[in_app_purchase] Implementation of platform interface

packages/in_app_purchase/in_app_purchase_platform_interface/CHANGELOG.md

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+## 1.0.0
+
+* Initial open-source release.

packages/in_app_purchase/in_app_purchase_platform_interface/LICENSE

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+Copyright 2013 The Flutter Authors. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without modification,
+are permitted provided that the following conditions are met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+    * Redistributions in binary form must reproduce the above
+      copyright notice, this list of conditions and the following
+      disclaimer in the documentation and/or other materials provided
+      with the distribution.
+    * Neither the name of Google Inc. nor the names of its
+      contributors may be used to endorse or promote products derived
+      from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
+ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

packages/in_app_purchase/in_app_purchase_platform_interface/README.md

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+# in_app_purchase_platform_interface
+
+A common platform interface for the [`in_app_purchase`][1] plugin.
+
+This interface allows platform-specific implementations of the `in_app_purchase`
+plugin, as well as the plugin itself, to ensure they are supporting the
+same interface.
+
+# Usage
+
+To implement a new platform-specific implementation of `in_app_purchase`, extend
+[`InAppPurchasePlatform`][2] with an implementation that performs the
+platform-specific behavior, and when you register your plugin, set the default
+`InAppPurchasePlatform` by calling
+`InAppPurchasePlatform.setInstance(MyPlatformInAppPurchase())`.
+
+To implement functionality that is specific to the platform and is not covered 
+by the [`InAppPurchasePlatform`][2] idiomatic API, extend 
+[`InAppPurchasePlatformAddition`][3] with the platform-specific functionality, 
+and when the plugin is registered, set the addition instance by calling
+`InAppPurchasePlatformAddition.instance = MyPlatformInAppPurchaseAddition()`.
+
+# Note on breaking changes
+
+Strongly prefer non-breaking changes (such as adding a method to the interface)
+over breaking changes for this package.
+
+See https://flutter.dev/go/platform-interface-breaking-changes for a discussion
+on why a less-clean interface is preferable to a breaking change.
+
+[1]: ../in_app_purchase
+[2]: lib/in_app_purchase_platform_interface.dart
+[3]: lib/in_app_purchase_platform_addition.dart

packages/in_app_purchase/in_app_purchase_platform_interface/lib/in_app_purchase_platform_interface.dart

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+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+export 'src/in_app_purchase_platform.dart';
+export 'src/in_app_purchase_platform_addition.dart';
+export 'src/in_app_purchase_platform_addition_provider.dart';
+export 'src/types/types.dart';

packages/in_app_purchase/in_app_purchase_platform_interface/lib/src/in_app_purchase_platform.dart

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+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:async';
+
+import 'package:plugin_platform_interface/plugin_platform_interface.dart';
+
+import 'types/types.dart';
+
+/// The interface that implementations of in_app_purchase must implement.
+///
+/// Platform implementations should extend this class rather than implement it as `in_app_purchase`
+/// does not consider newly added methods to be breaking changes. Extending this class
+/// (using `extends`) ensures that the subclass will get the default implementation, while
+/// platform implementations that `implements` this interface will be broken by newly added
+/// [InAppPurchasePlatform] methods.
+abstract class InAppPurchasePlatform extends PlatformInterface {
+  /// Constructs a InAppPurchasePlatform.
+  InAppPurchasePlatform() : super(token: _token);
+
+  static final Object _token = Object();
+
+  /// The instance of [InAppPurchasePlatform] to use.
+  ///
+  /// Defaults to `null`.
+  static InAppPurchasePlatform? get instance => _instance;
+
+  static InAppPurchasePlatform? _instance;
+
+  /// Platform-specific plugins should set this with their own platform-specific
+  /// class that extends [InAppPurchasePlatform] when they register themselves.
+  // TODO(amirh): Extract common platform interface logic.
+  // https://github.com/flutter/flutter/issues/43368
+  static void setInstance(InAppPurchasePlatform instance) {
+    PlatformInterface.verifyToken(instance, _token);
+    _instance = instance;
+  }
+
+  /// Listen to this broadcast stream to get real time update for purchases.
+  ///
+  /// This stream will never close as long as the app is active.
+  ///
+  /// Purchase updates can happen in several situations:
+  /// * When a purchase is triggered by user in the app.
+  /// * When a purchase is triggered by user from the platform specific store front.
+  /// * When a purchase is restored on the device by the user in the app.
+  /// * If a purchase is not completed ([completePurchase] is not called on the
+  ///   purchase object) from the last app session. Purchase updates will happen
+  ///   when a new app session starts instead.
+  ///
+  /// IMPORTANT! You must subscribe to this stream as soon as your app launches,
+  /// preferably before returning your main App Widget in main(). Otherwise you
+  /// will miss purchase updated made before this stream is subscribed to.
+  ///
+  /// We also recommend listening to the stream with one subscription at a given
+  /// time. If you choose to have multiple subscription at the same time, you
+  /// should be careful at the fact that each subscription will receive all the
+  /// events after they start to listen.
+  Stream<List<PurchaseDetails>> get purchaseStream =>
+      throw UnimplementedError('purchaseStream has not been implemented.');
+
+  /// Returns `true` if the payment platform is ready and available.
+  Future<bool> isAvailable() =>
+      throw UnimplementedError('isAvailable() has not been implemented.');
+
+  /// Query product details for the given set of IDs.
+  ///
+  /// Identifiers in the underlying payment platform, for example, [App Store
+  /// Connect](https://appstoreconnect.apple.com/) for iOS and [Google Play
+  /// Console](https://play.google.com/) for Android.
+  Future<ProductDetailsResponse> queryProductDetails(Set<String> identifiers) =>
+      throw UnimplementedError(
+          'queryProductDetails() had not been implemented.');
+
+  /// Buy a non consumable product or subscription.
+  ///
+  /// Non consumable items can only be bought once. For example, a purchase that
+  /// unlocks a special content in your app. Subscriptions are also non
+  /// consumable products.
+  ///
+  /// You always need to restore all the non consumable products for user when
+  /// they switch their phones.
+  ///
+  /// This method does not return the result of the purchase. Instead, after
+  /// triggering this method, purchase updates will be sent to
+  /// [purchaseStream]. You should [Stream.listen] to [purchaseStream] to get
+  /// [PurchaseDetails] objects in different [PurchaseDetails.status] and update
+  ///  your UI accordingly. When the [PurchaseDetails.status] is
+  /// [PurchaseStatus.purchased], [PurchaseStatus.restored] or
+  /// [PurchaseStatus.error] you should deliver the content or handle the error,
+  /// then call [completePurchase] to finish the purchasing process.
+  ///
+  /// This method does return whether or not the purchase request was initially
+  /// sent successfully.
+  ///
+  /// Consumable items are defined differently by the different underlying
+  /// payment platforms, and there's no way to query for whether or not the
+  /// [ProductDetail] is a consumable at runtime.
+  ///
+  /// See also:
+  ///
+  ///  * [buyConsumable], for buying a consumable product.
+  ///  * [restorePurchases], for restoring non consumable products.
+  ///
+  /// Calling this method for consumable items will cause unwanted behaviors!
+  Future<bool> buyNonConsumable({required PurchaseParam purchaseParam}) =>
+      throw UnimplementedError('buyNonConsumable() has not been implemented.');
+
+  /// Buy a consumable product.
+  ///
+  /// Consumable items can be "consumed" to mark that they've been used and then
+  /// bought additional times. For example, a health potion.
+  ///
+  /// To restore consumable purchases across devices, you should keep track of
+  /// those purchase on your own server and restore the purchase for your users.
+  /// Consumed products are no longer considered to be "owned" by payment
+  /// platforms and will not be delivered by calling [restorePurchases].
+  ///
+  /// Consumable items are defined differently by the different underlying
+  /// payment platforms, and there's no way to query for whether or not the
+  /// [ProductDetail] is a consumable at runtime.
+  ///
+  /// `autoConsume` is provided as a utility and will instruct the plugin to
+  /// automatically consume the product after a succesful purchase.
+  /// `autoConsume` is `true` by default.
+  ///
+  /// This method does not return the result of the purchase. Instead, after
+  /// triggering this method, purchase updates will be sent to
+  /// [purchaseStream]. You should [Stream.listen] to
+  /// [purchaseStream] to get [PurchaseDetails] objects in different
+  /// [PurchaseDetails.status] and update your UI accordingly. When the
+  /// [PurchaseDetails.status] is [PurchaseStatus.purchased] or
+  /// [PurchaseStatus.error], you should deliver the content or handle the
+  /// error, then call [completePurchase] to finish the purchasing process.
+  ///
+  /// This method does return whether or not the purchase request was initially
+  /// sent succesfully.
+  ///
+  /// See also:
+  ///
+  ///  * [buyNonConsumable], for buying a non consumable product or
+  ///    subscription.
+  ///  * [restorePurchases], for restoring non consumable products.
+  ///
+  /// Calling this method for non consumable items will cause unwanted
+  /// behaviors!
+  Future<bool> buyConsumable({
+    required PurchaseParam purchaseParam,
+    bool autoConsume = true,
+  }) =>
+      throw UnimplementedError('buyConsumable() has not been implemented.');
+
+  /// Mark that purchased content has been delivered to the user.
+  ///
+  /// You are responsible for completing every [PurchaseDetails] whose
+  /// [PurchaseDetails.status] is [PurchaseStatus.purchased] or
+  /// [PurchaseStatus.restored].
+  /// Completing a [PurchaseStatus.pending] purchase will cause an exception.
+  /// For convenience, [PurchaseDetails.pendingCompletePurchase] indicates if a
+  /// purchase is pending for completion.
+  ///
+  /// The method will throw a [PurchaseException] when the purchase could not be
+  /// finished. Depending on the [PurchaseException.errorCode] the developer
+  /// should try to complete the purchase via this method again, or retry the
+  /// [completePurchase] method at a later time. If the
+  /// [PurchaseException.errorCode] indicates you should not retry there might
+  /// be some issue with the app's code or the configuration of the app in the
+  /// respective store. The developer is responsible to fix this issue. The
+  /// [PurchaseException.message] field might provide more information on what
+  /// went wrong.
+  Future<void> completePurchase(PurchaseDetails purchase) =>
+      throw UnimplementedError('completePurchase() has not been implemented.');
+
+  /// Restore all previous purchases.
+  ///
+  /// The `applicationUserName` should match whatever was sent in the initial
+  /// `PurchaseParam`, if anything. If no `applicationUserName` was specified in the initial
+  /// `PurchaseParam`, use `null`.
+  ///
+  /// Restored purchases are delivered through the [purchaseStream] with a
+  /// status of [PurchaseStatus.restored]. You should listen for these purchases,
+  /// validate their receipts, deliver the content and mark the purchase complete
+  /// by calling the [finishPurchase] method for each purchase.
+  ///
+  /// This does not return consumed products. If you want to restore unused
+  /// consumable products, you need to persist consumable product information
+  /// for your user on your own server.
+  ///
+  /// See also:
+  ///
+  ///  * [refreshPurchaseVerificationData], for reloading failed
+  ///    [PurchaseDetails.verificationData].
+  Future<void> restorePurchases({String? applicationUserName}) =>
+      throw UnimplementedError('restorePurchases() has not been implemented.');
+}

packages/in_app_purchase/in_app_purchase_platform_interface/lib/src/in_app_purchase_platform_addition.dart

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+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// ignore: avoid_classes_with_only_static_members
+/// The interface that platform implementations must implement when they want to
+/// provide platform specific in_app_purchase features.
+abstract class InAppPurchasePlatformAddition {
+  /// The instance containing the platform-specific in_app_purchase
+  /// functionality.
+  ///
+  /// To implement additional functionality extend
+  /// [`InAppPurchasePlatformAddition`][3] with the platform-specific
+  /// functionality, and when the plugin is registered, set the
+  /// `InAppPurchasePlatformAddition.instance` with the new addition
+  /// implementationinstance.
+  ///
+  /// Example implementation might look like this:
+  /// ```dart
+  /// class InAppPurchaseMyPlatformAddition extends InAppPurchasePlatformAddition {
+  ///   Future<void> myPlatformMethod() {}
+  /// }
+  /// ```
+  ///
+  /// The following snippit shows how to register the `InAppPurchaseMyPlatformAddition`:
+  /// ```dart
+  /// class InAppPurchaseMyPlatformPlugin {
+  ///   static void registerWith(Registrar registrar) {
+  ///     // Register the platform-specific implementation of the idiomatic
+  ///     // InAppPurchase API.
+  ///     InAppPurchasePlatform.instance = InAppPurchaseMyPlatformPlugin();
+  ///
+  ///     // Register the [InAppPurchaseMyPlatformAddition] containing the
+  ///     // platform-specific functionality.
+  ///     InAppPurchasePlatformAddition.instance = InAppPurchaseMyPlatformAddition();
+  ///   }
+  /// }
+  /// ```
+  static InAppPurchasePlatformAddition? instance;
+}

packages/in_app_purchase/in_app_purchase_platform_interface/lib/src/in_app_purchase_platform_addition_provider.dart

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+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:in_app_purchase_platform_interface/src/in_app_purchase_platform_addition.dart';
+
+/// The [InAppPurchasePlatformAdditionProvider] is responsible for providing
+/// a platform specific [InAppPurchasePlatformAddition].
+///
+/// [InAppPurchasePlatformAddition] implementation contain platform specific
+/// features that are not available from the platform idiomatic
+/// [InAppPurchasePlatform] API.
+abstract class InAppPurchasePlatformAdditionProvider {
+  /// Provides a platform specific implementation of the [InAppPurchasePlatformAddition]
+  /// class.
+  T getPlatformAddition<T extends InAppPurchasePlatformAddition>();
+}

packages/in_app_purchase/in_app_purchase_platform_interface/lib/src/types/in_app_purchase_error.dart

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+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+/// Captures an error from the underlying purchase platform.
+///
+/// The error can happen during the purchase, restoring a purchase, or querying product.
+/// Errors from restoring a purchase are not indicative of any errors during the original purchase.
+/// See also:
+/// * [ProductDetailsResponse] for error when querying product details.
+/// * [PurchaseDetails] for error happened in purchase.
+class IAPError {
+  /// Creates a new IAP error object with the given error details.
+  IAPError(
+      {required this.source,
+      required this.code,
+      required this.message,
+      this.details});
+
+  /// Which source is the error on.
+  final String source;
+
+  /// The error code.
+  final String code;
+
+  /// A human-readable error message.
+  final String message;
+
+  /// Error details, possibly null.
+  final dynamic details;
+}

packages/in_app_purchase/in_app_purchase_platform_interface/lib/src/types/product_details.dart

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+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+/// The class represents the information of a product.
+class ProductDetails {
+  /// Creates a new product details object with the provided details.
+  ProductDetails({
+    required this.id,
+    required this.title,
+    required this.description,
+    required this.price,
+  });
+
+  /// The identifier of the product.
+  ///
+  /// For example, on iOS it is specified in App Store Connect; on Android, it is specified in Google Play Console.
+  final String id;
+
+  /// The title of the product.
+  ///
+  /// For example, on iOS it is specified in App Store Connect; on Android, it is specified in Google Play Console.
+  final String title;
+
+  /// The description of the product.
+  ///
+  /// For example, on iOS it is specified in App Store Connect; on Android, it is specified in Google Play Console.
+  final String description;
+
+  /// The price of the product, formatted with currency symbol ("$0.99").
+  ///
+  /// For example, on iOS it is specified in App Store Connect; on Android, it is specified in Google Play Console.
+  final String price;
+}