/*
 * Copyright (C) 2008-2019, Juick
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

package com.juick.server;

import com.juick.Message;
import com.juick.User;
import com.juick.server.api.SystemActivity;
import com.juick.service.EmailService;
import com.juick.service.MessagesService;
import com.juick.service.UserService;
import com.juick.service.component.*;
import com.juick.util.MessageUtils;
import com.mitchellbosecke.pebble.PebbleEngine;
import com.mitchellbosecke.pebble.template.PebbleTemplate;
import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;

import javax.annotation.Nonnull;
import javax.inject.Inject;
import javax.mail.MessagingException;
import javax.mail.Multipart;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeBodyPart;
import javax.mail.internet.MimeMessage;
import javax.mail.internet.MimeMultipart;
import java.io.IOException;
import java.io.StringWriter;
import java.io.Writer;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.Properties;

import static com.juick.formatters.PlainTextFormatter.formatPost;
import static com.juick.formatters.PlainTextFormatter.formatUrl;

@Component
public class EmailManager implements NotificationListener {

    public static final String MSGID_PATTERN = "\\.|@|<";

    private static final Logger logger = LoggerFactory.getLogger(EmailManager.class);
    @Inject
    private EmailService emailService;
    @Inject
    private MessagesService messagesService;
    @Inject
    private UserService userService;
    @Inject
    private PebbleEngine pebbleEngine;

    @Override
    public void processSystemEvent(@Nonnull SystemEvent systemEvent) {
        var activity = systemEvent.getActivity();
        var msg = activity.getMessage();
        var subscribers = activity.getTo();
        if (activity.getType().equals(SystemActivity.ActivityType.message)) {
            processMessage(msg, subscribers);
        }
    }
    private void processMessage(com.juick.Message msg, List<User> subscribedUsers) {
        if (msg.isService()) {
            return;
        }
        if (MessageUtils.isPM(msg)) {
            String subject = String.format("Private message from %s", msg.getUser().getName());
            emailService.getEmails(msg.getTo().getUid(), true).forEach(email -> emailNotify(email, subject, msg));
        } else if (MessageUtils.isReply(msg)) {
            Message originalMessage = messagesService.getMessage(msg.getMid()).orElseThrow(IllegalStateException::new);
            String subject = String.format("New reply to %s", originalMessage.getUser().getName());
            subscribedUsers.stream()
                    .flatMap(user -> emailService.getEmails(user.getUid(), true).stream())
                    .forEach(email -> emailNotify(email, subject, msg));
        } else {
            String subject = String.format("New message from %s", msg.getUser().getName());
            subscribedUsers
                    .forEach(user -> emailService.getEmails(user.getUid(), true)
                            .forEach(email -> emailNotify(email, subject, msg)));
        }
    }

    @Override
    public void processPingEvent(PingEvent pingEvent) {

    }

    private void emailNotify(String email, String subject, Message msg) {
        Map<String, String> headers = new HashMap<>();
        if (!MessageUtils.isPM(msg)) {
            headers.put("Message-ID", String.format("<%d.%d@juick.com>", msg.getMid(), msg.getRid()));
        }
        if (MessageUtils.isReply(msg)) {
            if (msg.getReplyto() > 0) {
                Message replyto = messagesService.getReply(msg.getMid(), msg.getReplyto());
                headers.put("In-Reply-To", String.format("<%d.%d@juick.com>", replyto.getMid(), replyto.getRid()));
            } else {
                Message original = messagesService.getMessage(msg.getMid()).orElseThrow(IllegalStateException::new);
                headers.put("In-Reply-To", String.format("<%d.%d@juick.com>", original.getMid(), original.getRid()));
            }
        }
        String plainText = renderPlaintext(formatPost(msg), formatUrl(msg)).orElseThrow(IllegalStateException::new);
        String hash = userService.getHashByUID(userService.getUserByEmail(email).getUid());
        String htmlText = renderHtml(MessageUtils.formatHtml(msg), formatUrl(msg), msg, hash).orElseThrow(IllegalStateException::new);
        sendEmail(StringUtils.EMPTY, email, subject, plainText, htmlText, headers);
    }
    public boolean sendEmail(String from, String to, String subject, String textPart, String htmlPart, Map<String, String> messageHeaders) {
        Properties prop = System.getProperties();
        prop.put("mail.smtp.starttls.enable", "true");
        Session session = Session.getDefaultInstance(prop);
        try {
            Transport transport = session.getTransport("smtp");
            MimeMessage message = new MimeMessage(session) {
                protected void updateMessageID() throws MessagingException {
                    for (Map.Entry<String, String> entry: messageHeaders.entrySet()) {
                        setHeader(entry.getKey(), entry.getValue());
                    }
                }
            };
            String fromAddress = StringUtils.isNotEmpty(from) ? from : "juick@juick.com";
            message.setFrom(fromAddress);
            message.addRecipient(javax.mail.Message.RecipientType.TO, new InternetAddress(to));
            message.setSubject(subject);
            MimeBodyPart textBodyPart = new MimeBodyPart();
            textBodyPart.setContent(textPart, "text/plain; charset=UTF-8");

            Multipart multipart = new MimeMultipart("alternative");
            multipart.addBodyPart(textBodyPart);
            if (StringUtils.isNotBlank(htmlPart)) {
                MimeBodyPart htmlBodyPart = new MimeBodyPart();
                htmlBodyPart.setContent(htmlPart, "text/html; charset=UTF-8");
                multipart.addBodyPart(htmlBodyPart);
            }
            message.setContent(multipart);
            User emailUser = userService.getUserByEmail(to);
            if (!emailUser.isAnonymous()) {
                message.setHeader("List-Id", "Juick notifications <mail-notifications.juick.com>");
                message.setHeader("List-Post", "<mailto:juick@juick.com>");
                message.setHeader("List-Owner", "<mailto:support@juick.com>");
                message.setHeader("List-Archive", "<https://juick.com/>");
                message.setHeader("List-Unsubscribe", String.format("https://juick.com/settings/unsubscribe?hash=%s",
                        userService.getHashByUID(emailUser.getUid())));
                message.setHeader("List-Unsubscribe-Post", "List-Unsubscribe=One-Click");
            }
            message.saveChanges();
            transport.connect();
            transport.sendMessage(message, message.getAllRecipients());
            return true;
        } catch (MessagingException ex) {
            logger.error("mail exception", ex);
            return false;
        }
    }

    public Optional<String> renderPlaintext(String body, String messageUrl) {
        PebbleTemplate noteTemplate = pebbleEngine.getTemplate("email/plaintext");
        Map<String, Object> context = new HashMap<>();
        context.put("messageBody", body);
        context.put("messageUrl", messageUrl);
        try {
            Writer writer = new StringWriter();
            noteTemplate.evaluate(writer, context);
            return Optional.of(writer.toString());
        } catch (IOException e) {
            return Optional.empty();
        }
    }

    public Optional<String> renderHtml(String body, String messageUrl, Message msg, String hash) {
        PebbleTemplate noteTemplate = pebbleEngine.getTemplate("email/html");
        Map<String, Object> context = new HashMap<>();
        context.put("messageBody", body);
        context.put("messageUrl", messageUrl);
        context.put("msg", msg);
        context.put("hash", hash);
        try {
            Writer writer = new StringWriter();
            noteTemplate.evaluate(writer, context);
            return Optional.of(writer.toString());
        } catch (IOException e) {
            return Optional.empty();
        }
    }
}