Load localizations automatically.

Also included a sample "backwards" localization to demonstrate that it does in fact work.

proxy/src/main/java/com/velocitypowered/proxy/VelocityServer.java

@@ -54,6 +54,7 @@ import com.velocitypowered.proxy.scheduler.VelocityScheduler;
 import com.velocitypowered.proxy.server.ServerMap;
 import com.velocitypowered.proxy.util.AddressUtil;
 import com.velocitypowered.proxy.util.EncryptionUtils;
+import com.velocitypowered.proxy.util.FileSystemUtils;
 import com.velocitypowered.proxy.util.VelocityChannelRegistrar;
 import com.velocitypowered.proxy.util.bossbar.AdventureBossBarManager;
 import com.velocitypowered.proxy.util.ratelimit.Ratelimiter;
@@ -246,9 +247,43 @@ public class VelocityServer implements ProxyServer, ForwardingAudience {
   private void registerTranslations() {
     final TranslationRegistry translationRegistry = TranslationRegistry
         .create(Key.key("velocity", "translations"));
-    translationRegistry.registerAll(Locale.US,
+    try {
-        ResourceBundle.getBundle("com/velocitypowered/proxy/messages", Locale.US,
+      FileSystemUtils.visitResources(VelocityServer.class,
-            UTF8ResourceBundleControl.get()), false);
+          Paths.get("com", "velocitypowered", "proxy", "l10n"), path -> {
+            logger.info("Loading localizations...");
+
+            try {
+              Files.walk(path).forEach(file -> {
+                if (!Files.isRegularFile(file)) {
+                  return;
+                }
+
+                String filename = com.google.common.io.Files
+                    .getNameWithoutExtension(file.getFileName().toString());
+                String localeName = filename.replace("messages_", "")
+                    .replace("messages", "")
+                    .replace('_', '-');
+                Locale locale;
+                if (localeName.isEmpty()) {
+                  locale = Locale.US;
+                } else {
+                  locale = Locale.forLanguageTag(localeName);
+                }
+
+                translationRegistry.registerAll(locale,
+                    ResourceBundle.getBundle("com/velocitypowered/proxy/l10n/messages",
+                        locale, UTF8ResourceBundleControl.get()), false);
+              });
+            } catch (IOException e) {
+              logger.error("Encountered an I/O error whilst loading translations", e);
+              System.exit(1);
+            }
+          });
+    } catch (IOException e) {
+      logger.error("Encountered an I/O error whilst loading translations", e);
+      System.exit(1);
+      return;
+    }
     GlobalTranslator.get().addSource(translationRegistry);
   }
 

proxy/src/main/java/com/velocitypowered/proxy/command/builtin/VelocityCommand.java

@@ -226,8 +226,8 @@ public class VelocityCommand implements SimpleCommand {
           .translatable("velocity.command.version-copyright",
               Component.text(version.getVendor()),
               Component.text(version.getName()));
-      source.sendMessage(Identity.nil(), velocity);
+      source.sendMessage(velocity);
-      source.sendMessage(Identity.nil(), copyright);
+      source.sendMessage(copyright);
 
       if (version.getName().equals("Velocity")) {
         TextComponent embellishment = Component.text()

proxy/src/main/java/com/velocitypowered/proxy/util/FileSystemUtils.java

@@ -0,0 +1,56 @@
+package com.velocitypowered.proxy.util;
+
+import java.io.File;
+import java.io.IOException;
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.net.URL;
+import java.nio.file.FileSystem;
+import java.nio.file.FileSystems;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.Collections;
+import java.util.function.Consumer;
+
+public class FileSystemUtils {
+
+  /**
+   * Visits the resources at the given {@link Path} within the resource
+   * path of the given {@link Class}.
+   *
+   * @param target The target class of the resource path to scan
+   * @param path The path to scan within the resource path
+   * @param consumer The consumer to visit the resolved path
+   */
+  public static boolean visitResources(Class<?> target, Path path, Consumer<Path> consumer)
+      throws IOException {
+    final File file = new File(target
+        .getProtectionDomain().getCodeSource().getLocation().getPath());
+
+    if (file.isFile()) { // jar
+      URI uri = file.toURI();
+      try (FileSystem fileSystem = FileSystems.newFileSystem(uri, Collections.emptyMap())) {
+        Path toVisit = fileSystem.getPath(path.toString());
+        if (Files.exists(toVisit)) {
+          consumer.accept(toVisit);
+          return true;
+        }
+        return false;
+      }
+    } else {
+      URI uri;
+      try {
+        URL url = target.getClassLoader().getResource(path.toString());
+        if (url == null) {
+          return false;
+        }
+        uri = url.toURI();
+      } catch (URISyntaxException e) {
+        throw new IllegalStateException(e);
+      }
+      consumer.accept(Paths.get(uri));
+      return true;
+    }
+  }
+}

proxy/src/main/resources/com/velocitypowered/proxy/l10n/messages.properties

@@ -27,7 +27,7 @@ velocity.error.online-mode-only=You are not logged into your Minecraft account.
 velocity.error.player-connection-error=An internal error occurred in your connection.
 velocity.error.modern-forwarding-needs-new-client=This server is only compatible with Minecraft 1.13 and above.
 velocity.error.modern-forwarding-failed=Your server did not send a forwarding request to the proxy. Make sure the server is configured for Velocity forwarding.
-velocity.error.moved-to-new-server=YOu were kicked from {0}: {1}
+velocity.error.moved-to-new-server=You were kicked from {0}: {1}
 velocity.error.no-available-servers=There are no available servers to connect you to. Try again later or contact an admin.
 
 # Commands

proxy/src/main/resources/com/velocitypowered/proxy/l10n/messages_en_UD.properties

@@ -0,0 +1,62 @@
+#
+# Copyright (C) 2018 Velocity Contributors
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+#
+
+velocity.error.already-connected=¡ɹǝʌɹǝs sᴉɥʇ oʇ pǝʇɔǝuuoɔ ʎpɐǝɹlɐ ǝɹɐ no⅄
+velocity.error.already-connected-proxy=¡ʎxoɹd sᴉɥʇ oʇ pǝʇɔǝuuoɔ ʎpɐǝɹlɐ ǝɹɐ no⅄
+velocity.error.already-connecting=¡ɹǝʌɹǝs ɐ oʇ ʇɔǝuuoɔ oʇ ƃuᴉʎɹʇ ʎpɐǝɹlɐ ǝɹɐ no⅄
+velocity.error.cant-connect={1} :{0} oʇ ʇɔǝuuoɔ oʇ ǝlqɐu∩
+velocity.error.connecting-server-error=˙ɹǝʇɐl uᴉɐƃɐ ʎɹʇ ǝsɐǝlԀ ˙{0} oʇ noʎ ʇɔǝuuoɔ oʇ ǝlqɐu∩
+velocity.error.connected-server-error=˙ɯǝlqoɹd ɐ pǝɹǝʇunoɔuǝ {0} oʇ uoᴉʇɔǝuuoɔ ɹno⅄
+velocity.error.internal-server-connection-error=˙pǝɹɹnɔɔo ɹoɹɹǝ uoᴉʇɔǝuuoɔ ɹǝʌɹǝs lɐuɹǝʇuᴉ u∀
+velocity.error.logging-in-too-fast=˙ɹǝʇɐl uᴉɐƃɐ ʎɹʇ 'ʇsɐɟ ooʇ uᴉ ƃuᴉƃƃol ǝɹɐ no⅄
+velocity.error.online-mode-only=˙ʇuǝᴉlɔ ʇɟɐɹɔǝuᴉW ɹnoʎ ƃuᴉʇɹɐʇsǝɹ ʎɹʇ 'ʇunoɔɔɐ ʇɟɐɹɔǝuᴉW ɹnoʎ oʇuᴉ pǝƃƃol ǝɹɐ noʎ ɟI ˙ʇunoɔɔɐ ʇɟɐɹɔǝuᴉW ɹnoʎ oʇuᴉ pǝƃƃol ʇou ǝɹɐ no⅄
+velocity.error.player-connection-error=˙uoᴉʇɔǝuuoɔ ɹnoʎ uᴉ pǝɹɹnɔɔo ɹoɹɹǝ lɐuɹǝʇuᴉ u∀
+velocity.error.modern-forwarding-needs-new-client=˙ǝʌoqɐ puɐ ƐƖ˙Ɩ ʇɟɐɹɔǝuᴉW ɥʇᴉʍ ǝlqᴉʇɐdɯoɔ ʎluo sᴉ ɹǝʌɹǝs sᴉɥ┴
+velocity.error.modern-forwarding-failed=˙ƃuᴉpɹɐʍɹoɟ ʎʇᴉɔolǝΛ ɹoɟ pǝɹnƃᴉɟuoɔ sᴉ ɹǝʌɹǝs ǝɥʇ ǝɹns ǝʞɐW ˙ʎxoɹd ǝɥʇ oʇ ʇsǝnbǝɹ ƃuᴉpɹɐʍɹoɟ ɐ puǝs ʇou pᴉp ɹǝʌɹǝs ɹno⅄
+velocity.error.moved-to-new-server={1} :{0} ɯoɹɟ pǝʞɔᴉʞ ǝɹǝʍ no⅄
+velocity.error.no-available-servers=˙uᴉɯpɐ uɐ ʇɔɐʇuoɔ ɹo ɹǝʇɐl uᴉɐƃɐ ʎɹ┴ ˙oʇ noʎ ʇɔǝuuoɔ oʇ sɹǝʌɹǝs ǝlqɐlᴉɐʌɐ ou ǝɹɐ ǝɹǝɥ┴
+
+# Commands
+velocity.command.generic-error=˙puɐɯɯoɔ sᴉɥʇ ƃuᴉuunɹ ǝlᴉɥʍ pǝɹɹnɔɔo ɹoɹɹǝ u∀
+velocity.command.command-does-not-exist=˙ʇsᴉxǝ ʇou sǝop puɐɯɯoɔ sᴉɥ┴
+
+velocity.command.players-only=Only players can run this command.
+velocity.command.server-does-not-exist=˙puɐɯɯoɔ sᴉɥʇ unɹ uɐɔ sɹǝʎɐld ʎluO
+
+velocity.command.server-current-server=˙{0} oʇ pǝʇɔǝuuoɔ ʎlʇuǝɹɹnɔ ǝɹɐ no⅄
+velocity.command.server-too-many=˙sʇunoɔ ɹǝʌɹǝs lɐnpᴉʌᴉpuᴉ ʇǝƃ oʇ uoᴉʇǝldɯoɔ qɐʇ ǝs∩ ˙dn ʇǝs sɹǝʌɹǝs ʎuɐɯ ooʇ ǝɹɐ ǝɹǝɥ┴
+velocity.command.server-available=:sɹǝʌɹǝs ǝlqɐlᴉɐʌ∀
+velocity.command.server-tooltip-player-online=ǝuᴉluo ɹǝʎɐld {0}
+velocity.command.server-tooltip-players-online=ǝuᴉluo sɹǝʎɐld {0}
+velocity.command.server-tooltip-current-server=ɹǝʌɹǝs sᴉɥʇ oʇ pǝʇɔǝuuoɔ ʎlʇuǝɹɹnƆ
+velocity.command.server-tooltip-offer-connect-server=ɹǝʌɹǝs sᴉɥʇ oʇ ʇɔǝuuoɔ oʇ ʞɔᴉlƆ
+
+velocity.command.glist-player-singular=ɹǝʎɐld
+velocity.command.glist-player-plural=sɹǝʎɐld
+velocity.command.glist-total-suffix=˙ʎxoɹd ǝɥʇ oʇ pǝʇɔǝuuoɔ ʎlʇuǝɹɹnɔ ǝɹɐ 
+velocity.command.glist-view-all=˙/glist all ǝsn 'sɹǝʌɹǝs uo sɹǝʎɐld llɐ ʍǝᴉʌ o┴
+
+velocity.command.reload-success=˙pǝpɐolǝɹ ʎllnɟssǝɔɔns uoᴉʇɐɹnƃᴉɟuoɔ ʎʇᴉɔolǝΛ
+velocity.command.reload-failure=˙slᴉɐʇǝp ǝɹoɯ ɹoɟ ǝlosuoɔ ǝɥʇ ʞɔǝɥƆ ˙uoᴉʇɐɹnƃᴉɟuoɔ ʎʇᴉɔolǝΛ ɹnoʎ pɐolǝɹ oʇ ǝlqɐu∩
+
+velocity.command.version-copyright=˙Ɛʌ ǝsuǝɔᴉ˥ ɔᴉlqnԀ lɐɹǝuǝפ ∩Nפ ǝɥʇ ɟo sɯɹǝʇ ǝɥʇ ɹǝpun pǝsuǝɔᴉl sᴉ {1} ˙{0} Ɩᄅ0ᄅ-8Ɩ0ᄅ ʇɥƃᴉɹʎdoƆ
+
+velocity.command.no-plugins=˙pǝllɐʇsuᴉ ʎlʇuǝɹɹnɔ suᴉƃnld ou ǝɹɐ ǝɹǝɥ┴
+velocity.command.plugins-list={0}: suᴉƃnlԀ
+velocity.command.plugin-tooltip-website={0}: ǝʇᴉsqǝM
+velocity.command.plugin-tooltip-author={0}: ɹoɥʇn∀
+velocity.command.plugin-tooltip-authors={0}: sɹoɥʇn∀