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/inline/rules.ts

@@ -0,0 +1,123 @@
+import { InlineMDRule } from './type';
+
+const MIN_ANY = '(.+?)';
+const URL_NEG_LB = '(?<!(https?|ftp|mailto|magnet):\\/\\/\\S*)';
+const ESC_NEG_LB = '(?<!\\\\)';
+
+const BOLD_MD_1 = '**';
+const BOLD_PREFIX_1 = `${ESC_NEG_LB}\\*{2}`;
+const BOLD_NEG_LA_1 = '(?!\\*)';
+const BOLD_REG_1 = new RegExp(
+  `${URL_NEG_LB}${BOLD_PREFIX_1}${MIN_ANY}${BOLD_PREFIX_1}${BOLD_NEG_LA_1}`
+);
+export const BoldRule: InlineMDRule = {
+  match: (text) => text.match(BOLD_REG_1),
+  html: (parse, match) => {
+    const [, , g2] = match;
+    return `<strong data-md="${BOLD_MD_1}">${parse(g2)}</strong>`;
+  },
+};
+
+const ITALIC_MD_1 = '*';
+const ITALIC_PREFIX_1 = `${ESC_NEG_LB}\\*`;
+const ITALIC_NEG_LA_1 = '(?!\\*)';
+const ITALIC_REG_1 = new RegExp(
+  `${URL_NEG_LB}${ITALIC_PREFIX_1}${MIN_ANY}${ITALIC_PREFIX_1}${ITALIC_NEG_LA_1}`
+);
+export const ItalicRule1: InlineMDRule = {
+  match: (text) => text.match(ITALIC_REG_1),
+  html: (parse, match) => {
+    const [, , g2] = match;
+    return `<i data-md="${ITALIC_MD_1}">${parse(g2)}</i>`;
+  },
+};
+
+const ITALIC_MD_2 = '_';
+const ITALIC_PREFIX_2 = `${ESC_NEG_LB}_`;
+const ITALIC_NEG_LA_2 = '(?!_)';
+const ITALIC_REG_2 = new RegExp(
+  `${URL_NEG_LB}${ITALIC_PREFIX_2}${MIN_ANY}${ITALIC_PREFIX_2}${ITALIC_NEG_LA_2}`
+);
+export const ItalicRule2: InlineMDRule = {
+  match: (text) => text.match(ITALIC_REG_2),
+  html: (parse, match) => {
+    const [, , g2] = match;
+    return `<i data-md="${ITALIC_MD_2}">${parse(g2)}</i>`;
+  },
+};
+
+const UNDERLINE_MD_1 = '__';
+const UNDERLINE_PREFIX_1 = `${ESC_NEG_LB}_{2}`;
+const UNDERLINE_NEG_LA_1 = '(?!_)';
+const UNDERLINE_REG_1 = new RegExp(
+  `${URL_NEG_LB}${UNDERLINE_PREFIX_1}${MIN_ANY}${UNDERLINE_PREFIX_1}${UNDERLINE_NEG_LA_1}`
+);
+export const UnderlineRule: InlineMDRule = {
+  match: (text) => text.match(UNDERLINE_REG_1),
+  html: (parse, match) => {
+    const [, , g2] = match;
+    return `<u data-md="${UNDERLINE_MD_1}">${parse(g2)}</u>`;
+  },
+};
+
+const STRIKE_MD_1 = '~~';
+const STRIKE_PREFIX_1 = `${ESC_NEG_LB}~{2}`;
+const STRIKE_NEG_LA_1 = '(?!~)';
+const STRIKE_REG_1 = new RegExp(
+  `${URL_NEG_LB}${STRIKE_PREFIX_1}${MIN_ANY}${STRIKE_PREFIX_1}${STRIKE_NEG_LA_1}`
+);
+export const StrikeRule: InlineMDRule = {
+  match: (text) => text.match(STRIKE_REG_1),
+  html: (parse, match) => {
+    const [, , g2] = match;
+    return `<s data-md="${STRIKE_MD_1}">${parse(g2)}</s>`;
+  },
+};
+
+const CODE_MD_1 = '`';
+const CODE_PREFIX_1 = `${ESC_NEG_LB}\``;
+const CODE_NEG_LA_1 = '(?!`)';
+const CODE_REG_1 = new RegExp(`${URL_NEG_LB}${CODE_PREFIX_1}(.+?)${CODE_PREFIX_1}${CODE_NEG_LA_1}`);
+export const CodeRule: InlineMDRule = {
+  match: (text) => text.match(CODE_REG_1),
+  html: (parse, match) => {
+    const [, , g2] = match;
+    return `<code data-md="${CODE_MD_1}">${g2}</code>`;
+  },
+};
+
+const SPOILER_MD_1 = '||';
+const SPOILER_PREFIX_1 = `${ESC_NEG_LB}\\|{2}`;
+const SPOILER_NEG_LA_1 = '(?!\\|)';
+const SPOILER_REG_1 = new RegExp(
+  `${URL_NEG_LB}${SPOILER_PREFIX_1}${MIN_ANY}${SPOILER_PREFIX_1}${SPOILER_NEG_LA_1}`
+);
+export const SpoilerRule: InlineMDRule = {
+  match: (text) => text.match(SPOILER_REG_1),
+  html: (parse, match) => {
+    const [, , g2] = match;
+    return `<span data-md="${SPOILER_MD_1}" data-mx-spoiler>${parse(g2)}</span>`;
+  },
+};
+
+const LINK_ALT = `\\[${MIN_ANY}\\]`;
+const LINK_URL = `\\((https?:\\/\\/.+?)\\)`;
+const LINK_REG_1 = new RegExp(`${LINK_ALT}${LINK_URL}`);
+export const LinkRule: InlineMDRule = {
+  match: (text) => text.match(LINK_REG_1),
+  html: (parse, match) => {
+    const [, g1, g2] = match;
+    return `<a data-md href="${g2}">${parse(g1)}</a>`;
+  },
+};
+
+export const INLINE_SEQUENCE_SET = '[*_~`|]';
+const ESC_SEQ_1 = `\\\\(${INLINE_SEQUENCE_SET})`;
+const ESC_REG_1 = new RegExp(`${URL_NEG_LB}${ESC_SEQ_1}`);
+export const EscapeRule: InlineMDRule = {
+  match: (text) => text.match(ESC_REG_1),
+  html: (parse, match) => {
+    const [, , g2] = match;
+    return g2;
+  },
+};