SystemUtils.swift

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

import Foundation

/**
 *  System helper methods written in Swift.
 */
public struct SystemUtils {

    /**
     Returns an accurate version of the system uptime even while the device is asleep.
     http://stackoverflow.com/questions/12488481/getting-ios-system-uptime-that-doesnt-pause-when-asleep

     - returns: Time interval since last reboot.
     */
    public static func systemUptime() -> TimeInterval {
        var boottime = timeval()
        var mib = [CTL_KERN, KERN_BOOTTIME]
        var size = MemoryLayout<timeval>.stride
        var now = time_t()
        time(&now)

        sysctl(&mib, u_int(mib.count), &boottime, &size, nil, 0)
        let tv_sec: time_t = withUnsafePointer(to: &boottime.tv_sec) { $0.pointee }
        return TimeInterval(now - tv_sec)
    }
}

extension SystemUtils {
    // This should be run on first run of the application.
    // It shouldn't be run from an extension.
    // Its function is to write a lock file that is only accessible from the application,
    // and not accessible from extension when the device is locked. Thus, we can tell if an extension is being run
    // when the device is locked.
    public static func onFirstRun() {
        guard let lockFileURL = lockedDeviceURL else {
            return
        }
        
        let lockFile = lockFileURL.path
        let fm = FileManager.default
        if fm.fileExists(atPath: lockFile) {
            return
        }
        let contents = "Device is unlocked".data(using: .utf8)
        fm.createFile(atPath: lockFile, contents: contents, attributes: [FileAttributeKey.protectionKey.rawValue: FileProtectionType.complete])
    }

    private static var lockedDeviceURL: URL? {
        let directoryURL = FileManager.default.containerURL(forSecurityApplicationGroupIdentifier: AppInfo.sharedContainerIdentifier)
        return directoryURL?.appendingPathComponent("security.dummy")
    }

    public static func isDeviceLocked() -> Bool {
        guard let lockFileURL = lockedDeviceURL else {
            return true
        }
        do {
            _ = try Data(contentsOf: lockFileURL, options: .mappedIfSafe)
            return false
        } catch let err as NSError {
            return err.code == 257
        } catch _ {
            return true
        }
    }
}