Add JetBrains annotations

12 files changed, 475 insertions, 110 deletions

diff --git a/common/src/main/java/com/leonardobishop/quests/common/player/QPlayer.java b/common/src/main/java/com/leonardobishop/quests/common/player/QPlayer.java
index f9f46078..d8b40cce 100644
--- a/common/src/main/java/com/leonardobishop/quests/common/player/QPlayer.java
+++ b/common/src/main/java/com/leonardobishop/quests/common/player/QPlayer.java
@@ -5,7 +5,10 @@ import com.leonardobishop.quests.common.player.questprogressfile.QuestProgressFi
 import com.leonardobishop.quests.common.plugin.Quests;
 import com.leonardobishop.quests.common.quest.Quest;
 import com.leonardobishop.quests.common.questcontroller.QuestController;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
+import java.util.Objects;
 import java.util.UUID;
 
 /**
@@ -27,7 +30,12 @@ public class QPlayer {
         this.questController = questController;
     }
 
-    public UUID getPlayerUUID() {
+    /**
+     * Get the player UUID associated with this quest player. The player may not be online.
+     *
+     * @return uuid
+     */
+    public @NotNull UUID getPlayerUUID() {
         return this.uuid;
     }
 
@@ -38,7 +46,9 @@ public class QPlayer {
      * @param quest the quest to complete
      * @return true (always)
      */
-    public boolean completeQuest(Quest quest) {
+    public boolean completeQuest(@NotNull Quest quest) {
+        Objects.requireNonNull(quest, "quest cannot be null");
+
         return questController.completeQuestForPlayer(this, quest);
     }
 
@@ -47,7 +57,7 @@ public class QPlayer {
      **
      * @param quest the quest to track
      */
-    public void trackQuest(Quest quest) {
+    public void trackQuest(@Nullable Quest quest) {
         questController.trackQuestForPlayer(this, quest);
     }
 
@@ -57,7 +67,9 @@ public class QPlayer {
      * @param quest the quest to test for
      * @return true if the quest is started or quest autostart is enabled and the quest is ready to start, false otherwise
      */
-    public boolean hasStartedQuest(Quest quest) {
+    public boolean hasStartedQuest(@NotNull Quest quest) {
+        Objects.requireNonNull(quest, "quest cannot be null");
+
         return questController.hasPlayerStartedQuest(this, quest);
     }
 
@@ -70,7 +82,9 @@ public class QPlayer {
      * @return the quest start result -- {@code QuestStartResult.QUEST_SUCCESS} indicates success
      */
     // TODO PlaceholderAPI support
-    public QuestStartResult startQuest(Quest quest) {
+    public @NotNull QuestStartResult startQuest(@NotNull Quest quest) {
+        Objects.requireNonNull(quest, "quest cannot be null");
+
         return questController.startQuestForPlayer(this, quest);
     }
 
@@ -80,7 +94,9 @@ public class QPlayer {
      * @param quest the quest to start
      * @return true if the quest was cancelled, false otherwise
      */
-    public boolean cancelQuest(Quest quest) {
+    public boolean cancelQuest(@NotNull Quest quest) {
+        Objects.requireNonNull(quest, "quest cannot be null");
+
         return questController.cancelQuestForPlayer(this, quest);
     }
 
@@ -92,24 +108,48 @@ public class QPlayer {
      * @param quest the quest to check
      * @return the quest start result
      */
-    public QuestStartResult canStartQuest(Quest quest) {
+    public @NotNull QuestStartResult canStartQuest(@NotNull Quest quest) {
+        Objects.requireNonNull(quest, "quest cannot be null");
+
         return questController.canPlayerStartQuest(this, quest);
     }
 
-
-    public QuestProgressFile getQuestProgressFile() {
+    /**
+     * Get this players associated {@link QuestProgressFile}
+     *
+     * @return the quest progress file
+     */
+    public @NotNull QuestProgressFile getQuestProgressFile() {
         return questProgressFile;
     }
 
-    public QPlayerPreferences getPlayerPreferences() {
+    /**
+     * Get this players associated {@link QPlayerPreferences}
+     *
+     * @return the players preferences
+     */
+    public @NotNull QPlayerPreferences getPlayerPreferences() {
         return playerPreferences;
     }
 
-    public QuestController getQuestController() {
+    /**
+     * Get this players associated {@link QuestController}, usually the servers active quest controller
+     *
+     * @see QPlayerManager#getActiveQuestController()
+     * @return the quest controller for this player
+     */
+    public @NotNull QuestController getQuestController() {
         return questController;
     }
 
-    public void setQuestController(QuestController questController) {
+    /**
+     * Sets this players associated {@link QuestController}
+     *
+     * @param questController new quest controller
+     */
+    public void setQuestController(@NotNull QuestController questController) {
+        Objects.requireNonNull(questController, "questController cannot be null");
+
         this.questController = questController;
     }
 
diff --git a/common/src/main/java/com/leonardobishop/quests/common/player/QPlayerManager.java b/common/src/main/java/com/leonardobishop/quests/common/player/QPlayerManager.java
index 3f256c05..eac0f255 100644
--- a/common/src/main/java/com/leonardobishop/quests/common/player/QPlayerManager.java
+++ b/common/src/main/java/com/leonardobishop/quests/common/player/QPlayerManager.java
@@ -5,9 +5,13 @@ import com.leonardobishop.quests.common.player.questprogressfile.QuestProgressFi
 import com.leonardobishop.quests.common.plugin.Quests;
 import com.leonardobishop.quests.common.questcontroller.QuestController;
 import com.leonardobishop.quests.common.storage.StorageProvider;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 import java.util.Collection;
+import java.util.Collections;
 import java.util.Map;
+import java.util.Objects;
 import java.util.UUID;
 import java.util.concurrent.ConcurrentHashMap;
 
@@ -32,9 +36,11 @@ public class QPlayerManager {
      * Gets the QPlayer from a given UUID.
      *
      * @param uuid the uuid
-     * @return {@link QPlayer} if they are loaded
+     * @return {@link QPlayer} if they are loaded, otherwise null
      */
-    public QPlayer getPlayer(UUID uuid) {
+    public @Nullable QPlayer getPlayer(@NotNull UUID uuid) {
+        Objects.requireNonNull(uuid, "uuid cannot be null");
+
         QPlayer qPlayer = qPlayers.get(uuid);
         if (qPlayer == null) {
             plugin.getQuestsLogger().debug("QPlayer of " + uuid + " is null, but was requested:");
@@ -50,7 +56,9 @@ public class QPlayerManager {
      *
      * @param uuid the uuid of the player
      */
-    public void removePlayer(UUID uuid) {
+    public void removePlayer(@NotNull UUID uuid) {
+        Objects.requireNonNull(uuid, "uuid cannot be null");
+
         plugin.getQuestsLogger().debug("Unloading and saving player " + uuid + ".");
         qPlayers.computeIfPresent(uuid, (mapUUID, qPlayer) -> {
             savePlayer(uuid);
@@ -64,7 +72,9 @@ public class QPlayerManager {
      *
      * @param uuid the uuid of the player
      */
-    public void savePlayer(UUID uuid) {
+    public void savePlayer(@NotNull UUID uuid) {
+        Objects.requireNonNull(uuid, "uuid cannot be null");
+
         QPlayer qPlayer = getPlayer(uuid);
         if (qPlayer == null) return;
         savePlayer(uuid, qPlayer.getQuestProgressFile());
@@ -77,7 +87,10 @@ public class QPlayerManager {
      * @param uuid the uuid of the player
      * @param originalProgressFile the quest progress file to associate with and save
      */
-    public void savePlayer(UUID uuid, QuestProgressFile originalProgressFile) {
+    public void savePlayer(@NotNull UUID uuid, @NotNull QuestProgressFile originalProgressFile) {
+        Objects.requireNonNull(uuid, "uuid cannot be null");
+        Objects.requireNonNull(originalProgressFile, "originalProgressFile cannot be null");
+
         QuestProgressFile clonedProgressFile = new QuestProgressFile(originalProgressFile);
         originalProgressFile.resetModified();
         plugin.getScheduler().doAsync(() -> save(uuid, clonedProgressFile));
@@ -89,7 +102,9 @@ public class QPlayerManager {
      *
      * @param uuid the uuid of the player
      */
-    public void savePlayerSync(UUID uuid) {
+    public void savePlayerSync(@NotNull UUID uuid) {
+        Objects.requireNonNull(uuid, "uuid cannot be null");
+
         QPlayer qPlayer = getPlayer(uuid);
         if (qPlayer == null) return;
         savePlayerSync(uuid, qPlayer.getQuestProgressFile());
@@ -102,11 +117,14 @@ public class QPlayerManager {
      * @param uuid the uuid of the player
      * @param questProgressFile the quest progress file to associate with and save
      */
-    public void savePlayerSync(UUID uuid, QuestProgressFile questProgressFile) {
+    public void savePlayerSync(@NotNull UUID uuid, @NotNull QuestProgressFile questProgressFile) {
         save(uuid, questProgressFile);
     }
 
-    private void save(UUID uuid, QuestProgressFile questProgressFile) {
+    private void save(@NotNull UUID uuid, @NotNull QuestProgressFile questProgressFile) {
+        Objects.requireNonNull(uuid, "uuid cannot be null");
+        Objects.requireNonNull(questProgressFile, "questProgressFile cannot be null");
+
         plugin.getQuestsLogger().debug("Saving player " + uuid + ".");
         storageProvider.saveProgressFile(uuid, questProgressFile);
     }
@@ -116,13 +134,20 @@ public class QPlayerManager {
      *
      * @param uuid the uuid of the player
      */
-    public void dropPlayer(UUID uuid) {
+    public void dropPlayer(@NotNull UUID uuid) {
+        Objects.requireNonNull(uuid, "uuid cannot be null");
+
         plugin.getQuestsLogger().debug("Dropping player " + uuid + ".");
         qPlayers.remove(uuid);
     }
 
+    /**
+     * Gets all QPlayers loaded on the server
+     *
+     * @return immutable map of quest players
+     */
     public Collection<QPlayer> getQPlayers() {
-        return qPlayers.values();
+        return Collections.unmodifiableCollection(qPlayers.values());
     }
 
     /**
diff --git a/common/src/main/java/com/leonardobishop/quests/common/player/QPlayerPreferences.java b/common/src/main/java/com/leonardobishop/quests/common/player/QPlayerPreferences.java
index 5278ae09..db1e9230 100644
--- a/common/src/main/java/com/leonardobishop/quests/common/player/QPlayerPreferences.java
+++ b/common/src/main/java/com/leonardobishop/quests/common/player/QPlayerPreferences.java
@@ -1,5 +1,7 @@
 package com.leonardobishop.quests.common.player;
 
+import org.jetbrains.annotations.Nullable;
+
 public class QPlayerPreferences {
 
     private String trackedQuestId;
@@ -8,11 +10,11 @@ public class QPlayerPreferences {
         this.trackedQuestId = trackedQuestId;
     }
 
-    public String getTrackedQuestId() {
+    public @Nullable String getTrackedQuestId() {
         return trackedQuestId;
     }
 
-    public void setTrackedQuestId(String trackedQuestId) {
+    public void setTrackedQuestId(@Nullable String trackedQuestId) {
         this.trackedQuestId = trackedQuestId;
     }
 }
diff --git a/common/src/main/java/com/leonardobishop/quests/common/plugin/Quests.java b/common/src/main/java/com/leonardobishop/quests/common/plugin/Quests.java
index fbfd6813..862d9b95 100644
--- a/common/src/main/java/com/leonardobishop/quests/common/plugin/Quests.java
+++ b/common/src/main/java/com/leonardobishop/quests/common/plugin/Quests.java
@@ -10,6 +10,7 @@ import com.leonardobishop.quests.common.scheduler.ServerScheduler;
 import com.leonardobishop.quests.common.storage.StorageProvider;
 import com.leonardobishop.quests.common.tasktype.TaskTypeManager;
 import com.leonardobishop.quests.common.updater.Updater;
+import org.jetbrains.annotations.NotNull;
 
 public interface Quests {
 
@@ -19,7 +20,7 @@ public interface Quests {
      * @see QuestsLogger
      * @return quests logger
      */
-    QuestsLogger getQuestsLogger();
+    @NotNull QuestsLogger getQuestsLogger();
 
     /**
      * Obtain an instance of the QuestManager.
@@ -27,7 +28,7 @@ public interface Quests {
      * @see QuestManager
      * @return quest manager
      */
-    QuestManager getQuestManager();
+    @NotNull QuestManager getQuestManager();
 
     /**
      * Obtain an instance of the QPlayerManager.
@@ -35,7 +36,7 @@ public interface Quests {
      * @see QPlayerManager
      * @return quest player manager
      */
-    QPlayerManager getPlayerManager();
+    @NotNull QPlayerManager getPlayerManager();
 
     /**
      * Obtain an instance of the QuestController.
@@ -43,7 +44,7 @@ public interface Quests {
      * @see QuestController
      * @return quest controller
      */
-    QuestController getQuestController();
+    @NotNull QuestController getQuestController();
 
     /**
      * Obtain an instance of the TaskTypeManager.
@@ -51,7 +52,7 @@ public interface Quests {
      * @see TaskTypeManager
      * @return task type manager
      */
-    TaskTypeManager getTaskTypeManager();
+    @NotNull TaskTypeManager getTaskTypeManager();
 
     /**
      * Obtain an instance of the QuestCompleter.
@@ -59,7 +60,7 @@ public interface Quests {
      * @see QuestCompleter
      * @return quest completer
      */
-    QuestCompleter getQuestCompleter();
+    @NotNull QuestCompleter getQuestCompleter();
 
     /**
      * Obtain an instance of the QuestConfig.
@@ -67,7 +68,7 @@ public interface Quests {
      * @see QuestsConfig
      * @return quest config
      */
-    QuestsConfig getQuestsConfig();
+    @NotNull QuestsConfig getQuestsConfig();
 
     /**
      * Obtain an instance of the Updater.
@@ -75,7 +76,7 @@ public interface Quests {
      * @see Updater
      * @return updater
      */
-    Updater getUpdater();
+    @NotNull Updater getUpdater();
 
     /**
      * Obtain an instance of the ServerScheduler.
@@ -83,7 +84,7 @@ public interface Quests {
      * @see ServerScheduler
      * @return server scheduler
      */
-    ServerScheduler getScheduler();
+    @NotNull ServerScheduler getScheduler();
 
     /**
      * Obtain an instance of the StorageProvider.
@@ -91,7 +92,7 @@ public interface Quests {
      * @see StorageProvider
      * @return storage provider
      */
-    StorageProvider getStorageProvider();
+    @NotNull StorageProvider getStorageProvider();
 
     /**
      * Performs a full reload of the plugin, unloading and re-registering quests to their task types.
diff --git a/common/src/main/java/com/leonardobishop/quests/common/quest/Category.java b/common/src/main/java/com/leonardobishop/quests/common/quest/Category.java
index 7bd8f10d..25abcef0 100644
--- a/common/src/main/java/com/leonardobishop/quests/common/quest/Category.java
+++ b/common/src/main/java/com/leonardobishop/quests/common/quest/Category.java
@@ -1,7 +1,11 @@
 package com.leonardobishop.quests.common.quest;
 
+import org.jetbrains.annotations.NotNull;
+
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
+import java.util.Objects;
 
 public class Category {
 
@@ -14,20 +18,42 @@ public class Category {
         this.permissionRequired = permissionRequired;
     }
 
-    public String getId() {
+    /**
+     * Get the id of this category.
+     *
+     * @return id
+     */
+    public @NotNull String getId() {
         return id;
     }
 
+    /**
+     * Get if a specific permission is required to open this category and start quests within it.
+     * This permission will be in the form of "quests.category.[category id]".
+     *
+     * @return boolean
+     */
     public boolean isPermissionRequired() {
         return permissionRequired;
     }
 
-    public void registerQuestId(String questid) {
-        registeredQuestIds.add(questid);
+    /**
+     * Register a new quest ID to this category
+     *
+     * @param questId quest id to register
+     */
+    public void registerQuestId(@NotNull String questId) {
+        Objects.requireNonNull(questId, "questId cannot be null");
+        registeredQuestIds.add(questId);
     }
 
-    public List<String> getRegisteredQuestIds() {
-        return registeredQuestIds;
+    /**
+     * Get quest IDs which are registered to this category
+     *
+     * @return immutable list of quest ids
+     */
+    public @NotNull List<String> getRegisteredQuestIds() {
+        return Collections.unmodifiableList(registeredQuestIds);
     }
 
 }
diff --git a/common/src/main/java/com/leonardobishop/quests/common/quest/Quest.java b/common/src/main/java/com/leonardobishop/quests/common/quest/Quest.java
index c1f6f47f..6a591e1d 100644
--- a/common/src/main/java/com/leonardobishop/quests/common/quest/Quest.java
+++ b/common/src/main/java/com/leonardobishop/quests/common/quest/Quest.java
@@ -1,15 +1,20 @@
 package com.leonardobishop.quests.common.quest;
 
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 
 public class Quest implements Comparable<Quest> {
 
     private final Map<String, Task> tasks = new HashMap<>();
+    private final Map<String, List<Task>> tasksByType = new HashMap<>();
     private String id;
     private List<String> rewards;
     private List<String> requirements;
@@ -26,83 +31,196 @@ public class Quest implements Comparable<Quest> {
 
     private Quest() { }
 
-    public void registerTask(Task task) {
+    /**
+     * Register a task to this quest.
+     *
+     * @param task the task to register
+     */
+    public void registerTask(@NotNull Task task) {
+        Objects.requireNonNull(task, "task cannot be null");
+
         tasks.put(task.getId(), task);
+        tasksByType.compute(task.getType(), (type, list) -> {
+            if (list == null) {
+                return new ArrayList<>(Collections.singletonList(task));
+            } else {
+                list.add(task);
+                return list;
+            }
+        });
     }
 
-    public Collection<Task> getTasks() {
-        return tasks.values();
+    /**
+     * Get all tasks registered to this quest.
+     *
+     * @return immutable list containing all {@link Task}
+     */
+    public @NotNull Collection<Task> getTasks() {
+        return Collections.unmodifiableCollection(tasks.values());
     }
 
-    public Task getTaskById(String id) {
+    /**
+     * Get a specific task registered to this quest.
+     *
+     * @param id task id
+     * @return {@link Task}, or null if not exists
+     */
+    public @Nullable Task getTaskById(@NotNull String id) {
+        Objects.requireNonNull(id, "id cannot be null");
+
         return tasks.get(id);
     }
 
-    public List<Task> getTasksOfType(String type) {
-        List<Task> tasks = new ArrayList<>();
-        for (Task task : getTasks()) {
-            if (task.getType().equals(type)) {
-                tasks.add(task);
-            }
-        }
-        return tasks;
+    /**
+     * Get a list of all task of a specific task type.
+     *
+     * @param type the task type
+     * @return list containing all tasks of type
+     */
+    public @NotNull List<Task> getTasksOfType(String type) {
+        Objects.requireNonNull(type, "type cannot be null");
+
+        List<Task> list = tasksByType.get(type);
+        return list == null ? Collections.emptyList() : Collections.unmodifiableList(list);
     }
 
 
+    /**
+     * Get if a specific permission is required to start this quest.
+     * This permission will be in the form of "quests.quest.[quest id]".
+     *
+     * @return boolean
+     */
     public boolean isPermissionRequired() {
         return permissionRequired;
     }
 
-    public List<String> getRewardString() {
-        return rewardString;
+    /**
+     * Get the reward string of the quest.
+     * The reward string is a series of messages sent to the player upon completing the quest.
+     *
+     * @return immutable list of messages to send
+     */
+    public @NotNull List<String> getRewardString() {
+        return Collections.unmodifiableList(rewardString);
     }
 
-    public List<String> getStartString() {
-        return startString;
+    /**
+     * Get the start string of the quest.
+     * The start string is a series of messages sent to the player upon starting the quest.
+     *
+     * @return immutable list of messages to send
+     */
+    public @NotNull List<String> getStartString() {
+        return Collections.unmodifiableList(startString);
     }
 
-    public String getId() {
+    /**
+     * Get the id of this quest.
+     *
+     * @return id
+     */
+    public @NotNull String getId() {
         return id;
     }
 
-    public List<String> getRewards() {
-        return rewards;
+    /**
+     * Get the rewards for this quest.
+     * The rewards is a list of commands to be executed upon completing the quest.
+     *
+     * @return immutable list of rewards
+     */
+    public @NotNull List<String> getRewards() {
+        return Collections.unmodifiableList(rewards);
     }
 
-    public List<String> getRequirements() {
-        return requirements;
+    /**
+     * Get the requirements for this quest.
+     * The requirements is a list of quests ids the player must have completed at least once to start this quest.
+     * The quest ids may or may not represent actual quests and are only validated by the plugin with a warning.
+     *
+     * @return immutable list of quest requirements
+     */
+    public @NotNull List<String> getRequirements() {
+        return Collections.unmodifiableList(requirements);
     }
 
+    /**
+     * Get if this quest can be repeated after completion.
+     *
+     * @return boolean
+     */
     public boolean isRepeatable() {
         return repeatEnabled;
     }
 
+    /**
+     * Get if this quest has a cooldown enabled after completion.
+     * Whether or not the quest enters a cooldown phase for the player depends
+     * on if it is repeatable in the first place: {@link Quest#isRepeatable()}
+     *
+     * @return boolean
+     */
     public boolean isCooldownEnabled() {
         return cooldownEnabled;
     }
 
+    /**
+     * Get the cooldown for this quest between completing and restarting the quest.
+     * Whether or not this cooldown is in use depends on {@link Quest#isCooldownEnabled()}.
+     *
+     * @return the cooldown, in seconds
+     */
     public int getCooldown() {
         return cooldown;
     }
 
-    public String getCategoryId() {
+    /**
+     * Get the category id this quest is in.
+     *
+     * @return the category id, or null
+     */
+    public @Nullable String getCategoryId() {
         return categoryid;
     }
 
-    public Map<String, String> getPlaceholders() {
-        return placeholders;
+    /**
+     * Get the local placeholders for this quest, which is exposed to PlaceholderAPI.
+     *
+     * @return immutable map of placeholders
+     */
+    public @NotNull Map<String, String> getPlaceholders() {
+        return Collections.unmodifiableMap(placeholders);
     }
 
+    /**
+     * Get the sort order for this quest in the GUI.
+     * Numbers closer to Integer.MIN_VALUE have greater priority.
+     *
+     * @return any integer, both negative or positive
+     */
     public int getSortOrder() {
         return sortOrder;
     }
 
+    /**
+     * Get if quest-specific autostart is enabled for this quest.
+     *
+     * @return boolean
+     */
     public boolean isAutoStartEnabled() {
         return autoStartEnabled;
     }
 
+    /**
+     * Compare the sort orders for this quest with another quest.
+     *
+     * @see Comparable#compareTo(Object)
+     * @param quest the quest to compare with
+     * @return a negative integer, zero, or a positive integer
+     */
     @Override
-    public int compareTo(Quest quest) {
+    public int compareTo(@NotNull Quest quest) {
         return (sortOrder - quest.sortOrder);
     }
 
diff --git a/common/src/main/java/com/leonardobishop/quests/common/quest/QuestCompleter.java b/common/src/main/java/com/leonardobishop/quests/common/quest/QuestCompleter.java
index cc498df9..704ec6e9 100644
--- a/common/src/main/java/com/leonardobishop/quests/common/quest/QuestCompleter.java
+++ b/common/src/main/java/com/leonardobishop/quests/common/quest/QuestCompleter.java
@@ -2,6 +2,7 @@ package com.leonardobishop.quests.common.quest;
 
 import com.leonardobishop.quests.common.player.questprogressfile.QuestProgress;
 import com.leonardobishop.quests.common.player.questprogressfile.QuestProgressFile;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * The quest completer is responsible for checking each player for completed quests. Implementations may split
@@ -9,7 +10,18 @@ import com.leonardobishop.quests.common.player.questprogressfile.QuestProgressFi
  */
 public interface QuestCompleter {
 
-    void queueSingular(QuestProgress questProgress);
-    void queueFullCheck(QuestProgressFile questProgressFile);
+    /**
+     * Queue an individual quest progress to check if the quest is completed.
+     *
+     * @param questProgress the questprogress to check
+     */
+    void queueSingular(@NotNull QuestProgress questProgress);
+
+    /**
+     * Queue a quest progress file for a full check if they have completed any quests.
+     *
+     * @param questProgressFile the questprogressfile to check
+     */
+    void queueFullCheck(@NotNull QuestProgressFile questProgressFile);
 
 }
diff --git a/common/src/main/java/com/leonardobishop/quests/common/quest/QuestManager.java b/common/src/main/java/com/leonardobishop/quests/common/quest/QuestManager.java
index af2afa52..2a569b2e 100644
--- a/common/src/main/java/com/leonardobishop/quests/common/quest/QuestManager.java
+++ b/common/src/main/java/com/leonardobishop/quests/common/quest/QuestManager.java
@@ -1,11 +1,15 @@
 package com.leonardobishop.quests.common.quest;
 
 import com.leonardobishop.quests.common.plugin.Quests;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 
 /**
  * The quests manager stores all present Quests and Categories on the server and is used as a registry.
@@ -13,40 +17,81 @@ import java.util.Map;
 public class QuestManager {
 
     private final Quests plugin;
+    private final Map<String, Quest> quests = new LinkedHashMap<>();
+    private final List<Category> categories = new ArrayList<>();
 
     public QuestManager(Quests plugin) {
         this.plugin = plugin;
     }
 
-    private Map<String, Quest> quests = new LinkedHashMap<>();
-    private List<Category> categories = new ArrayList<>();
+    /**
+     * Register a quest with the quest manager
+     *
+     * @param quest the category to register
+     */
+    public void registerQuest(@NotNull Quest quest) {
+        Objects.requireNonNull(quest, "quest cannot be null");
 
-    public void registerQuest(Quest quest) {
         quests.put(quest.getId(), quest);
     }
 
-    public Quest getQuestById(String id) {
+    /**
+     * @param id id to match
+     * @return {@link Quest}, or null
+     */
+    public @Nullable Quest getQuestById(@NotNull String id) {
+        Objects.requireNonNull(id, "id cannot be null");
+
         return quests.get(id);
     }
 
-    public Map<String, Quest> getQuests() {
-        return quests;
+    /**
+     * Get a map of id-quest of all quests registered
+     * @return immutable map of all {@link Quest}
+     */
+    public @NotNull Map<String, Quest> getQuests() {
+        return Collections.unmodifiableMap(quests);
     }
 
-    public void registerCategory(Category category) { categories.add(category); }
+    /**
+     * Register a category with the quest manager
+     *
+     * @param category the category to register
+     */
+    public void registerCategory(@NotNull Category category) {
+        Objects.requireNonNull(category, "category cannot be null");
+
+        categories.add(category);
+    }
 
-    public List<Category> getCategories() {
-        return categories;
+    /**
+     * @return immutable list of all {@link Category}
+     */
+    public @NotNull List<Category> getCategories() {
+        return Collections.unmodifiableList(categories);
     }
 
-    public Category getCategoryById(String id) {
+    /**
+     * Get a specific category by id
+     *
+     * @param id the id
+     * @return {@link Category}, or null
+     */
+    public @Nullable Category getCategoryById(@NotNull String id) {
+        Objects.requireNonNull(id, "id cannot be null");
+
         for (Category category : categories) {
             if (category.getId().equals(id)) return category;
         }
         return null;
     }
 
-    public Quests getPlugin() {
-        return this.plugin;
+    /**
+     * Reset the quest manager and clears all registered quests and categories
+     */
+    public void clear() {
+        quests.clear();
+        categories.clear();
     }
+
 }
diff --git a/common/src/main/java/com/leonardobishop/quests/common/quest/Task.java b/common/src/main/java/com/leonardobishop/quests/common/quest/Task.java
index 8189e06e..6e27aef6 100644
--- a/common/src/main/java/com/leonardobishop/quests/common/quest/Task.java
+++ b/common/src/main/java/com/leonardobishop/quests/common/quest/Task.java
@@ -1,7 +1,12 @@
 package com.leonardobishop.quests.common.quest;
 
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.Objects;
 
 public class Task {
 
@@ -14,27 +19,62 @@ public class Task {
         this.type = type;
     }
 
-    public String getId() {
+    /**
+     * @return the id of this task
+     */
+    public @NotNull String getId() {
         return id;
     }
 
-    public String getType() {
+    /**
+     * @return the configured task type for this task
+     */
+    public @NotNull String getType() {
         return type;
     }
 
-    public Object getConfigValue(String key) {
+    /**
+     * Get a specific configuration value for this task
+     *
+     * @param key key of config value to get
+     * @return config value, or null
+     */
+    public @Nullable Object getConfigValue(@NotNull String key) {
+        Objects.requireNonNull(key, "key cannot be null");
+
         return configValues.getOrDefault(key, null); //??? this will return null without the need of `OrDefault(key, null)`
     }
 
-    public Object getConfigValue(String key, Object def) {
+    /**
+     * Get a specific configuration value for this task
+     *
+     * @param key key of config value to get
+     * @param def default value if null
+     * @return config value, or null
+     */
+    public @Nullable Object getConfigValue(@NotNull String key, @Nullable Object def) {
+        Objects.requireNonNull(key, "key cannot be null");
+
         return configValues.getOrDefault(key, def);
     }
 
-    public Map<String, Object> getConfigValues() {
-        return configValues;
+    /**
+     * @return immutable list containing all config values
+     */
+    public @NotNull Map<String, Object> getConfigValues() {
+        return Collections.unmodifiableMap(configValues);
     }
 
-    public void addConfigValue(String key, Object value) {
+    /**
+     * Add a key-value pair to this tasks configuration
+     *
+     * @param key key
+     * @param value value
+     */
+    public void addConfigValue(@NotNull String key, @NotNull Object value) {
+        Objects.requireNonNull(key, "key cannot be null");
+        Objects.requireNonNull(value, "value cannot be null");
+
         configValues.put(key, value);
     }
 
diff --git a/common/src/main/java/com/leonardobishop/quests/common/storage/StorageProvider.java b/common/src/main/java/com/leonardobishop/quests/common/storage/StorageProvider.java
index 26cca4be..bd558c4e 100644
--- a/common/src/main/java/com/leonardobishop/quests/common/storage/StorageProvider.java
+++ b/common/src/main/java/com/leonardobishop/quests/common/storage/StorageProvider.java
@@ -1,6 +1,8 @@
 package com.leonardobishop.quests.common.storage;
 
 import com.leonardobishop.quests.common.player.questprogressfile.QuestProgressFile;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 import java.util.UUID;
 
@@ -14,8 +16,19 @@ public interface StorageProvider {
 
     void shutdown();
 
-    QuestProgressFile loadProgressFile(UUID uuid);
+    /**
+     * Load a QuestProgressFile from the data source by a specific UUID
+     *
+     * @param uuid the UUID to load
+     * @return {@link QuestProgressFile} or null
+     */
+    @Nullable QuestProgressFile loadProgressFile(@NotNull UUID uuid);
 
-    void saveProgressFile(UUID uuid, QuestProgressFile questProgressFile);
+    /**
+     * Save a QuestProgressFile to the data source with a specific UUID
+     * @param uuid the uuid to match the file to
+     * @param questProgressFile the file to save
+     */
+    void saveProgressFile(@NotNull UUID uuid, @NotNull QuestProgressFile questProgressFile);
 
 }
diff --git a/common/src/main/java/com/leonardobishop/quests/common/tasktype/TaskType.java b/common/src/main/java/com/leonardobishop/quests/common/tasktype/TaskType.java
index 79c7a0b0..efa62733 100644
--- a/common/src/main/java/com/leonardobishop/quests/common/tasktype/TaskType.java
+++ b/common/src/main/java/com/leonardobishop/quests/common/tasktype/TaskType.java
@@ -3,11 +3,14 @@ package com.leonardobishop.quests.common.tasktype;
 import com.leonardobishop.quests.common.config.ConfigProblem;
 import com.leonardobishop.quests.common.quest.Quest;
 import com.leonardobishop.quests.common.quest.Task;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
+import java.util.Objects;
 import java.util.UUID;
 
 /**
@@ -28,8 +31,8 @@ public abstract class TaskType {
      * @param author the name of the person (or people) who wrote it
      * @param description a short, simple description of the task type
      */
-    public TaskType(String type, String author, String description) {
-        this.type = type;
+    public TaskType(@NotNull String type, String author, String description) {
+        this(type);
         this.author = author;
         this.description = description;
     }
@@ -37,7 +40,9 @@ public abstract class TaskType {
     /**
      * @param type the name of the task type, should not contain spaces
      */
-    public TaskType(String type) {
+    public TaskType(@NotNull String type) {
+        Objects.requireNonNull(type, "type cannot be null");
+
         this.type = type;
     }
 
@@ -47,7 +52,9 @@ public abstract class TaskType {
      *
      * @param quest the {@link Quest} to register.
      */
-    public final void registerQuest(Quest quest) {
+    public final void registerQuest(@NotNull Quest quest) {
+        Objects.requireNonNull(quest, "quest cannot be null");
+
         if (!quests.contains(quest)) {
             quests.add(quest);
         }
@@ -56,39 +63,39 @@ public abstract class TaskType {
     /**
      * Clears the list which contains the registered quests.
      */
-    public final void unregisterAll() {
+    protected final void unregisterAll() {
         quests.clear();
     }
 
     /**
-     * @return {@link List} of type {@link Quest} of all registered quests.
+     * @return immutable {@link List} of type {@link Quest} of all registered quests.
      */
-    public final List<Quest> getRegisteredQuests() {
-        return quests;
+    public final @NotNull List<Quest> getRegisteredQuests() {
+        return Collections.unmodifiableList(quests);
     }
 
-    public final String getType() {
+    public final @NotNull String getType() {
         return type;
     }
 
-    public String getAuthor() {
+    public @Nullable String getAuthor() {
         return author;
     }
 
-    public String getDescription() {
+    public @Nullable String getDescription() {
         return description;
     }
 
     /**
-     * Called when Quests has finished registering all quests to the task type
-     * May be called several times if an operator uses /quests admin reload
+     * Called when Quests has finished registering all quests to the task type.
+     * May be called several times if an operator uses /quests admin reload.
      */
     public void onReady() {
         // not implemented here
     }
 
     /**
-     * Called when a player starts a quest containing a task of this type
+     * Called when a player starts a quest containing a task of this type.
      */
     public void onStart(Quest quest, Task task, UUID playerUUID) {
         // not implemented here
@@ -99,9 +106,12 @@ public abstract class TaskType {
     }
 
     /**
-     * Called when Quests reloads the configuration - used to detect errors in the configuration of your task type
+     * Called when Quests reloads the configuration - used to detect errors in the configuration of your task type.
+     *
+     * @param root the root path for the config
+     * @param config the config itself
      */
-    public List<ConfigProblem> validateConfig(String root, HashMap<String, Object> config) {
+    public @NotNull List<ConfigProblem> validateConfig(@NotNull String root, @NotNull HashMap<String, Object> config) {
         // not implemented here
         return Collections.emptyList();
     }
diff --git a/common/src/main/java/com/leonardobishop/quests/common/tasktype/TaskTypeManager.java b/common/src/main/java/com/leonardobishop/quests/common/tasktype/TaskTypeManager.java
index 284a1e0a..775d635a 100644
--- a/common/src/main/java/com/leonardobishop/quests/common/tasktype/TaskTypeManager.java
+++ b/common/src/main/java/com/leonardobishop/quests/common/tasktype/TaskTypeManager.java
@@ -3,8 +3,13 @@ package com.leonardobishop.quests.common.tasktype;
 import com.leonardobishop.quests.common.plugin.Quests;
 import com.leonardobishop.quests.common.quest.Quest;
 import com.leonardobishop.quests.common.quest.Task;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Objects;
 
 /**
  * The task type manager stores all registered task types and registers individual quests to each task type.
@@ -30,17 +35,30 @@ public abstract class TaskTypeManager {
         return allowRegistrations;
     }
 
-    public ArrayList<TaskType> getTaskTypes() {
-        return taskTypes;
+    /**
+     * @return immutable {@link List} containing all registered {@link TaskType}
+     */
+    public @NotNull List<TaskType> getTaskTypes() {
+        return Collections.unmodifiableList(taskTypes);
     }
 
+    /**
+     * Resets all quest to task type registrations. This does not clear the task types registered to the task type manager.
+     */
     public void resetTaskTypes() {
         for (TaskType taskType : taskTypes) {
-            taskType.getRegisteredQuests().clear();
+            taskType.unregisterAll();
         }
     }
 
-    public void registerTaskType(TaskType taskType) {
+    /**
+     * Register a task type with the task type manager.
+     *
+     * @param taskType the task type to register
+     */
+    public void registerTaskType(@NotNull TaskType taskType) {
+        Objects.requireNonNull(taskType, "taskType cannot be null");
+
         if (!allowRegistrations) {
             throw new IllegalStateException("No longer accepting new task types (must be done before quests are loaded)");
         }
@@ -48,7 +66,14 @@ public abstract class TaskTypeManager {
         taskTypes.add(taskType);
     }
 
-    public void registerQuestTasksWithTaskTypes(Quest quest) {
+    /**
+     * Register a quest with its task types. This will register the quest to each task type it contains.
+     *
+     * @param quest the quest to register
+     */
+    public void registerQuestTasksWithTaskTypes(@NotNull Quest quest) {
+        Objects.requireNonNull(quest, "quest cannot be null");
+
         if (allowRegistrations) {
             throw new IllegalStateException("Still accepting new task types (type registrations must be closed before registering quests)");
         }
@@ -60,9 +85,17 @@ public abstract class TaskTypeManager {
         }
     }
 
-    public TaskType getTaskType(String string) {
+    /**
+     * Get a registered task type by type
+     *
+     * @param type the type to check
+     * @return {@link TaskType}
+     */
+    public @Nullable TaskType getTaskType(@NotNull String type) {
+        Objects.requireNonNull(type, "type cannot be null");
+
         for (TaskType taskType : taskTypes) {
-            if (taskType.getType().equalsIgnoreCase(string)) {
+            if (taskType.getType().equalsIgnoreCase(type)) {
                 return taskType;
             }
         }