[In-app Purchases] Improve transaction handling logic

Networking/Networking/Model/WordPressApiError.swift

@@ -8,6 +8,10 @@ public enum WordPressApiError: Error, Decodable, Equatable {
     ///
     case unknown(code: String, message: String)
 
+    /// An order already exists for this IAP receipt
+    ///
+    case productPurchased
+
     /// Decodable Initializer.
     ///
     public init(from decoder: Decoder) throws {
@@ -16,6 +20,8 @@ public enum WordPressApiError: Error, Decodable, Equatable {
         let message = try container.decode(String.self, forKey: .message)
 
         switch code {
+        case Constants.productPurchased:
+            self = .productPurchased
         default:
             self = .unknown(code: code, message: message)
         }
@@ -25,6 +31,7 @@ public enum WordPressApiError: Error, Decodable, Equatable {
     /// Constants for Possible Error Identifiers
     ///
     private enum Constants {
+        static let productPurchased = "product_purchased"
     }
 
     /// Coding Keys
@@ -50,6 +57,10 @@ extension WordPressApiError: CustomStringConvertible {
 
     public var description: String {
         switch self {
+        case .productPurchased:
+            return NSLocalizedString(
+                "An order aready exists for this receipt",
+                comment: "Error message when an order already exists in the backend for a given receipt")
         case .unknown(let code, let message):
             let messageFormat = NSLocalizedString(
                 "WordPress API Error: [%1$@] %2$@",
@@ -59,3 +70,11 @@ extension WordPressApiError: CustomStringConvertible {
         }
     }
 }
+
+// MARK: - LocalizedError Conformance
+//
+extension WordPressApiError: LocalizedError {
+    public var errorDescription: String? {
+        description
+    }
+}

Yosemite/Yosemite/Stores/InAppPurchaseStore.swift

@@ -1,3 +1,4 @@
+import Combine
 import Foundation
 import Storage
 import StoreKit
@@ -9,6 +10,7 @@ public class InAppPurchaseStore: Store {
     private var listenTask: Task<Void, Error>?
     private let remote: InAppPurchasesRemote
     private var useBackend = true
+    private var pauseTransactionListener = CurrentValueSubject<Bool, Never>(false)
 
     public override init(dispatcher: Dispatcher, storageManager: StorageManagerType, network: Network) {
         remote = InAppPurchasesRemote(network: network)
@@ -93,6 +95,12 @@ private extension InAppPurchaseStore {
 
 
                 logInfo("Purchasing product \(product.id) for site \(siteID) with options \(purchaseOptions)")
+                logInfo("Pausing transaction listener")
+                pauseTransactionListener.send(true)
+                defer {
+                    logInfo("Resuming transaction listener")
+                    pauseTransactionListener.send(false)
+                }
                 let purchaseResult = try await product.purchase(options: purchaseOptions)
                 switch purchaseResult {
                 case .success(let result):
@@ -193,15 +201,22 @@ private extension InAppPurchaseStore {
         let receiptData = try await getAppReceipt()
 
         logInfo("Sending transaction to API for site \(siteID)")
-        let orderID = try await remote.createOrder(
-            for: siteID,
-            price: priceInCents,
-            productIdentifier: product.id,
-            appStoreCountryCode: countryCode,
-            receiptData: receiptData
-        )
-        logInfo("Successfully registered purchase with Order ID \(orderID)")
-
+        do {
+            let orderID = try await remote.createOrder(
+                for: siteID,
+                price: priceInCents,
+                productIdentifier: product.id,
+                appStoreCountryCode: countryCode,
+                receiptData: receiptData
+            )
+            logInfo("Successfully registered purchase with Order ID \(orderID)")
+        } catch WordPressApiError.productPurchased {
+            // Ignore errors for existing purchase
+            logInfo("Existing order found for transaction \(transaction.id) on site \(siteID), ignoring")
+        } catch {
+            // Rethrow any other error
+            throw error
+        }
     }
 
     func userIsEntitledToProduct(with id: String) async throws -> Bool {
@@ -251,11 +266,16 @@ private extension InAppPurchaseStore {
         assert(listenTask == nil, "InAppPurchaseStore.listenForTransactions() called while already listening for transactions")
 
         listenTask = Task.detached { [weak self] in
+            guard let self else {
+                return
+            }
             for await result in Transaction.updates {
                 do {
-                    try await self?.handleCompletedTransaction(result)
+                    // Wait until the purchase finishes
+                    _ = await self.pauseTransactionListener.values.contains(false)
+                    try await self.handleCompletedTransaction(result)
                 } catch {
-                    self?.logError("Error handling transaction update: \(error)")
+                    self.logError("Error handling transaction update: \(error)")
                 }
             }
         }