feat: arguments

src/main/kotlin/cc/modlabs/kpaper/command/arguments/PlayerArgument.kt

@@ -0,0 +1,43 @@
+package cc.modlabs.kpaper.command.arguments
+
+import com.mojang.brigadier.StringReader
+import com.mojang.brigadier.arguments.ArgumentType
+import com.mojang.brigadier.arguments.StringArgumentType
+import com.mojang.brigadier.context.CommandContext
+import com.mojang.brigadier.suggestion.Suggestions
+import com.mojang.brigadier.suggestion.SuggestionsBuilder
+import io.papermc.paper.command.brigadier.argument.CustomArgumentType
+import org.bukkit.Bukkit
+import org.bukkit.entity.Player
+import java.util.concurrent.CompletableFuture
+
+class PlayerArgument : CustomArgumentType<Player, String> {
+
+    override fun parse(reader: StringReader): Player {
+        val stringNotParsed = reader.readString()
+        val player = Bukkit.getPlayer(stringNotParsed)
+        if (player != null) {
+            return player
+        }
+
+        throw IllegalArgumentException("Player $stringNotParsed not found")
+    }
+
+    override fun getNativeType(): ArgumentType<String> {
+        return StringArgumentType.word()
+    }
+
+    override fun <S : Any> listSuggestions(
+        context: CommandContext<S>,
+        builder: SuggestionsBuilder
+    ): CompletableFuture<Suggestions> {
+        val currentArg = context.input.lastOrNull() ?: return builder.buildFuture()
+
+        Bukkit.getOnlinePlayers().filter { player -> player.name.startsWith(currentArg) }.forEach {
+            builder.suggest(it.name)
+        }
+
+        return builder.buildFuture()
+    }
+
+}