feat: add OneTag AI "ask this page" plugin

docs/plugins.md

@@ -219,6 +219,33 @@ Disqus comments. https://disqus.com/
 </script>
 ```
 
+## OneTag AI
+
+[OneTag AI](https://onetagai.com) adds an "ask this page" button. Visitors type a question and get an answer drawn from the page they are reading.
+
+The key is a public site key with a hard usage cap, so it can be committed with your docs. Get one for free at https://onetagai.com.
+
+```html
+<script>
+  window.$docsify = {
+    onetag: 'your-onetag-key',
+  };
+</script>
+<script src="//cdn.jsdelivr.net/npm/docsify@5/dist/plugins/onetag.min.js"></script>
+```
+
+Pass an object to set the [widget options](https://onetagai.com/docs#widget):
+
+```js
+window.$docsify = {
+  onetag: {
+    key: 'your-onetag-key',
+    title: 'Ask the docs',
+    theme: 'dark', // 'light', 'dark' or 'auto' (default)
+  },
+};
+```
+
 ## Pagination
 
 Pagination for docsify. By [@imyelo](https://github.com/imyelo)

src/plugins/onetag.js

@@ -0,0 +1,36 @@
+// OneTag AI "ask this page" button — https://onetagai.com
+// Visitors type a question and get an answer drawn from the page they are reading.
+
+const window = /** @type {any} */ (globalThis);
+
+function install(hook, vm) {
+  const config = vm.config.onetag;
+  const options = typeof config === 'string' ? { key: config } : { ...config };
+
+  if (!options.key) {
+    // eslint-disable-next-line no-console
+    console.error('[Docsify] onetag key is required.');
+    return;
+  }
+
+  hook.mounted(_ => {
+    const script = document.createElement('script');
+
+    script.async = true;
+    script.src = 'https://onetagai.com/widget.js';
+
+    // Answers are drawn from the rendered page, not from the sidebar or navbar.
+    Object.assign(script.dataset, {
+      ref: 'docsify',
+      source: '.markdown-section',
+      ...options,
+    });
+
+    document.body.appendChild(script);
+  });
+}
+
+window.$docsify = window.$docsify || {};
+window.$docsify.plugins = [install, ...(window.$docsify.plugins || [])];
+
+export {};

test/e2e/onetag.test.js

@@ -0,0 +1,73 @@
+import docsifyInit from '../helpers/docsify-init.js';
+import { test, expect } from './fixtures/docsify-init-fixture.js';
+
+test.describe('OneTag Plugin Tests', () => {
+  const widgetURL = 'https://onetagai.com/widget.js';
+  const widgetSelector = `script[src="${widgetURL}"]`;
+
+  // The widget script is replaced with a stub so that tests do not depend on the network
+  async function stubWidget(page) {
+    await page.route(widgetURL, route =>
+      route.fulfill({
+        contentType: 'text/javascript',
+        body: 'window.onetagDataset = { ...document.currentScript.dataset };',
+      }),
+    );
+  }
+
+  test('key as a string', async ({ page }) => {
+    await stubWidget(page);
+    await docsifyInit({
+      config: {
+        onetag: 'ot_test',
+      },
+      scriptURLs: ['/dist/plugins/onetag.js'],
+    });
+
+    await expect
+      .poll(() => page.evaluate(() => window.onetagDataset))
+      .toEqual({
+        key: 'ot_test',
+        ref: 'docsify',
+        source: '.markdown-section',
+      });
+    await expect(page.locator(widgetSelector)).toHaveCount(1);
+  });
+
+  test('options as an object', async ({ page }) => {
+    await stubWidget(page);
+    await docsifyInit({
+      config: {
+        onetag: {
+          key: 'ot_test',
+          position: 'left',
+          title: 'Ask the docs',
+        },
+      },
+      scriptURLs: ['/dist/plugins/onetag.js'],
+    });
+
+    await expect
+      .poll(() => page.evaluate(() => window.onetagDataset))
+      .toEqual({
+        key: 'ot_test',
+        position: 'left',
+        ref: 'docsify',
+        source: '.markdown-section',
+        title: 'Ask the docs',
+      });
+  });
+
+  test('nothing is loaded without a key', async ({ page }) => {
+    const consoleMsgs = [];
+
+    page.on('console', msg => consoleMsgs.push(msg.text()));
+    await stubWidget(page);
+    await docsifyInit({
+      scriptURLs: ['/dist/plugins/onetag.js'],
+    });
+
+    await expect(page.locator(widgetSelector)).toHaveCount(0);
+    expect(consoleMsgs).toContain('[Docsify] onetag key is required.');
+  });
+});