkData);
		} else {
			return "";
		}
	}

	public static getInstance(): Markdown {
		if (!Markdown.instance) {
			Markdown.instance = new Markdown();
		}
		return Markdown.instance;
	}
}