feat: rehypeMermaid

app/packages/rehype-mermaid/parser.ts

@@ -0,0 +1,6 @@
+import { unified } from "unified";
+import rehypeParse from "rehype-parse";
+
+const parser = unified().use(rehypeParse, { fragment: true });
+
+export { parser };

app/packages/rehype-mermaid/rehypeMermaid.ts

@@ -0,0 +1,96 @@
+import type { Plugin } from "unified";
+import type { Text, Element, Parent } from "hast";
+import { visit } from "unist-util-visit";
+import { renderMermaid } from "@mermaid-js/mermaid-cli";
+import puppeteer from "puppeteer";
+import { parser } from "./parser";
+
+interface MermaidCodeBlock {
+  textNode: Text;
+  index: number;
+  parent: Parent;
+}
+
+const checkIsMermaid = (lang: string): boolean => lang === "mermaid";
+
+const rehypeMermaid: Plugin = () => {
+  const parseLanguage = (classNames: string[]): string => {
+    for (const className of classNames) {
+      if (className.startsWith("language-")) {
+        return className.replace("language-", "");
+      }
+    }
+    return "";
+  };
+
+  return async (node) => {
+    const mermaidCodeBlocks: MermaidCodeBlock[] = [];
+
+    visit(node, "element", (node: Element, index, parent) => {
+      // Check if the node is a pre tag with a single child
+      if (!(node.tagName === "pre" && Array.isArray(node.children) && node.children.length === 1)) {
+        return;
+      }
+
+      // Check if the child is a code tag
+      const codeElem = node.children[0] as Element;
+      if (!(codeElem !== null && typeof codeElem === "object" && codeElem.tagName === "code")) {
+        return;
+      }
+
+      // Check if the code tag has a className property
+      const classNames = codeElem.properties?.className;
+      if (
+        !(
+          Array.isArray(classNames) &&
+          classNames.length > 0 &&
+          classNames.every((className) => typeof className === "string")
+        )
+      ) {
+        return;
+      }
+
+      // Check if the code tag has a text child
+      const textNode = codeElem.children[0] as Text;
+      if (typeof textNode.value !== "string") {
+        return;
+      }
+
+      // Parse the language from the class names and check if it is supported
+      const lang = parseLanguage(classNames);
+      const isMermaid = checkIsMermaid(lang);
+
+      if (isMermaid && index !== null && parent !== null) {
+        mermaidCodeBlocks.push({ textNode, index, parent });
+      }
+    });
+
+    if (mermaidCodeBlocks.length === 0) {
+      return;
+    }
+
+    const browser = await puppeteer.launch({
+      headless: true,
+    });
+
+    const decoder = new TextDecoder();
+
+    await Promise.all(
+      mermaidCodeBlocks.map(async ({ textNode, index, parent }, blockIndex) => {
+        const { data: svgBuffer } = await renderMermaid(browser, textNode.value, "svg");
+
+        const svgElem = decoder.decode(svgBuffer).replaceAll("my-svg", `my-svg-${blockIndex}`);
+        const parsedRoot = parser.parse(svgElem);
+
+        const content = parsedRoot.children[0] as Element;
+        content.properties.style = "width: 100%; background-color: white;";
+
+        parent.children[index] = content;
+      }),
+    );
+
+    await browser.close();
+  };
+};
+
+export default rehypeMermaid;

app/routes/posts/md-test.mdx

@@ -39,3 +39,22 @@ publishedAt: 2024/09/14
 ```ts title="sample.ts"
 console.log("Hello, TypeScript!");
 ```
+
+- こちらは、Mermaid のサンプルです。
+
+```mermaid
+classDiagram
+Class01 <|-- AveryLongClass : Cool
+Class03 *-- Class04
+Class05 o-- Class06
+Class07 .. Class08
+Class09 --> C2 : Where am i?
+Class09 --* C3
+Class09 --|> Class07
+Class07 : equals()
+Class07 : Object[] elementData
+Class01 : size()
+Class01 : int chimp
+Class01 : int gorilla
+Class08 <--> C2: Cool label
+```

package.json

@@ -24,6 +24,7 @@
     "@hono/vite-dev-server": "^0.14.0",
     "@hono/vite-ssg": "^0.1.0",
     "@mdx-js/rollup": "^3.0.1",
+    "@mermaid-js/mermaid-cli": "^11.4.0",
     "@types/hast": "^3.0.4",
     "@types/mdast": "^4.0.4",
     "@types/unist": "^3.0.3",
@@ -32,6 +33,7 @@
     "husky": "^9.1.1",
     "lint-staged": "^15.2.7",
     "mdast": "^3.0.0",
+    "puppeteer": "^23.8.0",
     "rehype-parse": "^9.0.1",
     "remark-breaks": "^4.0.0",
     "remark-frontmatter": "^5.0.0",