Editorial: Fix doc build.js for localized page

Fix build script to replace relative path in head
and tail content. Because localized page uses sub
dir so those failed to import playground.js and
etc.

docs/buildDocs.js

@@ -94,11 +94,21 @@ class CustomRenderer extends marked.Renderer {
   }
 }
 
-async function render(markdownFile, head, tail) {
+async function render(markdownFile, head, tail, basePath) {
   await mkdirp('../out/docs/assets');
   await mkdirp(path.join('../out/docs', path.dirname(markdownFile)));
   let markdownText = await fs.readFile(markdownFile, { encoding });
 
+  // replace relative path in header/footer for sub dir pages. this expects '.' is doc root
+  const replacePath = (html) => {
+    const replacingPathPart = [/(href=)"\./g, /(src=)"\./g];
+    let relativePath = path.relative(basePath, '.');
+    relativePath = relativePath === '' ? '.' : relativePath;
+    return replacingPathPart.reduce((pre, cur) => pre.replace(cur, `$1"${relativePath}`), html);
+  };
+  const _head = replacePath(head);
+  const _tail = replacePath(tail);
+
   // Resolve transcludes
   const lines = await Promise.all(
     markdownText.split('\n').map(async (line) => {
@@ -110,7 +120,7 @@ async function render(markdownFile, head, tail) {
   markdownText = lines.join('\n');
 
   const renderer = new CustomRenderer();
-  let htmlText = head + marked.parse(markdownText, { renderer }) + tail;
+  let htmlText = _head + marked.parse(markdownText, { renderer }) + _tail;
   htmlText = htmlText.replace(/^<!-- toc -->$/m, () => renderer.renderTOC());
 
   const htmlFile = path.resolve('../out/docs', markdownFile.replace(/\.md$/, '') + '.html');
@@ -122,13 +132,21 @@ async function go() {
   try {
     const head = await fs.readFile('head.html.part', { encoding });
     const tail = await fs.readFile('tail.html.part', { encoding });
+
+    // read files and return content with sub dir structure
+    const basePaths = ['.', './ja', './zh_CN'];
+    const files = await Promise.all(
+      basePaths.map(async (base) => {
+        return (await fs.readdir(base)).map((file) => ({
+          base,
+          file: `${base}/${file}`
+        }));
+      })
+    ).then((blocks) => blocks.flat());
+
     // copy or render /docs/* to /out/docs/
     await Promise.all(
-      [
-        ...(await fs.readdir('.')),
-        ...(await fs.readdir('ja')).map((x) => 'ja/' + x),
-        ...(await fs.readdir('zh_CN')).map((x) => 'zh_CN/' + x)
-      ].map((file) => {
+      files.map(({ base, file }) => {
         switch (path.extname(file)) {
           // copy files *.css, *.html, *.svg to /out/docs
           case '.css':
@@ -137,7 +155,7 @@ async function go() {
             return fs.copyFile(file, path.resolve('../out/docs/' + file));
           // convert files *.md to /out/docs/*.html
           case '.md':
-            return render(file, head, tail);
+            return render(file, head, tail, base);
           // skip remaining files
           default:
             return new Promise((resolve) => resolve());