Implemented ground mech boosting

core/src/mindustry/entities/comp/ItemsComp.java

@@ -0,0 +1,50 @@
+package mindustry.entities.comp;
+
+import arc.math.*;
+import mindustry.annotations.Annotations.*;
+import mindustry.gen.*;
+import mindustry.type.*;
+
+@Component
+abstract class ItemsComp implements Posc{
+    @ReadOnly ItemStack stack = new ItemStack();
+    transient float itemTime;
+
+    abstract int itemCapacity();
+
+    @Override
+    public void update(){
+        stack.amount = Mathf.clamp(stack.amount, 0, itemCapacity());
+        itemTime = Mathf.lerpDelta(itemTime, Mathf.num(hasItem()), 0.05f);
+    }
+
+    Item item(){
+        return stack.item;
+    }
+
+    void clearItem(){
+        stack.amount = 0;
+    }
+
+    boolean acceptsItem(Item item){
+        return !hasItem() || item == stack.item && stack.amount + 1 <= itemCapacity();
+    }
+
+    boolean hasItem(){
+        return stack.amount > 0;
+    }
+
+    void addItem(Item item){
+        addItem(item, 1);
+    }
+
+    void addItem(Item item, int amount){
+        stack.amount = stack.item == item ? stack.amount + amount : amount;
+        stack.item = item;
+        stack.amount = Mathf.clamp(stack.amount, 0, itemCapacity());
+    }
+
+    int maxAccepted(Item item){
+        return stack.item != item && stack.amount > 0 ? 0 : itemCapacity() - stack.amount;
+    }
+}