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Show time remaining estimate during conversion (#65)
Fixes #52
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,137 @@ | ||
| import Foundation | ||
|
|
||
| final class TimeEstimator { | ||
| /// The delay before revealing the estimated time remaining, allowing the estimation to stabilize. | ||
| let bufferDuration: TimeInterval = 3.0 | ||
|
|
||
| /// Don't show the estimate at all if the total time estimate (after it stabilizes) is less than this amount. | ||
| let skipThreshold: TimeInterval = 10.0 | ||
|
|
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| /// Begin fade out when remaining time reaches this amount. | ||
| let fadeOutThreshold: TimeInterval = 1.0 | ||
|
|
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| var progress: Progress? { | ||
| didSet { | ||
| progressObserver = progress?.observe(\.fractionCompleted) { sender, _ in | ||
| self.percentComplete = sender.fractionCompleted | ||
| } | ||
|
|
||
| cancelObserver = progress?.observe(\.isCancelled) { sender, _ in | ||
| if sender.isCancelled { | ||
| self.state = .done | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
|
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| init(label: Label) { | ||
| self.label = label | ||
| } | ||
|
|
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| func start() { | ||
| state = .buffering | ||
| startTime = Date() | ||
| } | ||
|
|
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| // MARK: - Private | ||
|
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| private enum State { | ||
| case buffering | ||
| case running | ||
| case done | ||
| } | ||
|
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| private var state: State = .buffering { | ||
| didSet { | ||
| guard state != oldValue else { | ||
| return | ||
| } | ||
|
|
||
| switch state { | ||
| case .buffering: | ||
| break | ||
| case .running: | ||
| fadeInLabel() | ||
| case .done: | ||
| fadeOutLabel() | ||
| } | ||
| } | ||
| } | ||
|
|
||
| private var nextState: State { | ||
| switch state { | ||
| case .buffering: | ||
| if finishedBuffering { | ||
| return shouldShowEstimation ? .running : .done | ||
| } else { | ||
| return .buffering | ||
| } | ||
| case .running: | ||
| return secondsRemaining < fadeOutThreshold ? .done : .running | ||
| case .done: | ||
| return .done | ||
| } | ||
| } | ||
|
|
||
| private var finishedBuffering: Bool { | ||
| return secondsElapsed > bufferDuration | ||
| } | ||
|
|
||
| private var shouldShowEstimation: Bool { | ||
| return secondsRemaining > skipThreshold | ||
| } | ||
|
|
||
| private var secondsElapsed: TimeInterval { | ||
| return Date().timeIntervalSince(startTime) | ||
| } | ||
|
|
||
| private var secondsRemaining: TimeInterval { | ||
| return (secondsElapsed / percentComplete) * (1 - percentComplete) | ||
| } | ||
|
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||
| private var label: Label | ||
| private var startTime = Date() | ||
| private var progressObserver: NSKeyValueObservation? | ||
| private var cancelObserver: NSKeyValueObservation? | ||
|
|
||
| private lazy var elapsedTimeFormatter = with(DateComponentsFormatter()) { | ||
| $0.unitsStyle = .full | ||
| $0.includesApproximationPhrase = true | ||
| $0.includesTimeRemainingPhrase = true | ||
| } | ||
|
|
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| private var formattedTimeRemaining: String? { | ||
| let seconds = secondsRemaining | ||
| elapsedTimeFormatter.allowedUnits = seconds < 60 ? .second : [.hour, .minute] | ||
| return elapsedTimeFormatter.string(from: seconds) | ||
| } | ||
|
|
||
| private var percentComplete: Double = 0.001 { | ||
| didSet { | ||
| state = nextState | ||
| updateLabel() | ||
| } | ||
| } | ||
|
|
||
| private func fadeInLabel() { | ||
| DispatchQueue.main.async { | ||
| if self.label.isHidden { | ||
| self.label.fadeIn() | ||
| } | ||
| } | ||
| } | ||
|
|
||
| private func fadeOutLabel() { | ||
| DispatchQueue.main.async { | ||
| if !self.label.isHidden { | ||
| self.label.fadeOut() | ||
| } | ||
| } | ||
| } | ||
|
|
||
| private func updateLabel() { | ||
| DispatchQueue.main.async { | ||
| self.label.text = self.formattedTimeRemaining ?? "" | ||
| } | ||
| } | ||
| } |