/*
 * 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.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.MediaType;
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 Discord by webhooks.
 *
 * @author Movitz Sunar
 * @see <a href=
 * "https://discordapp.com/developers/docs/resources/webhook#execute-webhook">https://discordapp.com/developers/docs/resources/webhook#execute-webhook</a>
 */
public class DiscordNotifier 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;

	private Expression message;

	/**
	 * Webhook URI for the Discord API (i.e.
	 * https://discordapp.com/api/webhooks/{webhook.id}/{webhook.token})
	 */
	@Nullable
	private URI webhookUrl;

	/**
	 * If the message is a text to speech message. False by default.
	 */
	private boolean tts = false;

	/**
	 * Optional username. Default is set in Discord.
	 */
	@Nullable
	private String username;

	/**
	 * Optional URL to avatar.
	 */
	@Nullable
	private String avatarUrl;

	public DiscordNotifier(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) {
		if (webhookUrl == null) {
			return Mono.error(new IllegalStateException("'webhookUrl' must not be null."));
		}
		return Mono.fromRunnable(
				() -> restTemplate.postForEntity(webhookUrl, createDiscordNotification(event, instance), Void.class));
	}

	protected Object createDiscordNotification(InstanceEvent event, Instance instance) {
		Map<String, Object> body = new HashMap<>();
		body.put("content", createContent(event, instance));
		body.put("tts", tts);

		if (avatarUrl != null) {
			body.put("avatar_url", avatarUrl);
		}
		if (username != null) {
			body.put("username", username);
		}

		HttpHeaders headers = new HttpHeaders();
		headers.setContentType(MediaType.APPLICATION_JSON);
		headers.add(HttpHeaders.USER_AGENT, "RestTemplate");
		return new HttpEntity<>(body, headers);
	}

	@Nullable
	protected String createContent(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);
	}

	@Nullable
	public URI getWebhookUrl() {
		return webhookUrl;
	}

	public void setWebhookUrl(@Nullable URI webhookUrl) {
		this.webhookUrl = webhookUrl;
	}

	public boolean isTts() {
		return tts;
	}

	public void setTts(boolean tts) {
		this.tts = tts;
	}

	@Nullable
	public String getUsername() {
		return username;
	}

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

	@Nullable
	public String getAvatarUrl() {
		return avatarUrl;
	}

	public void setAvatarUrl(@Nullable String avatarUrl) {
		this.avatarUrl = avatarUrl;
	}

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

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

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

}
