Display a “default” badge for the default PM (#4333)

## Summary
<!-- Simple summary of what was changed. -->
Display a "default" badge for the default PM in vertical and horizontal
mode across all UI shapes (payment sheet, flow controller, embedded)
## Motivation
<!-- Why are you making this change? If it's for fixing a bug, if
possible, please include a code snippet or example project that
demonstrates the issue. -->
[MOBILESDK-2800](https://jira.corp.stripe.com/browse/MOBILESDK-2800)
## Testing
<!-- How was the code tested? Be as specific as possible. -->


https://github.com/user-attachments/assets/e2dd8f48-e23c-4e4a-8732-bb55a98efa80


https://github.com/user-attachments/assets/8a0c25a5-7384-483d-9814-d8f8c70d898f


![test_all_saved_pms_and_apple_pay_and_link_default_badge@3x](https://github.com/user-attachments/assets/a32965f4-4b0f-4b07-a0e9-ce3d078f5e6b)


![test_VerticalSavedPaymentOptionsViewControllerSnapshotTestsDefaultBadge@3x](https://github.com/user-attachments/assets/01605dc3-b2a0-465f-a0a4-cfe641a1b860)

## Changelog
<!-- Is this a notable change that affects users? If so, add a line to
`CHANGELOG.md` and prefix the line with one of the following:
    - [Added] for new features.
    - [Changed] for changes in existing functionality.
    - [Deprecated] for soon-to-be removed features.
    - [Removed] for now removed features.
    - [Fixed] for any bug fixes.
    - [Security] in case of vulnerabilities.
-->

StripePaymentSheet/StripePaymentSheet/Source/Categories/String+Localized.swift

@@ -437,4 +437,11 @@ extension String.Localized {
             "Promotional text for Affirm, displayed in a button that lets the customer pay with Affirm"
         )
     }
+
+    static var default_text: String {
+        STPLocalizedString(
+            "Default",
+            "Label for identifying the default payment method."
+       )
+    }
 }

StripePaymentSheet/StripePaymentSheet/Source/Internal/API Bindings/v1-elements-sessions/ElementsCustomer.swift

@@ -40,13 +40,13 @@ struct ElementsCustomer: Equatable, Hashable {
         return ElementsCustomer(paymentMethods: paymentMethods, defaultPaymentMethod: defaultPaymentMethod, customerSession: customerSession)
     }
 
+    func getDefaultPaymentMethod() -> STPPaymentMethod? {
+        return paymentMethods.first { $0.stripeId == defaultPaymentMethod }
+    }
+
     func getDefaultOrFirstPaymentMethod() -> STPPaymentMethod? {
         // if customer has a default payment method from the elements session, return the default payment method
-        let defaultSavedPaymentMethod = paymentMethods.first { $0.stripeId == defaultPaymentMethod }
-        if let defaultSavedPaymentMethod = defaultSavedPaymentMethod {
-            return defaultSavedPaymentMethod
-        }
         // otherwise, return the first payment method from the customer's list of saved payment methods
-        return paymentMethods.first
+        return getDefaultPaymentMethod() ?? paymentMethods.first
     }
 }

StripePaymentSheet/StripePaymentSheet/Source/Internal/Link/Components/PaymentMethodPicker/LinkPaymentMethodPicker-Cell.swift

@@ -73,7 +73,7 @@ extension LinkPaymentMethodPicker {
 
         private let defaultBadge = LinkBadgeView(
             type: .neutral,
-            text: STPLocalizedString("Default", "Label for identifying the default payment method.")
+            text: String.Localized.default_text
         )
 
         private let alertIconView: UIImageView = {

StripePaymentSheet/StripePaymentSheet/Source/PaymentSheet/Saved Payment Method Screen/SavedPaymentMethodCollectionView.swift

@@ -16,6 +16,7 @@ import UIKit
 // MARK: - Constants
 /// Entire cell size
 private let cellSize: CGSize = CGSize(width: 106, height: 94)
+private let cellSizeWithDefaultBadge: CGSize = CGSize(width: 106, height: 112)
 /// Size of the rounded rectangle that contains the PM logo
 let roundedRectangleSize = CGSize(width: 100, height: 64)
 private let paymentMethodLogoSize: CGSize = CGSize(width: 54, height: 40)
@@ -24,12 +25,13 @@ private let paymentMethodLogoSize: CGSize = CGSize(width: 54, height: 40)
 /// For internal SDK use only
 @objc(STP_Internal_SavedPaymentMethodCollectionView)
 class SavedPaymentMethodCollectionView: UICollectionView {
-    init(appearance: PaymentSheet.Appearance) {
+    init(appearance: PaymentSheet.Appearance, needsVerticalPaddingForBadge: Bool = false) {
         let layout = UICollectionViewFlowLayout()
         layout.scrollDirection = .horizontal
         layout.sectionInset = UIEdgeInsets(
             top: -6, left: PaymentSheetUI.defaultPadding, bottom: 0,
             right: PaymentSheetUI.defaultPadding)
+        self.needsVerticalPaddingForBadge = needsVerticalPaddingForBadge
         layout.itemSize = cellSize
         layout.minimumInteritemSpacing = 12
         layout.minimumLineSpacing = 4
@@ -43,13 +45,23 @@ class SavedPaymentMethodCollectionView: UICollectionView {
     }
 
     var isRemovingPaymentMethods: Bool = false
+    let needsVerticalPaddingForBadge: Bool
 
     required init?(coder: NSCoder) {
         fatalError("init(coder:) has not been implemented")
     }
 
     override var intrinsicContentSize: CGSize {
-        return CGSize(width: UIView.noIntrinsicMetric, height: 100)
+        return needsVerticalPaddingForBadge && isRemovingPaymentMethods ? CGSize(width: UIView.noIntrinsicMetric, height: 118) : CGSize(width: UIView.noIntrinsicMetric, height: 100)
+    }
+
+    func updateLayout() {
+        guard let layout = collectionViewLayout as? UICollectionViewFlowLayout else { return }
+        let newCellSize = needsVerticalPaddingForBadge && isRemovingPaymentMethods ? cellSizeWithDefaultBadge : cellSize
+        guard newCellSize != layout.itemSize else { return }
+        layout.itemSize = newCellSize
+        collectionViewLayout.invalidateLayout()
+        invalidateIntrinsicContentSize()
     }
 }
 
@@ -91,15 +103,38 @@ extension SavedPaymentMethodCollectionView {
             button.accessibilityLabel = String.Localized.edit
             return button
         }()
+        lazy var defaultBadge: UILabel = {
+            let label = UILabel()
+            label.font = appearance.scaledFont(for: appearance.font.base.medium, style: .caption1, maximumPointSize: 20)
+            label.textColor = appearance.colors.textSecondary
+            label.adjustsFontForContentSizeCategory = true
+            label.text = String.Localized.default_text
+            label.isHidden = true
+            return label
+        }()
 
         fileprivate var viewModel: SavedPaymentOptionsViewController.Selection?
 
         var isRemovingPaymentMethods: Bool = false {
             didSet {
+                updateVerticalConstraintsIfNeeded()
                 update()
             }
         }
 
+        func updateVerticalConstraintsIfNeeded() {
+            guard needsVerticalPaddingForBadge else {
+                return
+            }
+            if isRemovingPaymentMethods {
+                activateDefaultBadgeConstraints()
+                defaultBadge.setHiddenIfNecessary(!showDefaultPMBadge)
+            } else {
+                deactivateDefaultBadgeConstraints()
+                defaultBadge.setHiddenIfNecessary(true)
+            }
+        }
+
         weak var delegate: PaymentOptionCellDelegate?
         var appearance = PaymentSheet.Appearance.default {
             didSet {
@@ -110,14 +145,17 @@ extension SavedPaymentMethodCollectionView {
 
         var cbcEligible: Bool = false
         var allowsPaymentMethodRemoval: Bool = true
+        var allowsSetAsDefaultPM: Bool = false
+        var needsVerticalPaddingForBadge: Bool = false
+        var showDefaultPMBadge: Bool = false
 
         /// Indicates whether the cell for a saved payment method should display the edit icon.
-        /// True if payment methods can be removed or edited (will update this to include allowing set as default)
+        /// True if payment methods can be removed or edited
         var showEditIcon: Bool {
             guard UpdatePaymentMethodViewModel.supportedPaymentMethods.contains(where: { viewModel?.savedPaymentMethod?.type == $0 }) else {
                 fatalError("Payment method does not match supported saved payment methods.")
             }
-            return allowsPaymentMethodRemoval || (viewModel?.savedPaymentMethod?.isCoBrandedCard ?? false && cbcEligible)
+            return allowsSetAsDefaultPM || allowsPaymentMethodRemoval || (viewModel?.savedPaymentMethod?.isCoBrandedCard ?? false && cbcEligible)
         }
 
         // MARK: - UICollectionViewCell
@@ -142,7 +180,7 @@ extension SavedPaymentMethodCollectionView {
             paymentMethodLogo.contentMode = .scaleAspectFit
             accessoryButton.addTarget(self, action: #selector(didSelectAccessory), for: .touchUpInside)
             let views = [
-                label, shadowRoundedRectangle, paymentMethodLogo, plus, selectedIcon, accessoryButton,
+                label, shadowRoundedRectangle, paymentMethodLogo, plus, selectedIcon, accessoryButton, defaultBadge
             ]
             views.forEach {
                 $0.translatesAutoresizingMaskIntoConstraints = false
@@ -159,7 +197,7 @@ extension SavedPaymentMethodCollectionView {
 
                 label.topAnchor.constraint(
                     equalTo: shadowRoundedRectangle.bottomAnchor, constant: 4),
-                label.bottomAnchor.constraint(equalTo: contentView.bottomAnchor),
+                labelBottomConstraint,
                 label.leadingAnchor.constraint(equalTo: contentView.leadingAnchor, constant: 2),
                 label.trailingAnchor.constraint(equalTo: contentView.trailingAnchor),
 
@@ -188,6 +226,7 @@ extension SavedPaymentMethodCollectionView {
                     equalTo: contentView.trailingAnchor, constant: 0),
                 accessoryButton.topAnchor.constraint(
                     equalTo: contentView.topAnchor, constant: 0),
+
             ])
         }
 
@@ -208,15 +247,33 @@ extension SavedPaymentMethodCollectionView {
             }
         }
 
-        // MARK: - Internal Methods
+        private lazy var labelBottomConstraint: NSLayoutConstraint = {
+            return label.bottomAnchor.constraint(equalTo: contentView.bottomAnchor)
+        }()
+        private lazy var labelHeightConstraint: NSLayoutConstraint = {
+            return label.heightAnchor.constraint(equalToConstant: 20)
+        }()
+        private lazy var defaultBadgeConstraints: [NSLayoutConstraint] = {
+            return [
+                defaultBadge.topAnchor.constraint(
+                    equalTo: label.bottomAnchor, constant: 4),
+                defaultBadge.bottomAnchor.constraint(equalTo: contentView.bottomAnchor),
+                defaultBadge.leadingAnchor.constraint(equalTo: contentView.leadingAnchor, constant: 2),
+                defaultBadge.trailingAnchor.constraint(equalTo: contentView.trailingAnchor)
+            ]
+        }()
 
-        func setViewModel(_ viewModel: SavedPaymentOptionsViewController.Selection, cbcEligible: Bool, allowsPaymentMethodRemoval: Bool) {
+        // MARK: - Internal Methods
+        func setViewModel(_ viewModel: SavedPaymentOptionsViewController.Selection, cbcEligible: Bool, allowsPaymentMethodRemoval: Bool, allowsSetAsDefaultPM: Bool = false, needsVerticalPaddingForBadge: Bool = false, showDefaultPMBadge: Bool = false) {
             paymentMethodLogo.isHidden = false
             plus.isHidden = true
             shadowRoundedRectangle.isHidden = false
             self.viewModel = viewModel
             self.cbcEligible = cbcEligible
             self.allowsPaymentMethodRemoval = allowsPaymentMethodRemoval
+            self.allowsSetAsDefaultPM = allowsSetAsDefaultPM
+            self.needsVerticalPaddingForBadge = needsVerticalPaddingForBadge
+            self.showDefaultPMBadge = showDefaultPMBadge
             update()
         }
 
@@ -372,6 +429,17 @@ extension SavedPaymentMethodCollectionView {
                 }()
             }
         }
+
+        private func activateDefaultBadgeConstraints() {
+            NSLayoutConstraint.deactivate([labelBottomConstraint])
+            NSLayoutConstraint.activate([labelHeightConstraint] + defaultBadgeConstraints)
+        }
+
+        private func deactivateDefaultBadgeConstraints() {
+            NSLayoutConstraint.deactivate(defaultBadgeConstraints + [labelHeightConstraint])
+            NSLayoutConstraint.activate([labelBottomConstraint])
+        }
+
     }
 
     // A circle with an image in the middle

StripePaymentSheet/StripePaymentSheet/Source/PaymentSheet/Saved Payment Method Screen/SavedPaymentOptionsViewController.swift

@@ -131,6 +131,10 @@ class SavedPaymentOptionsViewController: UIViewController {
         }
         set {
             collectionView.isRemovingPaymentMethods = newValue
+            collectionView.performBatchUpdates({
+                collectionView.reloadSections(IndexSet(integer: 0))
+                animateHeightChange{self.collectionView.updateLayout()}
+            })
             UIView.transition(with: collectionView,
                               duration: 0.3,
                               options: .transitionCrossDissolve,
@@ -147,6 +151,11 @@ class SavedPaymentOptionsViewController: UIViewController {
             }
         }
     }
+
+    var hasDefault: Bool {
+        return viewModels.contains(where: { isDefaultPaymentMethod(savedPaymentMethodId: $0.savedPaymentMethod?.stripeId) })
+    }
+
     var bottomNoticeAttributedString: NSAttributedString? {
         if case .saved(let paymentMethod, _) = selectedPaymentOption {
             if paymentMethod.usBankAccount != nil {
@@ -267,7 +276,7 @@ class SavedPaymentOptionsViewController: UIViewController {
 
     // MARK: - Views
     private lazy var collectionView: SavedPaymentMethodCollectionView = {
-        let collectionView = SavedPaymentMethodCollectionView(appearance: appearance)
+        let collectionView = SavedPaymentMethodCollectionView(appearance: appearance, needsVerticalPaddingForBadge: hasDefault)
         collectionView.delegate = self
         collectionView.dataSource = self
         return collectionView
@@ -439,6 +448,11 @@ class SavedPaymentOptionsViewController: UIViewController {
         collectionView.reloadItems(at: [selectedIndexPath])
     }
 
+    private func isDefaultPaymentMethod(savedPaymentMethodId: String?) -> Bool {
+        guard configuration.allowsSetAsDefaultPM, let savedPaymentMethodId, let defaultPaymentMethod = elementsSession.customer?.getDefaultPaymentMethod() else { return false }
+        return savedPaymentMethodId == defaultPaymentMethod.stripeId
+    }
+
     // MARK: - Helpers
 
     /// Creates the list of viewmodels to display in the "saved payment methods" carousel e.g. `["+ Add", "Apple Pay", "Link", "Visa 4242"]`
@@ -508,7 +522,7 @@ extension SavedPaymentOptionsViewController: UICollectionViewDataSource, UIColle
             stpAssertionFailure()
             return UICollectionViewCell()
         }
-        cell.setViewModel(viewModel, cbcEligible: cbcEligible, allowsPaymentMethodRemoval: self.configuration.allowsRemovalOfPaymentMethods)
+        cell.setViewModel(viewModel, cbcEligible: cbcEligible, allowsPaymentMethodRemoval: self.configuration.allowsRemovalOfPaymentMethods, allowsSetAsDefaultPM: configuration.allowsSetAsDefaultPM, needsVerticalPaddingForBadge: hasDefault, showDefaultPMBadge: isDefaultPaymentMethod(savedPaymentMethodId: viewModel.savedPaymentMethod?.stripeId))
         cell.delegate = self
         cell.isRemovingPaymentMethods = self.collectionView.isRemovingPaymentMethods
         cell.appearance = appearance

StripePaymentSheet/StripePaymentSheet/Source/PaymentSheet/Saved Payment Method Screen/Vertical Saved Payment Method Screen/SavedPaymentMethodRowButton.swift

@@ -47,6 +47,8 @@ final class SavedPaymentMethodRowButton: UIView {
         }
     }
 
+    let showDefaultPMBadge: Bool
+
     private var isEditing: Bool {
         switch state {
         case .selected, .unselected:
@@ -90,15 +92,21 @@ final class SavedPaymentMethodRowButton: UIView {
     }()
 
     private lazy var rowButton: RowButton = {
-        let button: RowButton = .makeForSavedPaymentMethod(paymentMethod: paymentMethod, appearance: appearance, rightAccessoryView: chevronButton, didTap: handleRowButtonTapped)
+        let button: RowButton = .makeForSavedPaymentMethod(paymentMethod: paymentMethod, appearance: appearance, badgeText: badgeText, rightAccessoryView: chevronButton, didTap: handleRowButtonTapped)
 
         return button
     }()
 
+    private lazy var badgeText: String? = {
+        return showDefaultPMBadge ? String.Localized.default_text : nil
+    }()
+
     init(paymentMethod: STPPaymentMethod,
-         appearance: PaymentSheet.Appearance) {
+         appearance: PaymentSheet.Appearance,
+         showDefaultPMBadge: Bool = false) {
         self.paymentMethod = paymentMethod
         self.appearance = appearance
+        self.showDefaultPMBadge = showDefaultPMBadge
         super.init(frame: .zero)
 
         addAndPinSubview(rowButton)

StripePaymentSheet/StripePaymentSheet/Source/PaymentSheet/Saved Payment Method Screen/Vertical Saved Payment Method Screen/VerticalSavedPaymentMethodsViewController.swift

@@ -88,13 +88,13 @@ class VerticalSavedPaymentMethodsViewController: UIViewController {
     }
 
     /// Indicates whether the chevron should be shown
-    /// True if any saved payment methods can be removed or edited (will update this to include allowing set as default)
+    /// True if any saved payment methods can be removed or edited
     var canRemoveOrEdit: Bool {
         let hasSupportedSavedPaymentMethods = paymentMethods.allSatisfy{ UpdatePaymentMethodViewModel.supportedPaymentMethods.contains($0.type) }
         guard hasSupportedSavedPaymentMethods else {
             fatalError("Saved payment methods contain unsupported payment methods.")
         }
-        return canRemovePaymentMethods || canEditPaymentMethods
+        return configuration.allowsSetAsDefaultPM || canRemovePaymentMethods || canEditPaymentMethods
     }
 
     private var selectedPaymentMethod: STPPaymentMethod? {
@@ -174,10 +174,16 @@ class VerticalSavedPaymentMethodsViewController: UIViewController {
         setInitialState(selectedPaymentMethod: selectedPaymentMethod)
     }
 
+    private func isDefaultPaymentMethod(paymentMethodId: String) -> Bool {
+        guard configuration.allowsSetAsDefaultPM, let defaultPaymentMethod = elementsSession.customer?.getDefaultPaymentMethod() else { return false }
+        return configuration.allowsSetAsDefaultPM && paymentMethodId == defaultPaymentMethod.stripeId
+    }
+
     private func buildPaymentMethodRows(paymentMethods: [STPPaymentMethod]) -> [SavedPaymentMethodRowButton] {
         return paymentMethods.map { paymentMethod in
             let button = SavedPaymentMethodRowButton(paymentMethod: paymentMethod,
-                                                     appearance: configuration.appearance)
+                                                     appearance: configuration.appearance,
+                                                     showDefaultPMBadge: isDefaultPaymentMethod(paymentMethodId: paymentMethod.stripeId))
             button.delegate = self
             return button
         }
@@ -363,7 +369,8 @@ extension VerticalSavedPaymentMethodsViewController: UpdatePaymentMethodViewCont
         }
 
         // Create the new button
-        let newButton = SavedPaymentMethodRowButton(paymentMethod: updatedPaymentMethod, appearance: configuration.appearance)
+        let newButton = SavedPaymentMethodRowButton(paymentMethod: updatedPaymentMethod, appearance: configuration.appearance, showDefaultPMBadge: isDefaultPaymentMethod(paymentMethodId: updatedPaymentMethod.stripeId))
+
         newButton.delegate = self
         newButton.previousSelectedState = oldButton.previousSelectedState
         newButton.state = oldButton.state