feat: Add beforeLanguageSwitch & onLanguageSwitched callbacks

Provides 2 callback called by the middleware when a language change is detected.
beforeLanguageSwitch is called right before setting the new locale, onLanguageSwitched is called
once the locale is set.

lib/module.js

@@ -13,7 +13,9 @@ module.exports = function (moduleOptions) {
     ignorePaths: [],
     detectBrowserLanguage: false,
     redirectCookieKey: 'redirected',
-    useRedirectCookie: true
+    useRedirectCookie: true,
+    beforeLanguageSwitch: (oldLocale, newLocale) => {},
+    onLanguageSwitched: (oldLocale, newLocale) => {}
   }
   const options = merge(defaults, moduleOptions, this.options.i18n)
 

lib/templates/i18n.plugin.js

@@ -9,6 +9,8 @@ export default ({ app, route, error }) => {
   app.i18n.locales = <%= JSON.stringify(options.locales) %>
   app.i18n.defaultLocale = '<%= options.defaultLocale %>'
   app.i18n.ignorePaths = <%= JSON.stringify(options.ignorePaths) %>
+  app.i18n.beforeLanguageSwitch = <%= options.beforeLanguageSwitch %>
+  app.i18n.onLanguageSwitched = <%= options.onLanguageSwitched %>
 
   // Get locale from params
   let locale = app.i18n.defaultLocale || null

lib/templates/i18n.routing.middleware.js

@@ -55,13 +55,17 @@ middleware['i18n'] = function ({ app, req, res, route, params, redirect, error,
     return error({ message: 'Page not found.', statusCode: 404 })
   }
   if (locale === app.i18n.locale) return
+  const oldLocale = app.i18n.locale
+  app.i18n.beforeLanguageSwitch(oldLocale, locale)
   if (<%= options.loadLanguagesAsync %>) {
     const { loadLanguageAsync } = require('./i18n.utils')
     loadLanguageAsync(app.i18n, locale)
       .then(() => {
         app.i18n.locale = locale
+        app.i18n.onLanguageSwitched(oldLocale, locale)
       })
   } else {
     app.i18n.locale = locale
+    app.i18n.onLanguageSwitched(oldLocale, locale)
   }
 }