✨ Added markdown and mermaid preview

frontend/src/common/markdown-it/plugins/markdown-it-sub/index.ts

@@ -0,0 +1,66 @@
+// Process ~subscript~
+
+import MarkdownIt, { StateInline, Token } from 'markdown-it';
+
+// same as UNESCAPE_MD_RE plus a space
+const UNESCAPE_RE = /\\([ \\!"#$%&'()*+,./:;<=>?@[\]^_`{|}~-])/g;
+
+function subscript(state: StateInline, silent: boolean): boolean {
+    const max = state.posMax;
+    const start = state.pos;
+
+    if (state.src.charCodeAt(start) !== 0x7E/* ~ */) { return false; }
+    if (silent) { return false; } // don't run any pairs in validation mode
+    if (start + 2 >= max) { return false; }
+
+    state.pos = start + 1;
+    let found = false;
+
+    while (state.pos < max) {
+        if (state.src.charCodeAt(state.pos) === 0x7E/* ~ */) {
+            found = true;
+            break;
+        }
+
+        state.md.inline.skipToken(state);
+    }
+
+    if (!found || start + 1 === state.pos) {
+        state.pos = start;
+        return false;
+    }
+
+    const content = state.src.slice(start + 1, state.pos);
+
+    // don't allow unescaped spaces/newlines inside
+    if (content.match(/(^|[^\\])(\\\\)*\s/)) {
+        state.pos = start;
+        return false;
+    }
+
+    // found!
+    state.posMax = state.pos;
+    state.pos = start + 1;
+
+    // Earlier we checked !silent, but this implementation does not need it
+    const token_so: Token = state.push('sub_open', 'sub', 1);
+    token_so.markup = '~';
+
+    const token_t: Token = state.push('text', '', 0);
+    token_t.content = content.replace(UNESCAPE_RE, '$1');
+
+    const token_sc: Token = state.push('sub_close', 'sub', -1);
+    token_sc.markup = '~';
+
+    state.pos = state.posMax + 1;
+    state.posMax = max;
+    return true;
+}
+
+/**
+ * markdown-it-sub 插件
+ * 用于支持下标语法 ~text~
+ */
+export default function sub_plugin(md: MarkdownIt): void {
+    md.inline.ruler.after('emphasis', 'sub', subscript);
+}