[GH-467] Unequip previously equipped item on equip

apps/champions/lib/champions/items.ex

@@ -19,10 +19,10 @@ defmodule Champions.Items do
   def get_items(user_id), do: Items.get_items(user_id)
 
   @doc """
-  Equip an item to a unit.
+  Equip an item to a unit. Unequips the previously eqyupped item of the same type if there is any.
   """
   def equip_item(user_id, item_id, unit_id) do
-    Items.equip_item(user_id, item_id, unit_id)
+    Items.equip_item_and_unequip_previous(user_id, item_id, unit_id)
     get_item(item_id)
   end
 
@@ -76,6 +76,9 @@ defmodule Champions.Items do
 
       {:consumed_items_valid, {false, _}} ->
         {:error, :consumed_items_invalid}
+
+      {:can_afford, false} ->
+        {:error, :cant_afford}
     end
   end
 

apps/game_backend/lib/game_backend/items.ex

@@ -44,6 +44,33 @@ defmodule GameBackend.Items do
     end
   end
 
+  @doc """
+  Equips an item to a unit and unequips the previous item of the same type
+
+  Returns an `{:ok, %Item{}}` tuple with the item's updated state.
+  """
+  def equip_item_and_unequip_previous(user_id, item_id, unit_id) do
+    with {:ok, item} <- get_item(item_id),
+         true <- item.user_id == user_id,
+         true <- Units.unit_belongs_to_user(unit_id, user_id) do
+      Multi.new()
+      |> Multi.run(:unequip_previous, fn _, _ ->
+        case get_unit_item_by_type(unit_id, item.template.type) do
+          {:ok, previous_item} ->
+            unequip_item(user_id, previous_item.id)
+
+          {:error, :not_found} ->
+            {:ok, nil}
+        end
+      end)
+      |> Multi.run(:equip_new, fn _, _ -> equip_item(user_id, item.id, unit_id) end)
+      |> Repo.transaction()
+    else
+      {:error, :not_found} -> {:error, :item_not_found}
+      false -> {:error, :item_not_owned}
+    end
+  end
+
   @doc """
   Unequips an item from its unit. Returns an `{:ok, %Item{}}` tuple with the item's updated state.
 
@@ -176,6 +203,29 @@ defmodule GameBackend.Items do
     end
   end
 
+  @doc """
+  Get a unit's item by type. Assumes only one item of each type per unit.
+
+  ## Examples
+
+      iex> get_unit_item_by_type(unit_id, :boots)
+      {:ok, %Item{}}
+
+      iex> get_unit_item_by_type(unit_id, :socks)
+      {:error, :not_found}
+  """
+  def get_unit_item_by_type(unit_id, type) do
+    case Repo.one(
+           from(item in Item,
+             join: t in assoc(item, :template),
+             where: item.unit_id == ^unit_id and t.type == ^type
+           )
+         ) do
+      nil -> {:error, :not_found}
+      item -> {:ok, item}
+    end
+  end
+
   @doc """
   Get all items for a user.
 

apps/gateway/test/champions_test.exs

@@ -489,7 +489,7 @@ defmodule Gateway.Test.Champions do
       defense_multiplier = 1.2
       health_adder = 100
 
-      {:ok, epic_item} =
+      {:ok, item_template} =
         Items.insert_item_template(%{
           game_id: Utils.get_game_id(:champions_of_mirra),
           name: "Epic Upgrader of All Stats",
@@ -515,7 +515,7 @@ defmodule Gateway.Test.Champions do
           ]
         })
 
-      {:ok, item} = Items.insert_item(%{user_id: user.id, template_id: epic_item.id, level: 1})
+      {:ok, item} = Items.insert_item(%{user_id: user.id, template_id: item_template.id, level: 1})
 
       # EquipItem
       attack_before_equip = Units.get_attack(unit)
@@ -524,10 +524,7 @@ defmodule Gateway.Test.Champions do
 
       :ok = SocketTester.equip_item(socket_tester, user.id, item.id, unit.id)
       fetch_last_message(socket_tester)
-
-      assert_receive %WebSocketResponse{
-        response_type: {:item, %Item{} = equipped_item}
-      }
+      assert_receive %WebSocketResponse{response_type: {:item, %Item{} = equipped_item}}
 
       # The item is now equipped to the unit
       assert equipped_item.user_id == user.id
@@ -559,10 +556,7 @@ defmodule Gateway.Test.Champions do
       another_unit = user.units |> Enum.at(1)
       :ok = SocketTester.equip_item(socket_tester, user.id, item.id, another_unit.id)
       fetch_last_message(socket_tester)
-
-      assert_receive %WebSocketResponse{
-        response_type: {:item, %Item{} = equipped_item}
-      }
+      assert_receive %WebSocketResponse{response_type: {:item, %Item{} = equipped_item}}
 
       # The item is now equipped to the second unit
       assert equipped_item.user_id == user.id
@@ -572,10 +566,7 @@ defmodule Gateway.Test.Champions do
       # UnequipItem
       :ok = SocketTester.unequip_item(socket_tester, user.id, item.id)
       fetch_last_message(socket_tester)
-
-      assert_receive %WebSocketResponse{
-        response_type: {:item, %Item{} = unequipped_item}
-      }
+      assert_receive %WebSocketResponse{response_type: {:item, %Item{} = unequipped_item}}
 
       # The item is now unequipped
       assert unequipped_item.user_id == user.id
@@ -593,6 +584,30 @@ defmodule Gateway.Test.Champions do
       assert Units.get_attack(unit_without_item) == attack_before_equip
       assert Units.get_defense(unit_without_item) == defense_before_equip
       assert Units.get_health(unit_without_item) == health_before_equip
+
+      # Equipping an item of the same type unequips the previous one.
+
+      {:ok, same_type_item} = Items.insert_item(%{user_id: user.id, template_id: item_template.id, level: 1})
+
+      :ok = SocketTester.equip_item(socket_tester, user.id, item.id, unit.id)
+      fetch_last_message(socket_tester)
+      assert_receive %WebSocketResponse{response_type: {:item, %Item{} = equipped_item}}
+
+      {:ok, equipped_item} = Items.get_item(equipped_item.id)
+      assert equipped_item.id == item.id
+      assert equipped_item.unit_id == unit.id
+
+      :ok = SocketTester.equip_item(socket_tester, user.id, same_type_item.id, unit.id)
+      fetch_last_message(socket_tester)
+      assert_receive %WebSocketResponse{response_type: {:item, %Item{} = equipped_item}}
+
+      {:ok, equipped_item} = Items.get_item(equipped_item.id)
+      assert equipped_item.id == same_type_item.id
+      assert equipped_item.unit_id == unit.id
+
+      # Unequipped item has no unit_id
+      {:ok, equipped_item} = Items.get_item(item.id)
+      assert is_nil(equipped_item.unit_id)
     end
 
     test "tier up item", %{socket_tester: socket_tester} do