joplin/packages/renderer/MdToHtml.ts

import InMemoryCache from './InMemoryCache';
import noteStyle from './noteStyle';
import { fileExtension } from './pathUtils';

const MarkdownIt = require('markdown-it');
const md5 = require('md5');

interface RendererRule {
	install(context: any, ruleOptions: any): any;
	assets?(theme: any): any;
	plugin?: any;
}

interface RendererRules {
	[pluginName: string]: RendererRule;
}

interface RendererPlugin {
	module: any;
	options?: any;
}

interface RendererPlugins {
	[pluginName: string]: RendererPlugin;
}

// /!\/!\ Note: the order of rules is important!! /!\/!\
const rules: RendererRules = {
	fence: require('./MdToHtml/rules/fence').default,
	sanitize_html: require('./MdToHtml/rules/sanitize_html').default,
	image: require('./MdToHtml/rules/image').default,
	checkbox: require('./MdToHtml/rules/checkbox').default,
	katex: require('./MdToHtml/rules/katex').default,
	link_open: require('./MdToHtml/rules/link_open').default,
	html_image: require('./MdToHtml/rules/html_image').default,
	highlight_keywords: require('./MdToHtml/rules/highlight_keywords').default,
	code_inline: require('./MdToHtml/rules/code_inline').default,
	fountain: require('./MdToHtml/rules/fountain').default,
	mermaid: require('./MdToHtml/rules/mermaid').default,
};

const setupLinkify = require('./MdToHtml/setupLinkify');
const hljs = require('highlight.js');
const uslug = require('uslug');
const markdownItAnchor = require('markdown-it-anchor');

// The keys must match the corresponding entry in Setting.js
const plugins: RendererPlugins = {
	mark: { module: require('markdown-it-mark') },
	footnote: { module: require('markdown-it-footnote') },
	sub: { module: require('markdown-it-sub') },
	sup: { module: require('markdown-it-sup') },
	deflist: { module: require('markdown-it-deflist') },
	abbr: { module: require('markdown-it-abbr') },
	emoji: { module: require('markdown-it-emoji') },
	insert: { module: require('markdown-it-ins') },
	multitable: { module: require('markdown-it-multimd-table'), options: { multiline: true, rowspan: true, headerless: true } },
	toc: { module: require('markdown-it-toc-done-right'), options: { listType: 'ul', slugify: slugify } },
	expand_tabs: { module: require('markdown-it-expand-tabs'), options: { tabWidth: 4 } },
};
const defaultNoteStyle = require('./defaultNoteStyle');

function slugify(s: string): string {
	return uslug(s);
}

// Share across all instances of MdToHtml
const inMemoryCache = new InMemoryCache(20);

export interface ExtraRendererRule {
	id: string,
	module: any,
	assetPath: string,
}

export interface Options {
	resourceBaseUrl?: string;
	ResourceModel?: any;
	pluginOptions?: any;
	tempDir?: string;
	fsDriver?: any;
	extraRendererRules?: ExtraRendererRule[];
}

interface PluginAsset {
	mime?: string;
	inline?: boolean;
	name?: string;
	text?: string;
}

// Types are a bit of a mess when it comes to plugin assets. Something
// called "pluginAsset" in this class might refer to sublty different
// types. The logic should be cleaned up before types are added.
interface PluginAssets {
	[pluginName: string]: PluginAsset[];
}

interface PluginContext {
	css: any;
	pluginAssets: any;
	cache: any;
	userData: any;
}

interface RenderResultPluginAsset {
	name: string;
	path: string;
	mime: string;
}

interface RenderResult {
	html: string;
	pluginAssets: RenderResultPluginAsset[];
	cssStrings: string[];
}

export interface RuleOptions {
	context: PluginContext;
	theme: any;
	postMessageSyntax: string;
	ResourceModel: any;
	resourceBaseUrl: string;
	resources: any; // resourceId: Resource

	// Used by checkboxes to specify how it should be rendered
	checkboxRenderingType?: number;

	// Used by the keyword highlighting plugin (mobile only)
	highlightedKeywords?: any[];

	// Use by resource-rendering logic to signify that it should be rendered
	// as a plain HTML string without any attached JavaScript. Used for example
	// when exporting to HTML.
	plainResourceRendering?: boolean;

	// Use in mobile app to enable long-pressing an image or a linkg
	// to display a context menu. Used in `image.ts` and `link_open.ts`
	enableLongPress?: boolean;

	// Used in mobile app when enableLongPress = true. Tells for how long
	// the resource should be pressed before the menu is shown.
	longPressDelay?: number;

	// Use by `link_open` rule.
	// linkRenderingType = 1 is the regular rendering and clicking on it is handled via embedded JS (in onclick attribute)
	// linkRenderingType = 2 gives a plain link with no JS. Caller needs to handle clicking on the link.
	linkRenderingType?: number;
}

export default class MdToHtml {

	private resourceBaseUrl_: string;
	private ResourceModel_: any;
	private contextCache_: any;
	private fsDriver_: any;

	private cachedOutputs_: any = {};
	private lastCodeHighlightCacheKey_: string = null;
	private cachedHighlightedCode_: any = {};

	// Markdown-It plugin options (not Joplin plugin options)
	private pluginOptions_: any = {};
	private extraRendererRules_: RendererRules = {};
	private allProcessedAssets_: any = {};

	public constructor(options: Options = null) {
		if (!options) options = {};

		// Must include last "/"
		this.resourceBaseUrl_ = 'resourceBaseUrl' in options ? options.resourceBaseUrl : null;

		this.ResourceModel_ = options.ResourceModel;
		this.pluginOptions_ = options.pluginOptions ? options.pluginOptions : {};
		this.contextCache_ = inMemoryCache;

		this.fsDriver_ = {
			writeFile: (/* path, content, encoding = 'base64'*/) => { throw new Error('writeFile not set'); },
			exists: (/* path*/) => { throw new Error('exists not set'); },
			cacheCssToFile: (/* cssStrings*/) => { throw new Error('cacheCssToFile not set'); },
		};

		if (options.fsDriver) {
			if (options.fsDriver.writeFile) this.fsDriver_.writeFile = options.fsDriver.writeFile;
			if (options.fsDriver.exists) this.fsDriver_.exists = options.fsDriver.exists;
			if (options.fsDriver.cacheCssToFile) this.fsDriver_.cacheCssToFile = options.fsDriver.cacheCssToFile;
		}

		if (options.extraRendererRules) {
			for (const rule of options.extraRendererRules) {
				this.loadExtraRendererRule(rule.id, rule.module);
			}
		}
	}

	private fsDriver() {
		return this.fsDriver_;
	}

	public static pluginNames() {
		const output = [];
		for (const n in rules) output.push(n);
		for (const n in plugins) output.push(n);
		return output;
	}

	private pluginOptions(name: string) {
		let o = this.pluginOptions_[name] ? this.pluginOptions_[name] : {};
		o = Object.assign({
			enabled: true,
		}, o);
		return o;
	}

	private pluginEnabled(name: string) {
		return this.pluginOptions(name).enabled;
	}

	// `module` is a file that has already been `required()`
	public loadExtraRendererRule(id: string, module: any) {
		if (this.extraRendererRules_[id]) throw new Error(`A renderer rule with this ID has already been loaded: ${id}`);
		this.extraRendererRules_[id] = module;
	}

	private processPluginAssets(pluginAssets: PluginAssets): RenderResult {
		const files: RenderResultPluginAsset[] = [];
		const cssStrings = [];
		for (const pluginName in pluginAssets) {
			for (const asset of pluginAssets[pluginName]) {
				let mime = asset.mime;

				if (!mime && asset.inline) throw new Error('Mime type is required for inline assets');

				if (!mime) {
					const ext = fileExtension(asset.name).toLowerCase();
					// For now it's only useful to support CSS and JS because that's what needs to be added
					// by the caller with <script> or <style> tags. Everything, like fonts, etc. is loaded
					// via CSS or some other ways.
					mime = 'application/octet-stream';
					if (ext === 'css') mime = 'text/css';
					if (ext === 'js') mime = 'application/javascript';
				}

				if (asset.inline) {
					if (mime === 'text/css') {
						cssStrings.push(asset.text);
					} else {
						throw new Error(`Unsupported inline mime type: ${mime}`);
					}
				} else {
					const name = `${pluginName}/${asset.name}`;
					files.push(Object.assign({}, asset, {
						name: name,
						path: `pluginAssets/${name}`,
						mime: mime,
					}));
				}
			}
		}

		return {
			html: '',
			pluginAssets: files,
			cssStrings: cssStrings,
		};
	}

	// This return all the assets for all the plugins. Since it is called
	// on each render, the result is cached.
	private allProcessedAssets(theme: any, codeTheme: string) {
		const cacheKey: string = theme.cacheKey + codeTheme;

		if (this.allProcessedAssets_[cacheKey]) return this.allProcessedAssets_[cacheKey];

		const assets: any = {};
		for (const key in rules) {
			if (!this.pluginEnabled(key)) continue;
			const rule = rules[key];

			if (rule.assets) {
				assets[key] = rule.assets(theme);
			}
		}

		assets['highlight.js'] = [{ name: codeTheme }];

		const output = this.processPluginAssets(assets);

		this.allProcessedAssets_ = {
			[cacheKey]: output,
		};

		return output;
	}

	// This is similar to allProcessedAssets() but used only by the Rich Text editor
	public async allAssets(theme: any) {
		const assets: any = {};
		for (const key in rules) {
			if (!this.pluginEnabled(key)) continue;
			const rule = rules[key];

			if (rule.assets) {
				assets[key] = rule.assets(theme);
			}
		}

		const processedAssets = this.processPluginAssets(assets);
		processedAssets.cssStrings.splice(0, 0, noteStyle(theme).join('\n'));
		const output = await this.outputAssetsToExternalAssets_(processedAssets);
		return output.pluginAssets;
	}

	private async outputAssetsToExternalAssets_(output: any) {
		for (const cssString of output.cssStrings) {
			output.pluginAssets.push(await this.fsDriver().cacheCssToFile(cssString));
		}
		delete output.cssStrings;
		return output;
	}

	// The string we are looking for is: <p></p>\n
	private removeMarkdownItWrappingParagraph_(html: string) {
		if (html.length < 8) return html;

		// If there are multiple <p> tags, we keep them because it's multiple lines
		// and removing the first and last tag will result in invalid HTML.
		if ((html.match(/<\/p>/g) || []).length > 1) return html;

		if (html.substr(0, 3) !== '<p>') return html;
		if (html.slice(-5) !== '</p>\n') return html;
		return html.substring(3, html.length - 5);
	}

	public clearCache() {
		this.cachedOutputs_ = {};
	}

	// "theme" is the theme as returned by themeStyle()
	public async render(body: string, theme: any = null, options: any = null): Promise<RenderResult> {
		options = Object.assign({}, {
			// In bodyOnly mode, the rendered Markdown is returned without the wrapper DIV
			bodyOnly: false,
			// In splitted mode, the CSS and HTML will be returned in separate properties.
			// In non-splitted mode, CSS and HTML will be merged in the same document.
			splitted: false,
			// When this is true, all assets such as CSS or JS are returned as external
			// files. Otherwise some of them might be in the cssStrings property.
			externalAssetsOnly: false,
			postMessageSyntax: 'postMessage',
			highlightedKeywords: [],
			codeTheme: 'atom-one-light.css',
			theme: Object.assign({}, defaultNoteStyle, theme),
			plugins: {},
		}, options);

		// The "codeHighlightCacheKey" option indicates what set of cached object should be
		// associated with this particular Markdown body. It is only used to allow us to
		// clear the cache whenever switching to a different note.
		// If "codeHighlightCacheKey" is not specified, code highlighting won't be cached.
		if (options.codeHighlightCacheKey !== this.lastCodeHighlightCacheKey_ || !options.codeHighlightCacheKey) {
			this.cachedHighlightedCode_ = {};
			this.lastCodeHighlightCacheKey_ = options.codeHighlightCacheKey;
		}

		const cacheKey = md5(escape(body + JSON.stringify(options) + JSON.stringify(options.theme)));
		const cachedOutput = this.cachedOutputs_[cacheKey];
		if (cachedOutput) return cachedOutput;

		const ruleOptions = Object.assign({}, options, {
			resourceBaseUrl: this.resourceBaseUrl_,
			ResourceModel: this.ResourceModel_,
		});

		const context: PluginContext = {
			css: {},
			pluginAssets: {},
			cache: this.contextCache_,
			userData: {},
		};

		const markdownIt = new MarkdownIt({
			breaks: !this.pluginEnabled('softbreaks'),
			typographer: this.pluginEnabled('typographer'),
			// linkify: true,
			html: true,
			highlight: (str: string, lang: string) => {
				let outputCodeHtml = '';

				// The strings includes the last \n that is part of the fence,
				// so we remove it because we need the exact code in the source block
				const trimmedStr = str.replace(/(.*)\n$/, '$1');
				const sourceBlockHtml = `<pre class="joplin-source" data-joplin-language="${lang}" data-joplin-source-open="\`\`\`${lang}&#10;" data-joplin-source-close="&#10;\`\`\`">${markdownIt.utils.escapeHtml(trimmedStr)}</pre>`;

				try {
					let hlCode = '';

					const cacheKey = md5(`${str}_${lang}`);

					if (options.codeHighlightCacheKey && this.cachedHighlightedCode_[cacheKey]) {
						hlCode = this.cachedHighlightedCode_[cacheKey];
					} else {
						if (lang && hljs.getLanguage(lang)) {
							hlCode = hljs.highlight(lang, trimmedStr, true).value;
						} else {
							hlCode = hljs.highlightAuto(trimmedStr).value;
						}
						this.cachedHighlightedCode_[cacheKey] = hlCode;
					}

					outputCodeHtml = hlCode;
				} catch (error) {
					outputCodeHtml = markdownIt.utils.escapeHtml(trimmedStr);
				}

				return {
					wrapCode: false,
					html: `<div class="joplin-editable">${sourceBlockHtml}<pre class="hljs"><code>${outputCodeHtml}</code></pre></div>`,
				};
			},
		});

		// To add a plugin, there are three options:
		//
		// 1. If the plugin does not need any application specific data, use the standard way:
		//
		//    const someMarkdownPlugin = require('someMarkdownPlugin');
		//    markdownIt.use(someMarkdownPlugin);
		//
		// 2. If the plugin does not need any application specific data, and you want the user
		//    to be able to toggle the plugin:
		//
		//    Add the plugin to the plugins object
		//    const plugins = {
		//      plugin: require('someMarkdownPlugin'),
		//    }
		//
		//    And add a corresponding entry into Setting.js
		//    'markdown.plugin.mark': {value: true, type: Setting.TYPE_BOOL, section: 'plugins', public: true, appTypes: ['mobile', 'desktop'], label: () => _('Enable ==mark== syntax')},
		//
		// 3. If the plugin needs application data (in ruleOptions) or needs to pass data (CSS, files to load, etc.) back
		//    to the application (using the context object), use the application-specific way:
		//
		//    const imagePlugin = require('./MdToHtml/rules/image');
		//    markdownIt.use(imagePlugin(context, ruleOptions));
		//
		// Using the `context` object, a plugin can define what additional assets they need (css, fonts, etc.) using context.pluginAssets.
		// The calling application will need to handle loading these assets.

		const allRules = Object.assign({}, rules, this.extraRendererRules_);

		for (const key in allRules) {
			if (!this.pluginEnabled(key)) continue;

			const rule = allRules[key];

			markdownIt.use(rule.plugin, {
				context: context,
				...ruleOptions,
				...(ruleOptions.plugins[key] ? ruleOptions.plugins[key] : {}),
			});
		}

		markdownIt.use(markdownItAnchor, { slugify: slugify });

		for (const key in plugins) {
			if (this.pluginEnabled(key)) {
				markdownIt.use(plugins[key].module, plugins[key].options);
			}
		}

		setupLinkify(markdownIt);

		const renderedBody = markdownIt.render(body, context);

		let cssStrings = noteStyle(options.theme);

		let output = { ...this.allProcessedAssets(options.theme, options.codeTheme) };
		cssStrings = cssStrings.concat(output.cssStrings);

		if (options.userCss) cssStrings.push(options.userCss);

		if (options.bodyOnly) {
			// Markdown-it wraps any content in <p></p> by default. There's a function to parse without
			// adding these tags (https://github.com/markdown-it/markdown-it/issues/540#issuecomment-471123983)
			// however when using it, it seems the loaded plugins are not used. In my tests, just changing
			// render() to renderInline() means the checkboxes would not longer be rendered. So instead
			// of using this function, we manually remove the <p></p> tags.
			output.html = this.removeMarkdownItWrappingParagraph_(renderedBody);
			output.cssStrings = cssStrings;
		} else {
			const styleHtml = `<style>${cssStrings.join('\n')}</style>`;
			output.html = `${styleHtml}<div id="rendered-md">${renderedBody}</div>`;

			if (options.splitted) {
				output.cssStrings = cssStrings;
				output.html = `<div id="rendered-md">${renderedBody}</div>`;
			}
		}

		if (options.externalAssetsOnly) output = await this.outputAssetsToExternalAssets_(output);

		// Fow now, we keep only the last entry in the cache
		this.cachedOutputs_ = {};
		this.cachedOutputs_[cacheKey] = output;

		return output;
	}

}