port over some more

lib/odinsea/game/inventory.ex

@@ -167,6 +167,17 @@ defmodule Odinsea.Game.Inventory do
     end
   end
 
+  @doc """
+  Gets the next available slot number.
+  Returns nil if the inventory is full (Elixir-style).
+  """
+  def get_next_free_slot(%__MODULE__{} = inv) do
+    case next_free_slot(inv) do
+      -1 -> nil
+      slot -> slot
+    end
+  end
+
   defp find_next_slot(items, limit, slot) when slot > limit, do: -1
 
   defp find_next_slot(items, limit, slot) do
@@ -205,6 +216,23 @@ defmodule Odinsea.Game.Inventory do
     end
   end
 
+  @doc """
+  Adds a plain map item to the inventory (used for drops).
+  Returns {:ok, new_inventory, assigned_item} or {:error, :inventory_full}.
+  """
+  def add_item(%__MODULE__{} = inv, %{} = item_map) when not is_struct(item_map) do
+    slot = next_free_slot(inv)
+
+    if slot < 0 do
+      {:error, :inventory_full}
+    else
+      # Convert map to item with assigned position
+      assigned_item = Map.put(item_map, :position, slot)
+      new_items = Map.put(inv.items, slot, assigned_item)
+      {:ok, %{inv | items: new_items}, assigned_item}
+    end
+  end
+
   @doc """
   Adds an item from the database (preserves position).
   """
@@ -391,4 +419,103 @@ defmodule Odinsea.Game.Inventory do
   end
 
   def equipped_items(%__MODULE__{}), do: []
+
+  @doc """
+  Gets the inventory type based on item ID.
+  """
+  def get_type_by_item_id(item_id) do
+    InventoryType.from_item_id(item_id)
+  end
+
+  @doc """
+  Checks if inventory has at least the specified quantity of an item.
+  """
+  def has_item_count(%__MODULE__{} = inv, item_id, quantity) do
+    count_by_id(inv, item_id) >= quantity
+  end
+
+  @doc """
+  Checks if there's at least one free slot in the inventory.
+  """
+  def has_free_slot(%__MODULE__{} = inv) do
+    next_free_slot(inv) >= 0
+  end
+
+  @doc """
+  Checks if inventory can hold the specified quantity of an item.
+  For stackable items, checks if there's room to stack or a free slot.
+  """
+  def can_hold_quantity(%__MODULE__{} = inv, item_id, quantity) do
+    # Find existing item to check stack space
+    existing = find_by_id(inv, item_id)
+    slot_max = InventoryType.slot_limit(inv.type)
+    
+    if existing do
+      # Check if we can stack
+      space_in_stack = slot_max - existing.quantity
+      remaining = quantity - space_in_stack
+      
+      if remaining <= 0 do
+        true
+      else
+        # Need additional slots
+        free_slots = count_free_slots(inv)
+        slots_needed = div(remaining, slot_max) + if rem(remaining, slot_max) > 0, do: 1, else: 0
+        free_slots >= slots_needed
+      end
+    else
+      # Need new slot(s)
+      free_slots = count_free_slots(inv)
+      slots_needed = div(quantity, slot_max) + if rem(quantity, slot_max) > 0, do: 1, else: 0
+      free_slots >= slots_needed
+    end
+  end
+
+  @doc """
+  Removes items by item ID.
+  Returns {:ok, new_inventory, removed_count} or {:error, reason}.
+  """
+  def remove_by_id(%__MODULE__{} = inv, item_id, quantity) do
+    items_with_id = 
+      inv.items
+      |> Map.values()
+      |> Enum.filter(fn item -> item.item_id == item_id end)
+      |> Enum.sort_by(fn item -> item.position end)
+    
+    total_available = Enum.map(items_with_id, fn i -> i.quantity end) |> Enum.sum()
+    
+    if total_available < quantity do
+      {:error, :insufficient_quantity}
+    else
+      {new_items, removed} = do_remove_by_id(inv.items, items_with_id, quantity, 0)
+      {:ok, %{inv | items: new_items}, removed}
+    end
+  end
+
+  defp do_remove_by_id(items, _items_to_remove, 0, removed), do: {items, removed}
+  defp do_remove_by_id(items, [], _quantity, removed), do: {items, removed}
+  defp do_remove_by_id(items, [item | rest], quantity, removed) do
+    if quantity <= 0 do
+      {items, removed}
+    else
+      to_remove = min(item.quantity, quantity)
+      new_quantity = item.quantity - to_remove
+      
+      new_items = if new_quantity <= 0 do
+        Map.delete(items, item.position)
+      else
+        Map.put(items, item.position, %{item | quantity: new_quantity})
+      end
+      
+      do_remove_by_id(new_items, rest, quantity - to_remove, removed + to_remove)
+    end
+  end
+
+  @doc """
+  Counts free slots in the inventory.
+  """
+  def count_free_slots(%__MODULE__{} = inv) do
+    used_slots = map_size(inv.items)
+    inv.slot_limit - used_slots
+  end
 end