Merge pull request #132 from tinode/fixes2

Logic to detect sequence id gaps in cached messages.

Author: aforge

TinodeSDK/Storage.swift

@@ -82,6 +82,10 @@ public protocol Storage: class {
 
     // Get seq IDs of the stored messages as a Range.
     func getCachedMessagesRange(topic: TopicProto) -> MsgRange?
+    // Get the maximum seq ID range of the messages missing in cache,
+    // inclusive-exclusive [low, hi).
+    // Returns null if all messages are present or no messages are found.
+    func getNextMissingRange(topic: TopicProto) -> MsgRange?
     // Local user reported messages as read.
     @discardableResult
     func setRead(topic: TopicProto, read: Int) -> Bool

TinodeSDK/Topic.swift

@@ -31,6 +31,7 @@ public protocol TopicProto: class {
     var lastSeen: LastSeen? { get set }
     var online: Bool { get set }
     var cachedMessageRange: MsgRange? { get }
+    var missingMessageRange: MsgRange? { get }
     var isArchived: Bool { get }
     var isJoiner: Bool { get }
     var isReader: Bool { get }
@@ -131,8 +132,8 @@ open class Topic<DP: Codable & Mergeable, DR: Codable & Mergeable, SP: Codable,
             return self
         }
         public func withEarlierData(limit: Int?) -> MetaGetBuilder {
-            if let r = topic.cachedMessageRange {
-                return withData(since: nil, before: r.low != 0 ? r.low : nil, limit: limit)
+            if let r = topic.missingMessageRange, r.low >= 1 {
+                return withData(since: r.lower, before: r.upper, limit: limit)
             }
             return withData(since: nil, before: nil, limit: limit)
         }
@@ -366,9 +367,11 @@ open class Topic<DP: Codable & Mergeable, DR: Codable & Mergeable, SP: Codable,
     public var isPersisted: Bool { get { return payload != nil } }
 
     public var cachedMessageRange: MsgRange? {
-        get {
-            return store?.getCachedMessagesRange(topic: self)
-        }
+        return store?.getCachedMessagesRange(topic: self)
+    }
+
+    public var missingMessageRange: MsgRange? {
+        return store?.getNextMissingRange(topic: self)
     }
 
     // Tells how many topic subscribers have reported the message as read or received.

Tinodios/MessageViewController.swift

@@ -94,7 +94,7 @@ class MessageViewController: UIViewController {
         // Insets around content inside the message bubble.
         static let kIncomingMessageContentInset = UIEdgeInsets(top: 4, left: 18, bottom: 13, right: 14)
         static let kOutgoingMessageContentInset = UIEdgeInsets(top: 4, left: 14, bottom: 13, right: 18)
-        static let kDeletedMessageContentInset = UIEdgeInsets(top: 4, left: 14, bottom: 4, right: 14)
+        static let kDeletedMessageContentInset = UIEdgeInsets(top: 4, left: 14, bottom: 0, right: 14)
 
         // Carve out for timestamp and delivery marker in the bottom-right corner.
         static let kIncomingMetadataCarveout = "     "

TinodiosDB/MessageDb.swift

@@ -353,4 +353,31 @@ public class MessageDb {
             return nil
         }
     }
+
+    func fetchNextMissingRange(topicId: Int64) -> MsgRange? {
+        let messages2 = self.table.alias("m2")
+        let hiQuery = self.table
+            .join(.leftOuter, messages2,
+                  on: self.table[self.seq] == (messages2[self.high] ?? messages2[self.seq] + 1) && messages2[self.topicId] == topicId)
+            .filter(self.table[self.topicId] == topicId &&
+                    self.table[self.seq] > 1 &&
+                    messages2[self.seq] == nil)
+
+        guard let hi = try? db.scalar(hiQuery.select(self.seq.max)) else {
+            // No gap is found.
+            return nil
+        }
+        // Find the first present message with ID less than the 'high'.
+        let seqExpr = self.high ?? (self.seq + 1)
+        let lowQuery = self.table
+            .filter(self.topicId == topicId && self.seq < hi)
+        let low: Int
+        if let low2 = try? db.scalar(lowQuery.select(seqExpr.max)) {
+            // Low is inclusive thus +1.
+            low = low2 + 1
+        } else {
+            low = 1
+        }
+        return MsgRange(low: low, hi: hi)
+    }
 }

TinodiosDB/SqlStore.swift

@@ -96,6 +96,11 @@ public class SqlStore : Storage {
         return MsgRange(low: st.minLocalSeq ?? 0, hi: (st.maxLocalSeq ?? 0) + 1)
     }
 
+    public func getNextMissingRange(topic: TopicProto) -> MsgRange? {
+        guard let st = topic.payload as? StoredTopic, let topicId = st.id, topicId > 0 else { return nil }
+        return dbh?.messageDb?.fetchNextMissingRange(topicId: topicId)
+    }
+
     public func setRead(topic: TopicProto, read: Int) -> Bool {
         guard let st = topic.payload as? StoredTopic,
             let topicId = st.id, topicId > 0 else { return false }