COVIDSafe code from version 2.0 (#37)

CovidSafe/Herald/Sensor/Data/SensorLogger.swift

@@ -0,0 +1,96 @@
+//
+//  Logger.swift
+//
+//  Copyright 2020 VMware, Inc.
+//  SPDX-License-Identifier: MIT
+//
+
+import Foundation
+import UIKit
+import os
+
+protocol SensorLogger {
+    init(subsystem: String, category: String)
+    
+    func log(_ level: SensorLoggerLevel, _ message: String)
+    
+    func debug(_ message: String)
+    
+    func info(_ message: String)
+    
+    func fault(_ message: String)
+}
+
+enum SensorLoggerLevel: String {
+    case debug, info, fault
+}
+
+class ConcreteSensorLogger: NSObject, SensorLogger {
+    private let subsystem: String
+    private let category: String
+    private let dateFormatter = DateFormatter()
+    private let log: OSLog?
+    private static let logFile = TextFile(filename: "log.txt")
+    
+    required init(subsystem: String, category: String) {
+        self.subsystem = subsystem
+        self.category = category
+        dateFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss"
+        if #available(iOS 10.0, *) {
+            log = OSLog(subsystem: subsystem, category: category)
+        } else {
+            log = nil
+        }
+    }
+    
+    private func suppress(_ level: SensorLoggerLevel) -> Bool {
+        switch level {
+        case .debug:
+            return (BLESensorConfiguration.logLevel == .info || BLESensorConfiguration.logLevel == .fault);
+        case .info:
+            return (BLESensorConfiguration.logLevel == .fault);
+        default:
+            return false;
+        }
+    }
+    
+    func log(_ level: SensorLoggerLevel, _ message: String) {
+        guard !suppress(level) else {
+            return
+        }
+        // Write to unified os log if available, else print to console
+        let timestamp = dateFormatter.string(from: Date())
+        let csvMessage = message.replacingOccurrences(of: "\"", with: "'")
+        let quotedMessage = (message.contains(",") ? "\"" + csvMessage + "\"" : csvMessage)
+        let entry = timestamp + "," + level.rawValue + "," + subsystem + "," + category + "," + quotedMessage
+        ConcreteSensorLogger.logFile.write(entry)
+        guard let log = log else {
+            print(entry)
+            return
+        }
+        if #available(iOS 10.0, *) {
+            switch (level) {
+            case .debug:
+                os_log("%s", log: log, type: .debug, message)
+            case .info:
+                os_log("%s", log: log, type: .info, message)
+            case .fault:
+                os_log("%s", log: log, type: .fault, message)
+            }
+            return
+        }
+    }
+    
+    func debug(_ message: String) {
+        log(.debug, message)
+    }
+    
+    func info(_ message: String) {
+        log(.debug, message)
+    }
+    
+    func fault(_ message: String) {
+        log(.debug, message)
+    }
+    
+}