Reworked best friends list

- Saving best friends' UUIDs now (instead of just the name), also checking for name changes periodically to keep best friends list up to date
- Moved best friends add/remove functionality from config GUI back to commands (`/moo <add|remove> <name>`)

14 files changed, 502 insertions, 133 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 14ac786..9132a76 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,15 @@ All notable changes to this project will be documented in this file.
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
+## 1.8.9-0.3.0 - unreleased
+### Added
+- `/moo nameChangeCheck`: Force a scan for changed names of best friends
+
+### Changed
+- Moved best friends add/remove functionality from config GUI back to commands (`/moo <add|remove> <name>`)
+- Saving best friends' UUIDs now (instead of just the name), also checking for name changes periodically to keep best friends list up to date
+
+
 ## [1.8.9-0.2.0] - 08.03.2020
 ### Added
 - Mod update notification (opt-out via config)
diff --git a/README.md b/README.md
index 8630a93..86b43c8 100644
--- a/README.md
+++ b/README.md
@@ -5,7 +5,7 @@ A client-side only Forge mod by [Cow](https://namemc.com/profile/Cow) providing
 | Feature                                                                 | Command/Usage                           |
 |-------------------------------------------------------------------------|-----------------------------------------|
 | Toggle to hide all join/leave notifications                             | `/moo toggle`                           |
-| 'Best friends' list to limit the amount of join and leave notifications | `/moo friends`                          |
+| 'Best friends' list to limit the amount of join and leave notifications | `/moo add/remove/list`                  |
 | Change guiScale to any value                                            | `/moo guiscale [newValue]`              |
 | Auto-replace `/r` with `/w <latest username>`                           | `/r `                                   |
 | Copy chat components                                                    | <kbd>ALT</kbd> + <kbd>right click</kbd> |
diff --git a/src/main/java/eu/olli/cowmoonication/Cowmoonication.java b/src/main/java/eu/olli/cowmoonication/Cowmoonication.java
index 78f1905..2b46e71 100644
--- a/src/main/java/eu/olli/cowmoonication/Cowmoonication.java
+++ b/src/main/java/eu/olli/cowmoonication/Cowmoonication.java
@@ -2,9 +2,10 @@ package eu.olli.cowmoonication;
 
 import eu.olli.cowmoonication.command.MooCommand;
 import eu.olli.cowmoonication.config.MooConfig;
+import eu.olli.cowmoonication.friends.Friends;
 import eu.olli.cowmoonication.listener.ChatListener;
 import eu.olli.cowmoonication.listener.PlayerListener;
-import eu.olli.cowmoonication.util.Utils;
+import eu.olli.cowmoonication.util.ChatHelper;
 import eu.olli.cowmoonication.util.VersionChecker;
 import net.minecraftforge.client.ClientCommandHandler;
 import net.minecraftforge.common.MinecraftForge;
@@ -26,10 +27,11 @@ public class Cowmoonication {
     public static final String MODID = "cowmoonication";
     public static final String VERSION = "1.8.9-0.2.0";
     public static final String MODNAME = "Cowmoonication";
+    private File modsDir;
     private MooConfig config;
     private Friends friends;
     private VersionChecker versionChecker;
-    private Utils utils;
+    private ChatHelper chatHelper;
     private Logger logger;
 
     @Mod.EventHandler
@@ -41,10 +43,11 @@ public class Cowmoonication {
             modDir.mkdirs();
         }
 
-        friends = new Friends(this);
-        config = new MooConfig(new Configuration(new File(modDir, MODID + ".cfg")), this);
+        friends = new Friends(this, new File(modDir, "friends.json"));
+        config = new MooConfig(new Configuration(new File(modDir, MODID + ".cfg")));
 
-        utils = new Utils(this, e.getSourceFile());
+        chatHelper = new ChatHelper();
+        modsDir = e.getSourceFile().getParentFile();
     }
 
     @EventHandler
@@ -72,8 +75,12 @@ public class Cowmoonication {
         return versionChecker;
     }
 
-    public Utils getUtils() {
-        return utils;
+    public ChatHelper getChatHelper() {
+        return chatHelper;
+    }
+
+    public File getModsFolder() {
+        return modsDir;
     }
 
     public Logger getLogger() {
diff --git a/src/main/java/eu/olli/cowmoonication/Friends.java b/src/main/java/eu/olli/cowmoonication/Friends.java
deleted file mode 100644
index 2becc74..0000000
--- a/src/main/java/eu/olli/cowmoonication/Friends.java
+++ /dev/null
@@ -1,28 +0,0 @@
-package eu.olli.cowmoonication;
-
-import java.util.Collections;
-import java.util.HashSet;
-import java.util.Set;
-import java.util.TreeSet;
-
-public class Friends {
-    private final Cowmoonication main;
-    private Set<String> bestFriends = new HashSet<>();
-
-    public Friends(Cowmoonication main) {
-        this.main = main;
-    }
-
-    public boolean isBestFriend(String playerName) {
-        return bestFriends.contains(playerName);
-    }
-
-    public Set<String> getBestFriends() {
-        return new TreeSet<>(bestFriends);
-    }
-
-    public void syncFriends(String[] bestFriends) {
-        this.bestFriends = new HashSet<>();
-        Collections.addAll(this.bestFriends, bestFriends);
-    }
-}
diff --git a/src/main/java/eu/olli/cowmoonication/command/MooCommand.java b/src/main/java/eu/olli/cowmoonication/command/MooCommand.java
index 08c377d..22d510a 100644
--- a/src/main/java/eu/olli/cowmoonication/command/MooCommand.java
+++ b/src/main/java/eu/olli/cowmoonication/command/MooCommand.java
@@ -4,6 +4,7 @@ import eu.olli.cowmoonication.Cowmoonication;
 import eu.olli.cowmoonication.config.MooConfig;
 import eu.olli.cowmoonication.config.MooGuiConfig;
 import eu.olli.cowmoonication.util.TickDelay;
+import eu.olli.cowmoonication.util.Utils;
 import net.minecraft.client.Minecraft;
 import net.minecraft.command.CommandBase;
 import net.minecraft.command.CommandException;
@@ -28,40 +29,52 @@ public class MooCommand extends CommandBase {
     @Override
     public void processCommand(ICommandSender sender, String[] args) throws CommandException {
         if (args.length == 0) {
-            main.getUtils().sendMessage(new ChatComponentTranslation(getCommandUsage(sender)));
+            main.getChatHelper().sendMessage(new ChatComponentTranslation(getCommandUsage(sender)));
             return;
         }
-        if (args[0].equalsIgnoreCase("friends") || args[0].equalsIgnoreCase("config")) {
-            new TickDelay(() -> Minecraft.getMinecraft().displayGuiScreen(new MooGuiConfig(null)), 1); // delay by 1 tick, because the chat closing would close the new gui instantly as well.
+        // sub commands: friends
+        if (args.length == 2 && args[0].equalsIgnoreCase("add")) {
+            handleBestFriendAdd(args[1]);
+        } else if (args.length == 2 && args[0].equalsIgnoreCase("remove")) {
+            handleBestFriendRemove(args[1]);
         } else if (args[0].equalsIgnoreCase("list")) {
             handleListBestFriends();
+        } else if (args[0].equalsIgnoreCase("nameChangeCheck")) {
+            main.getChatHelper().sendMessage(EnumChatFormatting.GOLD, "Looking for best friends that have changed their name... This will take a few seconds...");
+            main.getFriends().updateBestFriends(true);
         } else if (args[0].equalsIgnoreCase("toggle")) {
             main.getConfig().toggleNotifications();
-            main.getUtils().sendMessage(EnumChatFormatting.GREEN + "\u2714 Switched all non-best friend login/logout notifications " + (MooConfig.filterFriendNotifications ? EnumChatFormatting.DARK_GREEN + "off" : EnumChatFormatting.DARK_RED + "on"));
+            main.getChatHelper().sendMessage(EnumChatFormatting.GREEN, "\u2714 Switched all non-best friend login/logout notifications " + (MooConfig.filterFriendNotifications ? EnumChatFormatting.DARK_GREEN + "off" : EnumChatFormatting.DARK_RED + "on"));
+        }
+        // sub-commands: miscellaneous
+        else if (args[0].equalsIgnoreCase("config")) {
+            new TickDelay(() -> Minecraft.getMinecraft().displayGuiScreen(new MooGuiConfig(null)), 1); // delay by 1 tick, because the chat closing would close the new gui instantly as well.
         } else if (args[0].equalsIgnoreCase("guiscale")) {
             int currentGuiScale = (Minecraft.getMinecraft()).gameSettings.guiScale;
             if (args.length == 1) {
-                main.getUtils().sendMessage(EnumChatFormatting.GREEN + "\u279C Current GUI scale: " + EnumChatFormatting.DARK_GREEN + currentGuiScale);
+                main.getChatHelper().sendMessage(EnumChatFormatting.GREEN, "\u279C Current GUI scale: " + EnumChatFormatting.DARK_GREEN + currentGuiScale);
             } else {
                 int scale = Math.min(10, MathHelper.parseIntWithDefault(args[1], 6));
                 Minecraft.getMinecraft().gameSettings.guiScale = scale;
-                main.getUtils().sendMessage(EnumChatFormatting.GREEN + "\u2714 New GUI scale: " + EnumChatFormatting.DARK_GREEN + scale + EnumChatFormatting.GREEN + " (previous: " + EnumChatFormatting.DARK_GREEN + currentGuiScale + EnumChatFormatting.GREEN + ")");
+                main.getChatHelper().sendMessage(EnumChatFormatting.GREEN, "\u2714 New GUI scale: " + EnumChatFormatting.DARK_GREEN + scale + EnumChatFormatting.GREEN + " (previous: " + EnumChatFormatting.DARK_GREEN + currentGuiScale + EnumChatFormatting.GREEN + ")");
             }
-        } else if (args[0].equalsIgnoreCase("update")) {
+        }
+        // sub-commands: update mod
+        else if (args[0].equalsIgnoreCase("update")) {
             boolean updateCheckStarted = main.getVersionChecker().runUpdateCheck(true);
 
             if (updateCheckStarted) {
-                main.getUtils().sendMessage(EnumChatFormatting.GREEN + "\u279C Checking for a newer mod version...");
+                main.getChatHelper().sendMessage(EnumChatFormatting.GREEN, "\u279C Checking for a newer mod version...");
                 // VersionChecker#handleVersionStatus will run with a 5 seconds delay
             } else {
                 long nextUpdate = main.getVersionChecker().getNextCheck();
                 String waitingTime = String.format("%02d:%02d",
                         TimeUnit.MILLISECONDS.toMinutes(nextUpdate),
                         TimeUnit.MILLISECONDS.toSeconds(nextUpdate) - TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS.toMinutes(nextUpdate)));
-                main.getUtils().sendMessage(new ChatComponentText("\u26A0 Update checker is on cooldown. Please wait " + EnumChatFormatting.GOLD + EnumChatFormatting.BOLD + waitingTime + EnumChatFormatting.RESET + EnumChatFormatting.RED + " more minutes before checking again.").setChatStyle(new ChatStyle().setColor(EnumChatFormatting.RED)));
+                main.getChatHelper().sendMessage(EnumChatFormatting.RED, "\u26A0 Update checker is on cooldown. Please wait " + EnumChatFormatting.GOLD + EnumChatFormatting.BOLD + waitingTime + EnumChatFormatting.RESET + EnumChatFormatting.RED + " more minutes before checking again.");
             }
         } else if (args[0].equalsIgnoreCase("updateHelp")) {
-            main.getUtils().sendMessage(new ChatComponentText("\u279C Update instructions:").setChatStyle(new ChatStyle().setColor(EnumChatFormatting.GOLD).setBold(true))
+            main.getChatHelper().sendMessage(new ChatComponentText("\u279C Update instructions:").setChatStyle(new ChatStyle().setColor(EnumChatFormatting.GOLD).setBold(true))
                     .appendSibling(new ChatComponentText("\n\u278A" + EnumChatFormatting.YELLOW + " download latest mod version").setChatStyle(new ChatStyle().setColor(EnumChatFormatting.GOLD).setBold(false)
                             .setChatClickEvent(new ClickEvent(ClickEvent.Action.OPEN_URL, main.getVersionChecker().getDownloadUrl()))
                             .setChatHoverEvent(new HoverEvent(HoverEvent.Action.SHOW_TEXT, new ChatComponentText(EnumChatFormatting.YELLOW + "Download the latest version of Cowmoonication\n\u279C Click to download latest mod file")))))
@@ -76,21 +89,53 @@ public class MooCommand extends CommandBase {
             main.getVersionChecker().handleVersionStatus(true);
         } else if (args[0].equalsIgnoreCase("folder")) {
             try {
-                Desktop.getDesktop().open(main.getUtils().getModsFolder());
+                Desktop.getDesktop().open(main.getModsFolder());
             } catch (IOException e) {
-                main.getUtils().sendMessage(new ChatComponentText("\u2716 An error occurred trying to open the mod's folder. I guess you have to open it manually \u00af\\_(\u30c4)_/\u00af").setChatStyle(new ChatStyle().setColor(EnumChatFormatting.RED)));
+                main.getChatHelper().sendMessage(EnumChatFormatting.RED, "\u2716 An error occurred trying to open the mod's folder. I guess you have to open it manually \u00af\\_(\u30c4)_/\u00af");
                 e.printStackTrace();
             }
+        }
+        // "catch-all" remaining sub-commands
+        else {
+            main.getChatHelper().sendMessage(new ChatComponentTranslation(getCommandUsage(sender)));
+        }
+    }
+
+    private void handleBestFriendAdd(String username) {
+        if (!Utils.isValidMcName(username)) {
+            main.getChatHelper().sendMessage(EnumChatFormatting.RED, EnumChatFormatting.DARK_RED + username + EnumChatFormatting.RED + "? This... doesn't look like a valid username.");
+            return;
+        }
+
+        // TODO Add check if 'best friend' is on normal friend list
+        if (main.getFriends().isBestFriend(username, true)) {
+            main.getChatHelper().sendMessage(EnumChatFormatting.RED, EnumChatFormatting.DARK_RED + username + EnumChatFormatting.RED + " is a best friend already.");
+        } else {
+            main.getChatHelper().sendMessage(EnumChatFormatting.GOLD, "Fetching " + EnumChatFormatting.YELLOW + username + EnumChatFormatting.GOLD + "'s unique user id. This may take a few seconds...");
+            // add friend async
+            main.getFriends().addBestFriend(username);
+        }
+    }
+
+    private void handleBestFriendRemove(String username) {
+        if (!Utils.isValidMcName(username)) {
+            main.getChatHelper().sendMessage(EnumChatFormatting.RED, EnumChatFormatting.DARK_RED + username + EnumChatFormatting.RED + "? This... doesn't look like a valid username.");
+            return;
+        }
+
+        boolean removed = main.getFriends().removeBestFriend(username);
+        if (removed) {
+            main.getChatHelper().sendMessage(EnumChatFormatting.GREEN, "Removed " + EnumChatFormatting.DARK_GREEN + username + EnumChatFormatting.GREEN + " from best friends list.");
         } else {
-            main.getUtils().sendMessage(new ChatComponentTranslation(getCommandUsage(sender)));
+            main.getChatHelper().sendMessage(EnumChatFormatting.RED, EnumChatFormatting.DARK_RED + username + EnumChatFormatting.RED + " isn't a best friend.");
         }
     }
 
     private void handleListBestFriends() {
         Set<String> bestFriends = main.getFriends().getBestFriends();
 
-        // TODO show fancy gui with list of best friends (maybe just the mod's settings?)
-        main.getUtils().sendMessage(EnumChatFormatting.GREEN + "\u279C Best friends: " + EnumChatFormatting.DARK_GREEN + String.join(EnumChatFormatting.GREEN + ", " + EnumChatFormatting.DARK_GREEN, bestFriends));
+        // TODO show fancy gui with list of best friends; maybe with buttons to delete them
+        main.getChatHelper().sendMessage(EnumChatFormatting.GREEN, "\u279C Best friends: " + EnumChatFormatting.DARK_GREEN + String.join(EnumChatFormatting.GREEN + ", " + EnumChatFormatting.DARK_GREEN, bestFriends));
     }
 
     @Override
@@ -101,12 +146,14 @@ public class MooCommand extends CommandBase {
     @Override
     public String getCommandUsage(ICommandSender sender) {
         IChatComponent usage = new ChatComponentText("\u279C Cowmoonication commands:").setChatStyle(new ChatStyle().setColor(EnumChatFormatting.GOLD).setBold(true))
-                .appendSibling(createCmdHelpSection(1, "Login/Logout Notifications"))
-                .appendSibling(createCmdHelpEntry("friends", "Add/remove best friends"))
+                .appendSibling(createCmdHelpSection(1, "Friends"))
+                .appendSibling(createCmdHelpEntry("add", "Add best friends"))
+                .appendSibling(createCmdHelpEntry("remove", "Remove best friends"))
                 .appendSibling(createCmdHelpEntry("list", "View list of best friends"))
+                .appendSibling(createCmdHelpEntry("nameChangeCheck", "Force a scan for changed names of best friends"))
                 .appendSibling(createCmdHelpEntry("toggle", "Toggle show/hide all join/leave notifications"))
                 .appendSibling(createCmdHelpSection(2, "Miscellaneous"))
-                .appendSibling(createCmdHelpEntry("config", "Open configuration GUI"))
+                .appendSibling(createCmdHelpEntry("config", "Open mod's configuration"))
                 .appendSibling(createCmdHelpEntry("guiScale", "Change GUI scale"))
                 .appendSibling(createCmdHelpSection(3, "Update mod"))
                 .appendSibling(createCmdHelpEntry("update", "Check for new mod updates"))
@@ -139,7 +186,11 @@ public class MooCommand extends CommandBase {
     @Override
     public List<String> addTabCompletionOptions(ICommandSender sender, String[] args, BlockPos pos) {
         if (args.length == 1) {
-            return getListOfStringsMatchingLastWord(args, "config", "friends", "list", "toggle", "guiscale", "update", "updateHelp", "version", "folder", "help");
+            return getListOfStringsMatchingLastWord(args,
+                    /* friends */  "add", "remove", "list", "nameChangeCheck", "toggle",
+                    /* miscellaneous */ "guiscale", "config",
+                    /* update mod */ "update", "updateHelp", "version", "folder",
+                    /* help */ "help");
         }
         return null;
     }
diff --git a/src/main/java/eu/olli/cowmoonication/config/MooConfig.java b/src/main/java/eu/olli/cowmoonication/config/MooConfig.java
index e9b2146..d13758c 100644
--- a/src/main/java/eu/olli/cowmoonication/config/MooConfig.java
+++ b/src/main/java/eu/olli/cowmoonication/config/MooConfig.java
@@ -1,7 +1,6 @@
 package eu.olli.cowmoonication.config;
 
 import eu.olli.cowmoonication.Cowmoonication;
-import eu.olli.cowmoonication.util.Utils;
 import net.minecraftforge.common.MinecraftForge;
 import net.minecraftforge.common.config.Configuration;
 import net.minecraftforge.common.config.Property;
@@ -15,23 +14,19 @@ import java.util.List;
 public class MooConfig {
     public static boolean doUpdateCheck;
     public static boolean filterFriendNotifications;
-    private static String[] bestFriends;
     private static Configuration cfg = null;
-    private final Cowmoonication main;
 
-    public MooConfig(Configuration configuration, Cowmoonication main) {
-        this.main = main;
+    public MooConfig(Configuration configuration) {
         cfg = configuration;
         initConfig();
     }
 
-    public static Configuration getConfig() {
+    static Configuration getConfig() {
         return cfg;
     }
 
     private void initConfig() {
         syncFromFile();
-        main.getFriends().syncFriends(bestFriends);
         MinecraftForge.EVENT_BUS.register(new ConfigEventHandler());
     }
 
@@ -76,32 +71,22 @@ public class MooConfig {
         final boolean FILTER_FRIEND_NOTIFICATIONS = true;
         Property propFilterFriendNotify = cfg.get(Configuration.CATEGORY_CLIENT, "filterFriendNotifications", FILTER_FRIEND_NOTIFICATIONS, "Set to false to receive all login/logout messages, set to true to only get notifications of 'best friends' joining/leaving");
 
-        final String[] BEST_FRIENDS_DEFAULT_VALUE = new String[]{"Cow"};
-        Property propBestFriends = cfg.get(Configuration.CATEGORY_CLIENT, "bestFriends", BEST_FRIENDS_DEFAULT_VALUE, "List of best friends: receive login/logout notifications from them");
-        propBestFriends.setValidationPattern(Utils.VALID_USERNAME);
-
         List<String> propOrderGeneral = new ArrayList<>();
         propOrderGeneral.add(propDoUpdateCheck.getName());
         propOrderGeneral.add(propFilterFriendNotify.getName());
-        propOrderGeneral.add(propBestFriends.getName());
         cfg.setCategoryPropertyOrder(Configuration.CATEGORY_CLIENT, propOrderGeneral);
 
         if (readFieldsFromConfig) {
             doUpdateCheck = propDoUpdateCheck.getBoolean(DO_UPDATE_CHECK);
             filterFriendNotifications = propFilterFriendNotify.getBoolean(FILTER_FRIEND_NOTIFICATIONS);
-            bestFriends = propBestFriends.getStringList();
         }
 
         propDoUpdateCheck.set(doUpdateCheck);
         propFilterFriendNotify.set(filterFriendNotifications);
-        propBestFriends.set(bestFriends);
 
         if (cfg.hasChanged()) {
             cfg.save();
         }
-        if (propBestFriends.hasChanged()) {
-            main.getFriends().syncFriends(bestFriends);
-        }
     }
 
     public void toggleNotifications() {
diff --git a/src/main/java/eu/olli/cowmoonication/friends/Friend.java b/src/main/java/eu/olli/cowmoonication/friends/Friend.java
new file mode 100644
index 0000000..889e087
--- /dev/null
+++ b/src/main/java/eu/olli/cowmoonication/friends/Friend.java
@@ -0,0 +1,78 @@
+package eu.olli.cowmoonication.friends;
+
+import com.google.gson.InstanceCreator;
+
+import java.lang.reflect.Type;
+import java.util.Objects;
+import java.util.UUID;
+
+public class Friend {
+    public static final Friend FRIEND_NOT_FOUND = new Friend(null, null, -1);
+    private UUID id;
+    private String name;
+    private long lastChecked;
+
+    /**
+     * No-args constructor for GSON
+     */
+    private Friend() {
+        this.lastChecked = System.currentTimeMillis();
+    }
+
+    private Friend(UUID uuid, String name, long lastChecked) {
+        this.id = uuid;
+        this.name = name;
+        if (lastChecked > 0) {
+            this.lastChecked = lastChecked;
+        }
+    }
+
+    public UUID getUuid() {
+        return id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public long getLastChecked() {
+        return lastChecked;
+    }
+
+    public void setLastChecked(long lastChecked) {
+        this.lastChecked = lastChecked;
+    }
+
+    @Override
+    public String toString() {
+        return "Friend{" +
+                "uuid=" + id +
+                ", name='" + name + '\'' +
+                ", lastChecked=" + lastChecked +
+                '}';
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        Friend friend = (Friend) o;
+        return Objects.equals(id, friend.id);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(id);
+    }
+
+    public static class FriendCreator implements InstanceCreator {
+        @Override
+        public Friend createInstance(Type type) {
+            return new Friend();
+        }
+    }
+}
diff --git a/src/main/java/eu/olli/cowmoonication/friends/Friends.java b/src/main/java/eu/olli/cowmoonication/friends/Friends.java
new file mode 100644
index 0000000..e37b4a4
--- /dev/null
+++ b/src/main/java/eu/olli/cowmoonication/friends/Friends.java
@@ -0,0 +1,167 @@
+package eu.olli.cowmoonication.friends;
+
+import com.google.gson.Gson;
+import com.google.gson.JsonParseException;
+import com.google.gson.reflect.TypeToken;
+import eu.olli.cowmoonication.Cowmoonication;
+import eu.olli.cowmoonication.util.ApiUtils;
+import eu.olli.cowmoonication.util.TickDelay;
+import io.netty.util.internal.ConcurrentSet;
+import net.minecraft.event.ClickEvent;
+import net.minecraft.event.HoverEvent;
+import net.minecraft.util.ChatComponentText;
+import net.minecraft.util.ChatStyle;
+import net.minecraft.util.EnumChatFormatting;
+import org.apache.commons.io.FileUtils;
+
+import java.io.File;
+import java.io.IOException;
+import java.lang.reflect.Type;
+import java.nio.charset.StandardCharsets;
+import java.util.Set;
+import java.util.TreeSet;
+import java.util.UUID;
+import java.util.concurrent.TimeUnit;
+import java.util.stream.Collectors;
+
+public class Friends {
+    private static final long UPDATE_FREQUENCY_DEFAULT = TimeUnit.HOURS.toMillis(15);
+    private static final long UPDATE_FREQUENCY_MINIMUM = TimeUnit.MINUTES.toMillis(5);
+    private final Cowmoonication main;
+    private Set<Friend> bestFriends = new ConcurrentSet<>();
+    private File bestFriendsFile;
+    private UpdateStatus updateStatus;
+
+    public Friends(Cowmoonication main, File friendsFile) {
+        this.main = main;
+        this.bestFriendsFile = friendsFile;
+        this.updateStatus = UpdateStatus.IDLE;
+        loadBestFriends();
+        updateBestFriends(false);
+    }
+
+    public boolean isBestFriend(String playerName, boolean ignoreCase) {
+        if (ignoreCase) {
+            return bestFriends.stream().map(Friend::getName).anyMatch(playerName::equalsIgnoreCase);
+        } else {
+            return bestFriends.stream().map(Friend::getName).anyMatch(playerName::equals);
+        }
+    }
+
+    public void addBestFriend(String name) {
+        if (name.isEmpty()) {
+            return;
+        }
+
+        ApiUtils.fetchFriendData(name, friend -> {
+            if (friend == null) {
+                main.getChatHelper().sendMessage(EnumChatFormatting.RED, "Sorry, could contact Mojang's API and thus didn't add " + name + " as a best friend.");
+            } else if (friend.equals(Friend.FRIEND_NOT_FOUND)) {
+                main.getChatHelper().sendMessage(EnumChatFormatting.RED, "There is no player with the name " + EnumChatFormatting.DARK_RED + name + EnumChatFormatting.RED + ".");
+            } else {
+                boolean added = bestFriends.add(friend);
+                if (added) {
+                    main.getChatHelper().sendMessage(EnumChatFormatting.GREEN, "Added " + EnumChatFormatting.DARK_GREEN + friend.getName() + EnumChatFormatting.GREEN + " as best friend.");
+                    saveBestFriends();
+                }
+            }
+        });
+    }
+
+    public boolean removeBestFriend(String name) {
+        boolean removed = bestFriends.removeIf(friend -> friend.getName().equalsIgnoreCase(name));
+        if (removed) {
+            saveBestFriends();
+        }
+        return removed;
+    }
+
+    public Set<String> getBestFriends() {
+        return bestFriends.stream().map(Friend::getName).collect(Collectors.toCollection(TreeSet::new));
+    }
+
+    private Friend getBestFriend(UUID uuid) {
+        return bestFriends.stream().filter(friend -> friend.getUuid().equals(uuid)).findFirst().orElse(Friend.FRIEND_NOT_FOUND);
+    }
+
+    public void updateBestFriends(boolean isCommandTriggered) {
+        bestFriends.stream().filter(friend -> System.currentTimeMillis() - friend.getLastChecked() > (isCommandTriggered ? UPDATE_FREQUENCY_MINIMUM : UPDATE_FREQUENCY_DEFAULT)).forEach(this::updateBestFriend);
+
+        new TickDelay(() -> {
+            if (this.updateStatus != UpdateStatus.IDLE) {
+                if (isCommandTriggered && updateStatus == UpdateStatus.NO_NAME_CHANGES) {
+                    main.getChatHelper().sendMessage(EnumChatFormatting.GOLD, "No name changes detected.");
+                }
+                saveBestFriends();
+                this.updateStatus = UpdateStatus.IDLE;
+            }
+        }, 10 * 20);
+    }
+
+    private void updateBestFriend(Friend friend) {
+        ApiUtils.fetchCurrentName(friend, newName -> {
+            if (newName == null) {
+                // skipping friend, something went wrong with API request
+            } else if (newName.equals(ApiUtils.UUID_NOT_FOUND)) {
+                main.getChatHelper().sendMessage(EnumChatFormatting.RED, "How did you manage to get a unique id on your best friends list that has no name attached to it?");
+            } else if (newName.equals(friend.getName())) {
+                // name hasn't changed, only updating lastChecked timestamp
+                Friend bestFriend = getBestFriend(friend.getUuid());
+                if (!bestFriend.equals(Friend.FRIEND_NOT_FOUND)) {
+                    bestFriend.setLastChecked(System.currentTimeMillis());
+                    if (this.updateStatus == UpdateStatus.IDLE) {
+                        this.updateStatus = UpdateStatus.NO_NAME_CHANGES;
+                    }
+                }
+            } else {
+                // name has changed
+                main.getChatHelper().sendMessage(new ChatComponentText("Your best friend " + EnumChatFormatting.DARK_GREEN + friend.getName() + EnumChatFormatting.GREEN + " changed the name to " + EnumChatFormatting.DARK_GREEN + newName + EnumChatFormatting.GREEN + ".").setChatStyle(new ChatStyle()
+                        .setColor(EnumChatFormatting.GREEN)
+                        .setChatClickEvent(new ClickEvent(ClickEvent.Action.OPEN_URL, "https://namemc.com/search?q=" + newName))
+                        .setChatHoverEvent(new HoverEvent(HoverEvent.Action.SHOW_TEXT, new ChatComponentText(EnumChatFormatting.YELLOW + "View " + EnumChatFormatting.GOLD + newName + EnumChatFormatting.YELLOW + "'s name history on namemc.com")))));
+
+                Friend bestFriend = getBestFriend(friend.getUuid());
+                if (!bestFriend.equals(Friend.FRIEND_NOT_FOUND)) {
+                    bestFriend.setName(newName);
+                    bestFriend.setLastChecked(System.currentTimeMillis());
+                    this.updateStatus = UpdateStatus.NAME_CHANGED;
+                }
+            }
+        });
+    }
+
+    public synchronized void saveBestFriends() {
+        try {
+            String bestFriendsJsonZoned = dumpJson(this.bestFriends);
+            FileUtils.writeStringToFile(this.bestFriendsFile, bestFriendsJsonZoned, StandardCharsets.UTF_8);
+        } catch (IOException e) {
+            main.getLogger().error("Couldn't save best friends", e);
+        }
+    }
+
+    private void loadBestFriends() {
+        try {
+            this.bestFriends.clear();
+            String bestFriendsData = FileUtils.readFileToString(this.bestFriendsFile, StandardCharsets.UTF_8);
+            this.bestFriends.addAll(parseJson(bestFriendsData));
+        } catch (IOException e) {
+            main.getLogger().error("Couldn't read best friends file " + this.bestFriendsFile, e);
+        } catch (JsonParseException e) {
+            main.getLogger().error("Couldn't parse best friends file " + this.bestFriendsFile, e);
+        }
+    }
+
+    private Set<Friend> parseJson(String bestFriendsData) {
+        Type collectionType = new TypeToken<Set<Friend>>() {
+        }.getType();
+        return new Gson().fromJson(bestFriendsData, collectionType);
+    }
+
+    private String dumpJson(Set<Friend> bestFriends) {
+        return new Gson().toJson(bestFriends);
+    }
+
+    private enum UpdateStatus {
+        IDLE, NAME_CHANGED, NO_NAME_CHANGES
+    }
+}
diff --git a/src/main/java/eu/olli/cowmoonication/listener/ChatListener.java b/src/main/java/eu/olli/cowmoonication/listener/ChatListener.java
index 54f8025..42a45e0 100644
--- a/src/main/java/eu/olli/cowmoonication/listener/ChatListener.java
+++ b/src/main/java/eu/olli/cowmoonication/listener/ChatListener.java
@@ -44,7 +44,7 @@ public class ChatListener {
                 if (nameEnd == -1) {
                     nameEnd = text.indexOf(" left");
                 }
-                boolean isBestFriend = main.getFriends().isBestFriend(text.substring(0, nameEnd));
+                boolean isBestFriend = main.getFriends().isBestFriend(text.substring(0, nameEnd), false);
                 if (!isBestFriend) {
                     e.setCanceled(true);
                 }
@@ -58,10 +58,10 @@ public class ChatListener {
             if (!Mouse.getEventButtonState() && Mouse.getEventButton() == 1 && Keyboard.isKeyDown(Keyboard.KEY_LMENU)) { // alt key pressed and right mouse button being released
                 IChatComponent chatComponent = Minecraft.getMinecraft().ingameGUI.getChatGUI().getChatComponent(Mouse.getX(), Mouse.getY());
                 if (chatComponent != null) {
-                    String chatData = main.getUtils().cleanChatComponent(chatComponent);
+                    String chatData = main.getChatHelper().cleanChatComponent(chatComponent);
                     Clipboard clipboard = Toolkit.getDefaultToolkit().getSystemClipboard();
                     clipboard.setContents(new StringSelection(chatData), null);
-                    main.getUtils().sendAboveChatMessage(EnumChatFormatting.YELLOW + "Copied chat component to clipboard:", "" + EnumChatFormatting.BOLD + EnumChatFormatting.GOLD + "\u276E" + EnumChatFormatting.RESET + chatComponent.getUnformattedText() + EnumChatFormatting.BOLD + EnumChatFormatting.GOLD + "\u276F");
+                    main.getChatHelper().sendAboveChatMessage(EnumChatFormatting.YELLOW + "Copied chat component to clipboard:", "" + EnumChatFormatting.BOLD + EnumChatFormatting.GOLD + "\u276E" + EnumChatFormatting.RESET + chatComponent.getUnformattedText() + EnumChatFormatting.BOLD + EnumChatFormatting.GOLD + "\u276F");
                 }
             }
         }
@@ -76,7 +76,7 @@ public class ChatListener {
                 lastTypedChars += eventCharacter;
                 if (lastTypedChars.equalsIgnoreCase("/r ")) {
                     // replace /r with /msg <last user>
-                    main.getUtils().sendAboveChatMessage("Sending message to " + lastPMSender + "!");
+                    main.getChatHelper().sendAboveChatMessage("Sending message to " + lastPMSender + "!");
                     Minecraft.getMinecraft().displayGuiScreen(new GuiChat("/w " + lastPMSender + " "));
                 }
             } else if (Keyboard.getEventKey() == Keyboard.KEY_BACK) { // Backspace
@@ -106,7 +106,7 @@ public class ChatListener {
     public void onRenderChatGui(RenderGameOverlayEvent.Chat e) {
         if (e.type == RenderGameOverlayEvent.ElementType.CHAT) {
             // render message above chat box
-            String[] aboveChatMessage = main.getUtils().getAboveChatMessage();
+            String[] aboveChatMessage = main.getChatHelper().getAboveChatMessage();
             if (aboveChatMessage != null) {
                 float chatHeightFocused = Minecraft.getMinecraft().gameSettings.chatHeightFocused;
                 float chatScale = Minecraft.getMinecraft().gameSettings.chatScale;
diff --git a/src/main/java/eu/olli/cowmoonication/listener/PlayerListener.java b/src/main/java/eu/olli/cowmoonication/listener/PlayerListener.java
index b817ed8..304806d 100644
--- a/src/main/java/eu/olli/cowmoonication/listener/PlayerListener.java
+++ b/src/main/java/eu/olli/cowmoonication/listener/PlayerListener.java
@@ -1,6 +1,7 @@
 package eu.olli.cowmoonication.listener;
 
 import eu.olli.cowmoonication.Cowmoonication;
+import eu.olli.cowmoonication.util.TickDelay;
 import net.minecraftforge.fml.common.eventhandler.SubscribeEvent;
 import net.minecraftforge.fml.common.network.FMLNetworkEvent;
 
@@ -14,5 +15,11 @@ public class PlayerListener {
     @SubscribeEvent
     public void onServerJoin(FMLNetworkEvent.ClientConnectedToServerEvent e) {
         main.getVersionChecker().runUpdateCheck(false);
+        new TickDelay(() -> main.getChatHelper().sendOfflineMessages(), 6 * 20);
+    }
+
+    @SubscribeEvent
+    public void onServerLeave(FMLNetworkEvent.ClientDisconnectionFromServerEvent e) {
+        main.getFriends().saveBestFriends();
     }
 }
diff --git a/src/main/java/eu/olli/cowmoonication/util/ApiUtils.java b/src/main/java/eu/olli/cowmoonication/util/ApiUtils.java
new file mode 100644
index 0000000..5ff7d5d
--- /dev/null
+++ b/src/main/java/eu/olli/cowmoonication/util/ApiUtils.java
@@ -0,0 +1,70 @@
+package eu.olli.cowmoonication.util;
+
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+import com.google.gson.JsonArray;
+import com.google.gson.JsonParser;
+import com.mojang.util.UUIDTypeAdapter;
+import eu.olli.cowmoonication.friends.Friend;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.net.HttpURLConnection;
+import java.net.URL;
+import java.util.UUID;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.function.Consumer;
+
+public class ApiUtils {
+    public static final String UUID_NOT_FOUND = "UUID-NOT-FOUND";
+    private static final String NAME_TO_UUID_URL = "https://api.mojang.com/users/profiles/minecraft/";
+    private static final String UUID_TO_NAME_URL = "https://api.mojang.com/user/profiles/%s/names";
+    private static ExecutorService pool = Executors.newCachedThreadPool();
+    private static Gson gson = new GsonBuilder().registerTypeAdapter(UUID.class, new UUIDTypeAdapter()).registerTypeAdapter(Friend.class, new Friend.FriendCreator()).create();
+
+    private ApiUtils() {
+    }
+
+    public static void fetchFriendData(String name, Consumer<Friend> action) {
+        pool.execute(() -> action.accept(getFriend(name)));
+    }
+
+    private static Friend getFriend(String name) {
+        try {
+            HttpURLConnection connection = (HttpURLConnection) new URL(NAME_TO_UUID_URL + name).openConnection();
+            connection.setReadTimeout(5000);
+            if (connection.getResponseCode() == 204) {
+                return Friend.FRIEND_NOT_FOUND;
+            } else if (connection.getResponseCode() == 200) {
+                return gson.fromJson(new BufferedReader(new InputStreamReader(connection.getInputStream())), Friend.class);
+            }
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+        return null;
+    }
+
+    public static void fetchCurrentName(Friend friend, Consumer<String> action) {
+        pool.execute(() -> action.accept(getCurrentName(friend)));
+    }
+
+    private static String getCurrentName(Friend friend) {
+        try {
+            HttpURLConnection connection = (HttpURLConnection) new URL(String.format(UUID_TO_NAME_URL, UUIDTypeAdapter.fromUUID(friend.getUuid()))).openConnection();
+            connection.setReadTimeout(5000);
+            if (connection.getResponseCode() == 204) {
+                return UUID_NOT_FOUND;
+            } else if (connection.getResponseCode() == 200) {
+                JsonArray nameHistoryData = new JsonParser().parse(new BufferedReader(new InputStreamReader(connection.getInputStream()))).getAsJsonArray();
+                if (nameHistoryData.size() > 0) {
+                    return nameHistoryData.get(nameHistoryData.size() - 1).getAsJsonObject().get("name").getAsString();
+                }
+            }
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+        return null;
+    }
+}
diff --git a/src/main/java/eu/olli/cowmoonication/util/ChatHelper.java b/src/main/java/eu/olli/cowmoonication/util/ChatHelper.java
new file mode 100644
index 0000000..a0820c0
--- /dev/null
+++ b/src/main/java/eu/olli/cowmoonication/util/ChatHelper.java
@@ -0,0 +1,74 @@
+package eu.olli.cowmoonication.util;
+
+import net.minecraft.client.Minecraft;
+import net.minecraft.util.ChatComponentText;
+import net.minecraft.util.ChatStyle;
+import net.minecraft.util.EnumChatFormatting;
+import net.minecraft.util.IChatComponent;
+import net.minecraftforge.client.event.ClientChatReceivedEvent;
+import net.minecraftforge.common.MinecraftForge;
+
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+public class ChatHelper {
+    private static final Pattern USELESS_JSON_CONTENT_PATTERN = Pattern.compile("\"[A-Za-z]+\":false,?");
+    private static final int DISPLAY_DURATION = 5000;
+    private List<IChatComponent> offlineMessages = new ArrayList<>();
+    private String[] aboveChatMessage;
+    private long aboveChatMessageExpiration;
+
+    public ChatHelper() {
+    }
+
+    public void sendMessage(EnumChatFormatting color, String text) {
+        sendMessage(new ChatComponentText(text).setChatStyle(new ChatStyle().setColor(color)));
+    }
+
+    public void sendMessage(IChatComponent chatComponent) {
+        ClientChatReceivedEvent event = new ClientChatReceivedEvent((byte) 1, chatComponent);
+        MinecraftForge.EVENT_BUS.post(event);
+        if (!event.isCanceled()) {
+            if (Minecraft.getMinecraft().thePlayer == null) {
+                offlineMessages.add(event.message);
+            } else {
+                Minecraft.getMinecraft().thePlayer.addChatMessage(event.message);
+            }
+        }
+    }
+
+    public void sendOfflineMessages() {
+        if (Minecraft.getMinecraft().thePlayer != null) {
+            Iterator<IChatComponent> offlineMessages = this.offlineMessages.iterator();
+            if (offlineMessages.hasNext()) {
+                Minecraft.getMinecraft().thePlayer.playSound("random.levelup", 0.4F, 0.8F);
+            }
+            while (offlineMessages.hasNext()) {
+                Minecraft.getMinecraft().thePlayer.addChatMessage(offlineMessages.next());
+                offlineMessages.remove();
+            }
+        }
+    }
+
+    public void sendAboveChatMessage(String... text) {
+        aboveChatMessage = text;
+        aboveChatMessageExpiration = Minecraft.getSystemTime() + DISPLAY_DURATION;
+    }
+
+    public String[] getAboveChatMessage() {
+        if (aboveChatMessageExpiration < Minecraft.getSystemTime()) {
+            // message expired
+            aboveChatMessage = null;
+        }
+        return aboveChatMessage;
+    }
+
+    public String cleanChatComponent(IChatComponent chatComponent) {
+        String component = IChatComponent.Serializer.componentToJson(chatComponent);
+        Matcher jsonMatcher = USELESS_JSON_CONTENT_PATTERN.matcher(component);
+        return jsonMatcher.replaceAll("");
+    }
+}
diff --git a/src/main/java/eu/olli/cowmoonication/util/Utils.java b/src/main/java/eu/olli/cowmoonication/util/Utils.java
index 60e2ea3..0b890f0 100644
--- a/src/main/java/eu/olli/cowmoonication/util/Utils.java
+++ b/src/main/java/eu/olli/cowmoonication/util/Utils.java
@@ -1,65 +1,14 @@
 package eu.olli.cowmoonication.util;
 
-import eu.olli.cowmoonication.Cowmoonication;
-import net.minecraft.client.Minecraft;
-import net.minecraft.util.ChatComponentText;
-import net.minecraft.util.IChatComponent;
-import net.minecraftforge.client.event.ClientChatReceivedEvent;
-import net.minecraftforge.common.MinecraftForge;
-
-import java.io.File;
-import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
-public class Utils {
-    public static final Pattern VALID_USERNAME = Pattern.compile("^[\\w]{1,16}$");
-    private static final Pattern USELESS_JSON_CONTENT_PATTERN = Pattern.compile("\"[A-Za-z]+\":false,?");
-    private final Cowmoonication main;
-    private final File modsDir;
-    private String[] aboveChatMessage;
-    private long aboveChatMessageExpiration;
-
-    public Utils(Cowmoonication main, File sourceFile) {
-        this.main = main;
-        modsDir = sourceFile.getParentFile();
-    }
-
-    public void sendMessage(String text) {
-        sendMessage(new ChatComponentText(text));
-    }
-
-    public void sendMessage(IChatComponent chatComponent) {
-        ClientChatReceivedEvent event = new ClientChatReceivedEvent((byte) 1, chatComponent);
-        MinecraftForge.EVENT_BUS.post(event);
-        if (!event.isCanceled()) {
-            Minecraft.getMinecraft().thePlayer.addChatMessage(event.message);
-        }
-    }
+public final class Utils {
+    private static final Pattern VALID_USERNAME = Pattern.compile("^[\\w]{1,16}$");
 
-    public void sendAboveChatMessage(String... text) {
-        aboveChatMessage = text;
-        aboveChatMessageExpiration = Minecraft.getSystemTime() + 5000;
+    private Utils() {
     }
 
-    public String[] getAboveChatMessage() {
-        if (aboveChatMessageExpiration < Minecraft.getSystemTime()) {
-            // message expired
-            aboveChatMessage = null;
-        }
-        return aboveChatMessage;
-    }
-
-    public boolean isValidMcName(String username) {
+    public static boolean isValidMcName(String username) {
         return VALID_USERNAME.matcher(username).matches();
     }
-
-    public String cleanChatComponent(IChatComponent chatComponent) {
-        String component = IChatComponent.Serializer.componentToJson(chatComponent);
-        Matcher jsonMatcher = USELESS_JSON_CONTENT_PATTERN.matcher(component);
-        return jsonMatcher.replaceAll("");
-    }
-
-    public File getModsFolder() {
-        return modsDir;
-    }
 }
diff --git a/src/main/java/eu/olli/cowmoonication/util/VersionChecker.java b/src/main/java/eu/olli/cowmoonication/util/VersionChecker.java
index 5c29ae5..fa04c38 100644
--- a/src/main/java/eu/olli/cowmoonication/util/VersionChecker.java
+++ b/src/main/java/eu/olli/cowmoonication/util/VersionChecker.java
@@ -120,7 +120,7 @@ public class VersionChecker {
         }
 
         if (statusMsg != null) {
-            main.getUtils().sendMessage(statusMsg);
+            main.getChatHelper().sendMessage(statusMsg);
         }
     }