xmpp: Implement retrieving the device bundle

lib/xmpp/xeps/xep_0060.dart

@@ -216,7 +216,9 @@ class PubSubManager extends XmppManagerBase {
           XMLNode.xmlns(
             tag: 'pubsub',
             xmlns: pubsubXmlns,
-            children: [ XMLNode(tag: 'items', attributes: <String, String>{ 'node': node }) ],
+            children: [
+              XMLNode(tag: 'items', attributes: <String, String>{ 'node': node }),
+            ],
           )
         ],
       ),
@@ -238,4 +240,43 @@ class PubSubManager extends XmppManagerBase {
       })
       .toList();
   }
+
+  Future<PubSubItem?> getItem(String jid, String node, String id) async {
+    final result = await getAttributes().sendStanza(
+      Stanza.iq(
+        type: 'get',
+        to: jid,
+        children: [
+          XMLNode.xmlns(
+            tag: 'pubsub',
+            xmlns: pubsubXmlns,
+            children: [
+              XMLNode(
+                tag: 'items',
+                attributes: <String, String>{ 'node': node },
+                children: [
+                  XMLNode(
+                    tag: 'item',
+                    attributes: <String, String>{ 'id': id },
+                  ),
+                ],
+              ),
+            ],
+          ),
+        ],
+      ),
+    );
+
+    if (result.attributes['type'] != 'result') return null;
+
+    final pubsub = result.firstTag('pubsub', xmlns: pubsubXmlns);
+    if (pubsub == null) return null;
+
+    final item = pubsub.firstTag('items')!.firstTag('item')!;
+    return PubSubItem(
+      id: item.attributes['id']! as String,
+      payload: item.children[0],
+      node: node,
+    );
+  }
 }

lib/xmpp/xeps/xep_0384.dart

@@ -44,16 +44,40 @@ class OmemoManager extends XmppManagerBase {
   Future<void> commitState() async {}
 
   /// Retrieves the OMEMO device list from [jid].
-  Future<List<int>?> getDeviceList(JID jid) async {
+  Future<List<int>?> retrieveDeviceList(JID jid) async {
     final pm = getAttributes().getManagerById<PubSubManager>(pubsubManager)!;
     final items = await pm.getItems(jid.toBare().toString(), omemoDevicesXmlns);
     if (items == null) return null;
 
-    final item = items.first.payload;
-    final devicesElement = item.firstTag('devices', xmlns: omemoXmlns)!;
-
-    return devicesElement.children
+    return items.first.payload.children
       .map((child) => int.parse(child.attributes['id']! as String))
       .toList();
   }
+
+  /// Retrieves a bundle from entity [jid] with the device id [deviceId].
+  Future<OmemoBundle?> retrieveDeviceBundle(JID jid, int deviceId) async {
+    final pm = getAttributes().getManagerById<PubSubManager>(pubsubManager)!;
+    final bareJid = jid.toBare().toString();
+    final item = await pm.getItem(bareJid, omemoBundlesXmlns, '$deviceId');
+    if (item == null) return null;
+
+    final spk = item.payload.firstTag('spk')!;
+    final spks = item.payload.firstTag('spks')!;
+    final ik = item.payload.firstTag('ik')!;
+    final prekeysElement = item.payload.firstTag('prekeys')!;
+    final prekeys = <int, String>{};
+    for (final prekey in prekeysElement.children) {
+      prekeys[int.parse(prekey.attributes['id']! as String)] = prekey.innerText();
+    }
+    
+    return OmemoBundle(
+      bareJid,
+      deviceId,
+      spk.innerText(),
+      int.parse(spk.attributes['id']! as String),
+      spks.innerText(),
+      ik.innerText(),
+      prekeys,
+    );
+  }
 }