feat: Add PowerSyncDataConvertible protocol

Sources/PowerSync/Kotlin/db/KotlinConnectionContext.swift

@@ -97,6 +97,11 @@ final class KotlinTransactionContext: Transaction, KotlinConnectionContextProtoc
 // Allows nil values to be passed to the Kotlin [Any] params
 func mapParameters(_ parameters: [Any?]?) -> [Any] {
     parameters?.map { item in
-        item ?? NSNull()
+        switch item {
+            case .none: NSNull()
+            case let item as PowerSyncDataTypeConvertible:
+                item.psDataType?.unwrap() ?? NSNull()
+            default: item
+        }
     } ?? []
 }

Sources/PowerSync/Kotlin/db/PowerSyncDataTypeConvertible.swift

@@ -0,0 +1,32 @@
+import struct Foundation.Data
+
+/// Represents the set of types that are supported
+/// by the PowerSync Kotlin Multiplatform SDK
+public enum PowerSyncDataType {
+    case bool(Bool)
+    case string(String)
+    case int64(Int64)
+    case int32(Int32)
+    case double(Double)
+    case data(Data)
+}
+
+/// Types conforming to this protocol will be
+/// mapped to the specified ``PowerSyncDataType``
+/// before use by SQLite
+public protocol PowerSyncDataTypeConvertible {
+    var psDataType: PowerSyncDataType? { get }
+}
+
+extension PowerSyncDataType {
+    func unwrap() -> Any {
+        switch self {
+            case let .bool(bool): bool
+            case let .string(string): string
+            case let .int32(int32): int32
+            case let .int64(int64): int64
+            case let .double(double): double
+            case let .data(data): data
+        }
+    }
+}

Tests/PowerSyncTests/Kotlin/KotlinPowerSyncDatabaseImplTests.swift

@@ -1,4 +1,5 @@
 @testable import PowerSync
+import struct Foundation.UUID
 import XCTest
 
 final class KotlinPowerSyncDatabaseImplTests: XCTestCase {
@@ -156,6 +157,25 @@ final class KotlinPowerSyncDatabaseImplTests: XCTestCase {
         }
     }
 
+    func testCustomDataTypeConvertible() async throws {
+        let uuid = UUID()
+        try await database.execute(
+            sql: "INSERT INTO users (id, name, email) VALUES (?, ?, ?)",
+            parameters: [uuid, "Test User", "test@example.com"]
+        )
+
+        let _ = try await database.getOptional(
+            sql: "SELECT id, name, email FROM users WHERE id = ?",
+            parameters: [uuid]
+        ) { cursor throws in
+           try (
+                cursor.getString(name: "id"),
+                cursor.getString(name: "name"),
+                cursor.getString(name: "email")
+            )
+        }
+    }
+
     func testGetAll() async throws {
         try await database.execute(
             sql: "INSERT INTO users (id, name, email) VALUES (?, ?, ?), (?, ?, ?)",
@@ -698,3 +718,10 @@ final class KotlinPowerSyncDatabaseImplTests: XCTestCase {
         try deleteSQLiteFiles(dbFilename: testDbFilename, in: databaseDirectory)
     }
 }
+
+
+extension UUID: @retroactive PowerSyncDataTypeConvertible {
+    public var psDataType: PowerSyncDataType? {
+        .string(uuidString)
+    }
+}