Add support for merging same effect durations

build.gradle

@@ -146,7 +146,7 @@ dependencies {
     // Specify the version of Minecraft to use. If this is any group other than 'net.minecraft', it is assumed
     // that the dep is a ForgeGradle 'patcher' dependency, and its patches will be applied.
     // The userdev artifact is a special name and will get all sorts of transformations applied to it.
-    minecraft 'net.minecraftforge:forge:1.18.2-40.0.2'
+    minecraft 'net.minecraftforge:forge:1.18.2-40.1.0'
 
     runtimeOnly fg.deobf("curse.maven:jei-238222:3670018")
 //    runtimeOnly fg.deobf("curse.maven:top-245211:3586969")
@@ -190,3 +190,7 @@ publishing {
         }
     }
 }
+
+tasks.withType(JavaCompile).configureEach {
+    options.encoding = 'UTF-8' // Use the UTF-8 charset for Java compilation
+}

gradle.properties

@@ -6,4 +6,4 @@ org.gradle.daemon=false
 mc_version=1.18.2
 group=net.permutated
 mod_id=pylons
-version=2.0.8
+version=2.0.9

src/main/java/net/permutated/pylons/item/PotionFilterCard.java

@@ -63,6 +63,35 @@ public InteractionResultHolder<ItemStack> use(Level level, Player player, Intera
                     return InteractionResultHolder.success(stack);
                 }
 
+                // handle transferring effects between cards
+                if (hand == InteractionHand.MAIN_HAND) { // this should only run for cards held in the main hand
+                    final ItemStack offhand = player.getItemInHand(InteractionHand.OFF_HAND);
+                    if (offhand.getItem() instanceof PotionFilterCard) { // offhand is holding a potion filter card
+                        MobEffect offhandEffect = PotionFilterCard.getEffect(offhand);
+                        int offhandAmplifier = PotionFilterCard.getAmplifier(offhand);
+                        int offhandDuration = PotionFilterCard.getDuration(offhand);
+                        if (offhandEffect != null) { // offhand card has an effect
+                            ItemStack copy;
+                            if (effect == null) {
+                                // main hand card is blank
+                                // move effect from off hand card to main hand card
+                                copy = withEffect(stack, offhandEffect, offhandAmplifier, offhandDuration);
+                                // clear potion data from offhand card
+                                player.setItemInHand(InteractionHand.OFF_HAND, clearEffect(offhand));
+                                return InteractionResultHolder.success(copy);
+                            } else if(Objects.equals(effect, offhandEffect) && Objects.equals(amplifier, offhandAmplifier)) {
+                                // main hand card has the same effect and amplifier
+                                // merge effect from off hand card with main hand card
+                                copy = addDuration(stack, offhandDuration);
+                                // clear potion data from offhand card
+                                player.setItemInHand(InteractionHand.OFF_HAND, clearEffect(offhand));
+                                return InteractionResultHolder.success(copy);
+                            }
+                        }
+                    }
+                }
+
+
                 Optional<MobEffectInstance> active;
                 if (effect == null) {
                     active = player.getActiveEffects().stream()
@@ -213,6 +242,17 @@ public static ItemStack addDuration(final ItemStack stack, int duration) {
         return copy;
     }
 
+    /**
+     * Remove Pylons NBT from a potion filter card.
+     * @param stack the ItemStack containing NBT
+     * @return a copy of the ItemStack without the pylons tag
+     */
+    public static ItemStack clearEffect(final ItemStack stack) {
+        ItemStack copy = stack.copy();
+        copy.removeTagKey(Pylons.MODID);
+        return copy;
+    }
+
     @Nullable
     public static MobEffect getEffect(ItemStack stack) {
         CompoundTag tag = stack.getTagElement(Pylons.MODID);