Set up inbox skeleton

inc/inbox.php

@@ -5,5 +5,73 @@ When an Activity is received (i.e. POSTed) to an Actor's inbox, the server must:
   1. Forward the Activity as necessary
        See (https://www.w3.org/TR/activitypub/#x7-1-2-forwarding-from-inbox).
   2. Perform the side effects of receiving the Activity
+  3. Persist the activity in the actor's inbox (and the attached object, if necessary)
+
+To persist an activity or object:
+  1. Check if the activity or object already exists in the DB
+  2. If yes, do nothing
+  3. If no, add it to the DB
 */
+namespace inbox;
+
+function handle_activity( $actor, $activity ) {
+    if ( !array_key_exists( 'type', $activity ) ) {
+        return new \WP_Error(
+            'invalid_activity',
+            __( 'Activity must have a type', 'activitypub' ),
+            array( 'status' => 400 )
+        );
+    }
+    forward_activity( $activity );
+    switch ( $activity['type'] ) {
+    case 'Create':
+        break;
+    case 'Update':
+        break;
+    case 'Delete':
+        break;
+    case 'Follow':
+        break;
+    case 'Accept':
+        break;
+    case 'Reject':
+        break;
+    case 'Add':
+        break;
+    case 'Remove':
+        break;
+    case 'Announce':
+        break;
+    case 'Undo':
+        break;
+    }
+    if ( is_wp_error( $activity ) ) {
+        return $activity;
+    }
+    persist_activity( $activity );
+    return new \WP_REST_Response();
+}
+
+function forward_activity( $activity ) {
+
+}
+
+function persist_activity( $activity ) {
+
+}
+
+function create_inbox_table() {
+    global $wpdb;
+    $wpdb->query(
+        "
+        CREATE TABLE IF NOT EXISTS activitypub_inbox(
+            id INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
+            actor_id UNSIGNED INT NOT NULL,
+            activity_id INT UNSIGNED NOT NULL,
+            FOREIGN KEY activity_fk(activity_id)
+            REFERENCES activitypub_activities(id),
+        );
+        "
+    );
+}
 ?>