Initial commit

Package.swift

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+// swift-tools-version:5.5
+
+import PackageDescription
+
+let package = Package(
+    name: "LoggingPlayground",
+    products: [
+        .library(
+            name: "LoggingPlayground",
+            targets: ["LoggingPlayground"]
+        )
+    ],
+    dependencies: [],
+    targets: [
+        .target(
+            name: "LoggingPlayground",
+            dependencies: []
+        ),
+    ]
+)

README.md

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+# LoggingPlayground
+
+TBD

Sources/LoggingPlayground/PlaygroundHandler.swift

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+import Foundation
+import Logging
+
+public struct PlaygroundHandler {
+    private let label: String
+    private var prettyMetadata: String?
+    public var metadata = Logger.Metadata() {
+        didSet {
+            self.prettyMetadata = self.prettify(self.metadata)
+        }
+    }
+    public var logLevel = Logger.Level.info
+
+    public init(label: String) {
+        self.label = label
+    }
+
+    private func prettify(_ metadata: Logger.Metadata) -> String? {
+        guard !metadata.isEmpty else { return nil }
+        return metadata.lazy
+            .sorted(by: { $0.key < $1.key })
+            .map { "\($0)=\($1)" }
+            .joined(separator: " ")
+    }
+
+    private func timestamp() -> String {
+        var buffer = [Int8](repeating: 0, count: 255)
+        var timestamp = time(nil)
+        let localTime = localtime(&timestamp)
+        strftime(&buffer, buffer.count, "%Y-%m-%dT%H:%M:%S%z", localTime)
+        return buffer.withUnsafeBufferPointer {
+            $0.withMemoryRebound(to: CChar.self) {
+                String(cString: $0.baseAddress!)
+            }
+        }
+    }
+}
+
+extension PlaygroundHandler: LogHandler {
+    public func log(
+        level: Logger.Level,
+        message: Logger.Message,
+        metadata: Logger.Metadata?,
+        source: String,
+        file: String,
+        function: String,
+        line: UInt
+    ) {
+        let prettyMetadata: String?
+        if let metadata = metadata, !metadata.isEmpty {
+            prettyMetadata = self.prettify(
+                self.metadata.merging(
+                    metadata,
+                    uniquingKeysWith: { _, new in new }
+                )
+            )
+        } else {
+            prettyMetadata = self.prettyMetadata
+        }
+        print(
+            "\(self.timestamp()) [\(self.label)] \(level):\(prettyMetadata.map { " \($0)" } ?? "") \(message)"
+        )
+    }
+
+    public subscript(
+        metadataKey metadataKey: String
+    ) -> Logger.Metadata.Value? {
+        get { self.metadata[metadataKey] }
+        set { self.metadata[metadataKey] = newValue }
+    }
+}