Escape markdown sequences (#2208)

* escape inline markdown character

* fix typo

* improve document around custom markdown plugin and add escape sequence utils

* recover inline escape sequences on edit

* remove escape sequences from plain text body

* use `s` for strike-through instead of del

* escape block markdown sequences

* fix remove escape sequence was not removing all slashes from plain text

* recover block sequences on edit

src/app/plugins/markdown/block/rules.ts

@@ -0,0 +1,100 @@
+import { BlockMDRule } from './type';
+
+const HEADING_REG_1 = /^(#{1,6}) +(.+)\n?/m;
+export const HeadingRule: BlockMDRule = {
+  match: (text) => text.match(HEADING_REG_1),
+  html: (match, parseInline) => {
+    const [, g1, g2] = match;
+    const level = g1.length;
+    return `<h${level} data-md="${g1}">${parseInline ? parseInline(g2) : g2}</h${level}>`;
+  },
+};
+
+const CODEBLOCK_MD_1 = '```';
+const CODEBLOCK_REG_1 = /^`{3}(\S*)\n((?:.*\n)+?)`{3} *(?!.)\n?/m;
+export const CodeBlockRule: BlockMDRule = {
+  match: (text) => text.match(CODEBLOCK_REG_1),
+  html: (match) => {
+    const [, g1, g2] = match;
+    const classNameAtt = g1 ? ` class="language-${g1}"` : '';
+    return `<pre data-md="${CODEBLOCK_MD_1}"><code${classNameAtt}>${g2}</code></pre>`;
+  },
+};
+
+const BLOCKQUOTE_MD_1 = '>';
+const QUOTE_LINE_PREFIX = /^> */;
+const BLOCKQUOTE_TRAILING_NEWLINE = /\n$/;
+const BLOCKQUOTE_REG_1 = /(^>.*\n?)+/m;
+export const BlockQuoteRule: BlockMDRule = {
+  match: (text) => text.match(BLOCKQUOTE_REG_1),
+  html: (match, parseInline) => {
+    const [blockquoteText] = match;
+
+    const lines = blockquoteText
+      .replace(BLOCKQUOTE_TRAILING_NEWLINE, '')
+      .split('\n')
+      .map((lineText) => {
+        const line = lineText.replace(QUOTE_LINE_PREFIX, '');
+        if (parseInline) return `${parseInline(line)}<br/>`;
+        return `${line}<br/>`;
+      })
+      .join('');
+    return `<blockquote data-md="${BLOCKQUOTE_MD_1}">${lines}</blockquote>`;
+  },
+};
+
+const ORDERED_LIST_MD_1 = '-';
+const O_LIST_ITEM_PREFIX = /^(-|[\da-zA-Z]\.) */;
+const O_LIST_START = /^([\d])\./;
+const O_LIST_TYPE = /^([aAiI])\./;
+const O_LIST_TRAILING_NEWLINE = /\n$/;
+const ORDERED_LIST_REG_1 = /(^(?:-|[\da-zA-Z]\.) +.+\n?)+/m;
+export const OrderedListRule: BlockMDRule = {
+  match: (text) => text.match(ORDERED_LIST_REG_1),
+  html: (match, parseInline) => {
+    const [listText] = match;
+    const [, listStart] = listText.match(O_LIST_START) ?? [];
+    const [, listType] = listText.match(O_LIST_TYPE) ?? [];
+
+    const lines = listText
+      .replace(O_LIST_TRAILING_NEWLINE, '')
+      .split('\n')
+      .map((lineText) => {
+        const line = lineText.replace(O_LIST_ITEM_PREFIX, '');
+        const txt = parseInline ? parseInline(line) : line;
+        return `<li><p>${txt}</p></li>`;
+      })
+      .join('');
+
+    const dataMdAtt = `data-md="${listType || listStart || ORDERED_LIST_MD_1}"`;
+    const startAtt = listStart ? ` start="${listStart}"` : '';
+    const typeAtt = listType ? ` type="${listType}"` : '';
+    return `<ol ${dataMdAtt}${startAtt}${typeAtt}>${lines}</ol>`;
+  },
+};
+
+const UNORDERED_LIST_MD_1 = '*';
+const U_LIST_ITEM_PREFIX = /^\* */;
+const U_LIST_TRAILING_NEWLINE = /\n$/;
+const UNORDERED_LIST_REG_1 = /(^\* +.+\n?)+/m;
+export const UnorderedListRule: BlockMDRule = {
+  match: (text) => text.match(UNORDERED_LIST_REG_1),
+  html: (match, parseInline) => {
+    const [listText] = match;
+
+    const lines = listText
+      .replace(U_LIST_TRAILING_NEWLINE, '')
+      .split('\n')
+      .map((lineText) => {
+        const line = lineText.replace(U_LIST_ITEM_PREFIX, '');
+        const txt = parseInline ? parseInline(line) : line;
+        return `<li><p>${txt}</p></li>`;
+      })
+      .join('');
+
+    return `<ul data-md="${UNORDERED_LIST_MD_1}">${lines}</ul>`;
+  },
+};
+
+export const UN_ESC_BLOCK_SEQ = /^\\*(#{1,6} +|```|>|(-|[\da-zA-Z]\.) +|\* +)/;
+export const ESC_BLOCK_SEQ = /^\\(\\*(#{1,6} +|```|>|(-|[\da-zA-Z]\.) +|\* +))/;