Displays countdown for unreleased apps

AltStore/Components/PillButton.swift

@@ -36,8 +36,35 @@ class PillButton: UIButton
         }
     }
     
+    var countdownDate: Date? {
+        didSet {
+            self.isEnabled = (self.countdownDate == nil)
+            self.displayLink.isPaused = (self.countdownDate == nil)
+            
+            if self.countdownDate == nil
+            {
+                self.setTitle(nil, for: .disabled)
+            }
+        }
+    }
+    
     private let progressView = UIProgressView(progressViewStyle: .default)
     
+    private lazy var displayLink: CADisplayLink = {
+        let displayLink = CADisplayLink(target: self, selector: #selector(PillButton.updateCountdown))
+        displayLink.preferredFramesPerSecond = 15
+        displayLink.isPaused = true
+        displayLink.add(to: .main, forMode: .common)
+        return displayLink
+    }()
+    
+    private let dateComponentsFormatter: DateComponentsFormatter = {
+        let dateComponentsFormatter = DateComponentsFormatter()
+        dateComponentsFormatter.zeroFormattingBehavior = [.pad]
+        dateComponentsFormatter.collapsesLargestUnit = false
+        return dateComponentsFormatter
+    }()
+    
     override var intrinsicContentSize: CGSize {
         var size = super.intrinsicContentSize
         size.width += 26
@@ -45,6 +72,11 @@ class PillButton: UIButton
         return size
     }
     
+    deinit
+    {
+        self.displayLink.remove(from: .main, forMode: RunLoop.Mode.default)
+    }
+    
     override func awakeFromNib()
     {
         super.awakeFromNib()
@@ -101,4 +133,55 @@ private extension PillButton
             self.progressView.progressTintColor = self.tintColor
         }
     }
+    
+    @objc func updateCountdown()
+    {
+        guard let endDate = self.countdownDate else { return }
+        
+        let startDate = Date()
+        
+        let interval = endDate.timeIntervalSince(startDate)
+        guard interval > 0 else {
+            self.isEnabled = true
+            return
+        }
+        
+        let text: String?
+        
+        if interval < (1 * 60 * 60)
+        {
+            self.dateComponentsFormatter.unitsStyle = .positional
+            self.dateComponentsFormatter.allowedUnits = [.minute, .second]
+            
+            text = self.dateComponentsFormatter.string(from: startDate, to: endDate)
+        }
+        else if interval < (2 * 24 * 60 * 60)
+        {
+            self.dateComponentsFormatter.unitsStyle = .positional
+            self.dateComponentsFormatter.allowedUnits = [.hour, .minute, .second]
+            
+            text = self.dateComponentsFormatter.string(from: startDate, to: endDate)
+        }
+        else
+        {
+            self.dateComponentsFormatter.unitsStyle = .full
+            self.dateComponentsFormatter.allowedUnits = [.day]
+            
+            let numberOfDays = endDate.numberOfCalendarDays(since: startDate)
+            text = String(format: NSLocalizedString("%@ DAYS", comment: ""), NSNumber(value: numberOfDays))
+        }
+        
+        if let text = text
+        {            
+            UIView.performWithoutAnimation {
+                self.isEnabled = false
+                self.setTitle(text, for: .disabled)
+                self.layoutIfNeeded()
+            }
+        }
+        else
+        {
+            self.isEnabled = true
+        }
+    }
 }