package eu.ortlepp.notificationsender;

import com.amazonaws.services.lambda.runtime.Context;
import com.amazonaws.services.lambda.runtime.LambdaLogger;
import com.amazonaws.services.lambda.runtime.RequestHandler;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import eu.ortlepp.notificationsender.model.Notifications;
import eu.ortlepp.notificationsender.model.Response;
import eu.ortlepp.notificationsender.model.Status;
import eu.ortlepp.notificationsender.service.NotificationSender;
import eu.ortlepp.notificationsender.service.SnsNotificationSender;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Map;

/**
 * AWS Lambda implementation.
 */
public class NotificationHandler implements RequestHandler<Map<String, Object>, Response> {

  private LambdaLogger logger;

  private NotificationSender sender;


  /**
   * Standard constructor for AWS runtime. Uses default NotificationSender implementation.
   */
  public NotificationHandler() {
    this.sender = null;
  }


  /**
   * Constructor with custom NotificationSender implementation. Mainly for testing purposes.
   *
   * @param sender A custom NotificationSender
   */
  public NotificationHandler(final NotificationSender sender) {
    this.sender = sender;
  }


  /**
   * Constructor with custom NotificationSender and Context implementation.
   * Mainly for testing purposes.
   *
   * @param sender A custom NotificationSender
   * @param context A custom Context (to initialize the build-in logger)
   */
  public NotificationHandler(final NotificationSender sender, final Context context) {
    this.sender = sender;
    this.logger = context.getLogger();
  }


  /**
   * The AWS Lambda handler; executes the Lambda functionality.
   *
   * @param event The incoming event which triggered the Lambda
   * @param context The context of the Lambda execution
   * @return The final status of the execution
   */
  public Response handleRequest(final Map<String, Object> event, final Context context) {
    logger = context.getLogger();
    if (sender == null) {
      sender = new SnsNotificationSender(logger);
    }

    List<String> notifications = extractNotifications(event.get("body"));
    if (!notifications.isEmpty() && sender.sendNotifications(notifications)) {
      return new Response(Status.SUCCESS);
    }
    return new Response(Status.FAILED);
  }


  /**
   * Extract the notifications from the input JSON.
   *
   * @param body The input JSON
   * @return The extracted messages; empty list if an error occurred while parsing the JSON
   */
  protected List<String> extractNotifications(final Object body) {
    try {
      Notifications notifications =
          new ObjectMapper().readValue(body.toString(), Notifications.class);
      return Arrays.asList(notifications.messages());
    } catch (JsonProcessingException ex) {
      logger.log("parsing input JSON failed : " + ex.getMessage());
      return new ArrayList<>();
    }
  }

}