implement generic pagination

lib/models/params/notification_params.dart

@@ -14,6 +14,7 @@ class NotificationParams {
     this.types,
     this.excludeTypes,
     this.accountId,
+    this.cursor,
   });
 
   /// Converts JSON into a [NotificationParams] instance.
@@ -49,4 +50,8 @@ class NotificationParams {
   /// Return only notifications related from this account.
   @JsonKey(name: 'account_id')
   final String? accountId;
+
+  /// Arbitrary cursor string. This is not present in the Mastodon API, and
+  /// is only used by SkyBridge to make pagination easier.
+  final String? cursor;
 }

lib/util.dart

@@ -257,6 +257,20 @@ String sanitizeText(String text) {
 /// [Uri.toString] lowercases the host, which breaks the URI
 /// for some clients. This is just a simple function that preserves the casing.
 String stringifyModifiedUri(Uri uri, String originalUri) {
-  final host = originalUri.substring(0, uri.scheme.length + uri.host.length + 3);
+  final host =
+      originalUri.substring(0, uri.scheme.length + uri.host.length + 3);
   return host + uri.toString().substring(host.length);
 }
+
+Map<String, String> generatePaginationHeaders<T>({
+  required List<T> items,
+  required Uri requestUri,
+  required String nextCursor,
+  required BigInt Function(T) getId,
+}) {
+  final highestID = items.map(getId).reduce((a, b) => a > b ? a : b);
+  final prevURI = requestUri.replace(queryParameters: {'min_id': highestID.toString()});
+  final nextURI = requestUri.replace(queryParameters: {'cursor': nextCursor});
+
+  return {'Link': '<$prevURI>; rel="prev", <$nextURI>; rel="next"'};
+}

routes/api/v1/notifications/index.dart

@@ -27,7 +27,9 @@ Future<Response> onRequest<T>(RequestContext context) async {
   // Fetch the notifications with the given parameters.
   final response = await bluesky.notification.listNotifications(
     limit: limit,
+    cursor: encodedParams.cursor,
   );
+  final nextCursor = response.data.cursor;
 
   // Convert the response into a list of MastodonNotification objects with
   // the appropriate types and data.
@@ -36,7 +38,18 @@ Future<Response> onRequest<T>(RequestContext context) async {
     bluesky,
   );
 
+  var headers = <String, String>{};
+  if (notifs.isNotEmpty) {
+    headers = generatePaginationHeaders(
+      items: notifs,
+      requestUri: context.request.uri,
+      nextCursor: nextCursor ?? '',
+      getId: (notification) => BigInt.parse(notification.id),
+    );
+  }
+
   return threadedJsonResponse(
     body: notifs,
+    headers: headers,
   );
 }

routes/api/v1/timelines/home.dart

@@ -90,27 +90,23 @@ Future<Response> onRequest(RequestContext context) async {
   // Get the parent posts for each post.
   final processedPosts = await processParentPosts(bluesky, allPosts);
 
-  final headers = <String, Object>{};
-  if (processedPosts.isNotEmpty && backfillAllowed == 'true') {
-    final uri = context.request.uri;
-
-    var lowestID = BigInt.parse('99999999999999999999');
-    var highestID = BigInt.from(0);
-    for (final post in processedPosts) {
-      final id = BigInt.parse(post.id);
-      if (id < lowestID) {
-        lowestID = id;
-      }
-      if (id > highestID) {
-        highestID = id;
-      }
-    }
+  var headers = <String, String>{};
+  if (processedPosts.isNotEmpty) {
+    headers = generatePaginationHeaders(
+      items: processedPosts,
+      requestUri: context.request.uri,
+      nextCursor: nextCursor ?? '',
+      getId: (post) => BigInt.parse(post.id),
+    );
 
-    final prevParams = {'min_id': highestID.toString()};
-    final nextParams = {'cursor': nextCursor};
-    final prevURI = uri.replace(queryParameters: prevParams);
-    final nextURI = uri.replace(queryParameters: nextParams);
-    headers['Link'] = '<$prevURI>; rel="prev", <$nextURI>; rel="next"';
+    // final ids = processedPosts.map((post) => BigInt.parse(post.id)).toList();
+    // final highestID = ids.reduce((a, b) => a > b ? a : b);
+    //
+    // final prevParams = {'min_id': highestID.toString()};
+    // final nextParams = {'cursor': nextCursor};
+    // final prevURI = uri.replace(queryParameters: prevParams);
+    // final nextURI = uri.replace(queryParameters: nextParams);
+    // headers['Link'] = '<$prevURI>; rel="prev", <$nextURI>; rel="next"';
   }
 
   // If the user prefers not to see replies, we need to filter them out.