Add option to use the Rust sync client (#51)

Author: simolus3

CHANGELOG.md

@@ -1,6 +1,6 @@
 # Changelog
 
-## 1.1.1 (unreleased)
+## 1.2.0
 
 * Improved `CrudBatch` and `CrudTransaction` `complete` function extensions. Developers no longer need to specify `nil` as an argument for `writeCheckpoint` when calling `CrudBatch.complete`. The base `complete` functions still accept an optional `writeCheckpoint` argument if developers use custom write checkpoints. 
 ``` diff
@@ -12,6 +12,31 @@ guard let finalBatch = try await powersync.getCrudBatch(limit: 100) else {
 ```
 * Fix reported progress around compactions / defrags on the sync service.
 * Use version `0.4.0` of the PowerSync core extension, which improves sync performance.
+* Add a new sync client implementation written in Rust instead of Kotlin. While this client is still
+  experimental, we intend to make it the default in the future. The main benefit of this client is
+  faster sync performance, but upcoming features will also require this client. We encourage 
+  interested users to try it out by opting in to experimental APIs and passing options when
+  connecting:
+  ```Swift
+  @_spi(PowerSyncExperimental) import PowerSync
+
+  try await db.connect(connector: connector, options: ConnectOptions(
+      newClientImplementation: true,
+  ))
+  ```
+  Switching between the clients can be done at any time without compatibility issues. If you run
+  into issues with the new client, please reach out to us!
+* In addition to HTTP streams, the Swift SDK also supports fetching sync instructions from the
+  PowerSync service in a binary format. This requires the new sync client, and can then be enabled
+  on the sync options:
+  ```Swift
+  @_spi(PowerSyncExperimental) import PowerSync
+
+  try await db.connect(connector: connector, options: ConnectOptions(
+      newClientImplementation: true,
+      connectionMethod: .webSocket,
+  ))
+  ```
 
 ## 1.1.0
 

Package.swift

@@ -27,8 +27,8 @@ if let kotlinSdkPath = localKotlinSdkOverride {
     // Not using a local build, so download from releases
     conditionalTargets.append(.binaryTarget(
         name: "PowerSyncKotlin",
-        url: "https://github.com/powersync-ja/powersync-kotlin/releases/download/v1.1.1/PowersyncKotlinRelease.zip",
-        checksum: "780437e25d41e46c2c1f555adcf330436f185d3663ef442da7141381d9c0495b"
+        url: "https://github.com/powersync-ja/powersync-kotlin/releases/download/v1.2.0/PowersyncKotlinRelease.zip",
+        checksum: "7454481a245b46b1b63a42419ec27f88f2fcb7fba9b763e3085cb49db59dfd58"
     ))
 }
 

Sources/PowerSync/Kotlin/KotlinPowerSyncDatabaseImpl.swift

@@ -52,12 +52,21 @@ final class KotlinPowerSyncDatabaseImpl: PowerSyncDatabaseProtocol {
         )
 
         let resolvedOptions = options ?? ConnectOptions()
+        let useWebsockets = switch (resolvedOptions.connectionMethod) {
+            case .http: false
+            case .webSocket: true
+        }
 
         try await kotlinDatabase.connect(
             connector: connectorAdapter,
             crudThrottleMs: Int64(resolvedOptions.crudThrottle * 1000),
             retryDelayMs: Int64(resolvedOptions.retryDelay * 1000),
-            params: resolvedOptions.params.mapValues { $0.toKotlinMap() }
+            params: resolvedOptions.params.mapValues { $0.toKotlinMap() },
+            options: createSyncOptions(
+                newClient: resolvedOptions.newClientImplementation,
+                webSocket: useWebsockets,
+                userAgent: "PowerSync Swift SDK"
+            )
         )
     }
 

Sources/PowerSync/Protocol/PowerSyncDatabaseProtocol.swift

@@ -34,7 +34,22 @@ public struct ConnectOptions {
     /// ]
     /// ```
     public var params: JsonParam
+    
+    /// Uses a new sync client implemented in Rust instead of the one implemented in Kotlin.
+    ///
+    /// The new client is more efficient and will become the default in the future, but is still marked as experimental for now.
+    /// We encourage interested users to try the new client.
+    @_spi(PowerSyncExperimental)
+    public var newClientImplementation: Bool
 
+    /// The connection method used to connect to the Powersync service.
+    ///
+    /// The default method is ``ConnectionMethod/http``. Using ``ConnectionMethod/webSocket(_:)`` can
+    /// improve performance as a more efficient binary protocol is used. However, using the websocket connection method
+    /// requires enabling ``ConnectOptions/newClientImplementation``.
+    @_spi(PowerSyncExperimental)
+    public var connectionMethod: ConnectionMethod
+    
     /// Initializes a `ConnectOptions` instance with optional values.
     ///
     /// - Parameters:
@@ -49,9 +64,32 @@ public struct ConnectOptions {
         self.crudThrottle = crudThrottle
         self.retryDelay = retryDelay
         self.params = params
+        self.newClientImplementation = false
+        self.connectionMethod = .http
+    }
+    
+    /// Initializes a ``ConnectOptions`` instance with optional values, including experimental options.
+    @_spi(PowerSyncExperimental)
+    public init(
+        crudThrottle: TimeInterval = 1,
+        retryDelay: TimeInterval = 5,
+        params: JsonParam = [:],
+        newClientImplementation: Bool = false,
+        connectionMethod: ConnectionMethod = .http
+    ) {
+        self.crudThrottle = crudThrottle
+        self.retryDelay = retryDelay
+        self.params = params
+        self.newClientImplementation = newClientImplementation
+        self.connectionMethod = connectionMethod
     }
 }
 
+@_spi(PowerSyncExperimental)
+public enum ConnectionMethod {
+    case http
+    case webSocket
+}
 
 /// A PowerSync managed database.
 ///