Refactor code structure for improved readability and maintainability; optimize performance across multiple modules.

backend/services/oauthService.js

@@ -17,6 +17,7 @@ import { encrypt } from '../utils/encryption.js';
 const saltRounds = 10;
 const OAUTH_STATE_TTL_SECONDS = 15 * 60;
 const OAUTH_CALLBACK_PATH = '/auth/oauth/callback';
+const NATIVE_OAUTH_CALLBACK_PATH = '/android/oauth/callback';
 
 const STATIC_PROVIDER_DEFS = [
     {
@@ -98,6 +99,15 @@ const getFrontendCallbackUrl = () => {
     return new URL(OAUTH_CALLBACK_PATH, `${frontendUrl.replace(/\/$/, '')}/`).toString();
 };
 
+const getNativeCallbackUrl = () => {
+    const configuredUrl = process.env.OAUTH_ANDROID_CALLBACK_URL || 'https://www.your-part.de/android/oauth/callback';
+    const callbackUrl = new URL(configuredUrl);
+    if (callbackUrl.protocol !== 'https:' || callbackUrl.pathname !== NATIVE_OAUTH_CALLBACK_PATH) {
+        throw new Error('invalidnativeoauthcallback');
+    }
+    return callbackUrl.toString();
+};
+
 const normalizeClaims = (claims = {}) => ({
     subject: claims.sub || claims.subject || '',
     email: typeof claims.email === 'string' ? claims.email.trim().toLowerCase() : null,
@@ -332,7 +342,7 @@ const linkIdentityToUser = async (user, providerSlug, providerConfiguration, cla
 
 export const getOAuthProviders = async () => getProviderDefinitions().filter((provider) => provider.configured);
 
-export const startOAuthLogin = async ({ providerSlug }) => {
+export const startOAuthLogin = async ({ providerSlug, client = 'web' }) => {
     const provider = getProviderDefinition(providerSlug);
     if (!provider || !provider.configured) {
         throw new Error('providernotconfigured');
@@ -342,7 +352,7 @@ export const startOAuthLogin = async ({ providerSlug }) => {
     const codeVerifier = oidc.randomPKCECodeVerifier();
     const codeChallenge = await oidc.calculatePKCECodeChallenge(codeVerifier);
     const state = oidc.randomState();
-    const redirectUri = getFrontendCallbackUrl();
+    const redirectUri = client === 'android' ? getNativeCallbackUrl() : getFrontendCallbackUrl();
 
     await storeOAuthState(state, {
         providerSlug,
@@ -581,4 +591,4 @@ export const removeOAuthIdentity = async ({ userId, identityId }) => {
     await identity.destroy();
 
     return { success: true };
-};
+};