73 lines
2.8 KiB
Swift
73 lines
2.8 KiB
Swift
//
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// Copyright 2023 New Vector Ltd
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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import Foundation
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/// A timer that adds a grace-period to the app before locking it.
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class AppLockTimer {
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/// The amount of time the app should remain unlocked for whilst backgrounded.
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let gracePeriod: TimeInterval
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/// Whether the timer considers the app to be locked or not. Always starts with a locked app.
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///
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/// Internally this value may be incorrect, always call `needsUnlock` to get the correct value.
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private var isLocked = true
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/// The date when the app was last backgrounded whilst in an unlocked state.
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private var lastUnlockedBackground: Date?
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/// Whether or not the app has moved to the background.
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///
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/// This allows us to distinguish between `willResignActive` and `didEnterBackground`.
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private var isInBackground = false
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/// Creates a new timer.
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/// - Parameter gracePeriod: The amount of time the app should remain unlocked for whilst backgrounded.
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init(gracePeriod: TimeInterval) {
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self.gracePeriod = gracePeriod
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}
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/// Signals to the timer to track how long the app will be backgrounded for.
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func applicationDidEnterBackground(date: Date = .now) {
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isInBackground = true
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// Only update the last background date if the app is currently unlocked.
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guard !isLocked else { return }
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lastUnlockedBackground = date
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}
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/// Asks the timer to recompute the lock state when active. If ``applicationDidEnterBackground`` hasn't been
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/// called since the last computation, then this method won't recompute it, instead directly returning the previous state.
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func computeLockState(didBecomeActiveAt date: Date) -> Bool {
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guard isInBackground else { return isLocked }
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isInBackground = false
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guard !isLocked, let lastUnlockedBackground else { return true }
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isLocked = date.timeIntervalSince(lastUnlockedBackground) >= gracePeriod
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// Don't allow changing the device's clock to unlock the app.
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if date < lastUnlockedBackground {
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isLocked = true
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}
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return isLocked
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}
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/// Registers a successful unlock with the timer.
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func registerUnlock() {
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isLocked = false
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}
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}
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