package eu.siacs.conversations.services;

import android.util.Log;

import org.jetbrains.annotations.NotNull;

import java.math.BigInteger;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;

import eu.siacs.conversations.Config;
import eu.siacs.conversations.R;
import eu.siacs.conversations.entities.Account;
import eu.siacs.conversations.entities.Conversation;
import eu.siacs.conversations.entities.Conversational;
import eu.siacs.conversations.entities.ReceiptRequest;
import eu.siacs.conversations.generator.AbstractGenerator;
import eu.siacs.conversations.xml.Element;
import eu.siacs.conversations.xmpp.Jid;
import eu.siacs.conversations.xmpp.OnAdvancedStreamFeaturesLoaded;
import eu.siacs.conversations.xmpp.mam.MamReference;
import eu.siacs.conversations.xmpp.stanzas.IqPacket;
import eu.siacs.conversations.xmpp.stanzas.MessagePacket;

public class MessageArchiveService implements OnAdvancedStreamFeaturesLoaded {

	private final XmppConnectionService mXmppConnectionService;

	private final HashSet<Query> queries = new HashSet<>();
	private final ArrayList<Query> pendingQueries = new ArrayList<>();

	public enum Version {
		MAM_0("urn:xmpp:mam:0", true),
		MAM_1("urn:xmpp:mam:1", false),
		MAM_2("urn:xmpp:mam:2", false);

		public final boolean legacy;
		public final String namespace;

		Version(String namespace, boolean legacy) {
			this.namespace = namespace;
			this.legacy = legacy;
		}

		public static Version get(Account account) {
			return get(account,null);
		}

		public static Version get(Account account, Conversation conversation) {
			if (conversation == null || conversation.getMode() == Conversation.MODE_SINGLE) {
				return get(account.getXmppConnection().getFeatures().getAccountFeatures());
			} else {
				return get(conversation.getMucOptions().getFeatures());
			}
		}

		private static Version get(List<String> features) {
			final Version[] values = values();
			for(int i = values.length -1; i >= 0; --i) {
				for(String feature : features) {
					if (values[i].namespace.equals(feature)) {
						return values[i];
					}
				}
			}
			return MAM_0;
		}

		public static boolean has(List<String> features) {
			for(String feature : features) {
				for(Version version : values()) {
					if (version.namespace.equals(feature)) {
						return true;
					}
				}
			}
			return false;
		}

		public static Element findResult(MessagePacket packet) {
			for(Version version : values()) {
				Element result = packet.findChild("result", version.namespace);
				if (result != null) {
					return result;
				}
			}
			return null;
		}

	}

    MessageArchiveService(final XmppConnectionService service) {
		this.mXmppConnectionService = service;
	}

	private void catchup(final Account account) {
		synchronized (this.queries) {
			for (Iterator<Query> iterator = this.queries.iterator(); iterator.hasNext(); ) {
				Query query = iterator.next();
				if (query.getAccount() == account) {
					iterator.remove();
				}
			}
		}
		MamReference mamReference = MamReference.max(
				mXmppConnectionService.databaseBackend.getLastMessageReceived(account),
				mXmppConnectionService.databaseBackend.getLastClearDate(account)
		);
		mamReference = MamReference.max(mamReference, mXmppConnectionService.getAutomaticMessageDeletionDate());
		long endCatchup = account.getXmppConnection().getLastSessionEstablished();
		final Query query;
		if (mamReference.getTimestamp() == 0) {
			return;
		} else if (endCatchup - mamReference.getTimestamp() >= Config.MAM_MAX_CATCHUP) {
			long startCatchup = endCatchup - Config.MAM_MAX_CATCHUP;
			List<Conversation> conversations = mXmppConnectionService.getConversations();
			for (Conversation conversation : conversations) {
				if (conversation.getMode() == Conversation.MODE_SINGLE && conversation.getAccount() == account && startCatchup > conversation.getLastMessageTransmitted().getTimestamp()) {
					this.query(conversation, startCatchup, true);
				}
			}
			query = new Query(account, new MamReference(startCatchup), 0);
		} else {
			query = new Query(account, mamReference, 0);
		}
		synchronized (this.queries) {
			this.queries.add(query);
		}
		this.execute(query);
	}

	void catchupMUC(final Conversation conversation) {
		if (conversation.getLastMessageTransmitted().getTimestamp() < 0 && conversation.countMessages() == 0) {
			query(conversation,
					new MamReference(0),
					0,
					true);
		} else {
			query(conversation,
					conversation.getLastMessageTransmitted(),
					0,
					true);
		}
	}

	public Query query(final Conversation conversation) {
		if (conversation.getLastMessageTransmitted().getTimestamp() < 0 && conversation.countMessages() == 0) {
			return query(conversation,
					new MamReference(0),
					System.currentTimeMillis(),
					false);
		} else {
			return query(conversation,
					conversation.getLastMessageTransmitted(),
					conversation.getAccount().getXmppConnection().getLastSessionEstablished(),
					false);
		}
	}

	public boolean isCatchingUp(Conversation conversation) {
		final Account account = conversation.getAccount();
		if (account.getXmppConnection().isWaitingForSmCatchup()) {
			return true;
		} else {
			synchronized (this.queries) {
				for (Query query : this.queries) {
					if (query.getAccount() == account && query.isCatchup() && ((conversation.getMode() == Conversation.MODE_SINGLE && query.getWith() == null) || query.getConversation() == conversation)) {
						return true;
					}
				}
			}
			return false;
		}
	}

	public Query query(final Conversation conversation, long end, boolean allowCatchup) {
		return this.query(conversation, conversation.getLastMessageTransmitted(), end, allowCatchup);
	}

	public Query query(Conversation conversation, MamReference start, long end, boolean allowCatchup) {
		synchronized (this.queries) {
			final Query query;
			final MamReference startActual = MamReference.max(start, mXmppConnectionService.getAutomaticMessageDeletionDate());
			if (start.getTimestamp() == 0) {
				query = new Query(conversation, startActual, end, false);
				query.reference = conversation.getFirstMamReference();
			} else {
				if (allowCatchup) {
					MamReference maxCatchup = MamReference.max(startActual, System.currentTimeMillis() - Config.MAM_MAX_CATCHUP);
					if (maxCatchup.greaterThan(startActual)) {
						Query reverseCatchup = new Query(conversation, startActual, maxCatchup.getTimestamp(), false);
						this.queries.add(reverseCatchup);
						this.execute(reverseCatchup);
					}
					query = new Query(conversation, maxCatchup, end, true);
				} else {
					query = new Query(conversation, startActual, end, false);
				}
			}
			if (end != 0 && start.greaterThan(end)) {
				return null;
			}
			this.queries.add(query);
			this.execute(query);
			return query;
		}
	}

	void executePendingQueries(final Account account) {
		List<Query> pending = new ArrayList<>();
		synchronized (this.pendingQueries) {
			for (Iterator<Query> iterator = this.pendingQueries.iterator(); iterator.hasNext(); ) {
				Query query = iterator.next();
				if (query.getAccount() == account) {
					pending.add(query);
					iterator.remove();
				}
			}
		}
		for (Query query : pending) {
			this.execute(query);
		}
	}

	private void execute(final Query query) {
		final Account account = query.getAccount();
		if (account.getStatus() == Account.State.ONLINE) {
			final Conversation conversation = query.getConversation();
			if (conversation != null && conversation.getStatus() == Conversation.STATUS_ARCHIVED) {
				throw new IllegalStateException("Attempted to run MAM query for archived conversation");
			}
			Log.d(Config.LOGTAG, account.getJid().asBareJid().toString() + ": running mam query " + query.toString());
			final IqPacket packet = this.mXmppConnectionService.getIqGenerator().queryMessageArchiveManagement(query);
			this.mXmppConnectionService.sendIqPacket(account, packet, (a, p) -> {
				final Element fin = p.findChild("fin", query.version.namespace);
				if (p.getType() == IqPacket.TYPE.TIMEOUT) {
					synchronized (this.queries) {
						this.queries.remove(query);
						if (query.hasCallback()) {
							query.callback(false);
						}
					}
				} else if (p.getType() == IqPacket.TYPE.RESULT && fin != null) {
					final boolean running;
					synchronized (this.queries) {
						running = this.queries.contains(query);
					}
					if (running) {
						processFin(query, fin);
					} else {
						Log.d(Config.LOGTAG,account.getJid().asBareJid()+": ignoring MAM iq result because query had been killed");
					}
				} else if (p.getType() == IqPacket.TYPE.RESULT && query.isLegacy()) {
					//do nothing
				} else {
					Log.d(Config.LOGTAG, a.getJid().asBareJid().toString() + ": error executing mam: " + p.toString());
					finalizeQuery(query, true);
				}
			});
		} else {
			synchronized (this.pendingQueries) {
				this.pendingQueries.add(query);
			}
		}
	}

	private void finalizeQuery(final Query query, boolean done) {
		synchronized (this.queries) {
			if (!this.queries.remove(query)) {
				throw new IllegalStateException("Unable to remove query from queries");
			}
		}
		final Conversation conversation = query.getConversation();
		if (conversation != null) {
			conversation.sort();
			conversation.setHasMessagesLeftOnServer(!done);
		} else {
			for (Conversation tmp : this.mXmppConnectionService.getConversations()) {
				if (tmp.getAccount() == query.getAccount()) {
					tmp.sort();
				}
			}
		}
		if (query.hasCallback()) {
			query.callback(done);
		} else {
			this.mXmppConnectionService.updateConversationUi();
		}
	}

	boolean inCatchup(Account account) {
		synchronized (this.queries) {
			for (Query query : queries) {
				if (query.account == account && query.isCatchup() && query.getWith() == null) {
					return true;
				}
			}
		}
		return false;
	}

	public boolean isCatchupInProgress(Conversation conversation) {
		synchronized (this.queries) {
			for(Query query : queries) {
				if (query.account == conversation.getAccount() && query.isCatchup()) {
					final Jid with = query.getWith() == null ? null : query.getWith().asBareJid();
					if ((conversation.getMode() == Conversational.MODE_SINGLE && with == null) || (conversation.getJid().asBareJid().equals(with))) {
						return true;
					}
				}
			}
		}
		return false;
	}

	boolean queryInProgress(Conversation conversation, XmppConnectionService.OnMoreMessagesLoaded callback) {
		synchronized (this.queries) {
			for (Query query : queries) {
				if (query.conversation == conversation) {
					if (!query.hasCallback() && callback != null) {
						query.setCallback(callback);
					}
					return true;
				}
			}
			return false;
		}
	}

	public boolean queryInProgress(Conversation conversation) {
		return queryInProgress(conversation, null);
	}

	public void processFinLegacy(Element fin, Jid from) {
		Query query = findQuery(fin.getAttribute("queryid"));
		if (query != null && query.validFrom(from)) {
			processFin(query, fin);
		}
	}

	private void processFin(Query query, Element fin) {
		boolean complete = fin.getAttributeAsBoolean("complete");
		Element set = fin.findChild("set", "http://jabber.org/protocol/rsm");
		Element last = set == null ? null : set.findChild("last");
		String count = set == null ? null : set.findChildContent("count");
		Element first = set == null ? null : set.findChild("first");
		Element relevant = query.getPagingOrder() == PagingOrder.NORMAL ? last : first;
		boolean abort = (!query.isCatchup() && query.getTotalCount() >= Config.PAGE_SIZE) || query.getTotalCount() >= Config.MAM_MAX_MESSAGES;
		if (query.getConversation() != null) {
			query.getConversation().setFirstMamReference(first == null ? null : first.getContent());
		}
		if (complete || relevant == null || abort) {
			//TODO: FIX done logic to look at complete. using count is probably unreliable because it can be ommited and doesn’t work with paging.
			boolean done;
			if (query.isCatchup()) {
				done = false;
			} else {
				if (count != null) {
					try {
						done = Integer.parseInt(count) <= query.getTotalCount();
					} catch (NumberFormatException e) {
						done = false;
					}
				} else {
					done = query.getTotalCount() == 0;
				}
			}
			done = done || (query.getActualMessageCount() == 0 && !query.isCatchup());
			this.finalizeQuery(query, done);

			Log.d(Config.LOGTAG, query.getAccount().getJid().asBareJid() + ": finished mam after " + query.getTotalCount() + "(" + query.getActualMessageCount() + ") messages. messages left=" + !done + " count=" + count);
			if (query.isCatchup() && query.getActualMessageCount() > 0) {
				mXmppConnectionService.getNotificationService().finishBacklog(true, query.getAccount());
			}
			processPostponed(query);
		} else {
			final Query nextQuery;
			if (query.getPagingOrder() == PagingOrder.NORMAL) {
				nextQuery = query.next(last == null ? null : last.getContent());
			} else {
				nextQuery = query.prev(first == null ? null : first.getContent());
			}
			this.execute(nextQuery);
			this.finalizeQuery(query, false);
			synchronized (this.queries) {
				this.queries.add(nextQuery);
			}
		}
	}

	void kill(Conversation conversation) {
		final ArrayList<Query> toBeKilled = new ArrayList<>();
		synchronized (this.queries) {
			for (final Query q : queries) {
				if (q.conversation == conversation) {
					toBeKilled.add(q);
				}
			}
		}
		for (Query q : toBeKilled) {
			kill(q);
		}
	}

	private void kill(Query query) {
		Log.d(Config.LOGTAG, query.getAccount().getJid().asBareJid() + ": killing mam query prematurely");
		query.callback = null;
		this.finalizeQuery(query, false);
		if (query.isCatchup() && query.getActualMessageCount() > 0) {
			mXmppConnectionService.getNotificationService().finishBacklog(true, query.getAccount());
		}
		this.processPostponed(query);
	}

	private void processPostponed(Query query) {
		query.account.getAxolotlService().processPostponed();
		query.pendingReceiptRequests.removeAll(query.receiptRequests);
		Log.d(Config.LOGTAG, query.getAccount().getJid().asBareJid() + ": found " + query.pendingReceiptRequests.size() + " pending receipt requests");
		Iterator<ReceiptRequest> iterator = query.pendingReceiptRequests.iterator();
		while (iterator.hasNext()) {
			ReceiptRequest rr = iterator.next();
			mXmppConnectionService.sendMessagePacket(query.account, mXmppConnectionService.getMessageGenerator().received(query.account, rr.getJid(), rr.getId()));
			iterator.remove();
		}
	}

	public Query findQuery(String id) {
		if (id == null) {
			return null;
		}
		synchronized (this.queries) {
			for (Query query : this.queries) {
				if (query.getQueryId().equals(id)) {
					return query;
				}
			}
			return null;
		}
	}

	@Override
	public void onAdvancedStreamFeaturesAvailable(Account account) {
		if (account.getXmppConnection() != null && account.getXmppConnection().getFeatures().mam()) {
			this.catchup(account);
		}
	}

	public enum PagingOrder {
		NORMAL,
		REVERSE
	}

	public class Query {
		private HashSet<ReceiptRequest> pendingReceiptRequests = new HashSet<>();
		private HashSet<ReceiptRequest> receiptRequests = new HashSet<>();
		private int totalCount = 0;
		private int actualCount = 0;
		private int actualInThisQuery = 0;
		private long start;
		private final long end;
		private final String queryId;
		private String reference = null;
		private final Account account;
		private Conversation conversation;
		private PagingOrder pagingOrder = PagingOrder.NORMAL;
		private XmppConnectionService.OnMoreMessagesLoaded callback = null;
		private boolean catchup = true;
		public final Version version;


		Query(Conversation conversation, MamReference start, long end, boolean catchup) {
			this(conversation.getAccount(), Version.get(conversation.getAccount(), conversation), catchup ? start : start.timeOnly(), end);
			this.conversation = conversation;
			this.pagingOrder = catchup ? PagingOrder.NORMAL : PagingOrder.REVERSE;
			this.catchup = catchup;
		}

		Query(Account account, MamReference start, long end) {
			this(account, Version.get(account), start, end);
		}

		Query(Account account, Version version, MamReference start, long end) {
			this.account = account;
			if (start.getReference() != null) {
				this.reference = start.getReference();
			} else {
				this.start = start.getTimestamp();
			}
			this.end = end;
			this.queryId = new BigInteger(50, mXmppConnectionService.getRNG()).toString(32);
			this.version = version;
		}

		private Query page(String reference) {
			Query query = new Query(this.account, this.version, new MamReference(this.start, reference), this.end);
			query.conversation = conversation;
			query.totalCount = totalCount;
			query.actualCount = actualCount;
			query.pendingReceiptRequests = pendingReceiptRequests;
			query.receiptRequests = receiptRequests;
			query.callback = callback;
			query.catchup = catchup;
			return query;
		}

		public void removePendingReceiptRequest(ReceiptRequest receiptRequest) {
			if (!this.pendingReceiptRequests.remove(receiptRequest)) {
				this.receiptRequests.add(receiptRequest);
			}
		}

		public void addPendingReceiptRequest(ReceiptRequest receiptRequest) {
			this.pendingReceiptRequests.add(receiptRequest);
		}

		public boolean isLegacy() {
			return version.legacy;
		}

		public boolean safeToExtractTrueCounterpart() {
			return muc() && !isLegacy();
		}

		public Query next(String reference) {
			Query query = page(reference);
			query.pagingOrder = PagingOrder.NORMAL;
			return query;
		}

		Query prev(String reference) {
			Query query = page(reference);
			query.pagingOrder = PagingOrder.REVERSE;
			return query;
		}

		public String getReference() {
			return reference;
		}

		public PagingOrder getPagingOrder() {
			return this.pagingOrder;
		}

		public String getQueryId() {
			return queryId;
		}

		public Jid getWith() {
			return conversation == null ? null : conversation.getJid().asBareJid();
		}

		public boolean muc() {
			return conversation != null && conversation.getMode() == Conversation.MODE_MULTI;
		}

		public long getStart() {
			return start;
		}

		public boolean isCatchup() {
			return catchup;
		}

		public void setCallback(XmppConnectionService.OnMoreMessagesLoaded callback) {
			this.callback = callback;
		}

		public void callback(boolean done) {
			if (this.callback != null) {
				this.callback.onMoreMessagesLoaded(actualCount, conversation);
				if (done) {
					this.callback.informUser(R.string.no_more_history_on_server);
				}
			}
		}

		public long getEnd() {
			return end;
		}

		public Conversation getConversation() {
			return conversation;
		}

		public Account getAccount() {
			return this.account;
		}

		public void incrementMessageCount() {
			this.totalCount++;
		}

		public void incrementActualMessageCount() {
			this.actualInThisQuery++;
			this.actualCount++;
		}

		int getTotalCount() {
			return this.totalCount;
		}

		int getActualMessageCount() {
			return this.actualCount;
		}

		public int getActualInThisQuery() {
			return this.actualInThisQuery;
		}

		public boolean validFrom(Jid from) {
			if (muc()) {
				return getWith().equals(from);
			} else {
				return (from == null) || account.getJid().asBareJid().equals(from.asBareJid());
			}
		}

		@NotNull
		@Override
		public String toString() {
			StringBuilder builder = new StringBuilder();
			if (this.muc()) {
				builder.append("to=");
				builder.append(this.getWith().toString());
			} else {
				builder.append("with=");
				if (this.getWith() == null) {
					builder.append("*");
				} else {
					builder.append(getWith().toString());
				}
			}
			if (this.start != 0) {
				builder.append(", start=");
				builder.append(AbstractGenerator.getTimestamp(this.start));
			}
			if (this.end != 0) {
				builder.append(", end=");
				builder.append(AbstractGenerator.getTimestamp(this.end));
			}
			builder.append(", order=").append(pagingOrder.toString());
			if (this.reference != null) {
				if (this.pagingOrder == PagingOrder.NORMAL) {
					builder.append(", after=");
				} else {
					builder.append(", before=");
				}
				builder.append(this.reference);
			}
			builder.append(", catchup=").append(catchup);
			builder.append(", ns=").append(version.namespace);
			return builder.toString();
		}

		boolean hasCallback() {
			return this.callback != null;
		}
	}
}