add gradient to mergeButton (#2049)

Author: BrianLitwin

Classes/Issues/Merge/MergeButton.swift

@@ -24,6 +24,7 @@ final class MergeButton: UIView {
     private let mergeLabel = UILabel()
     private let optionBorder = UIView()
     private let activityView = UIActivityIndicatorView(activityIndicatorStyle: .gray)
+    private let gradientLayer = CAGradientLayer()
 
     override init(frame: CGRect) {
         super.init(frame: frame)
@@ -72,18 +73,43 @@ final class MergeButton: UIView {
     required init?(coder aDecoder: NSCoder) {
         fatalError("init(coder:) has not been implemented")
     }
+    
+    override func layoutSubviews() {
+        super.layoutSubviews()
+        gradientLayer.frame = bounds
+    }
 
     // MARK: Public
 
     func configure(title: String, enabled: Bool, loading: Bool) {
         isUserInteractionEnabled = enabled && !loading
 
-        backgroundColor = (enabled
-            ? Styles.Colors.Green.medium.color
-            : Styles.Colors.Gray.light.color)
-            .withAlphaComponent(loading ? 0.2 : 1)
-        alpha = enabled ? 1 : 0.3
-
+        switch (enabled, loading) {
+        case (false, false):
+            backgroundColor = Styles.Colors.Gray.light.color
+            alpha = 0.3
+            
+        case (false , true):
+            backgroundColor = Styles.Colors.Gray.light.color.withAlphaComponent(0.2)
+            alpha = 0.3
+            
+        case (true, true):
+            backgroundColor = Styles.Colors.Green.medium.color.withAlphaComponent(0.2)
+            
+        case (true, false):
+            guard gradientLayer.superlayer == nil else { break }
+            gradientLayer.cornerRadius = layer.cornerRadius
+            gradientLayer.colors = [
+                UIColor.fromHex("34d058").cgColor,
+                Styles.Colors.Green.medium.color.cgColor
+            ]
+            layer.addSublayer(gradientLayer)
+            
+            [mergeLabel, optionIconView, optionBorder, activityView].forEach {
+                bringSubview(toFront: $0)
+            }
+        }
+        
         let titleColor = enabled ? .white : Styles.Colors.Gray.dark.color
         mergeLabel.textColor = titleColor
         optionIconView.tintColor = titleColor