diff --git a/LegionWA/AutoVendor/Event.lua b/LegionWA/AutoVendor/Event.lua
index 9e1a87b..9641a43 100644
--- a/LegionWA/AutoVendor/Event.lua
+++ b/LegionWA/AutoVendor/Event.lua
@@ -2,12 +2,12 @@
 function(allstates, e)
     if (GetMerchantNumItems() > 0) then
         aura_env.allstates = allstates
-    
+
         if CanMerchantRepair() == true then RepairAllItems() end
-    
+
         for container = 0, 4 do
             for slot = 1, C_Container.GetContainerNumSlots(container) do
-                aura_env.filterService:run(container, slot)
+                aura_env.FilterService.Run(container, slot)
             end
         end
         return true 
diff --git a/LegionWA/AutoVendor/Init.lua b/LegionWA/AutoVendor/Init.lua
index d39f339..eacb450 100644
--- a/LegionWA/AutoVendor/Init.lua
+++ b/LegionWA/AutoVendor/Init.lua
@@ -1,92 +1,209 @@
 local debug = false
 local iconDisplayDuration = 3
 
+---@param container number
+---@param slot number
+---@return string, string|nil
 local function getItemLink(container, slot)
-    return select(7, GetContainerItemInfo(container, slot))
+    if container == nil then return "", string.format("Container is nil") end
+    if slot == nil then return "", string.format("Slot is nil") end
+    local link = select(7, C_Container.GetContainerItemInfo(container, slot))
+    if link == nil then return "", string.format("C_Container.GetContainerItemInfo returned nil for link (arg 7)") end
+    return link
 end
+---@param container number
+---@param slot number
+---@return string, string|nil
 local function getItemQuantity(container, slot)
-    return select(2, GetContainerItemInfo(container, slot))
+    if container == nil then return "", string.format("Container is nil") end
+    if slot == nil then return "", string.format("Slot is nil") end
+    local quantity = select(2, C_Container.GetContainerItemInfo(container, slot))
+    if quantity == nil then
+        return "",
+            string.format("C_Container.GetContainerItemInfo returned nil for quantity (arg 2)")
+    end
+    return quantity
 end
+---@param container number
+---@param slot number
+---@return string, string|nil
 local function getItemName(container, slot)
-    return select(1, GetItemInfo(getItemLink(container, slot)))
+    if container == nil then return "", string.format("Container is nil") end
+    if slot == nil then return "", string.format("Slot is nil") end
+    local name = select(1, GetItemInfo(getItemLink(container, slot)))
+    if name == nil then return "", string.format("GetItemInfo returned nil for name (arg 1)") end
+    return name
 end
+---@param container number
+---@param slot number
+---@return string, string|nil
 local function getItemType(container, slot)
-    return select(6, GetItemInfo(getItemLink(container, slot)))
+    if container == nil then return "", string.format("Container is nil") end
+    if slot == nil then return "", string.format("Slot is nil") end
+    local type = select(6, GetItemInfo(getItemLink(container, slot)))
+    if type == nil then return "", string.format("GetItemInfo returned nil for type (arg 6)") end
+    return type
 end
+---@param container number
+---@param slot number
+---@return string, string|nil
 local function getItemSubtype(container, slot)
-    return select(7, GetItemInfo(getItemLink(container, slot)))
+    if container == nil then return "", string.format("Container is nil") end
+    if slot == nil then return "", string.format("Slot is nil") end
+    local subtype = select(7, GetItemInfo(getItemLink(container, slot)))
+    if subtype == nil then return "", string.format("GetItemInfo returned nil for subtype (arg 7)") end
+    return subtype
 end
+---@param container number
+---@param slot number
+---@return string, string|nil
 local function getItemLevel(container, slot)
-    return select(4, GetItemInfo(getItemLink(container, slot)))
+    if container == nil then return "", string.format("Container is nil") end
+    if slot == nil then return "", string.format("Slot is nil") end
+    local level = select(4, GetItemInfo(getItemLink(container, slot)))
+    if level == nil then return "", string.format("GetItemInfo returned nil for level (arg 4)") end
+    return level
 end
+---@param container number
+---@param slot number
+---@return string, string|nil
 local function getItemValue(container, slot)
-    return select(11, GetItemInfo(getItemLink(container, slot)))
+    if container == nil then return "", string.format("Container is nil") end
+    if slot == nil then return "", string.format("Slot is nil") end
+    local value = select(11, GetItemInfo(getItemLink(container, slot)))
+    if value == nil then return "", string.format("GetItemInfo returned nil for value (arg 11)") end
+    return value
 end
+---@param container number
+---@param slot number
+---@return string, string|nil
 local function getItemQuality(container, slot)
-    return select(3, GetItemInfo(getItemLink(container, slot)))
+    if container == nil then return "", string.format("Container is nil") end
+    if slot == nil then return "", string.format("Slot is nil") end
+    local quality = select(3, GetItemInfo(getItemLink(container, slot)))
+    if quality == nil then return "", string.format("GetItemInfo returned nil for quality (arg 3)") end
+    return quality
 end
+---@param container number
+---@param slot number
+---@return string, string|nil
 local function getItemEquipLocation(container, slot)
-    return select(9, GetItemInfo(getItemLink(container, slot)))
+    if container == nil then return "", string.format("Container is nil") end
+    if slot == nil then return "", string.format("Slot is nil") end
+    local equipLoc = select(9, GetItemInfo(getItemLink(container, slot)))
+    if equipLoc == nil then return "", string.format("GetItemInfo returned nil for equipLoc (arg 9)") end
+    return equipLoc
 end
+---@param container number
+---@param slot number
+---@return string, string|nil
 local function getItemIcon(container, slot)
-    return select(10, GetItemInfo(getItemLink(container, slot)))
+    if container == nil then return "", string.format("Container is nil") end
+    if slot == nil then return "", string.format("Slot is nil") end
+    local icon = select(10, GetItemInfo(getItemLink(container, slot)))
+    if icon == nil then return "", string.format("GetItemInfo returned nil for icon (arg 10)") end
+    return icon
 end
+---@param container number
+---@param slot number
+---@return string, string|nil
 local function getBindType(container, slot)
-    return select(14, GetItemInfo(getItemLink(container, slot)))
+    if container == nil then return "", string.format("Container is nil") end
+    if slot == nil then return "", string.format("Slot is nil") end
+    local bindType = select(14, GetItemInfo(getItemLink(container, slot)))
+    if bindType == nil then return "", string.format("GetItemInfo returned nil for bindType (arg 14)") end
+    return bindType
 end
 
+---@class Filter
+---@field requires table<string, fun(container:number, slot: number): string|number|boolean> | nil
+---@field filter fun(container: number, slot: number, provided: table<string, string|number|boolean>): boolean
+Filter = {
+    ---@param requires table<string, fun(container:number, slot: number): string|number|boolean> | nil
+    ---@param filter fun(container: number, slot: number, provided: table<string, string|number|boolean>): boolean
+    ---@return Filter
+    new = function(requires, filter)
+        local self = setmetatable({}, {
+            __index = Filter
+        })
+        self.requires = requires
+        self.filter = filter
+        return self
+    end,
 
-
-local grayFilter = {
-    enabled = true,
-    filter = function(self, container, slot)
-        if (self.enabled) then
-            aura_env.debugLog("Gray filter; container = " .. container .. ", slot = " .. slot)
-            local itemQuality = getItemQuality(container, slot)
-            if (itemQuality and itemQuality == 0) then
-                aura_env.debugLog("Gray filter pass")
-                return true
+    ---@param self Filter
+    ---@param container number
+    ---@param slot number
+    ---@return boolean, string|nil
+    Run = function(self, container, slot)
+        ---@type table<string, string|number|boolean>
+        local provided = {}
+        if self.requires then
+            for k, v in pairs(self.requires) do
+                local res, err = v(container, slot)
+                if err then
+                    if debug then print(err) end
+                    return false, err
+                end
+                provided[k] = res
             end
         end
-    end
-}
-local gearFilter = {
-    enabled = true,
-    ilvlThreshold = 850,
-    sellBoe = false,
-    filter = function(self, container, slot)
-        if (self.enabled) then
-            aura_env.debugLog("Gear filter; container = " .. container .. ", slot = " .. slot)
-            local itemLevel = getItemLevel(container, slot)
-            local itemBindType = getBindType(container, slot)
-            local itemType = getItemType(container, slot)
-            local itemEquipLoc = getItemEquipLocation(container, slot)
-            if (itemType and itemEquipLoc and
-            (itemType == "Armor"
-            or itemType == "Weapon"
-            or itemEquipLoc == "INVTYPE_FINGER"
-            or itemEquipLoc == "INVTYPE_TRINKET"
-            or itemEquipLoc == "INVTYPE_CLOAK"
-            or itemEquipLoc == "INVTYPE_NECK")
-            and itemLevel and itemBindType and itemLevel < self.ilvlThreshold and (itemBindType == 1 or self.sellBoe)) then
-                aura_env.debugLog("Gear filter pass")
-                return true
-            end
+        local res, err = self.filter(container, slot, provided)
+        if err then
+            if debug then print(err) end
         end
+        return res, nil
     end
 }
 
+local grayFilter = Filter.new({
+        ["quality"] = getItemQuality
+    },
+    function(container, slot, provided)
+        if provided.quality == 0 then
+            return true
+        end
+        return false
+    end)
+local gearFilter = Filter.new({
+        ["ilvl"] = getItemLevel,
+        ["bindType"] = getBindType,
+        ["type"] = getItemType,
+        ["equipLoc"] = getItemEquipLocation
+    },
+    function(container, slot, provided)
+        local ilvlThreshold = 850
+        local sellBoe = false
+
+        if provided.type == "Armor"
+            or provided.type == "Weapon"
+            or provided.equipLoc == "INVTYPE_FINGER"
+            or provided.equipLoc == "INVTYPE_TRINKET"
+            or provided.equipLoc == "INVTYPE_CLOAK"
+            or provided.equipLoc == "INVTYPE_NECK" then
+            if provided.ilvl < ilvlThreshold and (provided.bindType == 1 or sellBoe) then
+                return true
+            end
+        end
+        return false
+    end)
+
+---@param container number
+---@param slot number
+---@return nil, string|nil
 local function doSell(container, slot)
-    local itemIcon = getItemIcon(container, slot)
-    local itemName = getItemName(container, slot)
-    local itemQuantity = getItemQuantity(container, slot)
-    local itemQuality = getItemQuality(container, slot)
+    local itemIcon, err = getItemIcon(container, slot)
+    if err then return nil, string.format("Error getting item icon: %s", err) end
+    local itemName, err = getItemName(container, slot)
+    if err then return nil, string.format("Error getting item name: %s", err) end
+    local itemQuantity, err = getItemQuantity(container, slot)
+    if err then return nil, string.format("Error getting item quantity: %s", err) end
+    local itemQuality, err = getItemQuality(container, slot)
+    if err then return nil, string.format("Error getting item quality: %s", err) end
 
-    aura_env.debugLog("Drawing icon for " .. itemName .. " with quality " .. itemQuality)
-    local nameWithColor = aura_env.qualityColors[itemQuality + 1] .. "[" .. itemName .. "]\124r"
-    local nameWithQuantity = nameWithColor .. " x" .. itemQuantity
+    local nameWithColor = string.format("%s[%s]\124r", aura_env.qualityColors[itemQuality + 1], itemName)
+    local nameWithQuantity = string.format("%s x%s", nameWithColor, itemQuantity)
 
-    aura_env.debugLog("Assigning name" .. nameWithQuantity)
     aura_env.allstates[#aura_env.allstates + 1] = {
         show = true,
         changed = true,
@@ -103,38 +220,37 @@ local function doSell(container, slot)
         autoHide = true,
     }
 
-    UseContainerItem(container, slot)
+    C_Container.UseContainerItem(container, slot)
+    return nil, nil
 end
 
-
-aura_env.filterService = {
-    filters = {
-        grayFilter,
-        gearFilter,
-    },
-    slotsToLoot = {},
-    run = function(self, container, slot)
-        aura_env.debugLog("Filtering item in container = " .. container .. ", slot = " .. slot .. "...")
-        if (not getItemLink(container, slot)) then
-            aura_env.debugLog("Slot empty")
-            return
-        end
-        for k, filter in pairs(self.filters) do
-            if (filter:filter(container, slot)) then
-                doSell(container, slot)
-                return
-            end
-        end
-    end
+---@type table<Filter>
+local filters = {
+    grayFilter,
+    gearFilter
 }
 
-aura_env.debugLog = function(obj)
-    if (debug) then
-        print(GetTime())
-        DevTools_Dump(obj)
-        print()
-    end
-end
+---@class FilterService
+aura_env.FilterService = {
+    ---@param container number
+    ---@param slot number
+    ---@return nil, nil
+    Run = function(container, slot)
+        local itemLink, err = getItemLink(container, slot)
+        if err then return nil, string.format("Err: slot empty (%d-%d) - %s", container, slot, err) end
+        for k, filter in pairs(filters) do
+            local res, err = filter:Run(container, slot)
+            if err then
+                if debug then print(err) end
+            else
+                if res then
+                    doSell(container, slot)
+                    return
+                end
+            end
+        end
+    end,
+}
 
 aura_env.qualityColors = {
     "\124cff9d9d9d", -- Poor
@@ -145,4 +261,4 @@ aura_env.qualityColors = {
     "\124cffff8000", -- Legendary
     "\124cffe6cc80", -- Artifact
     "\124cff00ccff", -- Heirloom
-}
\ No newline at end of file
+}