Cache open group preview images

SessionMessagingKit/Database/Storage+OpenGroups.swift

@@ -179,8 +179,8 @@ extension Storage {
 
     private static let openGroupUserCountCollection = "SNOpenGroupUserCountCollection"
     private static let openGroupMessageIDCollection = "LKMessageIDCollection"
-    private static let openGroupProfilePictureURLCollection = "LokiPublicChatAvatarURLCollection"
-
+    private static let openGroupImageCollection = "SNOpenGroupImageCollection"
+    
     public func getUserCount(forV2OpenGroupWithID openGroupID: String) -> UInt64? {
         var result: UInt64?
         Storage.read { transaction in
@@ -205,25 +205,20 @@ extension Storage {
         (transaction as! YapDatabaseReadWriteTransaction).setObject(messageID, forKey: String(serverID), inCollection: Storage.openGroupMessageIDCollection)
     }
     
-    public func setOpenGroupDisplayName(to displayName: String, for publicKey: String, inOpenGroupWithID openGroupID: String, using transaction: Any) {
-        let collection = openGroupID
-        (transaction as! YapDatabaseReadWriteTransaction).setObject(displayName, forKey: publicKey, inCollection: collection)
-    }
-    
     public func setLastProfilePictureUploadDate(_ date: Date)  {
         UserDefaults.standard[.lastProfilePictureUpload] = date
     }
     
-    public func getProfilePictureURL(forOpenGroupWithID openGroupID: String) -> String? {
-        var result: String?
+    public func getOpenGroupImage(for room: String, on server: String) -> Data? {
+        var result: Data?
         Storage.read { transaction in
-            result = transaction.object(forKey: openGroupID, inCollection: Storage.openGroupProfilePictureURLCollection) as? String
+            result = transaction.object(forKey: "\(server).\(room)", inCollection: Storage.openGroupImageCollection) as? Data
         }
         return result
     }
     
-    public func setProfilePictureURL(to profilePictureURL: String?, forOpenGroupWithID openGroupID: String, using transaction: Any) {
-        (transaction as! YapDatabaseReadWriteTransaction).setObject(profilePictureURL, forKey: openGroupID, inCollection: Storage.openGroupProfilePictureURLCollection)
+    public func setOpenGroupImage(to data: Data, for room: String, on server: String, using transaction: Any) {
+        (transaction as! YapDatabaseReadWriteTransaction).setObject(data, forKey: "\(server).\(room)", inCollection: Storage.openGroupImageCollection)
     }
 
 
@@ -350,4 +345,23 @@ extension Storage {
     public func removeLastDeletionServerID(for group: UInt64, on server: String, using transaction: Any) {
         (transaction as! YapDatabaseReadWriteTransaction).removeObject(forKey: "\(server).\(group)", inCollection: Storage.oldLastDeletionServerIDCollection)
     }
+    
+    public func setOpenGroupDisplayName(to displayName: String, for publicKey: String, inOpenGroupWithID openGroupID: String, using transaction: Any) {
+        let collection = openGroupID
+        (transaction as! YapDatabaseReadWriteTransaction).setObject(displayName, forKey: publicKey, inCollection: collection)
+    }
+    
+    private static let openGroupProfilePictureURLCollection = "LokiPublicChatAvatarURLCollection"
+    
+    public func getProfilePictureURL(forOpenGroupWithID openGroupID: String) -> String? {
+        var result: String?
+        Storage.read { transaction in
+            result = transaction.object(forKey: openGroupID, inCollection: Storage.openGroupProfilePictureURLCollection) as? String
+        }
+        return result
+    }
+    
+    public func setProfilePictureURL(to profilePictureURL: String?, forOpenGroupWithID openGroupID: String, using transaction: Any) {
+        (transaction as! YapDatabaseReadWriteTransaction).setObject(profilePictureURL, forKey: openGroupID, inCollection: Storage.openGroupProfilePictureURLCollection)
+    }
 }

SessionMessagingKit/Open Groups/V2/OpenGroupAPIV2.swift

@@ -1,8 +1,6 @@
 import PromiseKit
 import SessionSnodeKit
 
-// TODO: Cache group images
-
 @objc(SNOpenGroupAPIV2)
 public final class OpenGroupAPIV2 : NSObject {
     private static var moderators: [String:[String:Set<String>]] = [:] // Server URL to room ID to set of moderator IDs
@@ -97,10 +95,10 @@ public final class OpenGroupAPIV2 : NSObject {
         if request.useOnionRouting {
             guard let publicKey = SNMessagingKitConfiguration.shared.storage.getOpenGroupPublicKey(for: request.server) else { return Promise(error: Error.noPublicKey) }
             if request.isAuthRequired, let room = request.room { // Because auth happens on a per-room basis, we need both to make an authenticated request
-                return getAuthToken(for: room, on: request.server).then(on: DispatchQueue.global(qos: .default)) { authToken -> Promise<JSON> in
+                return getAuthToken(for: room, on: request.server).then(on: DispatchQueue.global(qos: .userInitiated)) { authToken -> Promise<JSON> in
                     tsRequest.setValue(authToken, forHTTPHeaderField: "Authorization")
                     let promise = OnionRequestAPI.sendOnionRequest(tsRequest, to: request.server, using: publicKey)
-                    promise.catch(on: DispatchQueue.global(qos: .default)) { error in
+                    promise.catch(on: DispatchQueue.global(qos: .userInitiated)) { error in
                         // A 401 means that we didn't provide a (valid) auth token for a route that required one. We use this as an
                         // indication that the token we're using has expired. Note that a 403 has a different meaning; it means that
                         // we provided a valid token but it doesn't have a high enough permission level for the route in question.
@@ -373,12 +371,33 @@ public final class OpenGroupAPIV2 : NSObject {
     }
     
     public static func getGroupImage(for room: String, on server: String) -> Promise<Data> {
-        if let promise = groupImagePromises["\(server).\(room)"] {
+        // Normally the image for a given group is stored with the group thread, so it's only
+        // fetched once. However, on the join open group screen we show images for groups the
+        // user * hasn't * joined yet. We don't want to re-fetch these images every time the
+        // user opens the app because that could slow the app down or be data-intensive. So
+        // instead we assume that these images don't change that often and just fetch them once
+        // a week. We also assume that they're all fetched at the same time as well, so that
+        // we only need to maintain one date in user defaults. On top of all of this we also
+        // don't double up on fetch requests by storing the existing request as a promise if
+        // there is one.
+        let lastOpenGroupImageUpdate = UserDefaults.standard[.lastOpenGroupImageUpdate]
+        let now = Date()
+        let timeSinceLastUpdate = given(lastOpenGroupImageUpdate) { now.timeIntervalSince($0) } ?? .greatestFiniteMagnitude
+        let updateInterval: TimeInterval = 7 * 24 * 60 * 60
+        if let data = Storage.shared.getOpenGroupImage(for: room, on: server), server == defaultServer, timeSinceLastUpdate < updateInterval {
+            return Promise.value(data)
+        } else if let promise = groupImagePromises["\(server).\(room)"] {
             return promise
         } else {
             let request = Request(verb: .get, room: room, server: server, endpoint: "group_image")
             let promise: Promise<Data> = send(request).map(on: DispatchQueue.global(qos: .userInitiated)) { json in
                 guard let base64EncodedFile = json["result"] as? String, let file = Data(base64Encoded: base64EncodedFile) else { throw Error.parsingFailed }
+                if server == defaultServer {
+                    Storage.shared.write { transaction in
+                        Storage.shared.setOpenGroupImage(to: file, for: room, on: server, using: transaction)
+                    }
+                    UserDefaults.standard[.lastOpenGroupImageUpdate] = now
+                }
                 return file
             }
             groupImagePromises["\(server).\(room)"] = promise

SessionUtilitiesKit/General/SNUserDefaults.swift

@@ -15,6 +15,7 @@ public enum SNUserDefaults {
         case lastConfigurationSync
         case lastDisplayNameUpdate
         case lastProfilePictureUpdate
+        case lastOpenGroupImageUpdate
     }
 
     public enum Double : Swift.String {