3 files changed, 21 insertions, 4 deletions
diff --git a/src/models/Group.ts b/src/models/Group.ts
index 9b3aa6d..c0d281d 100644
--- a/src/models/Group.ts
+++ b/src/models/Group.ts
@@ -19,7 +19,7 @@ export default interface Group {
   description?: string;
 
   /**
-   * Medias in the group.
+   * Media in the group.
    */
   media: MediaItem[];
 
@@ -32,4 +32,6 @@ export default interface Group {
    * Metadata that can be displayed in the description.
    */
   metadata?: { [key: string]: string | number };
+
+  [key: string]: any;
 }
diff --git a/src/models/Trip.ts b/src/models/Trip.ts
index 7f92669..46c462d 100644
--- a/src/models/Trip.ts
+++ b/src/models/Trip.ts
@@ -19,10 +19,22 @@ export default interface Trip {
   /**
    * URL to a JSON file containing data for the trip.
    */
-  url: string;
+  url?: string;
 
   /**
    * Property indicating if the trip data has been already downloaded.
    */
   downloaded: boolean;
+
+  /**
+   * A group property to use while sorting groups.
+   * Nested properties should be delimited with a dot.
+   * Default: name.
+   */
+  sortProperty?: string;
+
+  /**
+   * Sort order. true = descending, false = ascending.
+   */
+  sortOrder?: boolean;
 }
diff --git a/src/models/index.guard.ts b/src/models/index.guard.ts
index d564ff9..6e9265f 100644
--- a/src/models/index.guard.ts
+++ b/src/models/index.guard.ts
@@ -47,8 +47,11 @@ export function isTrip(obj: unknown): obj is Trip {
     typeof typedObj.id === 'string' &&
     typeof typedObj.name === 'string' &&
     (typeof typedObj.groups === 'undefined' ||
-      (Array.isArray(typedObj.groups) && typedObj.groups.every((e: any) => isGroup(e)))
-    );
+      (Array.isArray(typedObj.groups) && typedObj.groups.every((e: any) => isGroup(e)))) &&
+    (typeof typedObj.url === 'undefined' || typeof typedObj.url === 'string') &&
+    (typeof typedObj.downloaded === 'undefined' || typeof typedObj.downloaded === 'boolean') &&
+    (typeof typedObj.sortProperty === 'undefined' || typeof typedObj.sortProperty === 'string') &&
+    (typeof typedObj.sortOrder === 'undefined' || typeof typedObj.sortOrder === 'boolean');
 
   if (!isValid) {
     throw new Error(`Invalid object: ${JSON.stringify(obj)}`);