CompactChatClient: Migrate old .json5 files to .json

src/main/java/dev/caoimhe/compactchat/CompactChatClient.java

@@ -4,9 +4,11 @@
 import dev.caoimhe.compactchat.util.CollectionUtil;
 import dev.caoimhe.compactchat.util.FabricLoaderUtil;
 import net.fabricmc.api.ClientModInitializer;
+import net.fabricmc.loader.api.FabricLoader;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import java.nio.file.Files;
 import java.util.List;
 
 public class CompactChatClient implements ClientModInitializer {
@@ -22,12 +24,41 @@ public class CompactChatClient implements ClientModInitializer {
 
     @Override
     public void onInitializeClient() {
+        this.migrateJson5Configuration();
+
         Configuration.register();
-        // TODO: Migrate old .json5 config files to .json
 
         var message = CollectionUtil.randomFrom(STARTUP_MESSAGES);
         message = message.replace("{RANDOM_MOD}", FabricLoaderUtil.getRandomModName());
 
         LOGGER.info(message + " (Compact Chat is ready!)");
     }
+
+    /**
+     * Migrates the old JSON5 configuration file to the new JSON configuration file.
+     * We can't really remove this, because it would break the configuration for users who are updating from 2.0.1 or below.
+     */
+    private void migrateJson5Configuration() {
+        // Exceptions shouldn't really happen (apart from Files#move), but we don't want this to prevent the user from starting their game.
+        try {
+            var oldFile = FabricLoader.getInstance().getConfigDir().resolve("compact-chat.json5");
+            if (!Files.exists(oldFile)) {
+                LOGGER.debug("No old configuration file found. Skipping automatic migration.");
+                return;
+            }
+
+            var newFile = FabricLoader.getInstance().getConfigDir().resolve("compact-chat.json");
+            if (Files.exists(newFile)) {
+                LOGGER.warn("Both an old (<=2.0.1) and new configuration file (>=2.1.0) exist. Skipping automatic migration.");
+                return;
+            }
+
+            Files.move(oldFile, newFile);
+            LOGGER.info("Successfully migrated old configuration file.");
+        } catch (Exception e) {
+            LOGGER.error("Failed to migrate old configuration file!", e);
+            LOGGER.error("Please manually migrate your old configuration file (config/compact-chat.json5) to the new location (config/compact-chat.json).");
+            LOGGER.error("If you don't do this, your configuration will be reset to the default values.");
+        }
+    }
 }