Add swapping when attacking breaks tool

src/main/java/net/shadowfacts/autoswap/mixin/MixinServerPlayNetworkHandler.java

@@ -0,0 +1,49 @@
+package net.shadowfacts.autoswap.mixin;
+
+import net.minecraft.item.ItemStack;
+import net.minecraft.server.network.ServerPlayNetworkHandler;
+import net.minecraft.server.network.ServerPlayerEntity;
+import net.shadowfacts.autoswap.AutoSwap;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Shadow;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+/**
+ * @author shadowfacts
+ */
+@Mixin(ServerPlayNetworkHandler.class)
+public abstract class MixinServerPlayNetworkHandler {
+
+	@Shadow
+	private ServerPlayerEntity player;
+
+	private ItemStack heldStackBeforeAttack = ItemStack.EMPTY;
+
+	@Inject(
+			method = "onPlayerInteractEntity",
+			at = @At(
+					value = "INVOKE",
+					target = "Lnet/minecraft/server/network/ServerPlayerEntity;attack(Lnet/minecraft/entity/Entity;)V"
+			)
+	)
+	private void beforePlayerAttack(CallbackInfo cb) {
+		this.heldStackBeforeAttack = player.inventory.getMainHandStack().copy();
+	}
+
+	@Inject(
+			method = "onPlayerInteractEntity",
+			at = @At(
+					value = "INVOKE",
+					target = "Lnet/minecraft/server/network/ServerPlayerEntity;attack(Lnet/minecraft/entity/Entity;)V",
+					shift = At.Shift.AFTER
+			)
+	)
+	private void afterPlayerAttack(CallbackInfo cb) {
+		AutoSwap.INSTANCE.afterAttack(player.inventory, heldStackBeforeAttack);
+		heldStackBeforeAttack = ItemStack.EMPTY;
+	}
+
+
+}

src/main/java/net/shadowfacts/autoswap/mixin/MixinServerPlayerInteractionManager.java

@@ -1,6 +1,5 @@
 package net.shadowfacts.autoswap.mixin;
 
-import net.minecraft.entity.player.PlayerInventory;
 import net.minecraft.item.ItemStack;
 import net.minecraft.item.ItemUsageContext;
 import net.minecraft.server.network.ServerPlayerEntity;
@@ -24,12 +23,14 @@ public abstract class MixinServerPlayerInteractionManager {
 	@Shadow
 	private ServerPlayerEntity player;
 
+	@Shadow
+	abstract boolean isCreative();
+
 	private ItemStack heldStackAtBeginningOfBreak = ItemStack.EMPTY;
 
 	@Inject(method = "tryBreakBlock", at = @At("HEAD"))
 	private void beginTryBreakBlock(BlockPos pos, CallbackInfoReturnable<Void> cb) {
-		PlayerInventory playerInv = player.inventory;
-		heldStackAtBeginningOfBreak = playerInv.getInvStack(playerInv.selectedSlot).copy();
+		heldStackAtBeginningOfBreak = player.inventory.getMainHandStack().copy();
 	}
 
 	@Inject(method = "tryBreakBlock", at = @At("RETURN"))
@@ -45,7 +46,7 @@ public abstract class MixinServerPlayerInteractionManager {
 	private ActionResult useOnBlock(ItemStack self, ItemUsageContext context) {
 		ItemStack selfCopy = self.copy();
 		ActionResult result = self.useOnBlock(context);
-		if (result == ActionResult.SUCCESS) {
+		if (!isCreative() && result == ActionResult.SUCCESS) {
 			AutoSwap.INSTANCE.onUseOnItem(player, player.inventory, selfCopy);
 		}
 		return result;

src/main/kotlin/net/shadowfacts/autoswap/AutoSwap.kt

@@ -44,4 +44,16 @@ object AutoSwap: ModInitializer {
 		}
 	}
 
+	fun afterAttack(playerInv: PlayerInventory, heldStackBeforeAttack: ItemStack) {
+		val heldStack = playerInv.mainHandStack
+		if (!heldStackBeforeAttack.isEmpty && heldStack.isEmpty) {
+			val index = playerInv.main.indexOfFirst {
+				ItemStack.areItemsEqualIgnoreDamage(heldStackBeforeAttack, it)
+			}
+			if (index >= 0) {
+				playerInv.swapSlotWithHotbar(index)
+			}
+		}
+	}
+
 }

src/main/resources/autoswap.mixins.json

@@ -3,7 +3,8 @@
 	"package": "net.shadowfacts.autoswap.mixin",
 	"compatibilityLevel": "JAVA_8",
 	"mixins": [
-		"MixinServerPlayerInteractionManager"
+		"MixinServerPlayerInteractionManager",
+		"MixinServerPlayNetworkHandler"
 	],
 	"client": [
 	],