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

import static de.srsoftware.umbrella.core.ConnectionProvider.connect;
import static de.srsoftware.umbrella.core.constants.Constants.TIME_FORMATTER;
import static de.srsoftware.umbrella.core.constants.Constants.UTF8;
import static de.srsoftware.umbrella.core.constants.Field.*;
import static de.srsoftware.umbrella.core.constants.Path.READ;
import static de.srsoftware.umbrella.core.constants.Path.SETTINGS;
import static de.srsoftware.umbrella.core.constants.Text.LONG;
import static de.srsoftware.umbrella.core.exceptions.UmbrellaException.invalidField;
import static de.srsoftware.umbrella.core.exceptions.UmbrellaException.missingConfig;
import static de.srsoftware.umbrella.core.model.Translatable.t;
import static de.srsoftware.umbrella.message.Constants.*;
import static de.srsoftware.umbrella.message.model.Schedule.schedule;
import static de.srsoftware.umbrella.messagebus.MessageBus.messageBus;
import static java.lang.System.Logger.Level.*;
import static java.net.HttpURLConnection.HTTP_BAD_REQUEST;

import com.sun.net.httpserver.HttpExchange;
import de.srsoftware.configuration.Configuration;
import de.srsoftware.tools.Path;
import de.srsoftware.tools.SessionToken;
import de.srsoftware.umbrella.core.BaseHandler;
import de.srsoftware.umbrella.core.ModuleRegistry;
import de.srsoftware.umbrella.core.api.PostBox;
import de.srsoftware.umbrella.core.exceptions.UmbrellaException;
import de.srsoftware.umbrella.core.model.Envelope;
import de.srsoftware.umbrella.core.model.Token;
import de.srsoftware.umbrella.core.model.UmbrellaUser;
import de.srsoftware.umbrella.core.model.User;
import de.srsoftware.umbrella.message.model.*;
import de.srsoftware.umbrella.messagebus.EventListener;
import de.srsoftware.umbrella.messagebus.events.Event;
import jakarta.activation.DataHandler;
import jakarta.mail.Message.RecipientType;
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.io.IOException;
import java.util.*;
import java.util.concurrent.CopyOnWriteArrayList;

import org.json.JSONArray;
import org.json.JSONObject;

public class MessageSystem extends BaseHandler implements PostBox, EventListener {
	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 final List<Envelope> queue = new CopyOnWriteArrayList<>();
	private String debugAddress;
	private final HashMap<Receiver,List<Exception>> exceptions = new HashMap<>();

	public MessageSystem(Configuration config) throws UmbrellaException {
		var dbFile   = config.get(CONFIG_DB).orElseThrow(() -> missingConfig(CONFIG_DB));
		db           = new SqliteMessageDb(connect(dbFile));
		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;
		ModuleRegistry.add(this);
		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();
		messageBus().register(this);
	}

	@Override
	public boolean doGet(Path path, HttpExchange ex) throws IOException {
		addCors(ex);
		try {
			Optional<Token> token = SessionToken.from(ex).map(Token::of);
			var user = ModuleRegistry.userService().loadUser(token);
			if (user.isEmpty()) return unauthorized(ex);
			var head = path.pop();
			return switch (head){
				case null -> listMessages(ex,user.get());
				case SETTINGS -> getSettings(ex,user.get());
				default -> {
					try {
						yield getMessage(ex,user.get(),Integer.parseInt(head));
					} catch (NumberFormatException ignored) {

					}
					yield super.doGet(path, ex);
				}
			};
		} catch (NumberFormatException e){
			return sendContent(ex,HTTP_BAD_REQUEST,"Invalid project id");
		} catch (UmbrellaException e){
			return send(ex,e);
		}
	}

	@Override
	public boolean doPatch(Path path, HttpExchange ex) throws IOException {
		addCors(ex);
		try {
			Optional<Token> token = SessionToken.from(ex).map(Token::of);
			var user = ModuleRegistry.userService().loadUser(token);
			if (user.isEmpty()) return unauthorized(ex);
			var head = path.pop();
			return switch (head){
				case SETTINGS -> patchSettings(ex,user.get());
				case READ -> patchState(ex,user.get(),path.pop());
				default -> super.doGet(path,ex);
			};
		} catch (NumberFormatException e){
			return sendContent(ex,HTTP_BAD_REQUEST,"Invalid project id");
		} catch (UmbrellaException e){
			return send(ex,e);
		}
	}

	private boolean getMessage(HttpExchange ex, UmbrellaUser user, int hash) throws IOException {
		var envelope = queue.stream()
				.filter(msg -> msg.isFor(user))
				.filter(msg -> msg.hashCode() == hash)
				.findFirst();
		if (envelope.isPresent()) return sendMessage(ex, user, envelope.get());
		return notFound(ex);
	}

	private boolean getSettings(HttpExchange ex, UmbrellaUser user) throws IOException {
		return sendContent(ex,db.getSettings(user));
	}

	private boolean listMessages(HttpExchange ex, UmbrellaUser user) throws IOException {
		var messages = queue.stream().filter(e -> e.isFor(user)).map(e -> summary(e, user.language())).toList();
		return sendContent(ex,messages);
	}

	@Override
	public void onEvent(Event<?> event) {
		for (var user : event.audience()){
			if (debugAddress != null && !debugAddress.equals(user.email().toString())) continue;
			var message = new de.srsoftware.umbrella.core.model.Message(event.initiator(),event.subject(),event.describe(),null);
			var envelope = new Envelope(message,user);
			send(envelope);
		}
	}

	private boolean patchSettings(HttpExchange ex, UmbrellaUser user) throws IOException {
		var json = json(ex);
		Settings settings = null;
		if (json.has(INSTANTLY) && json.get(INSTANTLY) instanceof Boolean b && b){
			settings = new Instantly();
		} else {
			if (json.has(HOURS) && json.get(HOURS) instanceof JSONArray hrs){
				var hours = hrs.toList().stream().filter(v -> v instanceof Integer).map(Integer.class::cast).toList();
				settings = schedule(hours);
			} else settings = new Silent();
		}
		return sendContent(ex,db.update(user,settings));
	}

	private boolean patchState(HttpExchange ex, UmbrellaUser user, String path) {
		try {
			var hash = Integer.parseInt(path);
			var envelope = queue.stream().filter(env -> env.hashCode() == hash).findFirst().orElse(null);
			if (envelope != null){
				envelope.receivers().remove(user);
				return sendMessage(ex,user,envelope);
			}
			return notFound(ex);
		} catch (NumberFormatException | IOException e) {
			throw invalidField(HASH,LONG);
		}
	}

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

			try {
				send(combined,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 boolean sendMessage(HttpExchange ex, UmbrellaUser user, Envelope envelope) throws IOException {
		var message = envelope.message();
		var sender = message.sender().name();
		var subject = message.subject().translate(user.language());
		var body = message.body().translate(user.language());
		return sendContent(ex,Map.of(
				SENDER,sender,
				SUBJECT,subject,
				BODY,body
		));
	}

	private static JSONObject summary(Envelope envelope, String lang) {
		var sender  = envelope.message().sender().name();
		var subject = envelope.message().subject().translate(lang);
		var time    = envelope.time().format(TIME_FORMATTER);
		var hash      = envelope.hashCode();
		return new JSONObject(Map.of(SENDER,sender,SUBJECT,subject,TIMESTAMP,time,HASH,hash));
	}


	private void send(CombinedMessage message, Date date) throws MessagingException {
		var receiver = message.receiver();
		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(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);
	}

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

	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;
	}

}