Show a dialog when local storage cannot be accessed (#402)

It's possible that I/O errors happen when accessing the SQLite database
backing the local storage. In that case, accessing the data will result
in an exception.

public/i18n/de.json

@@ -35,6 +35,7 @@
         "MANUAL_START_STEP3": "Wählen Sie im Menu \"Sitzung starten\"",
         "MORE_ABOUT_WEB": "Mehr über Threema Web",
         "LOCAL_STORAGE_MISSING_DETAILS": "Zugriff auf LocalStorage ist nicht möglich. Dieses Problem kann auftreten, wenn in Ihrem Browser Cookies blockiert werden, oder wenn ein Browser-Add-On installiert ist, welches den Zugriff auf LocalStorage blockiert. Bitte erlauben Sie die Nutzung von LocalStorage in Ihrem Browser oder deaktivieren Sie die installierten Browser-Add-Ons.",
+        "LOCAL_STORAGE_EXCEPTION_DETAILS": "Kritischer Fehler beim Zugriff auf LocalStorage: {errorMsg}.<br>Bitte starten Sie Ihren Browser neu.",
         "ALREADY_CONNECTED": "Bereits Verbunden",
         "ALREADY_CONNECTED_DETAILS": "Sie sind bereits in einem anderen Tab oder Fenster mit Threema Web verbunden!"
     },

public/i18n/en.json

@@ -35,6 +35,7 @@
         "MANUAL_START_STEP3": "Select \"Start session\" to start the session",
         "MORE_ABOUT_WEB": "More about Threema Web",
         "LOCAL_STORAGE_MISSING_DETAILS": "Access to LocalStorage not possible. This can occur if your browser is configured to reject cookies, or if you installed a browser add-on that blocks access to LocalStorage. Please allow local storage in your browser settings or disable any add-ons you might have installed.",
+        "LOCAL_STORAGE_EXCEPTION_DETAILS": "Critical error when accessing LocalStorage: {errorMsg}.<br>Try restarting your browser.",
         "ALREADY_CONNECTED": "Already Connected",
         "ALREADY_CONNECTED_DETAILS": "You are already connected to Threema Web in another tab or window!"
     },

src/partials/welcome.ts

@@ -158,13 +158,22 @@ class WelcomeController {
         // Clear cache
         this.webClientService.clearCache();
 
+        // Determine whether trusted key is available
+        let hasTrustedKey = null;
+        try {
+            hasTrustedKey = this.TrustedKeyStore.hasTrustedKey();
+        } catch (e) {
+            $log.error('Exception while accessing local storage:', e);
+            this.showLocalStorageException(e);
+        }
+
         // Determine connection mode
         if ($stateParams.initParams !== null) {
             this.mode = 'unlock';
             const keyStore = $stateParams.initParams.keyStore;
             const peerTrustedKey = $stateParams.initParams.peerTrustedKey;
             this.reconnect(keyStore, peerTrustedKey);
-        } else if (TrustedKeyStore.hasTrustedKey()) {
+        } else if (hasTrustedKey) {
             this.mode = 'unlock';
             this.unlock();
         } else {
@@ -377,6 +386,21 @@ class WelcomeController {
         });
     }
 
+    /**
+     * Show a dialog indicating that local storage cannot be accessed.
+     */
+    private showLocalStorageException(e: Error): void {
+        this.$translate.onReady().then(() => {
+            const confirm = this.$mdDialog.alert()
+                .title(this.$translate.instant('common.ERROR'))
+                .htmlContent(this.$translate.instant('welcome.LOCAL_STORAGE_EXCEPTION_DETAILS', {
+                    errorMsg: e.name,
+                }))
+                .ok(this.$translate.instant('common.OK'));
+            this.$mdDialog.show(confirm);
+        });
+    }
+
     /**
      * Show the "decryption failed" dialog.
      */