Added effect for Stalinium chestplate and leggings

src/main/java/net/krituximon/stalinium/item/ModItems.java

@@ -45,11 +45,11 @@ public class ModItems {
                     new Item.Properties().durability(ArmorItem.Type.HELMET.getDurability(19))));
 
     public static final DeferredItem<ArmorItem> STALINIUM_CHESTPLATE = ITEMS.register("stalinium_chestplate",
-            () -> new ArmorItem(ModArmorMaterials.STALINIUM_ARMOR_MATERIAL, ArmorItem.Type.CHESTPLATE,
+            () -> new StaliniumChestplateLeggingsItem(ModArmorMaterials.STALINIUM_ARMOR_MATERIAL, ArmorItem.Type.CHESTPLATE,
                     new Item.Properties().durability(ArmorItem.Type.CHESTPLATE.getDurability(19))));
 
     public static final DeferredItem<ArmorItem> STALINIUM_LEGGINGS = ITEMS.register("stalinium_leggings",
-            () -> new ArmorItem(ModArmorMaterials.STALINIUM_ARMOR_MATERIAL, ArmorItem.Type.LEGGINGS,
+            () -> new StaliniumChestplateLeggingsItem(ModArmorMaterials.STALINIUM_ARMOR_MATERIAL, ArmorItem.Type.LEGGINGS,
                     new Item.Properties().durability(ArmorItem.Type.LEGGINGS.getDurability(19))));
 
     public static final DeferredItem<ArmorItem> STALINIUM_BOOTS = ITEMS.register("stalinium_boots",

src/main/java/net/krituximon/stalinium/item/custom/StaliniumChestplateLeggingsItem.java

@@ -0,0 +1,107 @@
+package net.krituximon.stalinium.item.custom;
+
+import com.google.common.collect.ImmutableMap;
+import net.krituximon.stalinium.item.ModArmorMaterials;
+import net.minecraft.core.Holder;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.effect.MobEffectInstance;
+import net.minecraft.world.effect.MobEffects;
+import net.minecraft.world.entity.Entity;
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.item.ArmorItem;
+import net.minecraft.world.item.ArmorMaterial;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.phys.AABB;
+
+import java.util.List;
+import java.util.Map;
+
+public class StaliniumChestplateLeggingsItem extends ArmorItem {
+    private static final Map<Holder<ArmorMaterial>, List<MobEffectInstance>> MATERIAL_TO_EFFECT_MAP =
+            (new ImmutableMap.Builder<Holder<ArmorMaterial>, List<MobEffectInstance>>())
+                    .put(ModArmorMaterials.STALINIUM_ARMOR_MATERIAL,
+                            List.of(new MobEffectInstance(MobEffects.DAMAGE_RESISTANCE, 100, 0, false, false)))
+                    .build();
+
+    public StaliniumChestplateLeggingsItem(Holder<ArmorMaterial> material, Type type, Properties properties) {
+        super(material, type, properties);
+    }
+
+    @Override
+    public void inventoryTick(ItemStack stack, Level level, Entity entity, int slotId, boolean isSelected) {
+        if (entity instanceof Player player && !level.isClientSide() && hasChestAndLeggingsOn(player)) {
+            evaluateArmorEffects(player);
+        }
+    }
+
+    private void evaluateArmorEffects(Player player) {
+        for (Map.Entry<Holder<ArmorMaterial>, List<MobEffectInstance>> entry : MATERIAL_TO_EFFECT_MAP.entrySet()) {
+            Holder<ArmorMaterial> mapArmorMaterial = entry.getKey();
+            List<MobEffectInstance> mapEffect = entry.getValue();
+
+            if (hasPlayerCorrectArmorOn(mapArmorMaterial, player)) {
+                addEffectToPlayer(player, mapEffect);
+            }
+        }
+    }
+
+    private void addEffectToPlayer(Player player, List<MobEffectInstance> mapEffect) {
+        AABB box = player.getBoundingBox().inflate(5.0);
+        List<Player> allies = player.level().getEntitiesOfClass(
+                Player.class,
+                box,
+                p -> p instanceof ServerPlayer && player.isAlliedTo(p)
+        );
+
+        for (MobEffectInstance effect : mapEffect) {
+            player.addEffect(new MobEffectInstance(
+                    effect.getEffect(),
+                    effect.getDuration(),
+                    effect.getAmplifier(),
+                    effect.isAmbient(),
+                    effect.isVisible()));
+            for (Player ally : allies) {
+                ally.addEffect(new MobEffectInstance(
+                        effect.getEffect(),
+                        effect.getDuration(),
+                        effect.getAmplifier(),
+                        effect.isAmbient(),
+                        effect.isVisible()
+                ));
+            }
+        }
+    }
+
+    private boolean hasPlayerCorrectArmorOn(Holder<ArmorMaterial> mapArmorMaterial, Player player) {
+        ItemStack leggingsStack   = player.getInventory().getArmor(1);
+        ItemStack chestplateStack = player.getInventory().getArmor(2);
+
+        if (leggingsStack.isEmpty() || chestplateStack.isEmpty()) {
+            return false;
+        }
+
+        ArmorItem leggingsItem   = (ArmorItem) leggingsStack.getItem();
+        ArmorItem chestplateItem = (ArmorItem) chestplateStack.getItem();
+
+        return leggingsItem.getMaterial()   == mapArmorMaterial
+            && chestplateItem.getMaterial() == mapArmorMaterial;
+    }
+
+    private boolean hasChestAndLeggingsOn(Player player) {
+        ItemStack leggings = player.getInventory().getArmor(1);
+        ItemStack chestplate = player.getInventory().getArmor(2);
+
+        return !leggings.isEmpty() && !chestplate.isEmpty();
+    }
+
+    @Override
+    public boolean isDamageable(ItemStack stack) {
+        return false;
+    }
+
+    @Override
+    public boolean isDamaged(ItemStack stack) {
+        return false;
+    }
+}