feat(protection): implement player opt-in lifecycle

design/log.md

@@ -27,3 +27,10 @@
 - Added defensive UUID-keyed YAML player state with RFC 3339 timestamps, forward-field preservation, and atomic replacement where supported.
 - Added safe plugin initialization and periodic dirty-state persistence.
 - US-006 remains in progress pending live runtime setting commands and Leaf effect ownership behavior.
+
+### US-001 player protection completed
+
+- Added permission-aware player commands with idempotent choice changes and detailed status reporting.
+- Added immediate durable opt-in persistence, join-time restoration, and quiet infinite Resistance reconciliation.
+- Leaf tracks its live Resistance fingerprint and conservatively preserves a visibly distinct Resistance effect.
+- Verified player choice, lock, persistence, command, autocomplete, and build behavior with `./gradlew clean check jar`.

design/user-stories/us-001-opt-into-leaf-protection.md

@@ -2,7 +2,7 @@
 type: User Story
 title: "US-001: Opt into Leaf protection"
 description: Let players voluntarily receive and relinquish a persistent Resistance boost.
-status: backlog
+status: done
 ---
 
 # US-001: Opt into Leaf protection
@@ -11,15 +11,15 @@ As a **player**, I want to opt into Leaf protection so that I can receive a mode
 
 ## Acceptance criteria
 
-- [ ] Players with the `leaf.use` permission, granted by default, can use `/leaf on`, `/leaf off`, and `/leaf status`.
+- [x] Players with the `leaf.use` permission, granted by default, can use `/leaf on`, `/leaf off`, and `/leaf status`.
-- [ ] `/leaf on` records the player's opt-in choice and grants Resistance I while Leaf is globally enabled.
+- [x] `/leaf on` records the player's opt-in choice and grants Resistance I while Leaf is globally enabled.
-- [ ] Resistance remains continuously effective without distracting expiry or renewal messages or particles.
+- [x] Resistance remains continuously effective without distracting expiry or renewal messages or particles.
-- [ ] `/leaf off` records the player's opt-out choice and immediately removes only the Resistance effect managed by Leaf.
+- [x] `/leaf off` records the player's opt-out choice and immediately removes only the Resistance effect managed by Leaf.
-- [ ] `/leaf status` clearly distinguishes the player's saved choice, active protection, administrative lock, and global Leaf state.
+- [x] `/leaf status` clearly distinguishes the player's saved choice, active protection, administrative lock, and global Leaf state.
-- [ ] Repeating an already-satisfied `on` or `off` command is safe and explains that no change was needed.
+- [x] Repeating an already-satisfied `on` or `off` command is safe and explains that no change was needed.
-- [ ] Opt-in choices are keyed by UUID and survive logout and server restart.
+- [x] Opt-in choices are keyed by UUID and survive logout and server restart.
-- [ ] A player who joins while opted in regains protection when Leaf is enabled.
+- [x] A player who joins while opted in regains protection when Leaf is enabled.
-- [ ] Player-command autocomplete suggests only valid next arguments available to the sender.
+- [x] Player-command autocomplete suggests only valid next arguments available to the sender.
 
 ## Related
 

src/main/java/games/dmg/leaf/LeafCommand.java

@@ -0,0 +1,106 @@
+package games.dmg.leaf;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Locale;
+import org.bukkit.command.Command;
+import org.bukkit.command.CommandSender;
+import org.bukkit.command.TabExecutor;
+import org.bukkit.entity.Player;
+
+/** Implements the permission-aware /leaf command tree. */
+public final class LeafCommand implements TabExecutor {
+    private static final List<String> PLAYER_COMMANDS = List.of("on", "off", "status");
+    private final LeafRuntime runtime;
+
+    public LeafCommand(LeafRuntime runtime) {
+        this.runtime = runtime;
+    }
+
+    @Override
+    public boolean onCommand(
+        CommandSender sender,
+        Command command,
+        String label,
+        String[] arguments
+    ) {
+        if (arguments.length != 1 || !PLAYER_COMMANDS.contains(arguments[0].toLowerCase(Locale.ROOT))) {
+            sender.sendMessage("Usage: /leaf <on|off|status>");
+            return true;
+        }
+        if (!(sender instanceof Player player)) {
+            sender.sendMessage("This Leaf command must be run by a player.");
+            return true;
+        }
+        if (!sender.hasPermission("leaf.use")) {
+            sender.sendMessage("You do not have permission to use Leaf.");
+            return true;
+        }
+
+        String action = arguments[0].toLowerCase(Locale.ROOT);
+        try {
+            switch (action) {
+                case "on" -> reportChoice(player, true, runtime.setOwnChoice(player, true));
+                case "off" -> reportChoice(player, false, runtime.setOwnChoice(player, false));
+                case "status" -> reportStatus(player);
+                default -> throw new IllegalStateException("validated action was not handled");
+            }
+        } catch (IOException | IllegalArgumentException exception) {
+            sender.sendMessage("Leaf could not save your request; no partial change was applied.");
+        }
+        return true;
+    }
+
+    @Override
+    public List<String> onTabComplete(
+        CommandSender sender,
+        Command command,
+        String alias,
+        String[] arguments
+    ) {
+        if (arguments.length != 1 || !sender.hasPermission("leaf.use")) {
+            return List.of();
+        }
+        return matching(PLAYER_COMMANDS, arguments[0]);
+    }
+
+    private void reportChoice(Player player, boolean enabled, LeafRuntime.Change change) {
+        if (change == LeafRuntime.Change.LOCKED) {
+            player.sendMessage(runtime.settings().lockedMessage());
+        } else if (change == LeafRuntime.Change.UNCHANGED) {
+            player.sendMessage("Leaf was already " + (enabled ? "enabled" : "disabled") + ".");
+        } else {
+            player.sendMessage("Leaf protection is now " + (enabled ? "enabled" : "disabled") + ".");
+        }
+    }
+
+    private void reportStatus(Player player) {
+        LeafRuntime.Status status = runtime.status(player.getUniqueId());
+        player.sendMessage(
+            "Leaf status — Saved choice: " + onOff(status.savedChoice())
+                + "; active: " + yesNo(status.activeProtection())
+                + "; locked: " + yesNo(status.locked())
+                + "; global: " + onOff(status.globallyEnabled()) + "."
+        );
+    }
+
+    static List<String> matching(List<String> candidates, String partial) {
+        String normalized = partial.toLowerCase(Locale.ROOT);
+        List<String> matches = new ArrayList<>();
+        for (String candidate : candidates) {
+            if (candidate.toLowerCase(Locale.ROOT).startsWith(normalized)) {
+                matches.add(candidate);
+            }
+        }
+        return List.copyOf(matches);
+    }
+
+    private static String onOff(boolean value) {
+        return value ? "on" : "off";
+    }
+
+    private static String yesNo(boolean value) {
+        return value ? "yes" : "no";
+    }
+}

src/main/java/games/dmg/leaf/LeafListener.java

@@ -0,0 +1,33 @@
+package games.dmg.leaf;
+
+import java.io.IOException;
+import java.time.Clock;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.Listener;
+import org.bukkit.event.player.PlayerJoinEvent;
+
+/** Handles player lifecycle events that affect Leaf protection. */
+public final class LeafListener implements Listener {
+    private final LeafRuntime runtime;
+    private final Clock clock;
+    private final Logger logger;
+
+    public LeafListener(LeafRuntime runtime, Clock clock, Logger logger) {
+        this.runtime = runtime;
+        this.clock = clock;
+        this.logger = logger;
+    }
+
+    @EventHandler
+    public void onJoin(PlayerJoinEvent event) {
+        try {
+            runtime.observe(event.getPlayer(), clock.instant());
+        } catch (IOException exception) {
+            logger.log(Level.SEVERE, "Could not persist Leaf player state on join", exception);
+            runtime.removeProtection(event.getPlayer());
+            event.getPlayer().sendMessage("Leaf protection is unavailable because state could not be saved.");
+        }
+    }
+}

src/main/java/games/dmg/leaf/LeafPlugin.java

@@ -1,13 +1,17 @@
 package games.dmg.leaf;
 
 import java.io.IOException;
+import java.time.Clock;
 import java.util.Map;
 import java.util.logging.Level;
+import org.bukkit.command.PluginCommand;
+import org.bukkit.entity.Player;
 import org.bukkit.plugin.java.JavaPlugin;
 
 public final class LeafPlugin extends JavaPlugin {
     private LeafSettingsProvider settingsProvider;
     private LeafStateManager stateManager;
+    private LeafRuntime runtime;
 
     @Override
     public void onEnable() {
@@ -18,6 +22,13 @@ public final class LeafPlugin extends JavaPlugin {
             stateManager = new LeafStateManager(
                 new YamlLeafStateRepository(getDataFolder().toPath().resolve("state.yml"))
             );
+            runtime = new LeafRuntime(
+                getServer(),
+                settingsProvider,
+                stateManager,
+                new LeafProtection()
+            );
+            registerRuntime();
         } catch (IllegalArgumentException | IOException exception) {
             getLogger().log(Level.SEVERE, "Could not initialize Leaf", exception);
             getServer().getPluginManager().disablePlugin(this);
@@ -30,9 +41,31 @@ public final class LeafPlugin extends JavaPlugin {
 
     @Override
     public void onDisable() {
+        if (runtime != null) {
+            for (Player player : getServer().getOnlinePlayers()) {
+                runtime.removeProtection(player);
+            }
+        }
         saveState();
     }
 
+    private void registerRuntime() {
+        LeafCommand leafCommand = new LeafCommand(runtime);
+        PluginCommand command = getCommand("leaf");
+        if (command == null) {
+            throw new IllegalStateException("Leaf command is missing from plugin.yml");
+        }
+        command.setExecutor(leafCommand);
+        command.setTabCompleter(leafCommand);
+        getServer().getPluginManager().registerEvents(
+            new LeafListener(runtime, Clock.systemUTC(), getLogger()),
+            this
+        );
+        for (Player player : getServer().getOnlinePlayers()) {
+            runtime.reconcile(player);
+        }
+    }
+
     LeafSettingsProvider settingsProvider() {
         return settingsProvider;
     }

src/main/java/games/dmg/leaf/LeafProtection.java

@@ -0,0 +1,66 @@
+package games.dmg.leaf;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.UUID;
+import org.bukkit.entity.Player;
+import org.bukkit.potion.PotionEffect;
+import org.bukkit.potion.PotionEffectType;
+
+/** Applies and conservatively removes the Resistance effect owned by Leaf. */
+public final class LeafProtection {
+    private final Map<UUID, PotionEffect> appliedEffects = new HashMap<>();
+
+    public synchronized boolean apply(Player player, int level) {
+        PotionEffect desired = effectForLevel(level);
+        PotionEffect previous = appliedEffects.get(player.getUniqueId());
+        if (previous != null && !previous.equals(desired)) {
+            removeMatching(player, previous);
+            appliedEffects.remove(player.getUniqueId());
+        }
+
+        PotionEffect active = player.getPotionEffect(PotionEffectType.RESISTANCE);
+        if (desired.equals(active) && desired.equals(appliedEffects.get(player.getUniqueId()))) {
+            return true;
+        }
+        boolean applied = player.addPotionEffect(desired);
+        if (applied) {
+            appliedEffects.put(player.getUniqueId(), desired);
+        }
+        return applied || desired.equals(active);
+    }
+
+    public synchronized void remove(Player player) {
+        PotionEffect expected = appliedEffects.remove(player.getUniqueId());
+        if (expected != null) {
+            removeMatching(player, expected);
+        }
+    }
+
+    public synchronized boolean owns(Player player) {
+        PotionEffect expected = appliedEffects.get(player.getUniqueId());
+        return expected != null
+            && expected.equals(player.getPotionEffect(PotionEffectType.RESISTANCE));
+    }
+
+    static PotionEffect effectForLevel(int level) {
+        if (level < 1 || level > 5) {
+            throw new IllegalArgumentException("Resistance level must be between 1 and 5");
+        }
+        return new PotionEffect(
+            PotionEffectType.RESISTANCE,
+            PotionEffect.INFINITE_DURATION,
+            level - 1,
+            true,
+            false,
+            false
+        );
+    }
+
+    private static void removeMatching(Player player, PotionEffect expected) {
+        PotionEffect active = player.getPotionEffect(PotionEffectType.RESISTANCE);
+        if (expected.equals(active)) {
+            player.removePotionEffect(PotionEffectType.RESISTANCE);
+        }
+    }
+}

src/main/java/games/dmg/leaf/LeafRuntime.java

@@ -0,0 +1,130 @@
+package games.dmg.leaf;
+
+import java.io.IOException;
+import java.time.Instant;
+import java.util.Objects;
+import java.util.UUID;
+import org.bukkit.Server;
+import org.bukkit.entity.Player;
+
+/** Coordinates durable player intent with live Leaf-managed protection. */
+public final class LeafRuntime {
+    public enum Change {
+        CHANGED,
+        UNCHANGED,
+        LOCKED
+    }
+
+    public record Status(
+        boolean savedChoice,
+        boolean activeProtection,
+        boolean locked,
+        boolean globallyEnabled,
+        Instant firstJoin
+    ) { }
+
+    private final Server server;
+    private final LeafSettingsProvider settingsProvider;
+    private final LeafStateManager stateManager;
+    private final LeafProtection protection;
+
+    public LeafRuntime(
+        Server server,
+        LeafSettingsProvider settingsProvider,
+        LeafStateManager stateManager,
+        LeafProtection protection
+    ) {
+        this.server = Objects.requireNonNull(server, "server");
+        this.settingsProvider = Objects.requireNonNull(settingsProvider, "settingsProvider");
+        this.stateManager = Objects.requireNonNull(stateManager, "stateManager");
+        this.protection = Objects.requireNonNull(protection, "protection");
+    }
+
+    public PlayerLeafState observe(Player player, Instant observedAt) throws IOException {
+        PlayerLeafState state = stateManager.observePlayer(
+            player.getUniqueId(),
+            player.getName(),
+            observedAt
+        );
+        stateManager.saveIfDirty();
+        reconcile(player);
+        return state;
+    }
+
+    public Change setOwnChoice(Player player, boolean optedIn) throws IOException {
+        PlayerLeafState state = requiredState(player.getUniqueId());
+        if (state.locked()) {
+            return Change.LOCKED;
+        }
+        return setChoice(player.getUniqueId(), optedIn);
+    }
+
+    public Change setChoice(UUID playerId, boolean optedIn) throws IOException {
+        PlayerLeafState state = requiredState(playerId);
+        if (state.optedIn() == optedIn) {
+            return Change.UNCHANGED;
+        }
+        stateManager.update(playerId, current -> current.withOptedIn(optedIn));
+        stateManager.saveIfDirty();
+        Player online = server.getPlayer(playerId);
+        if (online != null) {
+            reconcile(online);
+        }
+        return Change.CHANGED;
+    }
+
+    public Change setLocked(UUID playerId, boolean locked) throws IOException {
+        PlayerLeafState state = requiredState(playerId);
+        if (state.locked() == locked) {
+            return Change.UNCHANGED;
+        }
+        stateManager.update(playerId, current -> current.withLocked(locked));
+        stateManager.saveIfDirty();
+        return Change.CHANGED;
+    }
+
+    public Status status(UUID playerId) {
+        PlayerLeafState state = requiredState(playerId);
+        Player online = server.getPlayer(playerId);
+        boolean globallyEnabled = settingsProvider.current().enabled();
+        boolean active = online != null
+            && globallyEnabled
+            && state.optedIn()
+            && protection.owns(online);
+        return new Status(
+            state.optedIn(),
+            active,
+            state.locked(),
+            globallyEnabled,
+            state.firstJoin()
+        );
+    }
+
+    public void reconcile(Player player) {
+        PlayerLeafState state = stateManager.find(player.getUniqueId()).orElse(null);
+        LeafSettings settings = settingsProvider.current();
+        if (state != null && state.optedIn() && settings.enabled()) {
+            protection.apply(player, settings.resistanceLevel());
+        } else {
+            protection.remove(player);
+        }
+    }
+
+    public void removeProtection(Player player) {
+        protection.remove(player);
+    }
+
+    public LeafStateManager stateManager() {
+        return stateManager;
+    }
+
+    public LeafSettings settings() {
+        return settingsProvider.current();
+    }
+
+    private PlayerLeafState requiredState(UUID playerId) {
+        return stateManager.find(playerId).orElseThrow(
+            () -> new IllegalArgumentException("unknown player: " + playerId)
+        );
+    }
+}

src/test/java/games/dmg/leaf/LeafCommandTest.java

@@ -0,0 +1,67 @@
+package games.dmg.leaf;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.mockito.ArgumentMatchers.contains;
+import static org.mockito.Mockito.atLeastOnce;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import java.time.Instant;
+import java.util.List;
+import java.util.UUID;
+import org.bukkit.command.Command;
+import org.bukkit.entity.Player;
+import org.junit.jupiter.api.Test;
+
+final class LeafCommandTest {
+    @Test
+    void playerCommandsReportChangesLocksAndDetailedStatus() throws Exception {
+        Player player = mock(Player.class);
+        UUID id = UUID.randomUUID();
+        when(player.getUniqueId()).thenReturn(id);
+        when(player.hasPermission("leaf.use")).thenReturn(true);
+        LeafRuntime runtime = mock(LeafRuntime.class);
+        when(runtime.settings()).thenReturn(LeafSettings.from(java.util.Map.of()));
+        when(runtime.setOwnChoice(player, true)).thenReturn(LeafRuntime.Change.CHANGED);
+        when(runtime.setOwnChoice(player, false)).thenReturn(LeafRuntime.Change.LOCKED);
+        when(runtime.status(id)).thenReturn(new LeafRuntime.Status(
+            true,
+            true,
+            false,
+            true,
+            Instant.parse("2026-08-10T00:00:00Z")
+        ));
+        LeafCommand leaf = new LeafCommand(runtime);
+        Command command = mock(Command.class);
+
+        assertTrue(leaf.onCommand(player, command, "leaf", new String[] {"on"}));
+        assertTrue(leaf.onCommand(player, command, "leaf", new String[] {"off"}));
+        assertTrue(leaf.onCommand(player, command, "leaf", new String[] {"status"}));
+
+        verify(player, atLeastOnce()).sendMessage(contains("enabled"));
+        verify(player, atLeastOnce()).sendMessage(contains("locked"));
+        verify(player, atLeastOnce()).sendMessage(contains("Saved choice: on"));
+        verify(player, atLeastOnce()).sendMessage(contains("active: yes"));
+    }
+
+    @Test
+    void completionIncludesOnlyPlayerArgumentsAllowedToSender() {
+        LeafRuntime runtime = mock(LeafRuntime.class);
+        LeafCommand leaf = new LeafCommand(runtime);
+        Command command = mock(Command.class);
+        Player allowed = mock(Player.class);
+        when(allowed.hasPermission("leaf.use")).thenReturn(true);
+        Player denied = mock(Player.class);
+
+        assertEquals(
+            List.of("on", "off", "status"),
+            leaf.onTabComplete(allowed, command, "leaf", new String[] {""})
+        );
+        assertEquals(
+            List.of(),
+            leaf.onTabComplete(denied, command, "leaf", new String[] {""})
+        );
+    }
+}

src/test/java/games/dmg/leaf/LeafRuntimeTest.java

@@ -0,0 +1,104 @@
+package games.dmg.leaf;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import java.nio.file.Path;
+import java.time.Instant;
+import java.util.Map;
+import java.util.UUID;
+import org.bukkit.Server;
+import org.bukkit.entity.Player;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+final class LeafRuntimeTest {
+    @TempDir
+    Path temporaryDirectory;
+
+    @Test
+    void playerCanOptInAndProtectionIsRestoredFromPersistedChoice() throws Exception {
+        UUID playerId = UUID.randomUUID();
+        Player player = player(playerId, "Alex");
+        Server server = mock(Server.class);
+        when(server.getPlayer(playerId)).thenReturn(player);
+        LeafProtection protection = mock(LeafProtection.class);
+        when(protection.apply(player, 1)).thenReturn(true);
+        Path stateFile = temporaryDirectory.resolve("state.yml");
+        LeafRuntime runtime = runtime(server, protection, stateFile);
+        runtime.observe(player, Instant.parse("2026-08-10T00:00:00Z"));
+
+        assertEquals(LeafRuntime.Change.CHANGED, runtime.setOwnChoice(player, true));
+        verify(protection).apply(player, 1);
+
+        LeafRuntime restarted = runtime(server, protection, stateFile);
+        restarted.reconcile(player);
+        assertTrue(restarted.status(playerId).savedChoice());
+        verify(protection, org.mockito.Mockito.times(2)).apply(player, 1);
+    }
+
+    @Test
+    void lockedPlayerCannotChangeTheirChoice() throws Exception {
+        UUID playerId = UUID.randomUUID();
+        Player player = player(playerId, "Alex");
+        Server server = mock(Server.class);
+        when(server.getPlayer(playerId)).thenReturn(player);
+        LeafProtection protection = mock(LeafProtection.class);
+        LeafRuntime runtime = runtime(
+            server,
+            protection,
+            temporaryDirectory.resolve("locked.yml")
+        );
+        runtime.observe(player, Instant.parse("2026-08-10T00:00:00Z"));
+        runtime.setLocked(playerId, true);
+
+        assertEquals(LeafRuntime.Change.LOCKED, runtime.setOwnChoice(player, true));
+        assertFalse(runtime.status(playerId).savedChoice());
+        verify(protection, never()).apply(player, 1);
+    }
+
+    @Test
+    void optingOutRemovesLeafProtectionAndRepeatingIsANoOp() throws Exception {
+        UUID playerId = UUID.randomUUID();
+        Player player = player(playerId, "Alex");
+        Server server = mock(Server.class);
+        when(server.getPlayer(playerId)).thenReturn(player);
+        LeafProtection protection = mock(LeafProtection.class);
+        LeafRuntime runtime = runtime(
+            server,
+            protection,
+            temporaryDirectory.resolve("off.yml")
+        );
+        runtime.observe(player, Instant.parse("2026-08-10T00:00:00Z"));
+        runtime.setOwnChoice(player, true);
+
+        assertEquals(LeafRuntime.Change.CHANGED, runtime.setOwnChoice(player, false));
+        assertEquals(LeafRuntime.Change.UNCHANGED, runtime.setOwnChoice(player, false));
+        verify(protection, org.mockito.Mockito.atLeastOnce()).remove(player);
+    }
+
+    private static LeafRuntime runtime(
+        Server server,
+        LeafProtection protection,
+        Path stateFile
+    ) throws Exception {
+        return new LeafRuntime(
+            server,
+            new LeafSettingsProvider(LeafSettings.from(Map.of())),
+            new LeafStateManager(new YamlLeafStateRepository(stateFile)),
+            protection
+        );
+    }
+
+    private static Player player(UUID id, String name) {
+        Player player = mock(Player.class);
+        when(player.getUniqueId()).thenReturn(id);
+        when(player.getName()).thenReturn(name);
+        return player;
+    }
+}