package de.srsoftware.widerhall.mail;

import com.sun.mail.imap.IMAPFolder;
import de.srsoftware.widerhall.Constants;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.mail.*;
import java.time.Duration;
import java.util.Date;
import java.util.HashSet;
import java.util.Properties;

public class ImapClient {

    private static final Logger LOG = LoggerFactory.getLogger(ImapClient.class);
    private final int port;
    private final String host, username, password, folderName;
    private final ProblemListener problemListener;
    private IMAPFolder inbox;
    private ListeningThread listeningThread;
    private Heartbeat heartbeat;

    private class ListeningThread extends Thread {

        private static final Logger LOG = LoggerFactory.getLogger(ListeningThread.class);
        private HashSet<MessageHandler> listeners = new HashSet<>();
        private boolean stopped = false;
        private Session session;

        public ListeningThread addListener(MessageHandler messageHandler) {
            listeners.add(messageHandler);
            return this;
        }

        public ListeningThread doStop() {
            stopped = true;
            return this;
        }

        public ListeningThread dropListeners() {
            listeners.clear();
            return this;
        }


        private void handle(Message message) throws MessagingException {
            LOG.debug("Handling {}",message.getSubject());
            for (MessageHandler listener : listeners) listener.onMessageReceived(message);
        }

        private void handleMessages() throws MessagingException {
            LOG.debug("Reading email of {}:",username);
            if (!inbox.isOpen()) inbox.open(IMAPFolder.READ_WRITE);
            for (Message message : inbox.getMessages()){
                if (message.isSet(Flags.Flag.SEEN)) continue;
                handle(message);
                Folder folder = message.getFolder();
                if (!folder.isOpen()) folder.open(Folder.READ_WRITE);
                message.setFlag(Flags.Flag.SEEN,true);
            }
        }

        private Properties imapProps() {
            Properties props = new Properties();
            props.put(Constants.PROTOCOL,Constants.IMAPS);
            return props;
        }

        private void openInbox() throws MessagingException {
            LOG.debug("Connecting and logging in…");
            Properties props = imapProps();
            session = Session.getInstance(props);
            Store store = session.getStore(Constants.IMAPS);
            store.connect(host,username,password);
            LOG.debug("Connected, opening {}:",folderName);
            inbox = (IMAPFolder)store.getFolder(folderName);
            inbox.open(IMAPFolder.READ_WRITE);

            while (!stopped){
                handleMessages();
                problemListener.clearProblems();
                LOG.debug("Idling.");
                inbox.idle(true);
            }
        }

        @Override
        public void run() {
            while (!stopped) {
                try {
                    sleep(5000);
                } catch (InterruptedException interruptedException) {
                    interruptedException.printStackTrace();
                }
                try {
                    openInbox();
                } catch (MessagingException e){
                    LOG.warn("Connection problem:",e);
                    problemListener.onImapException(e);
                }
            }
        }
    }

    private class Heartbeat extends Thread{
        private static final Logger LOG = LoggerFactory.getLogger(Heartbeat.class);
        private boolean stopped = false;

        public Heartbeat doStop() {
            stopped = true;
            return this;
        }

        @Override
        public void run() {
            while (!stopped){
                try {
                    sleep(300034);
                    if (inbox != null) continue;
                    LOG.debug("sending NOOP");
                    inbox.doCommand(protocol -> {
                            protocol.simpleCommand("NOOP",null);
                            return null;
                    });
                } catch (InterruptedException | MessagingException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    public ImapClient(String host, int port, String username, String password, String folderName,ProblemListener listener) {
        this.host = host;
        this.port = port;
        this.username = username;
        this.password = password;
        this.folderName = folderName;
        this.problemListener = listener;
    }

    public ImapClient addListener(MessageHandler messageHandler) {
        if (listeningThread == null) listeningThread = new ListeningThread();
        listeningThread.addListener(messageHandler);
        return this;
    }

    public void dropMailsOlderThan(Integer holdTime) throws MessagingException {
        var now = new Date();
        if (holdTime == null) return;
        LOG.debug("Removing mails older than {} days:",holdTime);
        if (!inbox.isOpen()) inbox.open(IMAPFolder.READ_WRITE);
        for (Message message : inbox.getMessages()){
            Date receivedDate = message.getReceivedDate();
            Duration duration = Duration.between(receivedDate.toInstant(),now.toInstant());
            var days = duration.toDays();
            LOG.info("Message {} is {} days old!",message.getSubject(),days);
            if (days > holdTime){
                LOG.info("…removing");
                Folder folder = message.getFolder();
                if (!folder.isOpen()) folder.open(Folder.READ_WRITE);
                message.setFlag(Flags.Flag.DELETED, true);
            }
        }
        inbox.expunge();
    }

    public String folderName(){
        return folderName;
    }


    public String host(){
        return host;
    }

    public ImapClient move(Message message, String destinationFolder) throws MessagingException {
        if (listeningThread == null || listeningThread.stopped) throw new IllegalStateException("IMAP client not connected!");
        var source = message.getFolder();
        if (!source.isOpen()) source.open(Folder.READ_WRITE);
        var messages = new Message[]{message};
        var store = source.getStore();
        var dest = store.getFolder(new URLName(destinationFolder));
        if (!dest.exists()) dest.create(Folder.HOLDS_MESSAGES);
        source.copyMessages(messages,dest);
        source.setFlags(messages, new Flags(Flags.Flag.DELETED), true);
        source.close(true);
        return this;
    }

    public String password(){
        return password;
    }

    public int port(){
        return port;
    }


    public ImapClient start() {
        stop();

        LOG.info("Creating ListeningThread for {}…",username);
        (listeningThread = new ListeningThread()).start();

        LOG.info("Creating Heartbeat for {}…",username);
        (heartbeat = new Heartbeat()).start();

        return this;
    }

    public ImapClient stop(){
        if (listeningThread != null) {
            LOG.info("Stopping old ListeningThread for {}…",username);
            listeningThread.dropListeners().doStop();
            listeningThread = null;
        }
        if (heartbeat != null){
            heartbeat.doStop();
            heartbeat = null;
        }
        return this;
    }

    public String username(){
        return username;
    }
}