feat(swift-sdk): in-app log export for beta diagnostics (#4131)

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

Author: QuantumExplorer

packages/swift-sdk/Sources/SwiftDashSDK/Core/Services/SDKLogger.swift

@@ -23,22 +23,62 @@ public enum LoggingPreset: String {
 public enum LoggingPreferences {
     private static let defaultsKey = "SwiftSDKLogLevel"
 
+    /// Sessions beyond this count are deleted at startup, oldest
+    /// first. File logging runs on devices too (beta diagnostics),
+    /// so growth must stay bounded without anyone thinking about it.
+    private static let maxRetainedSessions = 20
+
+    /// Total-bytes quota across retained sessions. The Rust side
+    /// appends without rotation, so individual sessions can be
+    /// arbitrarily large — a count cap alone doesn't bound disk
+    /// use. Sessions are kept newest-first until the quota is hit;
+    /// the current session is always kept (its in-flight growth
+    /// can only be bounded by rotation on the Rust side).
+    private static let maxRetainedBytes: UInt64 = 100 * 1024 * 1024
+
+    /// Root under which each launch creates one timestamped session
+    /// directory of per-crate `run.log` files. Exposed so diagnostics
+    /// features (log export) can enumerate sessions without
+    /// re-deriving the layout.
+    public static var logsRootDirectory: URL? {
+        FileManager.default
+            .urls(for: .libraryDirectory, in: .userDomainMask).first?
+            .appendingPathComponent("Logs", isDirectory: true)
+            .appendingPathComponent("SwiftDashSDK", isDirectory: true)
+    }
+
+    /// Session directory of the current launch, set once `configure()`
+    /// installs the file subscriber. `nil` when file logging is off
+    /// (subscriber already installed, or the path wasn't writable).
+    @MainActor
+    public private(set) static var currentSessionDirectory: URL?
+
+    /// The tracing subscriber is process-global and first-init-wins,
+    /// so the install must run at most once per process. Without
+    /// this guard, every `configure()` call after the first (e.g.
+    /// a bootstrap retry) would make the Rust initializer lay out a
+    /// fresh session directory of empty log files before `try_init`
+    /// discovers the existing subscriber and bails — leaving decoy
+    /// "newest" sessions that logging never writes to.
+    @MainActor
+    private static var didInstallLogging = false
+
     @discardableResult
     @MainActor
     public static func configure() -> LoggingPreset {
         let preset = loadPreset()
         let enableSwiftVerbose: Bool
 
-        // File logging is gated to the iOS Simulator
-        #if targetEnvironment(simulator)
-        if let sessionRoot = launchLogPaths(),
-           SDK.enableFileLogging(level: .info, sessionRoot: sessionRoot) {
-        } else {
-            SDK.enableLogging(level: .info)
+        if !didInstallLogging {
+            didInstallLogging = true
+            if let sessionRoot = launchLogPaths(),
+               SDK.enableFileLogging(level: .info, sessionRoot: sessionRoot.path) {
+                currentSessionDirectory = sessionRoot
+                pruneOldSessions(keeping: sessionRoot)
+            } else {
+                SDK.enableLogging(level: .info)
+            }
         }
-        #else
-        SDK.enableLogging(level: .info)
-        #endif
 
         switch preset {
         case .high:
@@ -54,24 +94,79 @@ public enum LoggingPreferences {
         return preset
     }
 
-    private static func launchLogPaths() -> String? {
-        guard
-            let libraryURL = FileManager.default
-                .urls(for: .libraryDirectory, in: .userDomainMask).first
-        else {
-            return nil
-        }
+    private static func launchLogPaths() -> URL? {
+        guard let root = logsRootDirectory else { return nil }
 
         let formatter = DateFormatter()
         formatter.locale = Locale(identifier: "en_US_POSIX")
         formatter.timeZone = TimeZone(secondsFromGMT: 0)
         formatter.dateFormat = "yyyy-MM-dd'T'HH-mm-ss'Z'"
 
-        return libraryURL
-            .appendingPathComponent("Logs", isDirectory: true)
-            .appendingPathComponent("SwiftDashSDK", isDirectory: true)
+        return root
             .appendingPathComponent(formatter.string(from: Date()), isDirectory: true)
-            .path
+    }
+
+    /// Delete session directories past either retention bound —
+    /// `maxRetainedSessions` count or `maxRetainedBytes` total —
+    /// walking newest-first so what survives is always the most
+    /// recent history. The current session is always kept
+    /// regardless of where its stamp sorts or how big it is.
+    /// Runs detached — deleting multi-megabyte directories has no
+    /// business on the main actor during launch.
+    private static func pruneOldSessions(keeping current: URL) {
+        guard let root = logsRootDirectory else { return }
+        Task.detached(priority: .utility) {
+            let fm = FileManager.default
+            guard let entries = try? fm.contentsOfDirectory(
+                at: root,
+                includingPropertiesForKeys: [.isDirectoryKey],
+                options: [.skipsHiddenFiles]
+            ) else { return }
+
+            // Session stamps are fixed-width UTC ISO timestamps, so
+            // lexicographic order is chronological order.
+            let sessions = entries
+                .filter { (try? $0.resourceValues(forKeys: [.isDirectoryKey]))?.isDirectory == true }
+                .sorted { $0.lastPathComponent > $1.lastPathComponent }
+
+            let currentName = current.lastPathComponent
+            var keptCount = 0
+            var keptBytes: UInt64 = 0
+            for session in sessions {
+                if session.lastPathComponent == currentName {
+                    // Counted against the byte quota so a huge
+                    // just-finished-syncing session pushes old
+                    // history out, but never deleted itself.
+                    keptCount += 1
+                    keptBytes += directoryBytes(of: session)
+                    continue
+                }
+                let bytes = directoryBytes(of: session)
+                if keptCount >= maxRetainedSessions
+                    || keptBytes + bytes > maxRetainedBytes {
+                    try? fm.removeItem(at: session)
+                } else {
+                    keptCount += 1
+                    keptBytes += bytes
+                }
+            }
+        }
+    }
+
+    private static func directoryBytes(of directory: URL) -> UInt64 {
+        guard let enumerator = FileManager.default.enumerator(
+            at: directory,
+            includingPropertiesForKeys: [.totalFileAllocatedSizeKey, .fileSizeKey]
+        ) else { return 0 }
+
+        var total: UInt64 = 0
+        for case let file as URL in enumerator {
+            let values = try? file.resourceValues(
+                forKeys: [.totalFileAllocatedSizeKey, .fileSizeKey]
+            )
+            total += UInt64(values?.totalFileAllocatedSize ?? values?.fileSize ?? 0)
+        }
+        return total
     }
 
     public static var preset: LoggingPreset { loadPreset() }