Add MVInventoriesImporter for Multiverse data migration

Implemented a new importer to facilitate migration of world groups and player data from Multiverse Inventories. Supports reading group configurations and player UUID-name mappings.

Author: NonSwag

src/main/java/net/thenextlvl/perworlds/importer/multiverse/MVInventoriesImporter.java

@@ -0,0 +1,87 @@
+package net.thenextlvl.perworlds.importer.multiverse;
+
+import com.google.gson.JsonParseException;
+import com.google.gson.JsonParser;
+import com.google.gson.stream.JsonReader;
+import net.thenextlvl.perworlds.PerWorldsPlugin;
+import net.thenextlvl.perworlds.WorldGroup;
+import net.thenextlvl.perworlds.data.PlayerData;
+import net.thenextlvl.perworlds.group.PaperWorldGroup;
+import net.thenextlvl.perworlds.importer.Importer;
+import net.thenextlvl.perworlds.model.PaperPlayerData;
+import org.bukkit.configuration.file.YamlConfiguration;
+import org.jspecify.annotations.NullMarked;
+
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+import java.util.UUID;
+
+import static java.nio.file.StandardOpenOption.READ;
+
+@NullMarked
+public class MVInventoriesImporter extends Importer {
+
+    public MVInventoriesImporter(PerWorldsPlugin plugin) {
+        super(plugin, "Multiverse-Inventories");
+    }
+
+    @Override
+    public Map<String, Set<String>> readGroups() throws IOException {
+        var path = getDataPath().resolve("groups.yml");
+        if (!Files.exists(path)) return new HashMap<>();
+
+        try (var reader = Files.newBufferedReader(path, StandardCharsets.UTF_8)) {
+            var config = YamlConfiguration.loadConfiguration(reader);
+
+            var groups = config.getConfigurationSection("groups");
+            if (groups == null) return new HashMap<>();
+
+            var result = new HashMap<String, Set<String>>();
+            groups.getKeys(false).forEach(group -> {
+                var groupSection = groups.getConfigurationSection(group);
+                if (groupSection == null) return;
+
+                var worlds = groupSection.getStringList("worlds");
+                result.put(group, new HashSet<>(worlds));
+            });
+            return result;
+        }
+    }
+
+    @Override
+    public Map<UUID, String> readPlayers() throws IOException {
+        var path = getDataPath().resolve("playernames.json");
+        if (!Files.exists(path)) return new HashMap<>();
+        try (var reader = new JsonReader(new InputStreamReader(
+                Files.newInputStream(path, READ),
+                StandardCharsets.UTF_8
+        ))) {
+            var object = JsonParser.parseReader(reader).getAsJsonObject();
+            var result = new HashMap<UUID, String>(object.size());
+            for (var entry : object.entrySet()) {
+                try {
+                    var uuid = UUID.fromString(entry.getKey());
+                    result.put(uuid, entry.getValue().getAsString());
+                } catch (IllegalArgumentException ignored) {
+                }
+            }
+            return result;
+        } catch (JsonParseException e) {
+            plugin.getComponentLogger().warn("Failed to parse {}", path, e);
+            return new HashMap<>();
+        }
+    }
+
+    @Override
+    public PlayerData readPlayer(UUID uuid, String name, WorldGroup group) throws IOException {
+        var data = new PaperPlayerData(uuid, ((PaperWorldGroup) group));
+        
+        return data;
+    }
+}