Add tabs with code in different languages

components/Book/CodeTabs.tsx

@@ -0,0 +1,113 @@
+import React from "react";
+
+const STORAGE_KEY = "codeTabPreference";
+
+const createTabStore = () => {
+  let state: string[] = [];
+  if (typeof window !== "undefined") {
+    try {
+      state = JSON.parse(localStorage.getItem(STORAGE_KEY) || "[]");
+    } catch {
+    }
+  }
+
+  const listeners = new Set<() => void>();
+  return {
+    subscribe(fn: () => void) {
+      listeners.add(fn);
+      return () => listeners.delete(fn);
+    },
+
+    getSnapshot() {
+      return state;
+    },
+
+    bump(label: string) {
+      state = [label, ...state.filter(x => x !== label)].slice(0, 20);
+      if (typeof window !== "undefined") {
+        localStorage.setItem(STORAGE_KEY, JSON.stringify(state));
+      }
+      listeners.forEach(l => l());
+    },
+  };
+}
+
+let tabStore: ReturnType<typeof createTabStore> | null = null;
+
+function getTabStore() {
+  if (typeof window === "undefined") {
+    // SSR safety: return a dummy store
+    return {
+      subscribe: () => () => {},
+      getSnapshot: () => [],
+      bump: () => {},
+    };
+  }
+  if (!tabStore) {
+    tabStore = createTabStore();
+  }
+  return tabStore;
+}
+
+export function useTabPrefs() {
+  const store = getTabStore();
+  const order = React.useSyncExternalStore(
+    store.subscribe,
+    store.getSnapshot,
+    store.getSnapshot
+  );
+  return {
+    order,
+    bump: store.bump,
+  };
+}
+
+type CodeTabElement = React.ReactElement<{
+  label: string;
+  id?: string;
+  children: React.ReactNode;
+}>;
+
+export const CodeTabs = ({ children }: { children: React.ReactNode }) => {
+  const tabs = React.Children
+    .toArray(children)
+    .filter(child => child && React.isValidElement(child) && child.type === CodeTab
+    ) as CodeTabElement[];
+
+  const { order, bump } = useTabPrefs();
+  const active = React.useMemo(() => {
+    const labels = tabs.map(t => t.props.id ?? t.props.label);
+    for (const pref of order) {
+      const idx = labels.indexOf(pref);
+      if (idx !== -1) {
+        return idx;
+      }
+    }
+    return 0;
+  }, [order, tabs]);
+
+  return (
+    <div className="my-4 border border-gray-300 rounded-lg overflow-hidden" style={{boxShadow: "0.1rem 0.1rem 0.2rem #00000028"}}>
+      <div className="flex bg-gray-100 border-b border-gray-300">
+        {tabs.map((tab, i) => (
+          <button
+            key={i}
+            onClick={() => { bump(tab.props.id ?? tab.props.label); }}
+            className={`px-3 py-2 text-sm ${
+              i === active ? "bg-white border-b-2 border-blue-500" : ""
+            }`}
+          >
+            {tab.props.label}
+          </button>
+        ))}
+      </div>
+      <div className="p-0">
+        {tabs[active]}
+      </div>
+    </div>
+  );
+}
+
+
+export const CodeTab = ({ children }: { children: React.ReactNode }) =>
+  <div className="code-tab">{children}</div>;

components/MdxContent.tsx

@@ -10,6 +10,7 @@ import Question, { QuizPropsBase } from "./Quiz/Question";
 import { Quiz } from "@/components/Quiz/Quiz";
 import Image from "./Image";
 import { ExpandingSideImg, Sidenote } from "@/components/Book/Sidenote";
+import { CodeTab, CodeTabs } from "@/components/Book/CodeTabs";
 
 
 export interface QuestionProps extends QuizPropsBase {
@@ -73,6 +74,8 @@ export const MdxContent = ({content, chapterId, bookId, t, env, allAnswers}: {
     SideNote: Sidenote,
     ExpandingSideImg,
 
+    CodeTabs, CodeTab,
+
     FullWidth: ({ children }: { children: React.ReactNode }) =>
       <div className="full-width">
         {children}

styles/globals.scss

@@ -211,6 +211,10 @@ $gap: var(--gap);
   }
 }
 
+.code-tab > :not(.expressive-code) {
+  margin: 12px;
+}
+
 @page {
   margin: 0.75in;
 }