/*
 * Copyright 2014-2018 the original author or authors.
 *
 * 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.
 */

package de.codecentric.boot.admin.server.notify;

import java.net.URI;
import java.nio.charset.StandardCharsets;
import java.util.HashMap;
import java.util.Map;

import javax.annotation.Nullable;

import org.springframework.context.expression.MapAccessor;
import org.springframework.expression.Expression;
import org.springframework.expression.ParserContext;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.expression.spel.support.StandardEvaluationContext;
import org.springframework.http.HttpEntity;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpMethod;
import org.springframework.http.MediaType;
import org.springframework.util.Base64Utils;
import org.springframework.web.client.RestTemplate;
import reactor.core.publisher.Mono;

import de.codecentric.boot.admin.server.domain.entities.Instance;
import de.codecentric.boot.admin.server.domain.entities.InstanceRepository;
import de.codecentric.boot.admin.server.domain.events.InstanceEvent;

/**
 * Notifier submitting events to let´s Chat.
 *
 * @author Rico Pahlisch
 */
public class LetsChatNotifier extends AbstractStatusChangeNotifier {

	private static final String DEFAULT_MESSAGE = "*#{instance.registration.name}* (#{instance.id}) is *#{event.statusInfo.status}*";

	private final SpelExpressionParser parser = new SpelExpressionParser();

	private RestTemplate restTemplate;

	/**
	 * Host URL for Let´s Chat
	 */
	@Nullable
	private URI url;

	/**
	 * Name of the room
	 */
	@Nullable
	private String room;

	/**
	 * Token for the Let´s chat API
	 */
	@Nullable
	private String token;

	/**
	 * username which sends notification
	 */
	private String username = "Spring Boot Admin";

	/**
	 * Message template. SpEL template using event as root
	 */
	private Expression message;

	public LetsChatNotifier(InstanceRepository repository, RestTemplate restTemplate) {
		super(repository);
		this.restTemplate = restTemplate;
		this.message = parser.parseExpression(DEFAULT_MESSAGE, ParserContext.TEMPLATE_EXPRESSION);
	}

	@Override
	protected Mono<Void> doNotify(InstanceEvent event, Instance instance) {
		HttpHeaders headers = new HttpHeaders();
		headers.setContentType(MediaType.APPLICATION_JSON);
		// Let's Chat requiers the token as basic username, the password can be an
		// arbitrary string.
		String auth = Base64Utils
				.encodeToString(String.format("%s:%s", token, username).getBytes(StandardCharsets.UTF_8));
		headers.add(HttpHeaders.AUTHORIZATION, String.format("Basic %s", auth));
		return Mono.fromRunnable(() -> restTemplate.exchange(createUrl(), HttpMethod.POST,
				new HttpEntity<>(createMessage(event, instance), headers), Void.class));
	}

	private URI createUrl() {
		if (url == null) {
			throw new IllegalStateException("'url' must not be null.");
		}
		return URI.create(String.format("%s/rooms/%s/messages", url, room));
	}

	protected Object createMessage(InstanceEvent event, Instance instance) {
		Map<String, String> messageJson = new HashMap<>();
		messageJson.put("text", getText(event, instance));
		return messageJson;
	}

	@Nullable
	protected String getText(InstanceEvent event, Instance instance) {
		Map<String, Object> root = new HashMap<>();
		root.put("event", event);
		root.put("instance", instance);
		root.put("lastStatus", getLastStatus(event.getInstance()));
		StandardEvaluationContext context = new StandardEvaluationContext(root);
		context.addPropertyAccessor(new MapAccessor());
		return message.getValue(context, String.class);
	}

	public void setRestTemplate(RestTemplate restTemplate) {
		this.restTemplate = restTemplate;
	}

	public void setUrl(@Nullable URI url) {
		this.url = url;
	}

	@Nullable
	public URI getUrl() {
		return url;
	}

	public void setUsername(String username) {
		this.username = username;
	}

	public String getUsername() {
		return username;
	}

	public void setRoom(@Nullable String room) {
		this.room = room;
	}

	@Nullable
	public String getRoom() {
		return room;
	}

	public void setToken(@Nullable String token) {
		this.token = token;
	}

	@Nullable
	public String getToken() {
		return token;
	}

	public void setMessage(String message) {
		this.message = parser.parseExpression(message, ParserContext.TEMPLATE_EXPRESSION);
	}

	public String getMessage() {
		return message.getExpressionString();
	}

}
