Add subscription deferral for Google play

README.md

@@ -57,6 +57,21 @@ iap.cancelSubscription("google", payment, function (error, response) {
 });
 ```
 
+### Subscription deferral ( Google Play only )
+
+Google exposes [an API for deferral](https://developers.google.com/android-publisher/api-ref/purchases/subscriptions/defer) of recurring suscriptions. This might be
+be used to extend a user's subscription purchase until a specified future expiration time ( useful to grant your users some free days or months ).
+
+```javascript
+var deferralInfo = {
+	expectedExpiryTimeMillis: 1546616722237,
+  desiredExpiryTimeMillis: 1547716722237,
+};
+iap.deferSubscription("google", payment, deferralInfo, function (error, response) {
+	/* your code */
+});
+```
+
 ## Supported platforms
 
 ### Amazon

index.js

@@ -67,3 +67,35 @@ exports.cancelSubscription = function (platform, payment, cb) {
 		cb(null, result);
 	});
 };
+
+
+exports.deferSubscription = function (platform, payment, deferralInfo, cb) {
+	function syncError(error) {
+		process.nextTick(function () {
+			cb(error);
+		});
+	}
+
+	if (!payment) {
+		return syncError(new Error('No payment given'));
+	}
+
+	var engine = platforms[platform];
+
+	if (!engine) {
+		return syncError(new Error('Platform ' + platform + ' not recognized'));
+	}
+
+	if (!engine.deferSubscription) {
+		return syncError(new Error('Platform ' + platform +
+			' does not have deferSubscription method'));
+	}
+
+	engine.deferSubscription(payment, deferralInfo, function (error, result) {
+		if (error) {
+			return cb(error);
+		}
+
+		cb(null, result);
+	});
+};

lib/google/index.js

@@ -41,6 +41,14 @@ function validatePaymentAndParseKeyObject(payment) {
 	return keyObject;
 }
 
+function validateDeferralInfo(deferralInfo) {
+	assert.equal(typeof deferralInfo, 'object', 'deferralInfo must be an object');
+	assert.equal(typeof deferralInfo.expectedExpiryTimeMillis, 'number', 'expectedExpiryTimeMillis must be a number');
+	assert.equal(typeof deferralInfo.desiredExpiryTimeMillis, 'number', 'desiredExpiryTimeMillis must be a number');
+	assert(deferralInfo.desiredExpiryTimeMillis > deferralInfo.expectedExpiryTimeMillis, 'desiredExpiryTimeMillis must be greater than expectedExpiryTimeMillis');
+}
+
+
 exports.verifyPayment = function (payment, cb) {
 	var keyObject;
 
@@ -133,3 +141,54 @@ exports.cancelSubscription = function (payment, cb) {
 		});
 	});
 };
+
+
+exports.deferSubscription = function (payment, deferralInfo, cb) {
+	var keyObject;
+
+	try {
+		keyObject = validatePaymentAndParseKeyObject(payment);
+		validateDeferralInfo(deferralInfo);
+	} catch (error) {
+		return process.nextTick(function () {
+			cb(error);
+		});
+	}
+
+	jwt.getToken(keyObject.client_email, keyObject.private_key, apiUrls.publisherScope, function (error, token) {
+		if (error) {
+			return cb(error);
+		}
+
+		var requestUrl = apiUrls.purchasesSubscriptionsDefer(
+			payment.packageName,
+			payment.productId,
+			payment.receipt,
+			token
+		);
+
+		var options = {
+			json: {
+				deferralInfo
+			}
+		};
+		https.post(requestUrl, options, function (error, res, resultString) {
+			if (error) {
+				return cb(error);
+			}
+
+			if (res.statusCode !== 200) {
+				return cb(new Error('Received ' + res.statusCode + ' status code with body: ' + resultString));
+			}
+
+			var resultObject;
+			try {
+				resultObject = JSON.parse(resultString);
+			} catch (e) {
+				return cb(e);
+			}
+
+			return cb(null, resultObject);
+		});
+	});
+};

lib/google/urls.js

@@ -38,8 +38,6 @@ exports.purchasesSubscriptionsGet = function (packageName, productId, receipt, a
 	);
 };
 
-
-// Android Subscriptions URLs & generators
 exports.purchasesSubscriptionsCancel = function (packageName, productId, receipt, accessToken) {
 	var urlFormat = 'https://www.googleapis.com/androidpublisher/v2/applications/%s/purchases/subscriptions/%s/tokens/%s:cancel?access_token=%s';
 
@@ -51,3 +49,15 @@ exports.purchasesSubscriptionsCancel = function (packageName, productId, receipt
 		encodeURIComponent(accessToken)   // API access token
 	);
 };
+
+exports.purchasesSubscriptionsDefer = function (packageName, productId, receipt, accessToken) {
+	var urlFormat = 'https://www.googleapis.com/androidpublisher/v2/applications/%s/purchases/subscriptions/%s/tokens/%s:defer?access_token=%s';
+
+	return util.format(
+		urlFormat,
+		encodeURIComponent(packageName),  // application package name
+		encodeURIComponent(productId),    // productId
+		encodeURIComponent(receipt),      // purchase token
+		encodeURIComponent(accessToken)   // API access token
+	);
+};