feat: add math support for markdown render

common/render_helper.js

@@ -12,15 +12,16 @@
 
 var MarkdownIt = require('markdown-it');
 var _          = require('lodash');
-var config     = require('../config');
 var validator  = require('validator');
 var jsxss      = require('xss');
-var multiline = require('multiline')
+var multiline  = require('multiline');
+var config     = require('../config');
+var textmath   = require('./textmath');
 
 // Set default options
 var md = new MarkdownIt();
 
-md.set({
+md.use(textmath).set({
   html:         false,        // Enable HTML tags in source
   xhtmlOut:     false,        // Use '/' to close single tags (<br />)
   breaks:       false,        // Convert '\n' in paragraphs into <br>

common/textmath.js

@@ -0,0 +1,133 @@
+/**
+ * Simplify by https://github.com/goessner/markdown-it-texmath
+ */
+function texmath(md) {
+  texmath.rules.inline.forEach(function (rule) {
+    md.inline.ruler.before('escape', rule.name, texmath.inline(rule)); // !important
+    md.renderer.rules[rule.name] = function (tokens, idx) {
+      return rule.tmpl.replace(/\$1/, tokens[idx].content);
+    };
+  });
+  texmath.rules.block.forEach(function (rule) {
+    md.block.ruler.before('fence', rule.name, texmath.block(rule)); // !important for ```math delimiters
+    md.renderer.rules[rule.name] = function (tokens, idx) {
+      return rule.tmpl
+        .replace(/\$2/, tokens[idx].info) // equation number
+        .replace(/\$1/, tokens[idx].content);
+    };
+  });
+}
+
+texmath.inline = (rule) => (state, silent) => {
+  var pos = state.pos;
+  var str = state.src;
+  rule.rex.lastIndex = pos;
+
+  if (!str.startsWith(rule.tag, pos)) return false;
+  if (rule.pre && !rule.pre(str, pos)) return false;
+
+  var match = rule.rex.exec(str);
+  if (!match || pos >= rule.rex.lastIndex) return false;
+
+  if (rule.post && !rule.post(str, rule.rex.lastIndex - 1)) return false;
+  // match and valid post-condition ...
+  if (!silent) {
+    var token = state.push(rule.name, 'math', 0);
+    token.content = match[1];
+    token.markup = rule.tag;
+  }
+  state.pos = rule.rex.lastIndex;
+  return true;
+};
+
+texmath.block = (rule) => (state, begLine, endLine, silent) => {
+  var pos = state.bMarks[begLine] + state.tShift[begLine];
+  var str = state.src;
+  rule.rex.lastIndex = pos;
+
+  if (!str.startsWith(rule.tag, pos)) return false;
+  if (rule.pre && !rule.pre(str, pos)) return false;
+
+  var match = rule.rex.exec(str);
+  if (!match || pos >= rule.rex.lastIndex) return false;
+
+  if (rule.post && !rule.post(str, rule.rex.lastIndex - 1)) return false;
+  // match and valid post-condition ...
+  if (!silent) {
+    var endpos = rule.rex.lastIndex - 1;
+    var curline;
+    for (curline = begLine; curline < endLine; curline++) {
+      // line for end of block math found
+      if (endpos >= state.bMarks[curline] + state.tShift[curline] && endpos <= state.eMarks[curline]) {
+        break;
+      }
+    }
+    // "this will prevent lazy continuations from ever going past our end marker"
+    // s. https://github.com/markdown-it/markdown-it-container/blob/master/index.js
+    var oldLineMax = state.lineMax;
+    var oldParent = state.parentType;
+    state.lineMax = curline;
+    state.parentType = 'math';
+    // remove all leading '>' inside multiline formula
+    if (oldParent === 'blockquote') {
+      match[1] = match[1].replace(/(\n*?^(?:\s*>)+)/gm, '');
+    }
+    // 'math_block'
+    var token = state.push(rule.name, 'math', 1);
+    token.block = true;
+    token.markup = rule.tag;
+    token.content = match[1];
+    token.info = match[match.length - 1]; // eq.no
+    token.map = [begLine, curline];
+    // restore state
+    state.parentType = oldParent;
+    state.lineMax = oldLineMax;
+    state.line = curline + 1;
+  }
+  return true;
+};
+
+// used for enable/disable math rendering by `markdown-it`
+texmath.inlineRuleNames = ['math_inline', 'math_inline_double'];
+texmath.blockRuleNames = ['math_block', 'math_block_eqno'];
+
+texmath.$_pre = function (str, beg) {
+  // no backslash, digit before opening '$'
+  return /[^\\0-9]/.test(str[beg - 1]);
+};
+texmath.$_post = function (str, end) {
+  // no digit after closing '$'
+  return /[^0-9]/.test(str[end + 1]);
+};
+
+texmath.rules = {
+  inline: [{
+    name: 'math_inline_double',
+    rex: /\${2}((?:\S)|(?:\S.*?\S))\${2}/gy,
+    tmpl: '<section><eqn>$1</eqn></section>',
+    tag: '$$',
+    displayMode: true,
+    pre: texmath.$_pre,
+    post: texmath.$_post
+  }, {
+    name: 'math_inline',
+    rex: /\$((?:\S)|(?:\S.*?\S))\$/gy,
+    tmpl: '<eq>$1</eq>',
+    tag: '$',
+    pre: texmath.$_pre,
+    post: texmath.$_post
+  }],
+  block: [{
+    name: 'math_block_eqno',
+    rex: /\${2}([^$]+?)\${2}\s*?\(([^)\s]+?)\)/gmy,
+    tmpl: '<section><eqn>$1</eqn><span>($2)</span></section>',
+    tag: '$$'
+  }, {
+    name: 'math_block',
+    rex: /\${2}([^$]+?)\${2}/gmy,
+    tmpl: '<section><eqn>$1</eqn></section>',
+    tag: '$$'
+  }]
+};
+
+module.exports = texmath;

package.json

@@ -25,8 +25,8 @@
     "helmet": "1.3.0",
     "ioredis": "2.0.0",
     "jpush-sdk": "3.3.2",
-    "loader-builder": "2.4.1",
     "loader": "2.1.1",
+    "loader-builder": "2.4.1",
     "lodash": "4.17.21",
     "log4js": "^0.6.29",
     "markdown-it": "6.0.0",
@@ -46,12 +46,12 @@
     "ready": "0.1.1",
     "request": "2.81.0",
     "response-time": "2.3.1",
+    "snyk": "^1.88.0",
     "superagent": "2.0.0",
     "utility": "1.6.0",
     "validator": "5.1.0",
     "xmlbuilder": "7.0.0",
-    "xss": "0.2.10",
-    "snyk": "^1.88.0"
+    "xss": "0.2.10"
   },
   "devDependencies": {
     "errorhandler": "1.4.3",