/*-
 * ============LICENSE_START=======================================================
 * ONAP-PDP-REST
 * ================================================================================
 * Copyright (C) 2017 AT&T Intellectual Property. All rights reserved.
 * ================================================================================
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * ============LICENSE_END=========================================================
 */
package org.onap.policy.pdp.rest.api.services;

import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Date;
import java.util.List;
import java.util.Map;
import java.util.UUID;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.TimeUnit;
import java.util.stream.Collectors;
import java.util.stream.Stream;

import org.onap.policy.api.PolicyException;
import org.onap.policy.common.logging.flexlogger.FlexLogger;
import org.onap.policy.common.logging.flexlogger.Logger;
import org.onap.policy.rest.XACMLRestProperties;
import org.onap.policy.utils.BusPublisher;
import org.onap.policy.xacml.api.XACMLErrorConstants;
import org.springframework.http.HttpStatus;

import com.att.research.xacml.util.XACMLProperties;

public class NotificationService {
	public static final String BACKUPFILE = "topicBackup.txt";
	private static Logger logger = FlexLogger.getLogger(GetDictionaryService.class.getName());
	private static ConcurrentHashMap<String, Date> topicQueue = new ConcurrentHashMap<>();
	private static int interval = 15000;  
	private static Thread backUpthread = null;
	private static Object resourceLock = new Object();
	private static List<String> dmaapList = null;
	private static String dmaapServers = null;
	private static String aafLogin = null;
	private static String aafPassword = null;
	
	private String notificationResponse = null;
	private HttpStatus status = HttpStatus.BAD_REQUEST;
	
	/**
	 * NotificationService Constructor.  
	 * 
	 * @param notificationTopic Topic Name in String format. 
	 * @param requestID Request ID in String format. 
	 * @param serviceType Needs to be NotificationServiceType based enumeration value. 
	 */
	public NotificationService(String notificationTopic, String requestID, NotificationServiceType serviceType) {
		init();
		if(dmaapServers==null || aafLogin==null || aafPassword==null){
			notificationResponse = XACMLErrorConstants.ERROR_DATA_ISSUE + "DMaaP properties are missing from the property file";
			return;
		}
		UUID requestUUID = null;
		if (requestID != null && !requestID.isEmpty()) {
			try {
				requestUUID = UUID.fromString(requestID);
			} catch (IllegalArgumentException e) {
				requestUUID = UUID.randomUUID();
				logger.info("Generated Random UUID: " + requestUUID.toString(), e);
			}
		}else{
			requestUUID = UUID.randomUUID();
			logger.info("Generated Random UUID: " + requestUUID.toString());
		}
        try{
            run(notificationTopic, serviceType);
        }catch(PolicyException e){
        	notificationResponse = XACMLErrorConstants.ERROR_DATA_ISSUE + e;
            status = HttpStatus.BAD_REQUEST;
        }
	}

	private static void init() {
		if(dmaapServers==null || aafLogin==null || aafPassword==null){
			dmaapServers = XACMLProperties.getProperty(XACMLRestProperties.PROP_NOTIFICATION_SERVERS);
			aafLogin = XACMLProperties.getProperty("DMAAP_AAF_LOGIN");
			aafPassword = XACMLProperties.getProperty("DMAAP_AAF_PASSWORD");
			interval = Integer.parseInt(XACMLProperties.getProperty(XACMLRestProperties.PROP_NOTIFICATION_DELAY, Integer.toString(interval)));
			if(dmaapServers==null || aafLogin==null || aafPassword==null){
				logger.error(XACMLErrorConstants.ERROR_DATA_ISSUE + "DMaaP properties are missing from the property file ");
				return;
			}
			// Cleanup Values. 
			dmaapServers= dmaapServers.trim();
			aafLogin = aafLogin.trim();
			aafPassword = aafPassword.trim();
			// Get servers to List. 
			if(dmaapServers.contains(",")) {
				dmaapList = new ArrayList<>(Arrays.asList(dmaapServers.split("\\s*,\\s*")));
			} else {
				dmaapList = new ArrayList<>();
				dmaapList.add(dmaapServers);
			}
			callThread();
		}
	}
	
	public static void reloadProps(){
	    dmaapServers = null;
	    aafLogin = null;
	    aafPassword = null;
	    backUpthread = null;
	}

	private void run(String notificationTopic, NotificationServiceType serviceType) throws PolicyException{
		// Check Validation
        if(notificationTopic==null){
        	String message = "Notification Topic is null";
            logger.error(message);
            throw new PolicyException(message);
        }
        notificationTopic = notificationTopic.trim();
        if(notificationTopic.isEmpty()){
        	String message = "Notification Topic is not valid. ";
            logger.error(message);
            throw new PolicyException(message);
        }
        // if already exists give error.Saying already registered. 
        // Get Result. 
        try{
            status = HttpStatus.OK;
            switch (serviceType) {
			case ADD:
				addTopic(notificationTopic);
				notificationResponse = "Success!! Please give permissions to " + aafLogin + " that PDP will use to publish on given topic :" + notificationTopic +
	            		"\n Start calling /sendHeartbeat API at an interval less than " + Integer.toString(interval) + "ms";
				break;
			case REMOVE:
				removeTopic(notificationTopic);
				notificationResponse = "Notification Topic :" + notificationTopic + " has been removed and PDP will not publish notifications to this Topic.";
				break;
			case HB:
				heartBeat(notificationTopic);
				notificationResponse = "Success!! HeartBeat registered.";
				break;
			}
        }catch (Exception e){
            logger.error(XACMLErrorConstants.ERROR_DATA_ISSUE + e);
            status = HttpStatus.BAD_REQUEST;
            throw new PolicyException(e);
        }
	}
	
	// Used to register Heart beat. 
	private void heartBeat(String notificationTopic) throws PolicyException{
		if(!topicQueue.isEmpty()&& topicQueue.containsKey(notificationTopic)){
			topicQueue.put(notificationTopic, new Date());
		}else{
			logger.info("Failed HeartBeat, Topic " + notificationTopic + "is not registered.");
			throw new PolicyException("Failed HeartBeat, Topic " + notificationTopic + "is not registered.");
		}
	}

	// Used to remove Topic.
	private static void removeTopic(String notificationTopic) throws PolicyException{ 
		if(topicQueue.containsKey(notificationTopic)){
			topicQueue.remove(notificationTopic);
			removeTopicFromBackup(notificationTopic);
		}else{
			logger.info("Failed Removal, Topic " + notificationTopic + " is not registered.");
			throw new PolicyException("Failed Removal, Topic " + notificationTopic + " is not registered.");
		}
	}

	private static void removeTopicFromBackup(String notificationTopic) {
		synchronized (resourceLock) {
			try (Stream<String> lines = Files.lines(Paths.get(BACKUPFILE))) {
				List<String> replaced = lines.map(line-> (line.split("=")[0].equals(notificationTopic)?"":line)).collect(Collectors.toList());
				try (PrintWriter pw = new PrintWriter( BACKUPFILE, "UTF-8")) {
					replaced.forEach(line-> {
						if(line.trim().isEmpty()){
							return;
						}
						pw.println(line);
					});
				}
				lines.close();
			} catch (IOException e) {
				logger.error(XACMLErrorConstants.ERROR_DATA_ISSUE + " Could not remove/recreate the backup. ", e);
			}
		}
	}

	// Used to add Topic. 
	private void addTopic(String notificationTopic) throws PolicyException{
		// validate if topic exists. 
		if(!topicQueue.isEmpty()&& topicQueue.containsKey(notificationTopic)){
			topicQueue.put(notificationTopic, new Date());
			logger.info("Topic " + notificationTopic + " is already registered.");
			throw new PolicyException("Topic " + notificationTopic + " is already registered.");
		}
		topicQueue.put(notificationTopic, new Date());
		addTopictoBackUp(notificationTopic);
	}

	private void addTopictoBackUp(String notificationTopic) {
		synchronized (resourceLock) {
			try {
				Files.write(Paths.get(BACKUPFILE),( notificationTopic+"="+new Date().toString()+"\n").getBytes() , StandardOpenOption.APPEND);
			} catch (IOException e) {
				logger.error(XACMLErrorConstants.ERROR_DATA_ISSUE + " Could not add to the backup. ", e);
			}
		}
	}

	// Maintains BackUp and Queue Topic. 
	private static void callThread() {
		// Create the backup file if it not exists. 
		backup();
		if(backUpthread==null){
			Runnable task = () -> {
				logger.info("BackUpThread not set. Starting now !");
				threadTask();
			};
			backUpthread = new Thread(task);
			backUpthread.start();
		}
	}

	private static void backup(){
		synchronized (resourceLock) {
			try{
				File backUpFile = new File(BACKUPFILE);
				if(!backUpFile.exists() && backUpFile.createNewFile()){
					logger.info(" BackUp File for topic's has been created !");
				}else{
					// File Already exists. Process file and load the Memory. 
					Stream<String> stream = Files.lines(Paths.get(BACKUPFILE));
					Map<String,Date> data = stream.map(line -> line.split(",")).collect(Collectors.toMap(e->e[0],e-> new Date()));
					stream.close();
					data.forEach((key, value)->logger.debug("Topic retrieved from backUp : " + key + " with Time : " + value));
					topicQueue.putAll(data);
				}
			}catch(IOException e){
				logger.error(XACMLErrorConstants.ERROR_DATA_ISSUE + " Could not process the backup. ", e);
			}
		}
	}

	private static void threadTask() {
		while(true){
			try {
				TimeUnit.MILLISECONDS.sleep(interval);
				for(Map.Entry<String, Date> map : topicQueue.entrySet()){
					Date currentTime = new Date();
					long timeDiff = 0;
					timeDiff = currentTime.getTime()-map.getValue().getTime();
					if(timeDiff < (interval+1500)){
						removeTopic(map.getKey());
					}
				}
			} catch (InterruptedException | PolicyException e) {
				logger.error(XACMLErrorConstants.ERROR_PROCESS_FLOW + "Error during thread execution ", e);
			}
		}
	}

	public String getResult() {
		return notificationResponse;
	}

	public HttpStatus getResponseCode() {
		return status;
	}

	/**
	 * Entry point for sending Notifications from Notification Server. 
	 * @param notification String JSON format of notification message which needs to be sent. 
	 */
	public static void sendNotification(String notification) {
		init();
		for (String topic: topicQueue.keySet()){
			sendDmaapMessage(topic, notification);
		}
	}
	
	private static void sendDmaapMessage(String topic, String notification) {
		BusPublisher publisher = new BusPublisher.DmaapPublisherWrapper(dmaapList, 
						                               topic, 
						                               aafLogin, 
						                               aafPassword);
		// Sending notification through DMaaP Message Router
		publisher.send( "MyPartitionKey", notification);
		logger.debug("Message Published on DMaaP :" + dmaapList.get(0) + "for Topic: " + topic);
		publisher.close();
	}
	
	/**
	 *  Notification service Type Enumeration 
	 */
	public enum NotificationServiceType{
		ADD,
		REMOVE,
		HB
	}

}