Add ClassicAPI compatibility layer

Core/ClassicAPI.lua

@@ -0,0 +1,90 @@
+-- Guda ClassicAPI integration
+-- Centralizes ClassicAPI fast paths while keeping safe Vanilla fallbacks
+-- during the migration. This module is intentionally small so the rest of
+-- Guda does not need to know which backend supplied container data.
+
+local addon = Guda
+
+local ClassicAPI = {}
+addon.Modules.ClassicAPI = ClassicAPI
+
+local hasContainerInfo = type(C_Container) == "table"
+    and type(C_Container.GetContainerItemInfo) == "function"
+local hasContainerItemID = type(C_Container) == "table"
+    and type(C_Container.GetContainerItemID) == "function"
+
+local function ExtractItemID(link)
+    if not link then return nil end
+    local _, _, itemID = string.find(link, "item:(%d+)")
+    return itemID and tonumber(itemID) or nil
+end
+
+function ClassicAPI:IsAvailable()
+    return hasContainerInfo and hasContainerItemID
+end
+
+function ClassicAPI:HasContainerInfo()
+    return hasContainerInfo
+end
+
+function ClassicAPI:HasContainerItemID()
+    return hasContainerItemID
+end
+
+-- Returns a modern-style ContainerItemInfo table.
+-- ClassicAPI supplies this directly. The fallback normalizes Vanilla's flat
+-- GetContainerItemInfo tuple into the same shape so callers stay branch-free.
+function ClassicAPI:GetContainerItemInfo(bagID, slotID)
+    if bagID == nil or slotID == nil or slotID < 1 then return nil end
+
+    if hasContainerInfo then
+        return C_Container.GetContainerItemInfo(bagID, slotID)
+    end
+
+    local texture, count, locked, quality, readable, lootable =
+        GetContainerItemInfo(bagID, slotID)
+    local link = GetContainerItemLink(bagID, slotID)
+
+    if not texture and not link then return nil end
+
+    return {
+        iconFileID = texture,
+        stackCount = count or 1,
+        isLocked = locked and true or false,
+        quality = quality,
+        isReadable = readable and true or false,
+        hasLoot = lootable and true or false,
+        hyperlink = link,
+        itemID = ExtractItemID(link),
+    }
+end
+
+function ClassicAPI:GetContainerItemID(bagID, slotID, info)
+    if bagID == nil or slotID == nil or slotID < 1 then return nil end
+
+    if info and info.itemID then
+        return tonumber(info.itemID)
+    end
+
+    if hasContainerItemID then
+        local itemID = C_Container.GetContainerItemID(bagID, slotID)
+        return itemID and tonumber(itemID) or nil
+    end
+
+    return ExtractItemID(GetContainerItemLink(bagID, slotID))
+end
+
+function ClassicAPI:GetContainerItemLink(bagID, slotID, info)
+    if info and info.hyperlink then
+        return info.hyperlink
+    end
+    return GetContainerItemLink(bagID, slotID)
+end
+
+function ClassicAPI:GetStatus()
+    return {
+        available = self:IsAvailable(),
+        containerInfo = hasContainerInfo,
+        containerItemID = hasContainerItemID,
+    }
+end