import Foundationimport Logging#if canImport(Darwin)import Darwin#elseimport Glibc#endif struct JSONStderrLogHandler: LogHandler {    var metadata: Logger.Metadata = [:]    var logLevel: Logger.Level = .info     private let label: String    private let encoder: JSONEncoder     init(label: String) {        self.label = label        self.encoder = JSONEncoder()        self.encoder.dateEncodingStrategy = .iso8601        self.encoder.outputFormatting = [.sortedKeys]    }     subscript(metadataKey metadataKey: String) -> Logger.Metadata.Value? {        get { self.metadata[metadataKey] }        set { self.metadata[metadataKey] = newValue }    }     func log(event: LogEvent) {        let ts = Date()        var combined = self.metadata        if let metadata = event.metadata { combined.merge(metadata, uniquingKeysWith: { _, new in new }) }         let payload = JSONLogLine(            timestamp: ts,            level: event.level.rawValue,            label: self.label,            message: event.message.description,            source: event.source,            file: event.file,            function: event.function,            line: event.line,            metadata: combined.isEmpty ? nil : combined.mapValues(\.description))         guard let data = try? self.encoder.encode(payload),              let text = String(data: data, encoding: .utf8) else { return }        Self.writeStderr(text + "\n")    }} private struct JSONLogLine: Encodable {    let timestamp: Date    let level: String    let label: String    let message: String    let source: String    let file: String    let function: String    let line: UInt    let metadata: [String: String]?} extension JSONStderrLogHandler {    private static func writeStderr(_ text: String) {        let bytes = Array(text.utf8)        bytes.withUnsafeBytes { buffer in            guard let baseAddress = buffer.baseAddress else { return }            _ = write(STDERR_FILENO, baseAddress, buffer.count)        }    }}