notification system added

Author: kousiknath

src/com/lld/notificationsystem/MainApplication.java

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+package com.lld.notificationsystem;
+
+import com.lld.notificationsystem.constant.MessageType;
+import com.lld.notificationsystem.constant.NotificationChannel;
+import com.lld.notificationsystem.model.EndUser;
+import com.lld.notificationsystem.model.Message;
+import com.lld.notificationsystem.model.Template;
+import com.lld.notificationsystem.service.MessageTemplateService;
+import com.lld.notificationsystem.service.NotificationService;
+import com.lld.notificationsystem.service.impl.MessageTemplateServiceImpl;
+import com.lld.notificationsystem.service.impl.NotificationServiceImpl;
+
+import java.util.Arrays;
+
+public class MainApplication {
+
+    private static void test1() {
+        MessageTemplateService messageTemplateService = new MessageTemplateServiceImpl();
+
+        // Template creation is one time activity
+        String strTemplate = "Get straight %s rupee discount on ABC today. Special offer.";
+        Template template = messageTemplateService.createTemplate(MessageType.INFORMATIONAL, strTemplate);
+
+        String formattedMessage = String.format(template.getTemplate(), "100");
+        EndUser endUser = new EndUser("test1", "test1@test.com");
+
+        NotificationService notificationService = new NotificationServiceImpl();
+        notificationService.subscribeToChannels(endUser,
+                Arrays.asList(NotificationChannel.WHATSAPP, NotificationChannel.FACEBOOK, NotificationChannel.INSTAGRAM));
+        notificationService.sendMessageTo(endUser, new Message(formattedMessage, template.getMessageType()));
+    }
+
+    private static void test2() {
+        MessageTemplateService messageTemplateService = new MessageTemplateServiceImpl();
+
+        // Template creation is one time activity
+        String strTemplate = "Your OTP for transaction amount of INR %s is %s";
+        Template template = messageTemplateService.createTemplate(MessageType.OTP, strTemplate);
+
+        String formattedMessage = String.format(template.getTemplate(), "100000", "6839");
+        EndUser endUser = new EndUser("test2", "test2@test.com");
+
+        NotificationService notificationService = new NotificationServiceImpl();
+        notificationService.subscribeToChannels(endUser,
+                Arrays.asList(NotificationChannel.SMS, NotificationChannel.EMAIL));
+        notificationService.sendMessageTo(endUser, new Message(formattedMessage, template.getMessageType()));
+    }
+
+    public static void main(String[] args) {
+        test1();
+        test2();
+    }
+}

src/com/lld/notificationsystem/README.md

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+# Design a notification system.
+
+<b> Requirements </b>
+
+1. Applications should be able to send notification through different channels like
+SMS, Email, Slack, Facebook, Instagram, WhatsApp etc.
+2. Depending on what the end user subscribes to, different end user may get notifications
+through multiple channels. Ex: user A might get notification through SMS and WhatsApp, 
+whereas user B might get notifications through Facebook, Instagram, Slack etc.
+3. The system should be able to send high priority notifications like OTP as well as 
+low priority messages like promotional messages.

src/com/lld/notificationsystem/client/EmailClient.java

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+package com.lld.notificationsystem.client;
+
+public interface EmailClient {
+    void sendEmail(String address, String cc, String bcc, String content);
+}

src/com/lld/notificationsystem/client/FacebookClient.java

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+package com.lld.notificationsystem.client;
+
+public interface FacebookClient {
+    void sendNotification(String userDetailsEncrypted, String message);
+}

src/com/lld/notificationsystem/client/InstagramClient.java

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+package com.lld.notificationsystem.client;
+
+public interface InstagramClient {
+    void sendNotification(String userDetailsEncrypted, String message);
+}

src/com/lld/notificationsystem/client/MobilePushNotifierClient.java

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+package com.lld.notificationsystem.client;
+
+public interface MobilePushNotifierClient {
+    void sendPush(String deviceToken, String message);
+}

src/com/lld/notificationsystem/client/SMSClient.java

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+package com.lld.notificationsystem.client;
+
+public interface SMSClient {
+    void sendSMS(String phoneNo, String message);
+}

src/com/lld/notificationsystem/client/SlackNotificationClient.java

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+package com.lld.notificationsystem.client;
+
+public interface SlackNotificationClient {
+    void sendSlack(String userDetailsEncrypted, String message);
+}

src/com/lld/notificationsystem/client/WebPushClient.java

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+package com.lld.notificationsystem.client;
+
+public interface WebPushClient {
+    void sendNotification(String userDetailsEncrypted, String message);
+}

src/com/lld/notificationsystem/client/WhatsappClient.java

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+package com.lld.notificationsystem.client;
+
+public interface WhatsappClient {
+    void sendNotification(String phoneNo, String message);
+}