Initial basic implementation of trying each provider - nothing clever…

… happening for now

lib/resilient-mailer.js

@@ -7,6 +7,7 @@ module.exports = ResilientMailer;
  * @this {ResilientMailer}
  */
 function ResilientMailer() {
+	this.providers = [];
 }
 
 /**
@@ -16,6 +17,7 @@ function ResilientMailer() {
  * @param {Provider} provider The provider to register.
  */
 ResilientMailer.prototype.registerProvider = function (provider) {
+	this.providers.push(provider);
 }
 
 /**
@@ -32,4 +34,30 @@ ResilientMailer.prototype.registerProvider = function (provider) {
  * @param {ResilientMailer~onResult} [callback] Notified when the attempt fails or succeeds.
  */
 ResilientMailer.prototype.mail = function (message, callback) {
+	this._attempt(0, message, callback);
+}
+
+ResilientMailer.prototype._attempt = function (index, message, callback) {
+	var self = this; // any way around this?
+	var provider = this.providers[index];
+
+	provider.mail(message, function (error) {
+		if (!error) {
+			if (callback)
+				callback();
+
+			return;
+		}
+
+		index++;
+
+		if (self.providers.length == index) {
+			if (callback)
+				callback(error);
+
+			return;
+		}
+
+		self._attempt(index, message, callback);
+	});
 }

package.json

@@ -1,6 +1,6 @@
 {
 	"name": "resilient-mailer",
-	"version": "0.1.0",
+	"version": "0.1.1",
 	"description": "Provides fault-tolerant email delivery",
 
 	"license": "MIT",

test/resilient-mailer.js

@@ -18,3 +18,54 @@ test('correct types after initialization', function (t) {
 
 	t.end();
 });
+
+test('uses providers in correct order', function (t) {
+	t.plan(3);
+
+	var mailer = new ResilientMailer();
+	mailer.registerProvider(successProvider);
+	mailer.registerProvider(failureProvider);
+
+	mailer.mail({}, function (error) {
+		t.equal(typeof error, 'undefined');
+	});
+
+	var mailer2 = new ResilientMailer();
+	mailer2.registerProvider(failureProvider);
+	mailer2.registerProvider(failureProvider2);
+
+	mailer2.mail({}, function (error) {
+		t.notEqual(typeof error, 'undefined');
+		t.equal(error.message, 'different generic failure');
+	});
+});
+
+test('uses secondary as backup', function (t) {
+	t.plan(1);
+
+	var mailer = new ResilientMailer();
+	mailer.registerProvider(failureProvider);
+	mailer.registerProvider(successProvider);
+
+	mailer.mail({}, function (error) {
+		t.equal(typeof error, 'undefined');
+	});
+});
+
+var successProvider = {
+	mail: function (message, callback) {
+		callback();
+	}
+};
+
+var failureProvider = {
+	mail: function (message, callback) {
+		callback(new Error('generic failure'));
+	}
+};
+
+var failureProvider2 = {
+	mail: function (message, callback) {
+		callback(new Error('different generic failure'));
+	}
+};