use sync items query to update core data list

apple/OmnivoreKit/Sources/App/Views/Home/HomeFeedViewModel.swift

@@ -6,6 +6,8 @@ import Utils
 import Views
 
 @MainActor final class HomeFeedViewModel: NSObject, ObservableObject {
+  let dateFormatter = DateFormatter.formatterISO8601
+
   var currentDetailViewModel: LinkItemDetailViewModel?
 
   private var fetchedResultsController: NSFetchedResultsController<LinkedItem>?
@@ -26,7 +28,11 @@ import Views
   @Published var appliedFilter = LinkedItemFilter.inbox.rawValue
   @Published var appliedSort = LinkedItemSort.newest.rawValue
 
-  @AppStorage(UserDefaultKey.lastSelectedLinkedItemFilter.rawValue)
+//  @AppStorage(UserDefaultKey.lastSelectedLinkedItemFilter.rawValue) // TODO: missing value here?
+  // TODO: delete this value when needed (logout, clear core data, new app version
+  @AppStorage(UserDefaultKey.lastItemSyncTime.rawValue) var lastItemSyncTime = Date(
+    timeIntervalSinceReferenceDate: 0
+  ).toString()
 
   var cursor: String?
 
@@ -50,6 +56,11 @@ import Views
     items.insert(item, at: 0)
   }
 
+  func loadUpdatedItems(since _: Date, updatedCursor _: String?) {
+    isLoading = true
+    showLoadingBar = true
+  }
+
   func loadItems(dataService: DataService, isRefresh: Bool) async {
     let thisSearchIdx = searchIdx
     searchIdx += 1
@@ -62,6 +73,14 @@ import Views
       Task { _ = try? await dataService.fetchViewer() }
     }
 
+    // Sync items if necessary
+    let lastSyncDate = dateFormatter.date(from: lastItemSyncTime) ?? Date(timeIntervalSinceReferenceDate: 0)
+
+    let syncResult = try? await dataService.syncLinkedItems(since: lastSyncDate, cursor: nil)
+    if syncResult != nil {
+      lastItemSyncTime = Date().toString()
+    }
+
     let queryResult = try? await dataService.loadLinkedItems(
       limit: 10,
       searchQuery: searchQuery,

apple/OmnivoreKit/Sources/Models/DataModels/FeedItem.swift

@@ -154,4 +154,12 @@ public extension LinkedItem {
       }
     }
   }
+
+  static func deleteItems(ids: [String], context: NSManagedObjectContext) {
+    for itemID in ids {
+      if let linkedItem = lookup(byID: itemID, inContext: context) {
+        linkedItem.remove(inContext: context)
+      }
+    }
+  }
 }

apple/OmnivoreKit/Sources/Services/DataService/Public/LinkedItemLoading.swift

@@ -3,6 +3,49 @@ import Foundation
 import Models
 
 public extension DataService {
+  /// Requests `LinkedItem`s updates from the server since a certain datae
+  /// and stores it in CoreData while deleting all the items with ids the server says
+  /// have been deleted.
+  /// - Parameters:
+  ///   - limit: max count of items
+  ///   - searchQuery: search terms and filters
+  ///   - cursor: cursor when loading batch for infinite list
+  /// - Returns: `LinkedItemQueryResult` (managed object IDs and an optional cursor)
+  func syncLinkedItems(
+    since date: Date,
+    cursor: String?,
+    previousQueryResult: LinkedItemQueryResult? = nil
+  ) async throws -> LinkedItemQueryResult {
+    if previousQueryResult == nil {
+      // Send offline changes to server before fetching items
+      // only on the first call of this function
+      try? await syncOfflineItemsWithServerIfNeeded()
+    }
+
+    let fetchResult = try await linkedItemUpdates(since: date, limit: 20, cursor: cursor)
+
+    LinkedItem.deleteItems(ids: fetchResult.deletedItemIDs, context: backgroundContext)
+
+    guard let itemIDs = fetchResult.items.persist(context: backgroundContext) else {
+      throw BasicError.message(messageText: "CoreData error")
+    }
+
+    let result = LinkedItemQueryResult(
+      itemIDs: itemIDs + (previousQueryResult?.itemIDs ?? []),
+      cursor: fetchResult.cursor
+    )
+
+    if fetchResult.hasMoreItems, (previousQueryResult?.itemIDs.count ?? 0) < 200 {
+      return try await syncLinkedItems(
+        since: date,
+        cursor: fetchResult.cursor,
+        previousQueryResult: result
+      )
+    }
+
+    return result
+  }
+
   /// Requests `LinkedItem`s from the server and stores it in CoreData.
   /// - Parameters:
   ///   - limit: max count of items

apple/OmnivoreKit/Sources/Services/DataService/Queries/LinkedItemNetworkQuery.swift

@@ -12,6 +12,7 @@ struct InternalLinkedItemUpdatesQueryResult {
   let items: [InternalLinkedItem]
   let deletedItemIDs: [String]
   let cursor: String?
+  let hasMoreItems: Bool
 }
 
 private struct SyncItemEdge {
@@ -23,13 +24,14 @@ private struct SyncItemEdge {
 extension DataService {
   // swiftlint:disable:next function_body_length
   func linkedItemUpdates(
+    since: Date,
     limit: Int,
-    cursor: String?,
-    since: Date?
+    cursor: String?
   ) async throws -> InternalLinkedItemUpdatesQueryResult {
     struct QuerySuccessResult {
       let edges: [SyncItemEdge]
       let cursor: String?
+      let hasMoreItems: Bool
     }
     enum QueryResult {
       case success(result: QuerySuccessResult)
@@ -50,6 +52,9 @@ extension DataService {
               edges: try $0.edges(selection: syncItemEdgeSelection.list),
               cursor: try $0.pageInfo(selection: Selection.PageInfo {
                 try $0.endCursor()
+              }),
+              hasMoreItems: try $0.pageInfo(selection: Selection.PageInfo {
+                try $0.hasNextPage()
               })
             )
           )
@@ -61,7 +66,7 @@ extension DataService {
       try $0.updatesSince(
         after: OptionalArgument(cursor),
         first: OptionalArgument(limit),
-        since: DateTime(from: since ?? Date(timeIntervalSinceReferenceDate: 0)),
+        since: DateTime(from: since),
         selection: selection
       )
     }
@@ -90,7 +95,8 @@ extension DataService {
             returning: InternalLinkedItemUpdatesQueryResult(
               items: items,
               deletedItemIDs: deletedItemIDs,
-              cursor: result.cursor
+              cursor: result.cursor,
+              hasMoreItems: result.hasMoreItems
             )
           )
         case let .error(error):

apple/OmnivoreKit/Sources/Utils/UserDefaultKeys.swift

@@ -12,4 +12,5 @@ public enum UserDefaultKey: String {
   case lastSelectedLinkedItemFilter
   case lastUsedAppVersion
   case lastUsedAppBuildNumber
+  case lastItemSyncTime
 }