TreeState support

- @str4d please check this implementation, I believe it's what you were looking for.
- the new service's method getTreeState needs some documentation though

Sources/ZcashLightClientKit/Block/Scan/BlockScanner.swift

@@ -23,6 +23,7 @@ protocol BlockScanner {
 struct BlockScannerImpl {
     let config: BlockScannerConfig
     let rustBackend: ZcashRustBackendWelding
+    let service: LightWalletService
     let transactionRepository: TransactionRepository
     let metrics: SDKMetrics
     let logger: Logger
@@ -56,7 +57,9 @@ extension BlockScannerImpl: BlockScanner {
             let scanSummary: ScanSummary
             let scanStartTime = Date()
             do {
-                scanSummary = try await self.rustBackend.scanBlocks(fromHeight: Int32(startHeight), limit: batchSize)
+                let fromState = try await service.getTreeState(BlockID(height: startHeight))
+
+                scanSummary = try await self.rustBackend.scanBlocks(fromHeight: Int32(startHeight), fromState: fromState, limit: batchSize)
             } catch {
                 logger.debug("block scanning failed with error: \(String(describing: error))")
                 throw error

Sources/ZcashLightClientKit/Modules/Service/GRPC/LightWalletGRPCService.swift

@@ -277,6 +277,10 @@ extension LightWalletGRPCService: LightWalletService {
             }
         }
     }
+
+    func getTreeState(_ id: BlockID) async throws -> TreeState {
+        try await compactTxStreamer.getTreeState(id)
+    }
 
     func closeConnection() {
         _ = channel.close()

Sources/ZcashLightClientKit/Modules/Service/LightWalletService.swift

@@ -196,4 +196,6 @@ protocol LightWalletService: AnyObject {
     /// - Parameters:
     ///   - request: Request to send to GetSubtreeRoots.
     func getSubtreeRoots(_ request: GetSubtreeRootsArg) -> AsyncThrowingStream<SubtreeRoot, Error>
+
+    func getTreeState(_ id: BlockID) async throws -> TreeState
 }

Sources/ZcashLightClientKit/Synchronizer/Dependencies.swift

@@ -120,6 +120,7 @@ enum Dependencies {
         }
 
         container.register(type: BlockScanner.self, isSingleton: true) { di in
+            let service = di.resolve(LightWalletService.self)
             let rustBackend = di.resolve(ZcashRustBackendWelding.self)
             let transactionRepository = di.resolve(TransactionRepository.self)
             let metrics = di.resolve(SDKMetrics.self)
@@ -133,6 +134,7 @@ enum Dependencies {
             return BlockScannerImpl(
                 config: blockScannerConfig,
                 rustBackend: rustBackend,
+                service: service,
                 transactionRepository: transactionRepository,
                 metrics: metrics,
                 logger: logger

Tests/TestUtils/Sourcery/GeneratedMocks/AutoMockable.generated.swift

@@ -963,6 +963,30 @@ class LightWalletServiceMock: LightWalletService {
         }
     }
 
+    // MARK: - getTreeState
+
+    var getTreeStateThrowableError: Error?
+    var getTreeStateCallsCount = 0
+    var getTreeStateCalled: Bool {
+        return getTreeStateCallsCount > 0
+    }
+    var getTreeStateReceivedId: BlockID?
+    var getTreeStateReturnValue: TreeState!
+    var getTreeStateClosure: ((BlockID) async throws -> TreeState)?
+
+    func getTreeState(_ id: BlockID) async throws -> TreeState {
+        if let error = getTreeStateThrowableError {
+            throw error
+        }
+        getTreeStateCallsCount += 1
+        getTreeStateReceivedId = id
+        if let closure = getTreeStateClosure {
+            return try await closure(id)
+        } else {
+            return getTreeStateReturnValue
+        }
+    }
+
 }
 class LightWalletdInfoMock: LightWalletdInfo {