refactoring

Resolve #7779

packages/backend/src/mfm/from-html.ts

@@ -0,0 +1,209 @@
+import * as parse5 from 'parse5';
+import treeAdapter = require('parse5/lib/tree-adapters/default');
+import { URL } from 'url';
+
+const urlRegex     = /^https?:\/\/[\w\/:%#@$&?!()\[\]~.,=+\-]+/;
+const urlRegexFull = /^https?:\/\/[\w\/:%#@$&?!()\[\]~.,=+\-]+$/;
+
+export function fromHtml(html: string, hashtagNames?: string[]): string | null {
+	if (html == null) return null;
+
+	const dom = parse5.parseFragment(html);
+
+	let text = '';
+
+	for (const n of dom.childNodes) {
+		analyze(n);
+	}
+
+	return text.trim();
+
+	function getText(node: parse5.Node): string {
+		if (treeAdapter.isTextNode(node)) return node.value;
+		if (!treeAdapter.isElementNode(node)) return '';
+		if (node.nodeName === 'br') return '\n';
+
+		if (node.childNodes) {
+			return node.childNodes.map(n => getText(n)).join('');
+		}
+
+		return '';
+	}
+
+	function appendChildren(childNodes: parse5.ChildNode[]): void {
+		if (childNodes) {
+			for (const n of childNodes) {
+				analyze(n);
+			}
+		}
+	}
+
+	function analyze(node: parse5.Node) {
+		if (treeAdapter.isTextNode(node)) {
+			text += node.value;
+			return;
+		}
+
+		// Skip comment or document type node
+		if (!treeAdapter.isElementNode(node)) return;
+
+		switch (node.nodeName) {
+			case 'br':
+				text += '\n';
+				break;
+
+			case 'a':
+			{
+				const txt = getText(node);
+				const rel = node.attrs.find(x => x.name === 'rel');
+				const href = node.attrs.find(x => x.name === 'href');
+
+				// ハッシュタグ
+				if (hashtagNames && href && hashtagNames.map(x => x.toLowerCase()).includes(txt.toLowerCase())) {
+					text += txt;
+				// メンション
+				} else if (txt.startsWith('@') && !(rel && rel.value.match(/^me /))) {
+					const part = txt.split('@');
+
+					if (part.length === 2 && href) {
+						//#region ホスト名部分が省略されているので復元する
+						const acct = `${txt}@${(new URL(href.value)).hostname}`;
+						text += acct;
+						//#endregion
+					} else if (part.length === 3) {
+						text += txt;
+					}
+				// その他
+				} else {
+					const generateLink = () => {
+						if (!href && !txt) {
+							return '';
+						}
+						if (!href) {
+							return txt;
+						}
+						if (!txt || txt === href.value) {	// #6383: Missing text node
+							if (href.value.match(urlRegexFull)) {
+								return href.value;
+							} else {
+								return `<${href.value}>`;
+							}
+						}
+						if (href.value.match(urlRegex) && !href.value.match(urlRegexFull)) {
+							return `[${txt}](<${href.value}>)`;	// #6846
+						} else {
+							return `[${txt}](${href.value})`;
+						}
+					};
+
+					text += generateLink();
+				}
+				break;
+			}
+
+			case 'h1':
+			{
+				text += '【';
+				appendChildren(node.childNodes);
+				text += '】\n';
+				break;
+			}
+
+			case 'b':
+			case 'strong':
+			{
+				text += '**';
+				appendChildren(node.childNodes);
+				text += '**';
+				break;
+			}
+
+			case 'small':
+			{
+				text += '<small>';
+				appendChildren(node.childNodes);
+				text += '</small>';
+				break;
+			}
+
+			case 's':
+			case 'del':
+			{
+				text += '~~';
+				appendChildren(node.childNodes);
+				text += '~~';
+				break;
+			}
+
+			case 'i':
+			case 'em':
+			{
+				text += '<i>';
+				appendChildren(node.childNodes);
+				text += '</i>';
+				break;
+			}
+
+			// block code (<pre><code>)
+			case 'pre': {
+				if (node.childNodes.length === 1 && node.childNodes[0].nodeName === 'code') {
+					text += '\n```\n';
+					text += getText(node.childNodes[0]);
+					text += '\n```\n';
+				} else {
+					appendChildren(node.childNodes);
+				}
+				break;
+			}
+
+			// inline code (<code>)
+			case 'code': {
+				text += '`';
+				appendChildren(node.childNodes);
+				text += '`';
+				break;
+			}
+
+			case 'blockquote': {
+				const t = getText(node);
+				if (t) {
+					text += '> ';
+					text += t.split('\n').join(`\n> `);
+				}
+				break;
+			}
+
+			case 'p':
+			case 'h2':
+			case 'h3':
+			case 'h4':
+			case 'h5':
+			case 'h6':
+			{
+				text += '\n\n';
+				appendChildren(node.childNodes);
+				break;
+			}
+
+			// other block elements
+			case 'div':
+			case 'header':
+			case 'footer':
+			case 'article':
+			case 'li':
+			case 'dt':
+			case 'dd':
+			{
+				text += '\n';
+				appendChildren(node.childNodes);
+				break;
+			}
+
+			default:	// includes inline elements
+			{
+				appendChildren(node.childNodes);
+				break;
+			}
+		}
+	}
+}