/* © SRSoftware 2025 */
package de.srsoftware.umbrella.message;

import static de.srsoftware.tools.PathHandler.CONTENT_TYPE;
import static de.srsoftware.umbrella.core.ConnectionProvider.connect;
import static de.srsoftware.umbrella.core.Constants.*;
import static de.srsoftware.umbrella.core.exceptions.UmbrellaException.missingConfigException;
import static de.srsoftware.umbrella.message.Constants.*;
import static java.lang.System.Logger.Level.*;

import de.srsoftware.configuration.Configuration;
import de.srsoftware.umbrella.core.api.PostBox;
import de.srsoftware.umbrella.core.api.Translator;
import de.srsoftware.umbrella.core.exceptions.UmbrellaException;
import de.srsoftware.umbrella.core.model.Envelope;
import de.srsoftware.umbrella.core.model.UmbrellaUser;
import de.srsoftware.umbrella.core.model.User;
import de.srsoftware.umbrella.message.model.CombinedMessage;
import jakarta.activation.DataHandler;
import jakarta.mail.Message;
import jakarta.mail.MessagingException;
import jakarta.mail.Session;
import jakarta.mail.Transport;
import jakarta.mail.internet.MimeBodyPart;
import jakarta.mail.internet.MimeMessage;
import jakarta.mail.internet.MimeMultipart;
import jakarta.mail.util.ByteArrayDataSource;
import java.util.*;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.function.BiFunction;

public class MessageSystem implements PostBox {
	public static final System.Logger LOG = System.getLogger(MessageSystem.class.getSimpleName());
	private final Timer timer = new Timer();
	private record Receiver(User user, de.srsoftware.umbrella.core.model.Message message){}

	private class SubmissionTask extends TimerTask{


		private final Integer hour;

		public SubmissionTask(Integer hour) {
			this.hour = hour;
		}

		@Override
		public void run() {
			processMessages(hour);
		}

		public void schedule() {
			var date = Calendar.getInstance();
			date.set(Calendar.HOUR_OF_DAY, hour);
			date.set(Calendar.MINUTE, 0);
			date.set(Calendar.SECOND, 0);
			date.set(Calendar.MILLISECOND,0);
			if (date.before(Calendar.getInstance())) date.add(Calendar.HOUR, 24);
			timer.schedule(this,date.getTime());
			LOG.log(INFO,"Scheduled {0} at {1}",getClass().getSimpleName(),date.getTime());
		}



	}
	private final String from,host,user,pass;
	private final int port;
	private final SqliteMessageDb db;
	private Session session;
	private List<Envelope> queue = new CopyOnWriteArrayList<>();
	private String debugAddress;
	private final HashMap<Receiver,List<Exception>> exceptions = new HashMap<>();
	private final Translator translator;

	public MessageSystem(Translator translator, Configuration config) throws UmbrellaException {
		var messageDbFile = config.get(CONFIG_DB).orElseThrow(() -> missingConfigException(CONFIG_DB));
		db        = new SqliteMessageDb(connect(messageDbFile));

		this.translator = translator;
		debugAddress = config.get(DEBUG_ADDREESS).map(Object::toString).orElse(null);
		port = config.get(CONFIG_SMTP_PORT,587);
		host = config.get(CONFIG_SMTP_HOST).map(Object::toString).orElseThrow(() -> new RuntimeException("umbrella.modules.message.smtp.host not configured!"));
		user = config.get(CONFIG_SMTP_USER).map(Object::toString).orElseThrow(()       -> new RuntimeException("umbrella.modules.message.smtp.user not configured!"));
		pass = config.get(CONFIG_SMTP_PASS).map(Object::toString).orElseThrow(()   -> new RuntimeException("umbrella.modules.message.smtp.pass not configured!"));
		from = user;
		new SubmissionTask(8).schedule();
		new SubmissionTask(10).schedule();
		new SubmissionTask(12).schedule();
		new SubmissionTask(14).schedule();
		new SubmissionTask(16).schedule();
		new SubmissionTask(18).schedule();
		new SubmissionTask(20).schedule();
	}

	@Override
	public void send(Envelope envelope) {
		queue.add(envelope);
		new Thread(() -> processMessages(null)).start();
	}

	private synchronized void processMessages(Integer scheduledHour) {
		LOG.log(INFO,"Running {0}…",scheduledHour == null ? "instantly" : "scheduled at "+scheduledHour);
		var queue = new ArrayList<>(this.queue);
		var dueRecipients = new ArrayList<User>();
		List<User> recipients = queue.stream().map(Envelope::receivers).flatMap(Set::stream).filter(Objects::nonNull).distinct().toList();

		{ // for known users: get notification preferences, fallback to _immediately_ for unknown users
			for (User recv : recipients) {
				if (recv instanceof UmbrellaUser uu) {
					try {
						if (!db.getSettings(uu).sendAt(scheduledHour)) continue;
					} catch (UmbrellaException ignored) {}
				}
				dueRecipients.add(recv);
			}
		}

		var date = new Date();

		for (var receiver : dueRecipients){
			BiFunction<String,Map<String,String>,String> translateFunction = (text,fills) -> translator.translate(receiver.language(),text,fills);

			var combined = new CombinedMessage("Collected messages",translateFunction);
			var envelopes = queue.stream().filter(env -> env.isFor(receiver)).toList();
			for (var envelope : envelopes) combined.merge(envelope.message());

			try {
				send(combined,receiver,date);
				for (var envelope : envelopes){
					var audience = envelope.receivers();
					audience.remove(receiver);
					if (audience.isEmpty()) queue.remove(envelope);
				}
			} catch (Exception ex){
				LOG.log(WARNING,"Failed to deliver mail ({0}) to {1}.",combined.subject(),receiver,ex);
				for (var message : combined.messages()) exceptions.computeIfAbsent(new Receiver(receiver,message), k -> new ArrayList<>()).add(ex);

			}
		}

		if (scheduledHour != null) new SubmissionTask(scheduledHour).schedule();
	}

	private Session session() {
		if (session == null){
			Properties props = new Properties();
			props.put(HOST, host);
			props.put(PORT, port);
			props.put(AUTH, true);
			props.put(SSL, true);
			props.put(ENVELOPE_FROM,from);
			session = Session.getInstance(props);
		}
		return session;
	}

	public void setDebugAddress(String newVal) {
		this.debugAddress = newVal;
	}


	private void send(CombinedMessage message, User receiver, Date date) throws MessagingException {
		LOG.log(TRACE,"Sending combined message to {0}…",receiver);
		session = session();
		MimeMessage msg = new MimeMessage(session);
		msg.addHeader(CONTENT_TYPE, "text/markdown; charset=UTF-8");
		msg.addHeader("format", "flowed");
		msg.addHeader("Content-Transfer-Encoding", "8bit");
		msg.setFrom(message.sender().email().toString());
		msg.setSubject(message.subject(), UTF8);
		msg.setSentDate(date);
		var toEmail = debugAddress != null ? debugAddress : receiver.email().toString();
		msg.setRecipients(Message.RecipientType.TO, toEmail);

		if (message.attachments().isEmpty()){
			msg.setText(message.body(), UTF8);
		} else {
			var multipart = new MimeMultipart();
			var body = new MimeBodyPart();
			body.setText(message.body(),UTF8);

			multipart.addBodyPart(body);
			for (var attachment : message.attachments()){
				var part = new MimeBodyPart();
				part.setDataHandler(new DataHandler(new ByteArrayDataSource(attachment.content(),attachment.mime())));
				part.setFileName(attachment.name());
				multipart.addBodyPart(part);
				msg.setContent(multipart);
			}
		}



		LOG.log(TRACE, "Message to {0} is ready…", receiver);
		Transport.send(msg,user,pass);
		LOG.log(DEBUG, "Sent message to {0}.", receiver);
	}
}