feat: Added Inventory::transferAllFrom(), getItemQuantity() returns 0…

… if no item, closes #1131

fxgl-gameplay/src/main/kotlin/com/almasb/fxgl/inventory/Inventory.kt

@@ -82,10 +82,14 @@ class Inventory<T>(
     }
 
     /**
-     * @return the total sum of all [item] stack quantities
+     * @return the total sum of all [item] stack quantities or 0 if [item] not present
      */
     fun getItemQuantity(item: T): Int
-        = itemQuantityProperty(item).value
+        = try {
+            itemQuantityProperty(item).value
+        } catch (e: IllegalArgumentException) {
+            0
+        }
 
     @Deprecated("Use add(ItemConfig)", ReplaceWith("add(com.almasb.fxgl.inventory.ItemConfig)"))
     fun add(item: T, name: String, description: String, view: Node, quantity: Int): Boolean {
@@ -202,6 +206,23 @@ class Inventory<T>(
         return true
     }
 
+    /**
+     * Transfer all items from [other] to this inventory.
+     *
+     * @return true if operation was (at least partially) successful, if returns false then no modifications were made to either inventory objects
+     */
+    fun transferAllFrom(other: Inventory<T>): Boolean {
+        var isPartiallySuccess = false
+
+        // toList() to create a copy since [transferFrom] modifies [other.items]
+        other.items.toList().forEach {
+            if (transferFrom(other, it.userItem, it.quantity))
+                isPartiallySuccess = true
+        }
+
+        return isPartiallySuccess
+    }
+
     /**
      * Transfer [item] with [quantity] amount from [other] to this inventory.
      *

fxgl-gameplay/src/test/kotlin/com/almasb/fxgl/inventory/InventoryTest.kt

@@ -286,6 +286,31 @@ class InventoryTest {
         assertTrue(!inventory.hasItem("Hello"))
     }
 
+    @Test
+    fun `Transfer all from inventory`() {
+        inventory = Inventory(5)
+
+        inventory.add("Hello", quantity = 5)
+        inventory.add("Hi", quantity = 3)
+
+        val other = Inventory<String>(5)
+
+        assertTrue(other.transferAllFrom(inventory))
+        assertThat(other.getItemQuantity("Hello"), `is`(5))
+        assertThat(other.getItemQuantity("Hi"), `is`(3))
+
+        val other2 = Inventory<String>(1)
+
+        // true because [other2] only has 1 space, so partially succeeds
+        assertTrue(other2.transferAllFrom(other))
+        assertThat(other2.getItemQuantity("Hello"), `is`(5))
+        assertThat(other2.getItemQuantity("Hi"), `is`(0))
+
+
+        // false because [other2] now has no space, so op fails
+        assertFalse(other2.transferAllFrom(other))
+    }
+
     @Test
     fun `Transfer from inventory does not work if no item in inventory`() {
         inventory = Inventory(5)