Ios log 4 (#569)

iOS logging refactoring

client/platforms/ios/LogRecord.swift

@@ -0,0 +1,82 @@
+import Foundation
+import os.log
+
+extension Log {
+  struct Record {
+    let date: Date
+    let level: Level
+    let message: String
+    
+    init?(_ str: String) {
+      let dateStr = String(str.prefix(19))
+      guard let date = Log.dateFormatter.date(from: dateStr) else { return nil }
+      
+      let str = str.dropFirst(20)
+      
+      guard let endIndex = str.firstIndex(of: " ") else { return nil }
+      let levelStr = String(str[str.startIndex..<endIndex])
+      guard let level = Level(rawValue: levelStr) else { return nil }
+      
+      let messageStartIndex = str.index(after: endIndex)
+      let message = String(str[messageStartIndex..<str.endIndex])
+      
+      self.init(date: date, level: level, message: message)
+    }
+    
+    init(date: Date, level: Level, message: String) {
+      self.date = date
+      self.level = level
+      self.message = message
+    }
+    
+    func save(at url: URL) {
+      guard let data = "\n\(description)".data(using: .utf8) else { return }
+              
+      if !FileManager.default.fileExists(atPath: url.path) {
+        guard let _ = try? "".data(using: .utf8)?.write(to: url) else { return }
+      }
+      
+      guard let fileHandle = try? FileHandle(forUpdating: url) else { return }
+      
+      defer { fileHandle.closeFile() }
+      
+      guard let _ = try? fileHandle.seekToEnd() else { return }
+      try? fileHandle.write(contentsOf: data)
+    }
+  }
+}
+
+extension Log.Record: CustomStringConvertible {
+  var description: String {
+    "\(Log.dateFormatter.string(from: date)) \(level.rawValue) \(message)"
+  }
+}
+
+extension Log.Record {
+  enum Level: String {
+    case debug
+    case warning
+    case error
+    case critical
+    case fatal
+    case info
+    case system // critical
+    
+    init(from osLogType: OSLogType) {
+      switch osLogType {
+      case OSLogType.default:
+        self = .info
+      case OSLogType.info:
+        self = .info
+      case OSLogType.debug:
+        self = .debug
+      case OSLogType.error:
+        self = .error
+      case OSLogType.fault:
+        self = .fatal
+      default:
+        self = .info
+      }
+    }
+  }
+}