Refactor list type checking in EventCheckerCommand

Introduced methods 'handleEmptyPartition' and 'isListTypeEnabled' to simplify validation of list types and corresponding partitions. This refactoring enhances the readability and maintainability by eliminating repetitive code for 'all', 'blacklist', and 'whitelist' list types. It also improves the handling and messaging around empty or disabled list types.

src/main/kotlin/de/thelooter/eventchecker/commands/EventCheckerCommand.kt

@@ -1,6 +1,5 @@
 package de.thelooter.eventchecker.commands
 
-import com.google.common.collect.ImmutableList
 import com.google.common.collect.Lists
 import de.thelooter.eventchecker.EventChecker
 import org.bukkit.command.Command
@@ -14,6 +13,11 @@ import java.util.function.Consumer
  * @since 1.2.0
  */
 class EventCheckerCommand : CommandExecutor {
+    companion object {
+        private var BLACKLIST_KEY = "blacklist"
+        private var WHITELIST_KEY = "whitelist"
+        private var ALL_KEY = "all"
+    }
     override fun onCommand(sender: CommandSender, command: Command, label: String, args: Array<out String>?): Boolean {
 
         args?.let {
@@ -28,13 +32,13 @@ class EventCheckerCommand : CommandExecutor {
             }
 
             if (it.size == 1 && it[0] == "list") {
-                sender.sendMessage("§cUsage: /eventchecker list <all> <page>")
+                sender.sendMessage("§cUsage: /eventchecker list <all|$BLACKLIST_KEY|$WHITELIST_KEY> <page>")
                 return true
             }
 
             if (it.size == 2 && it[0] == "list") {
                 val listType = it[1]
-                if (listType == "all" || listType == "blacklist" || listType == "whitelist") {
+                if (listType == ALL_KEY || listType == BLACKLIST_KEY || listType == WHITELIST_KEY) {
                     return sendListUsageCommand(sender, listType)
                 }
             }
@@ -44,24 +48,18 @@ class EventCheckerCommand : CommandExecutor {
 
                 val pageSize = 25
 
-                if (it[1] == "all") {
+                if (it[1] == ALL_KEY) {
                     val partition = Lists.partition<String>(EventChecker.eventNames, pageSize)
                     val page = it[2].toInt()
                     if (handleNonExistentPage(page, partition, sender)) return true
                     sender.sendMessage("§7Events (Page $page):")
                     sendEvents(partition, page, sender)
                 }
-                if (it[1] == "blacklist") {
-                    if (!EventChecker.instance.config.getBoolean("blacklist", false)) {
-                        sender.sendMessage("§cThe blacklist is disabled!")
-                        return true
-                    }
+                if (it[1] == BLACKLIST_KEY) {
+                    if (isListTypeEnabled(sender, BLACKLIST_KEY)) return true
                     val partition = handlePartition(pageSize, "excluded-events")
 
-                    if (partition.isEmpty()) {
-                        sender.sendMessage("§cThe blacklist is empty!")
-                        return true
-                    }
+                    if (handleEmptyPartition(partition, sender, BLACKLIST_KEY)) return true
 
                     val page = it[2].toInt()
 
@@ -73,17 +71,11 @@ class EventCheckerCommand : CommandExecutor {
                     return true
                 }
 
-                if (it[1] == "whitelist") {
-                    if (!EventChecker.instance.config.getBoolean("whitelist", false)) {
-                        sender.sendMessage("§cThe whitelist is disabled!")
-                        return true
-                    }
+                if (it[1] == WHITELIST_KEY) {
+                    if (isListTypeEnabled(sender, WHITELIST_KEY)) return true
                     val partition = handlePartition(pageSize, "included-events")
 
-                    if (partition.isEmpty()) {
-                        sender.sendMessage("§cThe whitelist is empty!")
-                        return true
-                    }
+                    if (handleEmptyPartition(partition, sender, WHITELIST_KEY)) return true
 
                     val page = it[2].toInt()
 
@@ -100,6 +92,26 @@ class EventCheckerCommand : CommandExecutor {
         return true
     }
 
+    private fun handleEmptyPartition(
+        partition: List<List<String>>,
+        sender: CommandSender,
+        listType: String
+    ): Boolean {
+        if (partition.isEmpty()) {
+            sender.sendMessage("§cThe $listType is empty!")
+            return true
+        }
+        return false
+    }
+
+    private fun isListTypeEnabled(sender: CommandSender,listType: String): Boolean {
+        if (!EventChecker.instance.config.getBoolean(listType, false)) {
+            sender.sendMessage("§cThe $listType is disabled!")
+            return true
+        }
+        return false
+    }
+
     private fun handleNonExistentPage(
         page: Int,
         partition: List<List<String>>,