Add quick utility methods to JoinOffer

src/main/java/xyz/nucleoid/plasmid/api/game/GameTexts.java

@@ -156,6 +156,14 @@ public static MutableText inOtherGame() {
         public static MutableText notAllowed() {
             return Text.translatable("text.plasmid.join_result.not_allowed");
         }
+
+        public static MutableText spectatorsOnly() {
+            return Text.translatable("text.plasmid.join_result.spectators_only");
+        }
+
+        public static MutableText participantsOnly() {
+            return Text.translatable("text.plasmid.join_result.participants_only");
+        }
     }
 
     public static final class Kick {

src/main/java/xyz/nucleoid/plasmid/api/game/player/JoinOffer.java

@@ -8,6 +8,7 @@
 
 import java.util.Set;
 import java.util.UUID;
+import java.util.function.Function;
 import java.util.stream.Collectors;
 
 /**
@@ -83,4 +84,54 @@ default JoinOfferResult.Accept accept() {
     default JoinOfferResult pass() {
         return JoinOfferResult.PASS;
     }
+
+    /**
+     * Returns an offer result that accepts this offer only if the intent is to spectate.
+     * <p>
+     * This function does not do anything on its own, but its result must be returned within a
+     * {@link GamePlayerEvents#OFFER} listener.
+     *
+     * @return an "accept" offer result for spectators and "reject" offer result for participants
+     */
+    default JoinOfferResult acceptSpectators() {
+        return this.acceptSpectatorsOrElse((x) -> x.reject(GameTexts.Join.spectatorsOnly()));
+    }
+
+    /**
+     * Returns an offer result that accepts this offer only if the intent is to spectate.
+     * Others will be resolved in the orElse method.
+     * <p>
+     * This function does not do anything on its own, but its result must be returned within a
+     * {@link GamePlayerEvents#OFFER} listener.
+     *
+     * @return an "accept" offer result for spectators and "reject" offer result for participants
+     */
+    default JoinOfferResult acceptSpectatorsOrElse(Function<JoinOffer, JoinOfferResult> function) {
+        return this.intent() == JoinIntent.SPECTATE ? this.accept() : function.apply(this);
+    }
+
+    /**
+     * Returns an offer result that accepts this offer only if the intent is to participate / play.
+     * <p>
+     * This function does not do anything on its own, but its result must be returned within a
+     * {@link GamePlayerEvents#OFFER} listener.
+     *
+     * @return an "accept" offer result for participants and "reject" offer result for spectators
+     */
+    default JoinOfferResult acceptParticipants() {
+        return this.acceptParticipantsOrElse((x) -> x.reject(GameTexts.Join.participantsOnly()));
+    }
+
+    /**
+     * Returns an offer result that accepts this offer only if the intent is to participate / play.
+     * Others will be resolved in the orElse method.
+     * <p>
+     * This function does not do anything on its own, but its result must be returned within a
+     * {@link GamePlayerEvents#OFFER} listener.
+     *
+     * @return an "accept" offer result for spectators and "reject" offer result for participants
+     */
+    default JoinOfferResult acceptParticipantsOrElse(Function<JoinOffer, JoinOfferResult> function) {
+        return this.intent() == JoinIntent.PLAY ? this.accept() : function.apply(this);
+    }
 }

src/main/java/xyz/nucleoid/plasmid/api/game/player/MutablePlayerSet.java

@@ -4,20 +4,32 @@
 import it.unimi.dsi.fastutil.objects.ObjectOpenHashSet;
 import net.minecraft.server.MinecraftServer;
 import net.minecraft.server.network.ServerPlayerEntity;
+import net.minecraft.server.world.ServerWorld;
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
+import xyz.nucleoid.plasmid.api.game.GameSpace;
 import xyz.nucleoid.plasmid.api.util.PlayerRef;
 
 import java.util.Iterator;
 import java.util.Set;
 import java.util.UUID;
+import java.util.function.Function;
 
 public final class MutablePlayerSet implements PlayerSet {
-    private final MinecraftServer server;
+    private final Function<UUID, ServerPlayerEntity> playerGetter;
 
     private final Set<UUID> players = new ObjectOpenHashSet<>();
 
     public MutablePlayerSet(MinecraftServer server) {
-        this.server = server;
+        this.playerGetter = server.getPlayerManager()::getPlayer;
+    }
+
+    public MutablePlayerSet(ServerWorld world) {
+        this.playerGetter = (uuid) -> world.getPlayerByUuid(uuid) instanceof ServerPlayerEntity player ? player : null;
+    }
+
+    public MutablePlayerSet(GameSpace gameSpace) {
+        this.playerGetter = gameSpace.getPlayers()::getEntity;
     }
 
     public void clear() {
@@ -47,7 +59,7 @@ public boolean remove(UUID id) {
     @Nullable
     @Override
     public ServerPlayerEntity getEntity(UUID id) {
-        return this.players.contains(id) ? this.server.getPlayerManager().getPlayer(id) : null;
+        return this.players.contains(id) ? this.playerGetter.apply(id) : null;
     }
 
     @Override
@@ -56,16 +68,16 @@ public boolean contains(UUID id) {
     }
 
     @Override
-    public Iterator<ServerPlayerEntity> iterator() {
-        var playerManager = this.server.getPlayerManager();
+    public @NotNull Iterator<ServerPlayerEntity> iterator() {
+        var playerGetter = this.playerGetter;
         var ids = this.players.iterator();
 
         return new AbstractIterator<>() {
             @Override
             protected ServerPlayerEntity computeNext() {
                 while (ids.hasNext()) {
                     var id = ids.next();
-                    var player = playerManager.getPlayer(id);
+                    var player = playerGetter.apply(id);
                     if (player != null) {
                         return player;
                     }

src/main/java/xyz/nucleoid/plasmid/api/game/player/PlayerSet.java

@@ -3,6 +3,7 @@
 import net.minecraft.server.MinecraftServer;
 import net.minecraft.server.network.ServerPlayerEntity;
 import net.minecraft.server.world.ServerWorld;
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import xyz.nucleoid.plasmid.api.util.PlayerRef;
 import xyz.nucleoid.plasmid.impl.player.EmptyPlayerSet;
@@ -104,5 +105,6 @@ default MutablePlayerSet copy(MinecraftServer server) {
      * @return an iterator over the online {@link ServerPlayerEntity} within this {@link PlayerSet}
      */
     @Override
+    @NotNull
     Iterator<ServerPlayerEntity> iterator();
 }

src/main/java/xyz/nucleoid/plasmid/impl/game/manager/ManagedGameSpacePlayers.java

@@ -1,6 +1,7 @@
 package xyz.nucleoid.plasmid.impl.game.manager;
 
 import net.minecraft.server.network.ServerPlayerEntity;
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import xyz.nucleoid.plasmid.api.game.player.*;
 import xyz.nucleoid.plasmid.impl.player.LocalJoinAcceptor;
@@ -174,7 +175,7 @@ public int size() {
     }
 
     @Override
-    public Iterator<ServerPlayerEntity> iterator() {
+    public @NotNull Iterator<ServerPlayerEntity> iterator() {
         return this.set.iterator();
     }
 

src/main/java/xyz/nucleoid/plasmid/impl/player/ServerPlayerSet.java

@@ -2,6 +2,7 @@
 
 import net.minecraft.server.PlayerManager;
 import net.minecraft.server.network.ServerPlayerEntity;
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import xyz.nucleoid.plasmid.api.game.player.PlayerSet;
 
@@ -26,7 +27,7 @@ public int size() {
     }
 
     @Override
-    public Iterator<ServerPlayerEntity> iterator() {
+    public @NotNull Iterator<ServerPlayerEntity> iterator() {
         return this.players.getPlayerList().iterator();
     }
 }

src/main/java/xyz/nucleoid/plasmid/impl/player/ServerWorldPlayerSet.java

@@ -2,6 +2,7 @@
 
 import net.minecraft.server.network.ServerPlayerEntity;
 import net.minecraft.server.world.ServerWorld;
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import xyz.nucleoid.plasmid.api.game.player.PlayerSet;
 
@@ -26,7 +27,7 @@ public int size() {
     }
 
     @Override
-    public Iterator<ServerPlayerEntity> iterator() {
+    public @NotNull Iterator<ServerPlayerEntity> iterator() {
         return this.world.getPlayers().iterator();
     }
 }

src/main/resources/data/plasmid/lang/en_us.json

@@ -68,6 +68,8 @@
   "text.plasmid.join_result.in_other_game": "You must %s before joining another game!",
   "text.plasmid.join_result.in_other_game.leave_this_game": "leave this game",
   "text.plasmid.join_result.not_allowed": "You are not allowed to join this game!",
+  "text.plasmid.join_result.spectators_only": "You are not allowed to participate in this game!",
+  "text.plasmid.join_result.participants_only": "You are not allowed to spectate this game!",
   "text.plasmid.map_workspace.workspace_not_found": "Map with id '%s' was not found!",
   "text.plasmid.map.bounds.get": "The bounds for the workspace are %s to %s",
   "text.plasmid.map.bounds.set": "Updated bounds for workspace",