feat(commands): view and set online player heights

src/main/java/games/dmg/spigotheights/BukkitPlayerHeights.java

@@ -0,0 +1,34 @@
+package games.dmg.spigotheights;
+
+import java.util.List;
+import org.bukkit.Server;
+import org.bukkit.attribute.Attribute;
+import org.bukkit.attribute.AttributeInstance;
+import org.bukkit.entity.Player;
+
+/** Bukkit boundary for exact online-player lookup; used only on the server thread. */
+public final class BukkitPlayerHeights {
+    private final Server server;
+
+    public BukkitPlayerHeights(Server server) {
+        this.server = server;
+    }
+
+    public PlayerHeights.Target find(String name) {
+        Player player = server.getPlayerExact(name);
+        if (player == null) {
+            return null;
+        }
+        AttributeInstance scale = player.getAttribute(Attribute.SCALE);
+        if (scale == null) {
+            throw new IllegalArgumentException("Player " + player.getName() + " has no scale attribute.");
+        }
+        return new PlayerHeights.Target(player.getUniqueId(), player.getName(), scale.getBaseValue(),
+                scale.getValue(), scale::setBaseValue);
+    }
+
+    public List<String> names() {
+        return server.getOnlinePlayers().stream().map(Player::getName)
+                .sorted(String.CASE_INSENSITIVE_ORDER).toList();
+    }
+}

src/main/java/games/dmg/spigotheights/HeightStore.java

@@ -8,11 +8,12 @@ import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.StandardCopyOption;
 import java.util.UUID;
+import org.bukkit.configuration.InvalidConfigurationException;
 import org.bukkit.configuration.file.YamlConfiguration;
 
 public final class HeightStore {
     private final Path statePath;
-    private final YamlConfiguration state;
+    private YamlConfiguration state;
 
     public HeightStore(File dataFolder) {
         statePath = dataFolder.toPath().resolve("state.yml");
@@ -25,16 +26,23 @@ public final class HeightStore {
     }
 
     public synchronized void save(UUID playerId, double scale) throws IOException {
-        state.set(path(playerId), scale);
+        YamlConfiguration next = new YamlConfiguration();
+        try {
+            next.loadFromString(state.saveToString());
+        } catch (InvalidConfigurationException exception) {
+            throw new IOException("Could not copy player state", exception);
+        }
+        next.set(path(playerId), scale);
         Files.createDirectories(statePath.getParent());
         Path temporary = statePath.resolveSibling("state.yml.tmp");
-        Files.writeString(temporary, state.saveToString(), StandardCharsets.UTF_8);
+        Files.writeString(temporary, next.saveToString(), StandardCharsets.UTF_8);
         try {
             Files.move(temporary, statePath, StandardCopyOption.ATOMIC_MOVE,
                     StandardCopyOption.REPLACE_EXISTING);
         } catch (AtomicMoveNotSupportedException exception) {
             Files.move(temporary, statePath, StandardCopyOption.REPLACE_EXISTING);
         }
+        state = next;
     }
 
     private static String path(UUID playerId) {

src/main/java/games/dmg/spigotheights/HeightsCommand.java

@@ -11,21 +11,27 @@ import org.bukkit.command.TabExecutor;
 
 public final class HeightsCommand implements TabExecutor {
     private static final String PERMISSION = "spigotheights.admin";
-    private static final String USAGE = "Usage: /heights settings | /heights set min|max <value>";
+    private static final String USAGE = "Usage: /heights settings | /heights set min|max <value>"
+            + " | /heights player <name> [scale]";
     private final LiveHeightSettings settings;
     private final Logger logger;
+    private final PlayerHeights players;
 
-    public HeightsCommand(LiveHeightSettings settings, Logger logger) {
+    public HeightsCommand(LiveHeightSettings settings, PlayerHeights players, Logger logger) {
         this.settings = settings;
+        this.players = players;
         this.logger = logger;
     }
 
     @Override
     public boolean onCommand(CommandSender sender, Command command, String label, String[] args) {
         if (!sender.hasPermission(PERMISSION)) {
-            sender.sendMessage("You do not have permission to manage Spigot Heights settings.");
+            sender.sendMessage("You do not have permission to manage Spigot Heights.");
             return true;
         }
+        if (args.length > 0 && args[0].equalsIgnoreCase("player")) {
+            return playerCommand(sender, args);
+        }
         if (args.length == 1 && args[0].equalsIgnoreCase("settings")) {
             HeightSettings current = settings.get();
             sender.sendMessage("Spigot Heights: min=" + current.minimum() + ", max=" + current.maximum()
@@ -55,13 +61,41 @@ public final class HeightsCommand implements TabExecutor {
         return true;
     }
 
+    private boolean playerCommand(CommandSender sender, String[] args) {
+        if (args.length != 2 && args.length != 3) {
+            sender.sendMessage(USAGE);
+            return true;
+        }
+        try {
+            sender.sendMessage(args.length == 2 ? players.describe(args[1])
+                    : players.set(args[1], Double.parseDouble(args[2])));
+        } catch (NumberFormatException exception) {
+            sender.sendMessage("Invalid scale: enter a finite number, for example 0.5 or 1.0.");
+        } catch (IllegalArgumentException exception) {
+            sender.sendMessage(exception.getMessage());
+        } catch (IOException exception) {
+            logger.warning("Could not save player height: " + exception.getMessage());
+            sender.sendMessage("Could not save player height. Their height is unchanged; check the server log.");
+        }
+        return true;
+    }
+
     @Override
     public List<String> onTabComplete(CommandSender sender, Command command, String alias, String[] args) {
         if (!sender.hasPermission(PERMISSION)) {
             return List.of();
         }
         if (args.length == 1) {
-            return matching(Stream.of("settings", "set"), args[0]);
+            return matching(Stream.of("settings", "set", "player"), args[0]);
+        }
+        if (args.length == 2 && args[0].equalsIgnoreCase("player")) {
+            return matching(players.names().stream(), args[1]);
+        }
+        if (args.length == 3 && args[0].equalsIgnoreCase("player")
+                && players.names().stream().anyMatch(name -> name.equalsIgnoreCase(args[1]))) {
+            HeightSettings current = settings.get();
+            return matching(Stream.of(current.minimum(), current.maximum(), 0.0625, 0.2, 0.4, 0.5, 1.0, 2.0, 3.0, 16.0)
+                    .distinct().sorted().filter(players::isValid).map(String::valueOf), args[2]);
         }
         if (args.length == 2 && args[0].equalsIgnoreCase("set")) {
             return matching(Stream.of("min", "max"), args[1]);
@@ -92,6 +126,6 @@ public final class HeightsCommand implements TabExecutor {
 
     private static List<String> matching(Stream<String> candidates, String prefix) {
         String normalized = prefix.toLowerCase(Locale.ROOT);
-        return candidates.filter(value -> value.startsWith(normalized)).toList();
+        return candidates.filter(value -> value.toLowerCase(Locale.ROOT).startsWith(normalized)).toList();
     }
 }

src/main/java/games/dmg/spigotheights/PlayerHeights.java

@@ -0,0 +1,65 @@
+package games.dmg.spigotheights;
+
+import java.io.IOException;
+import java.util.List;
+import java.util.UUID;
+import java.util.function.DoubleConsumer;
+import java.util.function.Function;
+import java.util.function.Supplier;
+
+/** Online-player operations, called on the server thread. */
+public final class PlayerHeights {
+    public record Target(UUID id, String name, double baseScale, double effectiveScale, DoubleConsumer applyScale) {}
+
+    private final Supplier<HeightSettings> settings;
+    private final HeightStore store;
+    private final Function<String, Target> lookup;
+    private final Supplier<List<String>> onlineNames;
+
+    public PlayerHeights(Supplier<HeightSettings> settings, HeightStore store,
+            Function<String, Target> lookup, Supplier<List<String>> onlineNames) {
+        this.settings = settings;
+        this.store = store;
+        this.lookup = lookup;
+        this.onlineNames = onlineNames;
+    }
+
+    public String describe(String name) {
+        Target target = requireTarget(name);
+        String message = target.name() + " has scale " + target.baseScale() + " (1.0 = normal)";
+        if (target.effectiveScale() != target.baseScale()) {
+            message += "; effective scale with modifiers: " + target.effectiveScale();
+        }
+        return message + ".";
+    }
+
+    public String set(String name, double value) throws IOException {
+        Target target = requireTarget(name);
+        if (!isValid(value)) {
+            HeightSettings current = settings.get();
+            throw new IllegalArgumentException("Scale must be a finite number between " + current.minimum()
+                    + " and " + current.maximum() + ", or exactly 1.0 for normal size.");
+        }
+        store.save(target.id(), value);
+        target.applyScale().accept(value);
+        return "Set " + target.name() + "'s base scale to " + value + ". Saved and active.";
+    }
+
+    public List<String> names() {
+        return onlineNames.get();
+    }
+
+    public boolean isValid(double value) {
+        HeightSettings current = settings.get();
+        return Double.isFinite(value) && (value == 1.0
+                || value >= current.minimum() && value <= current.maximum());
+    }
+
+    private Target requireTarget(String name) {
+        Target target = lookup.apply(name);
+        if (target == null) {
+            throw new IllegalArgumentException("No online player named '" + name + "'. Use their full name.");
+        }
+        return target;
+    }
+}

src/main/java/games/dmg/spigotheights/SpigotHeightsPlugin.java

@@ -24,12 +24,14 @@ public final class SpigotHeightsPlugin extends JavaPlugin {
             getConfig().set("height.minimum", next.minimum());
             getConfig().set("height.maximum", next.maximum());
         });
-        HeightsCommand executor = new HeightsCommand(liveSettings, getLogger());
+        HeightStore store = new HeightStore(getDataFolder());
+        BukkitPlayerHeights onlinePlayers = new BukkitPlayerHeights(getServer());
+        PlayerHeights playerHeights = new PlayerHeights(liveSettings, store, onlinePlayers::find, onlinePlayers::names);
+        HeightsCommand executor = new HeightsCommand(liveSettings, playerHeights, getLogger());
         PluginCommand command = Objects.requireNonNull(getCommand("heights"), "Missing heights command declaration");
         command.setExecutor(executor);
         command.setTabCompleter(executor);
 
-        HeightStore store = new HeightStore(getDataFolder());
         PotionRecipes potions = new PotionRecipes(this);
         potions.register();
         getServer().getPluginManager().registerEvents(