Add SQLDataTable.toJson() - render rows as clean JSON array

Uses JSONSerialization for native type mapping:
- bool/int/double/decimal → native JSON types
- string → JSON string
- null → JSON null
- date → ISO-8601 string
- bytes → base64 string
- uuid → UUID string

pretty: true (default) for indented output, false for compact.
Mirrors .NET ToJson() added in CosmoSQLClient v1.2.5.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: vkuttyp

Sources/CosmoSQLCore/SQLDataTable.swift

@@ -54,6 +54,25 @@ public enum SQLCellValue: Sendable, Equatable {
 
     public var isNull: Bool { if case .null = self { return true }; return false }
 
+    /// Native value for use with JSONSerialization (nil = JSON null).
+    var jsonValue: Any? {
+        switch self {
+        case .null:           return nil
+        case .bool(let v):    return v
+        case .int(let v):     return v
+        case .int64(let v):   return v
+        case .double(let v):  return v
+        case .decimal(let v): return NSDecimalNumber(decimal: v)
+        case .string(let v):  return v
+        case .bytes(let v):   return Data(v).base64EncodedString()
+        case .uuid(let v):    return v.uuidString
+        case .date(let v):
+            let f = ISO8601DateFormatter()
+            f.formatOptions = [.withInternetDateTime, .withFractionalSeconds]
+            return f.string(from: v)
+        }
+    }
+
     /// Human-readable string for display / Markdown rendering.
     public var displayString: String {
         switch self {
@@ -208,6 +227,23 @@ public struct SQLDataTable: Sendable {
         return try toSQLRows().map { try decoder.decode(T.self, from: $0) }
     }
 
+    // MARK: JSON rendering
+
+    /// Renders the table as a JSON array of objects (column name → native value).
+    /// SQL NULL becomes JSON `null`. Dates are ISO-8601 strings.
+    public func toJson(pretty: Bool = true) -> String {
+        let array = rows.map { row -> [String: Any?] in
+            Dictionary(uniqueKeysWithValues: zip(columns.map(\.name), row.map(\.jsonValue)))
+        }
+        // JSONSerialization needs [String: Any] with NSNull for nulls
+        let sanitized = array.map { dict in
+            dict.mapValues { $0 ?? NSNull() as Any }
+        }
+        let opts: JSONSerialization.WritingOptions = pretty ? [.prettyPrinted, .sortedKeys] : []
+        let data = (try? JSONSerialization.data(withJSONObject: sanitized, options: opts)) ?? Data()
+        return String(data: data, encoding: .utf8) ?? "[]"
+    }
+
     // MARK: Markdown rendering
 
     /// Renders the table as a GitHub-flavored Markdown table string.

cosmo-swift/Package.resolved

@@ -0,0 +1,18 @@
+// swift-tools-version: 6.0
+import PackageDescription
+
+let package = Package(
+    name: "cosmo-swift",
+    platforms: [.macOS(.v13)],
+    dependencies: [
+        .package(path: ".."),
+    ],
+    targets: [
+        .executableTarget(
+            name: "cosmo-swift",
+            dependencies: [
+                .product(name: "CosmoMSSQL", package: "sql-nio"),
+            ]
+        ),
+    ]
+)

cosmo-swift/Package.swift

@@ -0,0 +1,15 @@
+import CosmoMSSQL
+import CosmoSQLCore
+
+print("Hello, World!")
+
+let conn = try await MSSQLConnection.connect(configuration: .init(
+    connectionString: "Server=localhost,1433;Database=MurshiDb;User Id=sa;Password=aBCD111;Encrypt=true;TrustServerCertificate=true"
+))
+defer { Task { try? await conn.close() } }
+
+let rows = try await conn.query("SELECT TOP 3 AccountNo, AccountName, AccountTypeID, IsMain FROM Accounts", [])
+let table = rows.asDataTable(name: "Accounts")
+
+print("Rows: \(table.rowCount), Columns: \(table.columnCount)")
+print(table.toJson())

cosmo-swift/Sources/cosmo-swift/main.swift

@@ -0,0 +1,19 @@
+// See https://aka.ms/new-console-template for more information
+using CosmoSQLClient.Core;
+using CosmoSQLClient.MsSql;
+
+Console.WriteLine("Hello, World!");
+await using var conn = await MsSqlConnection.OpenAsync(
+    "Server=localhost,1433;Database=MurshiDb;User Id=sa;Password=aBCD111;Encrypt=True;TrustServerCertificate=True;");
+
+var table = await conn.QueryTableAsync("SELECT TOP 3 AccountNo, AccountName, AccountTypeID, IsMain FROM Accounts");
+
+Console.WriteLine(table.ToJson());
+
+public class Account
+{
+    public string? AccountNo { get; set; }
+    public string? AccountName { get; set; }
+    public int AccountTypeID { get; set; }
+    public bool IsMain { get; set; }
+}