Add support for multiple queued TPA requests

Essentials/src/main/java/com/earth2me/essentials/ISettings.java

@@ -231,6 +231,8 @@ public interface ISettings extends IConf {
 
     long getTpaAcceptCancellation();
 
+    int getTpaMaxRequests();
+
     long getTeleportInvulnerability();
 
     boolean isTeleportInvulnerability();

Essentials/src/main/java/com/earth2me/essentials/IUser.java

@@ -12,13 +12,16 @@
 import org.bukkit.Material;
 import org.bukkit.block.Block;
 import org.bukkit.entity.Player;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 import java.math.BigDecimal;
+
 import java.util.ArrayList;
 import java.util.Date;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.UUID;
 import java.util.regex.Pattern;
 
 /**
@@ -61,8 +64,11 @@ public interface IUser {
     /**
      * Returns whether this user has an outstanding teleport request to deal with.
      *
+     * @deprecated The teleport request system has been moved into a multi-user teleport request queue.
+     * @see IUser#hasPendingTpaRequests(boolean, boolean)
      * @return whether there is a teleport request
      */
+    @Deprecated
     boolean hasOutstandingTeleportRequest();
 
     /**
@@ -98,6 +104,11 @@ public interface IUser {
 
     boolean canBuild();
 
+    /**
+     * @deprecated The teleport request system has been moved into a multi-user teleport request queue.
+     * @see IUser#getNextTpaRequest(boolean, boolean, boolean)
+     */
+    @Deprecated
     long getTeleportRequestTime();
 
     void enableInvulnerabilityAfterTeleport();
@@ -205,6 +216,8 @@ public interface IUser {
 
     String getName();
 
+    UUID getUUID();
+
     String getDisplayName();
 
     String getFormattedNickname();
@@ -238,4 +251,74 @@ public interface IUser {
     void setToggleShout(boolean toggleShout);
 
     boolean isToggleShout();
+
+    /**
+     * Gets information about the most-recently-made, non-expired TPA request in the tpa queue of this {@link IUser}.
+     * <p>
+     * The TPA Queue is Last-In-First-Out queue which stores all the active pending teleport
+     * requests of this {@link IUser}. Timeout calculations are also done during the
+     * iteration process of this method, ensuring that teleport requests made past the timeout
+     * period are removed from queue and therefore not returned here. The maximum size of this
+     * queue is determined by {@link ISettings#getTpaMaxRequests()}.
+     *
+     * @param inform             true if the underlying {@link IUser} should be informed if a request expires during iteration.
+     * @param performExpirations true if this method should not spend time validating time for all items in the queue and just return the first item in the queue.
+     * @param excludeHere        true if /tphere requests should be ignored in fetching the next tpa request.
+     * @return A {@link TpaRequest} corresponding to the next available request or null if no valid request is present.
+     */
+    @Nullable TpaRequest getNextTpaRequest(boolean inform, boolean performExpirations, boolean excludeHere);
+
+    /**
+     * Whether or not this {@link IUser} has any valid TPA requests in queue.
+     *
+     * @param inform      true if the user should be informed if a request expires during iteration.
+     * @param excludeHere true if /tpahere requests should be ignored in checking if a tpa request is available.
+     * @return true if the user has an available pending request in queue.
+     */
+    boolean hasPendingTpaRequests(boolean inform, boolean excludeHere);
+
+    class TpaRequest {
+        private final String name;
+        private final UUID requesterUuid;
+        private boolean here;
+        private Location location;
+        private long time;
+
+        public TpaRequest(String name, UUID requesterUuid) {
+            this.name = name;
+            this.requesterUuid = requesterUuid;
+        }
+
+        public String getName() {
+            return name;
+        }
+
+        public UUID getRequesterUuid() {
+            return requesterUuid;
+        }
+
+        public boolean isHere() {
+            return here;
+        }
+
+        public void setHere(boolean here) {
+            this.here = here;
+        }
+
+        public Location getLocation() {
+            return location;
+        }
+
+        public void setLocation(Location location) {
+            this.location = location;
+        }
+
+        public long getTime() {
+            return time;
+        }
+
+        public void setTime(long time) {
+            this.time = time;
+        }
+    }
 }

Essentials/src/main/java/com/earth2me/essentials/Settings.java

@@ -1232,6 +1232,11 @@ public long getTpaAcceptCancellation() {
         return config.getLong("tpa-accept-cancellation", 120);
     }
 
+    @Override
+    public int getTpaMaxRequests() {
+        return config.getInt("tpa-max-requests", 15);
+    }
+
     private long _getTeleportInvulnerability() {
         return config.getLong("teleport-invulnerability", 0) * 1000;
     }

Essentials/src/main/java/com/earth2me/essentials/User.java

@@ -30,16 +30,21 @@
 import org.bukkit.inventory.PlayerInventory;
 import org.bukkit.potion.PotionEffect;
 import org.bukkit.potion.PotionEffectType;
+import org.checkerframework.checker.nullness.qual.Nullable;
 
 import java.math.BigDecimal;
 import java.util.Calendar;
+import java.util.Collection;
 import java.util.GregorianCalendar;
+import java.util.Iterator;
+import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
 import java.util.UUID;
 import java.util.WeakHashMap;
 import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.TimeUnit;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 
@@ -48,28 +53,37 @@
 public class User extends UserData implements Comparable<User>, IMessageRecipient, net.ess3.api.IUser {
     private static final Statistic PLAY_ONE_TICK = EnumUtil.getStatistic("PLAY_ONE_MINUTE", "PLAY_ONE_TICK");
     private static final Logger logger = Logger.getLogger("Essentials");
+
+    // User modules
     private final IMessageRecipient messageRecipient;
     private transient final AsyncTeleport teleport;
     private transient final Teleport legacyTeleport;
+
+    // User command confirmation strings
     private final Map<User, BigDecimal> confirmingPayments = new WeakHashMap<>();
-    private transient UUID teleportRequester;
-    private transient boolean teleportRequestHere;
-    private transient Location teleportLocation;
+
+    // User teleport variables
+    private final transient LinkedHashMap<String, TpaRequest> teleportRequestQueue = new LinkedHashMap<>();
+
+    // User properties
     private transient boolean vanished;
-    private transient long teleportRequestTime;
-    private transient long lastOnlineActivity;
-    private transient long lastThrottledAction;
-    private transient long lastActivity = System.currentTimeMillis();
     private boolean hidden = false;
     private boolean rightClickJump = false;
-    private transient Location afkPosition = null;
     private boolean invSee = false;
     private boolean recipeSee = false;
     private boolean enderSee = false;
-    private transient long teleportInvulnerabilityTimestamp = 0;
     private boolean ignoreMsg = false;
+
+    // User afk variables
     private String afkMessage;
     private long afkSince;
+    private transient Location afkPosition = null;
+
+    // Misc
+    private transient long lastOnlineActivity;
+    private transient long lastThrottledAction;
+    private transient long lastActivity = System.currentTimeMillis();
+    private transient long teleportInvulnerabilityTimestamp = 0;
     private String confirmingClearCommand;
     private long lastNotifiedAboutMailsMs;
     private String lastHomeConfirmation;
@@ -90,9 +104,8 @@ public User(final Player base, final IEssentials ess) {
         this.messageRecipient = new SimpleMessageRecipient(ess, this);
     }
 
-    User update(final Player base) {
+    void update(final Player base) {
         setBase(base);
-        return this;
     }
 
     @Override
@@ -327,44 +340,95 @@ public void setLogoutLocation() {
 
     @Override
     public void requestTeleport(final User player, final boolean here) {
-        teleportRequestTime = System.currentTimeMillis();
-        teleportRequester = player == null ? null : player.getBase().getUniqueId();
-        teleportRequestHere = here;
-        if (player == null) {
-            teleportLocation = null;
-        } else {
-            teleportLocation = here ? player.getLocation() : this.getLocation();
+        final TpaRequest request = teleportRequestQueue.getOrDefault(player.getName(), new TpaRequest(player.getName(), player.getUUID()));
+        request.setTime(System.currentTimeMillis());
+        request.setHere(here);
+        request.setLocation(here ? player.getLocation() : this.getLocation());
+
+        // Handle max queue size
+        teleportRequestQueue.remove(request.getName());
+        if (teleportRequestQueue.size() >= ess.getSettings().getTpaMaxRequests()) {
+            String lastKey = null;
+            for (Map.Entry<String, TpaRequest> entry : teleportRequestQueue.entrySet()) {
+                lastKey = entry.getKey();
+            }
+            teleportRequestQueue.remove(lastKey);
         }
+
+        // Add request to queue
+        teleportRequestQueue.put(request.getName(), request);
     }
 
     @Override
+    @Deprecated
     public boolean hasOutstandingTeleportRequest() {
-        if (getTeleportRequest() != null) { // Player has outstanding teleport request.
-            final long timeout = ess.getSettings().getTpaAcceptCancellation();
-            if (timeout != 0) {
-                if ((System.currentTimeMillis() - getTeleportRequestTime()) / 1000 <= timeout) { // Player has outstanding request
-                    return true;
-                } else { // outstanding request expired.
-                    requestTeleport(null, false);
-                    return false;
-                }
-            } else { // outstanding request does not expire
-                return true;
-            }
-        }
-        return false;
+        return getNextTpaRequest(false, false, false) != null;
+    }
+
+    public Collection<String> getPendingTpaKeys() {
+        return teleportRequestQueue.keySet();
     }
 
-    public UUID getTeleportRequest() {
-        return teleportRequester;
+    @Override
+    public boolean hasPendingTpaRequests(boolean inform, boolean excludeHere) {
+        return getNextTpaRequest(inform, false, excludeHere) != null;
+    }
+
+    public boolean hasOutstandingTpaRequest(String playerUsername, boolean here) {
+        final TpaRequest request = getOutstandingTpaRequest(playerUsername, false);
+        return request != null && request.isHere() == here;
+    }
+
+    public @Nullable TpaRequest getOutstandingTpaRequest(String playerUsername, boolean inform) {
+        if (!teleportRequestQueue.containsKey(playerUsername)) {
+            return null;
+        }
+
+        final long timeout = ess.getSettings().getTpaAcceptCancellation();
+        final TpaRequest request = teleportRequestQueue.get(playerUsername);
+        if (timeout < 1 || System.currentTimeMillis() - request.getTime() <= timeout * 1000) {
+            return request;
+        }
+        teleportRequestQueue.remove(playerUsername);
+        if (inform) {
+            sendMessage(tl("requestTimedOutFrom", ess.getUser(request.getRequesterUuid()).getDisplayName()));
+        }
+        return null;
     }
 
-    public boolean isTpRequestHere() {
-        return teleportRequestHere;
+    public TpaRequest removeTpaRequest(String playerUsername) {
+        return teleportRequestQueue.remove(playerUsername);
     }
 
-    public Location getTpRequestLocation() {
-        return teleportLocation;
+    @Override
+    public TpaRequest getNextTpaRequest(boolean inform, boolean performExpirations, boolean excludeHere) {
+        if (teleportRequestQueue.isEmpty()) {
+            return null;
+        }
+
+        final long timeout = ess.getSettings().getTpaAcceptCancellation();
+        final Iterator<Map.Entry<String, TpaRequest>> iterator = teleportRequestQueue.entrySet().iterator();
+        TpaRequest nextRequest = null;
+        while (iterator.hasNext()) {
+            final TpaRequest request = iterator.next().getValue();
+            if (timeout < 1 || (System.currentTimeMillis() - request.getTime()) <= TimeUnit.SECONDS.toMillis(timeout)) {
+                if (excludeHere && request.isHere()) {
+                    continue;
+                }
+
+                if (performExpirations) {
+                    return request;
+                } else if (nextRequest == null) {
+                    nextRequest = request;
+                }
+            } else {
+                if (inform) {
+                    sendMessage(tl("requestTimedOutFrom", ess.getUser(request.getRequesterUuid()).getDisplayName()));
+                }
+                iterator.remove();
+            }
+        }
+        return nextRequest;
     }
 
     public String getNick() {
@@ -823,8 +887,11 @@ public boolean canBuild() {
         return ess.getPermissionsHandler().canBuild(base, getGroup());
     }
 
+    @Override
+    @Deprecated
     public long getTeleportRequestTime() {
-        return teleportRequestTime;
+        final TpaRequest request = getNextTpaRequest(false, false, false);
+        return request == null ? 0L : request.getTime();
     }
 
     public boolean isInvSee() {
@@ -990,7 +1057,7 @@ public String getName() {
 
     @Override
     public UUID getUUID() {
-        return getBase().getUniqueId();
+        return this.getBase().getUniqueId();
     }
 
     @Override

Essentials/src/main/java/com/earth2me/essentials/commands/Commandtpa.java

@@ -37,11 +37,12 @@ public void run(final Server server, final User user, final String commandLabel,
         if (user.getWorld() != player.getWorld() && ess.getSettings().isWorldTeleportPermissions() && !user.isAuthorized("essentials.worlds." + player.getWorld().getName())) {
             throw new Exception(tl("noPerm", "essentials.worlds." + player.getWorld().getName()));
         }
+
         // Don't let sender request teleport twice to the same player.
-        if (user.getConfigUUID().equals(player.getTeleportRequest()) && player.hasOutstandingTeleportRequest() // Check timeout
-            && !player.isTpRequestHere()) { // Make sure the last teleport request was actually tpa and not tpahere
+        if (player.hasOutstandingTpaRequest(user.getName(), false)) {
             throw new Exception(tl("requestSentAlready", player.getDisplayName()));
         }
+
         if (player.isAutoTeleportEnabled() && !player.isIgnoredPlayer(user)) {
             final Trade charge = new Trade(this.getName(), ess);
             final AsyncTeleport teleport = user.getAsyncTeleport();
@@ -71,6 +72,7 @@ public void run(final Server server, final User user, final String commandLabel,
                 player.sendMessage(tl("teleportRequestTimeoutInfo", ess.getSettings().getTpaAcceptCancellation()));
             }
         }
+
         user.sendMessage(tl("requestSent", player.getDisplayName()));
         if (user.isAuthorized("essentials.tpacancel")) {
             user.sendMessage(tl("typeTpacancel"));