playerSwitchItem: add sub-command switch for player command

src/main/java/heyblack/flexiblepcb/mixin/carpet/command/playerSwitchItem/PlayerCommandMixin.java

@@ -0,0 +1,56 @@
+package heyblack.flexiblepcb.mixin.carpet.command.playerSwitchItem;
+
+import carpet.commands.PlayerCommand;
+import com.llamalad7.mixinextras.injector.ModifyReceiver;
+import com.mojang.brigadier.arguments.StringArgumentType;
+import com.mojang.brigadier.builder.RequiredArgumentBuilder;
+import com.mojang.brigadier.context.CommandContext;
+import com.mojang.brigadier.exceptions.CommandSyntaxException;
+import com.mojang.brigadier.suggestion.SuggestionProvider;
+import net.minecraft.entity.player.PlayerEntity;
+import net.minecraft.item.ItemStack;
+import net.minecraft.server.command.ServerCommandSource;
+import net.minecraft.server.network.ServerPlayerEntity;
+import net.minecraft.util.Hand;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Unique;
+import org.spongepowered.asm.mixin.injection.At;
+
+import static net.minecraft.server.command.CommandManager.literal;
+
+@Mixin(PlayerCommand.class)
+public class PlayerCommandMixin {
+    @ModifyReceiver(
+            method = "register",
+            at = @At(
+                    value = "INVOKE",
+                    target = "Lcom/mojang/brigadier/builder/RequiredArgumentBuilder;suggests(Lcom/mojang/brigadier/suggestion/SuggestionProvider;)Lcom/mojang/brigadier/builder/RequiredArgumentBuilder;",
+                    remap = false
+            ),
+            remap = false
+    )
+    private static RequiredArgumentBuilder<ServerCommandSource, ?> addCommand(RequiredArgumentBuilder<ServerCommandSource, ?> builder, SuggestionProvider<?> provider) {
+        return builder.then(literal("switch").executes(PlayerCommandMixin::switchItem));
+    }
+
+    @Unique
+    private static int switchItem(CommandContext<ServerCommandSource> context) throws CommandSyntaxException {
+        if (context.getSource().getEntity() instanceof ServerPlayerEntity) {
+            PlayerEntity fake = context.getSource().getMinecraftServer().getPlayerManager().getPlayer(StringArgumentType.getString(context, "player"));
+
+            if (fake != null) {
+                PlayerEntity player = context.getSource().getPlayer();
+
+                ItemStack fakeItem = fake.getMainHandStack();
+                ItemStack playerItem = player.getMainHandStack();
+
+                fake.setStackInHand(Hand.MAIN_HAND, playerItem);
+                player.setStackInHand(Hand.MAIN_HAND, fakeItem);
+            }
+
+            return 1;
+        }
+
+        return 0;
+    }
+}

src/main/resources/flexiblepcb.mixins.json

@@ -4,6 +4,7 @@
   "package": "heyblack.flexiblepcb.mixin",
   "compatibilityLevel": "JAVA_8",
   "mixins": [
+    "carpet.command.playerSwitchItem.PlayerCommandMixin",
     "command.commandChunkSaveState.ChunkSerializerMixin",
     "command.commandUpdateBlock.BlockStateArgumentAccessor",
     "rule.debugStickSendBlockUpdate.DebugStickItemMixin",