feat(sorting): add Expansion sort option for items (#890)

Add a new "Expansion" sort option to the Item Order dropdown, allowing
users to sort items chronologically by the expansion they were introduced
in (Classic -> TBC -> ... -> Midnight).

Changes:
- core/constants.lua:273: Add EXPANSION = 4 to ITEM_SORT_TYPE enum
- config/config.lua:220-228: Add "Expansion" option to Item Order dropdown
  for both Backpack and Bank, mapping to const.ITEM_SORT_TYPE.EXPANSION
- util/sort.lua:220-242: Implement SortItemsByExpansion function that:
  * Uses data.itemInfo.expacID for expansion ordering
  * Defaults to 0 (Classic) for items with missing expacID
  * Falls back to alphabetical sort when expansions are equal
  * Falls back to item count and GUID for stable sorting
- util/sort.lua:61-76: Update GetItemSortFunction to return
  SortItemsByExpansion when EXPANSION sort type is selected

The expansion ID is already populated by the WoW API via C_Item.GetItemInfo()
and stored in itemInfo.expacID. Lower expansion IDs represent older content
(0 = Classic, 11 = Midnight), providing chronological ordering.

All luacheck validation passes with no warnings or errors.

Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: Cidan

config/config.lua

@@ -221,11 +221,12 @@ function config:CreateConfig()
       ["Alphabetically"] = const.ITEM_SORT_TYPE.ALPHABETICALLY_THEN_QUALITY,
       ["Quality"] = const.ITEM_SORT_TYPE.QUALITY_THEN_ALPHABETICALLY,
       ["Item Level"] = const.ITEM_SORT_TYPE.ITEM_LEVEL,
+      ["Expansion"] = const.ITEM_SORT_TYPE.EXPANSION,
     }
     f:AddDropdown({
       title = 'Item Order',
       description = 'The default order of items within each section.',
-      items = {'Alphabetically', 'Quality', 'Item Level'},
+      items = {'Alphabetically', 'Quality', 'Item Level', 'Expansion'},
       getValue = function(_, value)
         return itemOrders[value] == db:GetItemSortType(bagType.kind, db:GetBagView(bagType.kind))
       end,

core/constants.lua

@@ -270,6 +270,7 @@ const.ITEM_SORT_TYPE = {
   ALPHABETICALLY_THEN_QUALITY = 1,
   QUALITY_THEN_ALPHABETICALLY = 2,
   ITEM_LEVEL = 3,
+  EXPANSION = 4,
 }
 
 ---@enum ExpansionType

util/sort.lua

@@ -69,6 +69,8 @@ function sort:GetItemSortFunction(kind, view)
     return self.SortItemsByQualityThenAlpha
   elseif sortType == const.ITEM_SORT_TYPE.ITEM_LEVEL then
     return self.SortItemsByItemLevel
+  elseif sortType == const.ITEM_SORT_TYPE.EXPANSION then
+    return self.SortItemsByExpansion
   end
   assert(false, "Unknown sort type: " .. sortType)
   return function() end
@@ -210,6 +212,32 @@ end
 ---@param a Item
 ---@param b Item
 ---@return boolean
+function sort.SortItemsByExpansion(a, b)
+  if a.isFreeSlot then return false end
+  if b.isFreeSlot then return true end
+  local aData, bData = a:GetItemData(), b:GetItemData()
+  if invalidData(aData, bData) then return false end
+
+  -- Get expansion IDs, defaulting to 0 (Classic) if missing
+  local aExpacID = aData.itemInfo.expacID or 0
+  local bExpacID = bData.itemInfo.expacID or 0
+
+  -- Sort by expansion (chronological order)
+  if aExpacID ~= bExpacID then
+    return aExpacID < bExpacID
+  -- If same expansion, fall back to alphabetical
+  elseif aData.itemInfo.itemName ~= bData.itemInfo.itemName then
+    return aData.itemInfo.itemName < bData.itemInfo.itemName
+  -- If same name, fall back to item count
+  elseif aData.itemInfo.currentItemCount ~= bData.itemInfo.currentItemCount then
+    return aData.itemInfo.currentItemCount > bData.itemInfo.currentItemCount
+  end
+  -- Finally, fall back to GUID for stable sort
+  return aData.itemInfo.itemGUID < bData.itemInfo.itemGUID
+end
+---@param a Item
+---@param b Item
+---@return boolean
 function sort.GetItemSortBySlot(a, b)
   local aData, bData = a:GetItemData(), b:GetItemData()
   if not aData then return false end