2 files changed, 104 insertions, 0 deletions
diff --git a/src/main/java/eu/ortlepp/notificationsender/service/NotificationSender.java b/src/main/java/eu/ortlepp/notificationsender/service/NotificationSender.java
new file mode 100644
index 0000000..8c39c72
--- /dev/null
+++ b/src/main/java/eu/ortlepp/notificationsender/service/NotificationSender.java
@@ -0,0 +1,41 @@
+package eu.ortlepp.notificationsender.service;
+
+import java.util.List;
+
+/**
+ * Interface for notification senders.
+ */
+public interface NotificationSender {
+
+  /**
+   * Send a list of notifications.
+   *
+   * @param notifications The notifications to send
+   * @return The result of the sending; true = successful, false = error occurred
+   */
+  boolean sendNotifications(final List<String> notifications);
+
+
+  /**
+   * Format notifications for sending.
+   * If only one notification is passed, it is returned as is.
+   * If multiple notifications are passed, a numbered list of notifications is returned.
+   *
+   * @param notifications The notifications to format
+   * @return The formatted notifications
+   */
+  default String formatNotifications(final List<String> notifications) {
+    if (notifications.size() == 1) {
+      return notifications.getFirst() + "\n\n";
+    }
+    StringBuilder builder = new StringBuilder();
+    for (int i = 0; i < notifications.size(); i++) {
+      builder.append(i + 1)
+              .append(". Notification:\n")
+              .append(notifications.get(i))
+              .append("\n\n");
+    }
+    return builder.toString();
+  }
+
+}
diff --git a/src/main/java/eu/ortlepp/notificationsender/service/SnsNotificationSender.java b/src/main/java/eu/ortlepp/notificationsender/service/SnsNotificationSender.java
new file mode 100644
index 0000000..958365a
--- /dev/null
+++ b/src/main/java/eu/ortlepp/notificationsender/service/SnsNotificationSender.java
@@ -0,0 +1,63 @@
+package eu.ortlepp.notificationsender.service;
+
+import com.amazonaws.services.lambda.runtime.LambdaLogger;
+import eu.ortlepp.notificationsender.util.Config;
+import java.util.List;
+import software.amazon.awssdk.http.HttpStatusCode;
+import software.amazon.awssdk.services.sns.SnsClient;
+import software.amazon.awssdk.services.sns.model.PublishRequest;
+import software.amazon.awssdk.services.sns.model.PublishResponse;
+import software.amazon.awssdk.services.sns.model.SnsException;
+
+/**
+ * A notification sender for Amazon SNS.
+ */
+public class SnsNotificationSender implements NotificationSender {
+
+  private final LambdaLogger logger;
+
+
+  /**
+   * Constructor to initialize the sender.
+   *
+   * @param logger The logger of the AWS Lambda
+   */
+  public SnsNotificationSender(final LambdaLogger logger) {
+    this.logger = logger;
+  }
+
+
+  /**
+   * Send a list of notifications to the configured SNS topic.
+   * All notifications are combined into a single message.
+   *
+   * @param notifications The notifications to send
+   * @return The result of the sending; true = successful, false = error occurred
+   */
+  @Override
+  public boolean sendNotifications(final List<String> notifications) {
+    String notification = formatNotifications(notifications);
+
+    try (SnsClient snsClient = SnsClient.builder().region(Config.REGION).build()) {
+      PublishRequest request =
+          PublishRequest.builder().message(notification).topicArn(Config.ARN).build();
+      PublishResponse result = snsClient.publish(request);
+      int resultStatusCode = result.sdkHttpResponse().statusCode();
+
+      if (resultStatusCode ==  HttpStatusCode.OK) {
+        logger.log("notification sent successfully");
+        return true;
+      }
+
+      logger.log("sending notification failed with status " + resultStatusCode);
+      logger.log("failed message was " + notification);
+      return false;
+
+    } catch (SnsException ex) {
+      logger.log("sending notification failed: " + ex.getMessage());
+      logger.log("failed message was " + notification);
+      return false;
+    }
+  }
+
+}