feat(baoyu-md): add Mermaid preprocessing and utility modules

packages/baoyu-md/src/mermaid-utils.ts

@@ -0,0 +1,74 @@
+import { createHash } from "node:crypto";
+import { Marked, type Tokens } from "marked";
+
+export const MERMAID_VERSION = "10.9.1";
+
+export interface MermaidBlock {
+  raw: string;
+  code: string;
+  infoString: string;
+}
+
+export interface HashMermaidInput {
+  code: string;
+  theme?: string;
+  scale?: number;
+  background?: string;
+  minWidth?: number;
+  version?: string;
+}
+
+export function extractMermaidBlocks(markdown: string): MermaidBlock[] {
+  const blocks: MermaidBlock[] = [];
+  const lexer = new Marked({ breaks: true });
+  const tokens = lexer.lexer(markdown);
+  walkTokens(tokens, (token) => {
+    if (token.type !== "code") return;
+    const codeToken = token as Tokens.Code;
+    const lang = (codeToken.lang ?? "").trim();
+    if (!lang.startsWith("mermaid")) return;
+    const infoString = lang.slice("mermaid".length).trim();
+    const code = codeToken.text ?? "";
+    if (code.trim() === "") return;
+    blocks.push({
+      raw: codeToken.raw,
+      code,
+      infoString,
+    });
+  });
+  return blocks;
+}
+
+export function replaceMermaidBlocks(
+  markdown: string,
+  replacements: Map<string, string>,
+): string {
+  let result = markdown;
+  for (const [raw, replacement] of replacements) {
+    if (!raw || replacement === undefined) continue;
+    result = result.split(raw).join(replacement);
+  }
+  return result;
+}
+
+export function hashMermaidCode(input: HashMermaidInput): string {
+  const payload = JSON.stringify({
+    code: input.code.replace(/\s+$/g, ""),
+    theme: input.theme ?? "default",
+    scale: input.scale ?? 2,
+    minWidth: input.minWidth ?? null,
+    background: input.background ?? "white",
+    version: input.version ?? MERMAID_VERSION,
+  });
+  return createHash("sha256").update(payload).digest("hex").slice(0, 12);
+}
+
+type AnyToken = { type?: string; tokens?: AnyToken[]; items?: AnyToken[] };
+
+function walkTokens(tokens: AnyToken[], visit: (token: AnyToken) => void): void {
+  for (const token of tokens) {
+    visit(token);
+    if (Array.isArray(token.tokens)) walkTokens(token.tokens, visit);
+    if (Array.isArray(token.items)) walkTokens(token.items, visit);
+  }
+}