Consume stockpiled resources when purchasing constructions that require them

core/src/com/unciv/logic/city/CityConstructions.kt

@@ -690,6 +690,17 @@ class CityConstructions : IsPartOfGameInfoSerialization {
             ) {
                 city.civ.civConstructions.boughtItemsWithIncreasingPrice.add(construction.name, 1)
             }
+            
+            // Consume stockpiled resources - usually consumed when construction starts, but not when bought
+            if (getWorkDone(construction.name) == 0){ // we didn't pay the resources when we started building
+                val costUniques = construction.getMatchingUniques(UniqueType.CostsResources, conditionalState)
+
+                for (unique in costUniques) {
+                    val amount = unique.params[0].toInt()
+                    val resourceName = unique.params[1]
+                    city.civ.resourceStockpiles.add(resourceName, -amount)
+                }
+            }
         }
 
         if (queuePosition in 0 until constructionQueue.size)

tests/src/com/unciv/uniques/ResourceTests.kt

@@ -304,4 +304,18 @@ class ResourceTests {
         game.gameInfo.nextTurn()
         assert(civInfo.getCivResourcesByName()[resource.name] == 1) // 1 was consumed because production started
     }
+    
+    @Test
+    fun stockpiledResourcesConsumedWhenConstructionPurchased() {
+        // given
+        val resource = game.createResource(UniqueType.Stockpiled.text)
+        val building = game.createBuilding("Instantly provides [2] [${resource.name}]")
+        city.cityConstructions.addBuilding(building)
+        assert(civInfo.getCivResourcesByName()[resource.name] == 2)
+
+        val consumingBuilding = game.createBuilding("Costs [1] [${resource.name}]")
+        assert(civInfo.getCivResourcesByName()[resource.name] == 2) // no change yet
+        city.cityConstructions.purchaseConstruction(consumingBuilding.name, -1, false)
+        assert(civInfo.getCivResourcesByName()[resource.name] == 1) // 1 was consumed because production started
+    }
 }