refactor: Use OpenIapSerialization for all type conversions

- Replace manual JSON encoding with OpenIapSerialization helper
- Use OpenIapSerialization.products() for product serialization
- Use OpenIapSerialization.purchases() for purchase serialization
- Use OpenIapSerialization.encode() for single objects
- Consistent and cleaner serialization across all @objc methods
- Proper handling of Product/Purchase enum cases

Author: hyochan

Sources/OpenIapModule+ObjC.swift

@@ -43,27 +43,11 @@ import StoreKit
                 let request = ProductRequest(skus: skus, type: productType)
                 let result = try await fetchProducts(request)
 
-                let encoder = JSONEncoder()
-                encoder.dateEncodingStrategy = .millisecondsSince1970
-
-                switch result {
-                case .products(let products):
-                    // Cast to concrete type ProductIOS and convert to dictionaries
-                    let productIOS = products?.compactMap { $0 as? ProductIOS }
-                    let dictionaries = try productIOS?.compactMap { product -> [String: Any]? in
-                        let jsonData = try encoder.encode(product)
-                        return try JSONSerialization.jsonObject(with: jsonData) as? [String: Any]
-                    }
-                    completion(dictionaries, nil)
-                case .subscriptions(let subscriptions):
-                    // Cast to concrete type ProductSubscriptionIOS and convert to dictionaries
-                    let subscriptionIOS = subscriptions?.compactMap { $0 as? ProductSubscriptionIOS }
-                    let dictionaries = try subscriptionIOS?.compactMap { subscription -> [String: Any]? in
-                        let jsonData = try encoder.encode(subscription)
-                        return try JSONSerialization.jsonObject(with: jsonData) as? [String: Any]
-                    }
-                    completion(dictionaries, nil)
+                // Use OpenIapSerialization to convert products to dictionaries
+                let dictionaries = OpenIapSerialization.products(result) { message in
+                    print("[OpenIAP] \(message)")
                 }
+                completion(dictionaries, nil)
             } catch {
                 completion(nil, error)
             }
@@ -74,7 +58,13 @@ import StoreKit
         Task {
             do {
                 let product = try await getPromotedProductIOS()
-                completion(product as Any?, nil)
+                if let productIOS = product {
+                    // Convert ProductIOS to dictionary
+                    let dictionary = OpenIapSerialization.encode(productIOS)
+                    completion(dictionary, nil)
+                } else {
+                    completion(nil, nil)
+                }
             } catch {
                 completion(nil, error)
             }
@@ -110,9 +100,15 @@ import StoreKit
 
                 switch result {
                 case .purchase(let purchase):
-                    completion(purchase as Any, nil)
+                    let dictionary = OpenIapSerialization.purchase(purchase)
+                    completion(dictionary, nil)
                 case .purchases(let purchases):
-                    completion(purchases?.first as Any, nil)
+                    if let firstPurchase = purchases?.first {
+                        let dictionary = OpenIapSerialization.purchase(firstPurchase)
+                        completion(dictionary, nil)
+                    } else {
+                        completion(nil, nil)
+                    }
                 case .none:
                     completion(nil, nil)
                 }
@@ -137,7 +133,8 @@ import StoreKit
         Task {
             do {
                 let purchases = try await getAvailablePurchases(nil)
-                completion(purchases as [Any], nil)
+                let dictionaries = OpenIapSerialization.purchases(purchases)
+                completion(dictionaries, nil)
             } catch {
                 completion(nil, error)
             }
@@ -177,7 +174,8 @@ import StoreKit
         Task {
             do {
                 let transactions = try await getPendingTransactionsIOS()
-                completion(transactions as [Any], nil)
+                let dictionaries = OpenIapSerialization.purchases(transactions)
+                completion(dictionaries, nil)
             } catch {
                 completion(nil, error)
             }
@@ -227,7 +225,8 @@ import StoreKit
         Task {
             do {
                 let subscriptions = try await getActiveSubscriptions(nil)
-                completion(subscriptions as [Any], nil)
+                let dictionaries = subscriptions.map { OpenIapSerialization.encode($0) }
+                completion(dictionaries, nil)
             } catch {
                 completion(nil, error)
             }
@@ -251,7 +250,8 @@ import StoreKit
         Task {
             do {
                 let purchases = try await showManageSubscriptionsIOS()
-                completion(purchases as [Any], nil)
+                let dictionaries = OpenIapSerialization.purchases(purchases)
+                completion(dictionaries, nil)
             } catch {
                 completion(nil, error)
             }