iap: move StoreKit logic out of DamusPurpleView and into a new PurpleStoreKitManager

This commit moves most of StoreKit-specific logic that was embedded into
DamusPurpleView and places it into a new PurpleStoreKitManager struct,
to make code more reusable and readable by separating view concerns from
StoreKit-specific concerns.

Most of the code here should be in feature parity with the previous
behavior. However, a few logical improvements were made alongside this
refactoring:

- Improved StoreKit transaction update monitoring logic: Previously the
  view would stop listening for purchase updates after the first update.
  However, I made the program continuously listen for purchase updates,
  as recommended by Apple's documentation
  (https://developer.apple.com/documentation/storekit/transaction/3851206-updates)

- Improved/simplified logic around getting extra information from the
  products: Information and the handling of product information was
  spread in a few separate places. I incorporated those bits of
  information into central and uniform interfaces on DamusPurpleType, to
  simplify logic and future changes.

Signed-off-by: Daniel D’Aquino <daniel@daquino.me>
Reviewed-by: William Casarin <jb55@jb55.com>
Signed-off-by: William Casarin <jb55@jb55.com>

damus.xcodeproj/project.pbxproj

@@ -442,6 +442,7 @@
 		D7100C582B76FC8400C59298 /* MarketingContentView.swift in Sources */ = {isa = PBXBuildFile; fileRef = D7100C572B76FC8400C59298 /* MarketingContentView.swift */; };
 		D7100C5A2B76FD5100C59298 /* LogoView.swift in Sources */ = {isa = PBXBuildFile; fileRef = D7100C592B76FD5100C59298 /* LogoView.swift */; };
 		D7100C5C2B77016700C59298 /* IAPProductStateView.swift in Sources */ = {isa = PBXBuildFile; fileRef = D7100C5B2B77016700C59298 /* IAPProductStateView.swift */; };
+		D7100C5E2B7709ED00C59298 /* PurpleStoreKitManager.swift in Sources */ = {isa = PBXBuildFile; fileRef = D7100C5D2B7709ED00C59298 /* PurpleStoreKitManager.swift */; };
 		D71DC1EC2A9129C3006E207C /* PostViewTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = D71DC1EB2A9129C3006E207C /* PostViewTests.swift */; };
 		D72341192B6864F200E1E135 /* DamusPurpleEnvironment.swift in Sources */ = {isa = PBXBuildFile; fileRef = D72341182B6864F200E1E135 /* DamusPurpleEnvironment.swift */; };
 		D723411A2B6864F200E1E135 /* DamusPurpleEnvironment.swift in Sources */ = {isa = PBXBuildFile; fileRef = D72341182B6864F200E1E135 /* DamusPurpleEnvironment.swift */; };
@@ -1344,6 +1345,7 @@
 		D7100C572B76FC8400C59298 /* MarketingContentView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MarketingContentView.swift; sourceTree = "<group>"; };
 		D7100C592B76FD5100C59298 /* LogoView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = LogoView.swift; sourceTree = "<group>"; };
 		D7100C5B2B77016700C59298 /* IAPProductStateView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = IAPProductStateView.swift; sourceTree = "<group>"; };
+		D7100C5D2B7709ED00C59298 /* PurpleStoreKitManager.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = PurpleStoreKitManager.swift; sourceTree = "<group>"; };
 		D71DC1EB2A9129C3006E207C /* PostViewTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = PostViewTests.swift; sourceTree = "<group>"; };
 		D72341182B6864F200E1E135 /* DamusPurpleEnvironment.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = DamusPurpleEnvironment.swift; sourceTree = "<group>"; };
 		D723C38D2AB8D83400065664 /* ContentFilters.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ContentFilters.swift; sourceTree = "<group>"; };
@@ -2670,6 +2672,7 @@
 				D74F430B2B23FB9B00425B75 /* StoreObserver.swift */,
 				D7ADD3DD2B53854300F104C4 /* DamusPurpleURL.swift */,
 				D72341182B6864F200E1E135 /* DamusPurpleEnvironment.swift */,
+				D7100C5D2B7709ED00C59298 /* PurpleStoreKitManager.swift */,
 			);
 			path = Purple;
 			sourceTree = "<group>";
@@ -3370,6 +3373,7 @@
 				3AA247FF297E3D900090C62D /* RepostsView.swift in Sources */,
 				3AE45AF6297BB2E700C1D842 /* LibreTranslateServer.swift in Sources */,
 				4C5D5C9A2A6AF8F80024563C /* NdbTagIterator.swift in Sources */,
+				D7100C5E2B7709ED00C59298 /* PurpleStoreKitManager.swift in Sources */,
 				4CE879502996B2BD00F758CC /* RelayStatusView.swift in Sources */,
 				4CC7AAF4297F18B400430951 /* ReplyDescription.swift in Sources */,
 				4C75EFA427FA577B0006080F /* PostView.swift in Sources */,

damus/Models/Purple/DamusPurple.swift

@@ -6,10 +6,12 @@
 //
 
 import Foundation
+import StoreKit
 
 class DamusPurple: StoreObserverDelegate {
     let settings: UserSettingsStore
     let keypair: Keypair
+    var storekit_manager: StoreKitManager
 
     @MainActor
     var account_cache: [Pubkey: Account]
@@ -18,6 +20,7 @@ class DamusPurple: StoreObserverDelegate {
         self.settings = settings
         self.keypair = keypair
         self.account_cache = [:]
+        self.storekit_manager = .init()
     }
     
     // MARK: Functions
@@ -123,6 +126,10 @@ class DamusPurple: StoreObserverDelegate {
         try await self.create_account(pubkey: pubkey)
     }
     
+    func make_iap_purchase(product: Product) async throws -> Product.PurchaseResult {
+        return try await self.storekit_manager.purchase(product: product)
+    }
+    
     func send_receipt() async {
         // Get the receipt if it's available.
         if let appStoreReceiptURL = Bundle.main.appStoreReceiptURL,

damus/Models/Purple/PurpleStoreKitManager.swift

@@ -0,0 +1,86 @@
+//
+//  PurpleStoreKitManager.swift
+//  damus
+//
+//  Created by Daniel D’Aquino on 2024-02-09.
+//
+
+import Foundation
+import StoreKit
+
+extension DamusPurple {
+    struct StoreKitManager {
+        var delegate: DamusPurpleStoreKitManagerDelegate? = nil
+        
+        struct PurchasedProduct {
+            let tx: StoreKit.Transaction
+            let product: Product
+        }
+        
+        init() {
+            self.start()
+        }
+        
+        func start() {
+            Task {
+                try await monitor_updates()
+            }
+        }
+        
+        func get_products() async throws -> [Product] {
+            return try await Product.products(for: DamusPurpleType.allCases.map({ $0.rawValue }))
+        }
+        
+        private func monitor_updates() async throws {
+            for await update in StoreKit.Transaction.updates {
+                switch update {
+                    case .verified(let tx):
+                        let products = try await self.get_products()
+                        let prod = products.filter({ prod in tx.productID == prod.id }).first
+                        
+                        if let prod,
+                           let expiration = tx.expirationDate,
+                           Date.now < expiration
+                        {
+                            self.delegate?.product_was_purchased(product: PurchasedProduct(tx: tx, product: prod))
+                        }
+                    case .unverified:
+                        continue
+                }
+            }
+        }
+        
+        func purchase(product: Product) async throws -> Product.PurchaseResult {
+            return try await product.purchase(options: [])
+        }
+    }
+}
+
+extension DamusPurple.StoreKitManager {
+    enum DamusPurpleType: String, CaseIterable {
+        case yearly = "purpleyearly"
+        case monthly = "purple"
+        
+        func non_discounted_price(product: Product) -> String? {
+            switch self {
+                case .yearly:
+                    return (product.price * 1.1984569224).formatted(product.priceFormatStyle)
+                case .monthly:
+                    return nil
+            }
+        }
+        
+        func label() -> String {
+            switch self {
+                case .yearly:
+                    return NSLocalizedString("Annually", comment: "Annual renewal of purple subscription")
+                case .monthly:
+                    return NSLocalizedString("Monthly", comment: "Monthly renewal of purple subscription")
+            }
+        }
+    }
+}
+
+protocol DamusPurpleStoreKitManagerDelegate {
+    func product_was_purchased(product: DamusPurple.StoreKitManager.PurchasedProduct)
+}

damus/Views/Purple/DamusPurpleView.swift

@@ -8,8 +8,6 @@
 import SwiftUI
 import StoreKit
 
-fileprivate let damus_products = ["purpleyearly","purple"]
-
 // MARK: - Helper structures
 
 enum AccountInfoState {
@@ -19,25 +17,16 @@ enum AccountInfoState {
     case error(message: String)
 }
 
-func non_discounted_price(_ product: Product) -> String {
-    return (product.price * 1.1984569224).formatted(product.priceFormatStyle)
-}
-
-enum DamusPurpleType: String {
-    case yearly = "purpleyearly"
-    case monthly = "purple"
-}
-
 // MARK: - Main view
 
-struct DamusPurpleView: View {
+struct DamusPurpleView: View, DamusPurpleStoreKitManagerDelegate {
     let damus_state: DamusState
     let keypair: Keypair
     
     @State var my_account_info_state: AccountInfoState = .loading
     @State var products: ProductState
     @State var purchased: PurchasedProduct? = nil
-    @State var selection: DamusPurpleType = .yearly
+    @State var selection: DamusPurple.StoreKitManager.DamusPurpleType = .yearly
     @State var show_welcome_sheet: Bool = false
     @State var show_manage_subscriptions = false
     @State private var shouldDismissView = false
@@ -48,6 +37,7 @@ struct DamusPurpleView: View {
         self._products = State(wrappedValue: .loading)
         self.damus_state = damus_state
         self.keypair = damus_state.keypair
+        damus_state.purple.storekit_manager.delegate = self
     }
     
     // MARK: - Top level view
@@ -159,30 +149,10 @@ struct DamusPurpleView: View {
         }
     }
     
-    func handle_transactions(products: [Product]) async {
-        for await update in StoreKit.Transaction.updates {
-            switch update {
-                case .verified(let tx):
-                    let prod = products.filter({ prod in tx.productID == prod.id }).first
-                    
-                    if let prod,
-                       let expiration = tx.expirationDate,
-                       Date.now < expiration
-                    {
-                        self.purchased = PurchasedProduct(tx: tx, product: prod)
-                        break
-                    }
-                case .unverified:
-                    continue
-            }
-        }
-    }
-    
     func load_products() async {
         do {
-            let products = try await Product.products(for: damus_products)
+            let products = try await self.damus_state.purple.storekit_manager.get_products()
             self.products = .loaded(products)
-            await handle_transactions(products: products)
 
             print("loaded products", products)
         } catch {
@@ -191,8 +161,13 @@ struct DamusPurpleView: View {
         }
     }
     
+    // For DamusPurple.StoreKitManager.Delegate conformance. This gets called by the StoreKitManager when a new product was purchased
+    func product_was_purchased(product: DamusPurple.StoreKitManager.PurchasedProduct) {
+        self.purchased = product
+    }
+    
     func subscribe(_ product: Product) async throws {
-        let result = try await product.purchase()
+        let result = try await self.damus_state.purple.make_iap_purchase(product: product)
         switch result {
             case .success(.verified(let tx)):
                 print("success \(tx.debugDescription)")
@@ -219,12 +194,6 @@ struct DamusPurpleView: View {
                 break
         }
     }
-    
-    var product: Product? {
-        return self.products.products?.filter({
-            prod in prod.id == selection.rawValue
-        }).first
-    }
 }
 
 struct DamusPurpleView_Previews: PreviewProvider {

damus/Views/Purple/Detail/IAPProductStateView.swift

@@ -11,6 +11,8 @@ import StoreKit
 // MARK: - IAPProductStateView
 
 extension DamusPurpleView {
+    typealias PurchasedProduct = DamusPurple.StoreKitManager.PurchasedProduct
+    
     struct IAPProductStateView: View {
         let products: ProductState
         let purchased: PurchasedProduct?
@@ -82,28 +84,20 @@ extension DamusPurpleView {
         }
         
         func price_description(product: Product) -> some View {
-            if product.id == "purpleyearly" {
+            let purple_type = DamusPurple.StoreKitManager.DamusPurpleType(rawValue: product.id)
-                return (
+            return (
-                    AnyView(
+                HStack(spacing: 10) {
-                        HStack(spacing: 10) {
+                    Text(purple_type?.label() ?? product.displayName)
-                            Text(NSLocalizedString("Annually", comment: "Annual renewal of purple subscription"))
+                    Spacer()
-                            Spacer()
+                    if let non_discounted_price = purple_type?.non_discounted_price(product: product) {
-                            Text(verbatim: non_discounted_price(product)).strikethrough().foregroundColor(DamusColors.white.opacity(0.5))
+                        Text(verbatim: non_discounted_price)
-                            Text(verbatim: product.displayPrice).fontWeight(.bold)
+                            .strikethrough()
-                        }
+                            .foregroundColor(DamusColors.white.opacity(0.5))
-                    )
+                    }
-                )
+                    Text(verbatim: product.displayPrice)
-            } else {
+                        .fontWeight(.bold)
-                return (
+                }
-                    AnyView(
+            )
-                        HStack(spacing: 10) {
-                            Text(NSLocalizedString("Monthly", comment: "Monthly renewal of purple subscription"))
-                            Spacer()
-                            Text(verbatim: product.displayPrice).fontWeight(.bold)
-                        }
-                    )
-                )
-            }
         }
     }
 }
@@ -127,11 +121,6 @@ extension DamusPurpleView {
             }
         }
     }
-    
-    struct PurchasedProduct {
-        let tx: StoreKit.Transaction
-        let product: Product
-    }
 }
 
 #Preview {