Caches Friend Zone patrons to offset slow loading time

The Patreon API doesn’t have a way to fetch just the patrons belonging to our Friend Zone tier. Instead, we need to fetch ALL patrons (including inactive ones) and filter out those not in the tier. This is very inefficient, and takes over a minute to complete as of April 14, 2022, due to the number of patrons we have.

We can’t do much to change this, but AltStore will now at least cache the fetched patrons with Core Data. Additionally, AltStore will only perform this long fetch whenever the Friend Zone list actually changes, rather than every time the Patreon screen appears.

AltStore/Operations/UpdatePatronsOperation.swift

@@ -0,0 +1,107 @@
+//
+//  UpdatePatronsOperation.swift
+//  AltStore
+//
+//  Created by Riley Testut on 4/11/22.
+//  Copyright © 2022 Riley Testut. All rights reserved.
+//
+
+import Foundation
+import CoreData
+
+import AltStoreCore
+
+private extension URL
+{
+    #if STAGING
+    static let patreonInfo = URL(string: "https://f000.backblazeb2.com/file/altstore-staging/altstore/patreon.json")!
+    #else
+    static let patreonInfo = URL(string: "https://cdn.altstore.io/file/altstore/altstore/patreon.json")!
+    #endif
+}
+
+extension UpdatePatronsOperation
+{
+    private struct Response: Decodable
+    {
+        var version: Int
+        var accessToken: String
+        var refreshID: String
+    }
+}
+
+class UpdatePatronsOperation: ResultOperation<Void>
+{
+    let context: NSManagedObjectContext
+    
+    init(context: NSManagedObjectContext = DatabaseManager.shared.persistentContainer.newBackgroundContext())
+    {
+        self.context = context
+    }
+    
+    override func main()
+    {
+        super.main()
+        
+        let dataTask = URLSession.shared.dataTask(with: .patreonInfo) { (data, response, error) in
+            do
+            {
+                guard let data = data else { throw error! }
+                
+                let response = try AltStoreCore.JSONDecoder().decode(Response.self, from: data)
+                
+                let previousRefreshID = UserDefaults.shared.patronsRefreshID
+                guard response.refreshID != previousRefreshID else {
+                    self.finish(.success(()))
+                    return
+                }
+                
+                PatreonAPI.shared.fetchPatrons { (result) in
+                    self.context.perform {
+                        do
+                        {
+                            let patrons = try result.get()
+                            let managedPatrons = patrons.map { (patron) -> PatreonAccount in
+                                let account = PatreonAccount(patron: patron, context: self.context)
+                                account.isFriendZonePatron = true
+                                return account
+                            }
+                            
+                            var patronIDs = Set(managedPatrons.map { $0.identifier })
+                            if let userAccountID = Keychain.shared.patreonAccountID
+                            {
+                                // Insert userAccountID into patronIDs to prevent it from being deleted.
+                                patronIDs.insert(userAccountID)
+                            }
+                                                
+                            let removedPredicate = NSPredicate(format: "NOT (%K IN %@)", #keyPath(PatreonAccount.identifier), patronIDs)
+                            let removedPatrons = PatreonAccount.all(satisfying: removedPredicate, in: self.context)
+                            for patreonAccount in removedPatrons
+                            {
+                                self.context.delete(patreonAccount)
+                            }
+                            
+                            try self.context.save()
+                            
+                            UserDefaults.shared.patronsRefreshID = response.refreshID
+                            
+                            self.finish(.success(()))
+                            
+                            print("Updated Friend Zone Patrons!")
+                        }
+                        catch
+                        {
+                            self.finish(.failure(error))
+                        }
+                    }
+                }
+            }
+            catch
+            {
+                self.finish(.failure(error))
+            }
+        }
+        
+        dataTask.resume()
+    }
+}