Add I18n

app/Middleware/DetectUserLocale.ts

@@ -0,0 +1,45 @@
+import I18n from '@ioc:Adonis/Addons/I18n'
+import { HttpContextContract } from '@ioc:Adonis/Core/HttpContext'
+
+/**
+ * The middleware detects the user language using the "Accept-language" HTTP header
+ * or the "lang" query string parameter.
+ *
+ * Feel free to change the middleware implementation to what suits your needs. Just
+ * make sure
+ *
+ * - You always ensure the user selected language is supported by your app.
+ * - Only call "switchLocale" when the detected language is valid string value and
+ *   not "null" or "undefined"
+ */
+export default class DetectUserLocale {
+  /**
+   * Detect user language using "Accept-language" header or
+   * the "lang" query string parameter.
+   *
+   * The user language must be part of the "supportedLocales", otherwise
+   * this method should return null.
+   */
+  protected getUserLanguage(ctx: HttpContextContract) {
+    const availableLocales = I18n.supportedLocales()
+    return ctx.request.language(availableLocales) || ctx.request.input('lang')
+  }
+
+  /**
+   * Handle method is called by AdonisJS automatically on every middleware
+   * class.
+   */
+  public async handle(ctx: HttpContextContract, next: () => Promise<void>) {
+    const language = this.getUserLanguage(ctx)
+
+    /**
+     * Switch locale when we are able to detect the user language and it
+     * is supported by the application
+     */
+    if (language) {
+      ctx.i18n.switchLocale(language)
+    }
+
+    await next()
+  }
+}