Added sync progress definition.

Author: Chriztiaan

PowerSync/PowerSync.Common/Client/Sync/Stream/StreamingSyncImplementation.cs

@@ -493,7 +493,7 @@ async Task HandleInstruction(Instruction instruction)
                     Options.Remote.InvalidateCredentials();
                     break;
                 case FetchCredentials:
-                    await Options.Remote.PrefetchCredentials();
+                    Options.Remote.InvalidateCredentials();
                     break;
                 case CloseSyncStream:
                     CancellationTokenSource?.Cancel();

PowerSync/PowerSync.Common/DB/Crud/SyncProgress.cs

@@ -1,6 +1,117 @@
 namespace PowerSync.Common.DB.Crud;
 
-public class SyncProgress
+/// <summary>
+/// Provides realtime progress on how PowerSync is downloading rows.
+///
+/// The reported progress always reflects the status towards th end of a sync iteration (after
+/// which a consistent snapshot of all buckets is available locally).
+///
+/// In rare cases (in particular, when a [compacting](https://docs.powersync.com/usage/lifecycle-maintenance/compacting-buckets)
+/// operation takes place between syncs), it's possible for the returned numbers to be slightly
+/// inaccurate. For this reason, the sync progress should be seen as an approximation of progress.
+/// The information returned is good enough to build progress bars, but not exact enough to track
+/// individual download counts.
+///
+/// Also note that data is downloaded in bulk, which means that individual counters are unlikely
+/// to be updated one-by-one.
+/// </summary>
+public class SyncProgress : ProgressWithOperations
 {
     public static readonly int FULL_SYNC_PRIORITY = 2147483647;
+
+    private InternalProgressInformation internalProgress;
+
+    public SyncProgress(InternalProgressInformation progress)
+    {
+        this.internalProgress = progress;
+        var untilCompletion = UntilPriority(FULL_SYNC_PRIORITY);
+
+        TotalOperations = untilCompletion.TotalOperations;
+        DownloadedOperations = untilCompletion.DownloadedOperations;
+        DownloadedFraction = untilCompletion.DownloadedFraction;
+    }
+
+    private ProgressWithOperations UntilPriority(int priority)
+    {
+        var total = 0;
+        var downloaded = 0;
+
+        foreach (var progress in internalProgress.Buckets.Values)
+        {
+            // Include higher-priority buckets, which are represented by lower numbers.
+            if (progress.Priority <= priority)
+            {
+                downloaded += progress.SinceLast;
+                total += progress.TargetCount - progress.AtLast;
+            }
+        }
+
+        return new ProgressWithOperations
+        {
+            TotalOperations = total,
+            DownloadedOperations = downloaded,
+            DownloadedFraction = total == 0 ? 1.0 : (double)downloaded / total
+        };
+    }
+}
+
+/// <summary>
+/// Represents progress information for sync operations.
+/// </summary>
+public class InternalProgressInformation
+{
+    /// <summary>
+    /// Dictionary mapping bucket names to their progress information.
+    /// </summary>
+    public Dictionary<string, BucketProgressInfo> Buckets { get; set; } = new();
+}
+
+/// <summary>
+/// Represents progress information for a single bucket.
+/// </summary>
+public class BucketProgressInfo
+{
+    /// <summary>
+    /// Priority of the associated buckets
+    /// </summary>
+    public int Priority { get; set; }
+
+    /// <summary>
+    /// Total ops at last completed sync, or 0
+    /// </summary>
+    public int AtLast { get; set; }
+
+    /// <summary>
+    /// Total ops since the last completed sync
+    /// </summary>
+    public int SinceLast { get; set; }
+
+    /// <summary>
+    /// Total opcount for next checkpoint as indicated by service
+    /// </summary>
+    public int TargetCount { get; set; }
+}
+
+/// <summary>
+/// Information about a progressing download made by the PowerSync SDK.
+/// 
+/// </summary>
+public class ProgressWithOperations
+{
+    /// <summary>
+    /// The total number of operations to download for the current sync iteration to complete.
+    /// </summary>
+    public int TotalOperations { get; set; }
+
+    /// <summary>
+    /// The numnber of operations that have already been downloaded.
+    /// </summary>
+    public int DownloadedOperations { get; set; }
+
+    /// <summary>
+    /// This will be a number between 0.0 and 1.0 (inclusive).
+    /// 
+    /// When this number reaches 1.0, all changes have been received from the sync service.
+    /// </summary>
+    public double DownloadedFraction { get; set; }
 }