[semlar]

This is probably more complicated than it needs to be.

local InventorySlots = {
    ['INVTYPE_HEAD'] = 1,
    ['INVTYPE_NECK'] = 2,
    ['INVTYPE_SHOULDER'] = 3,
    ['INVTYPE_BODY'] = 4,
    ['INVTYPE_CHEST'] = 5,
    ['INVTYPE_ROBE'] = 5,
    ['INVTYPE_WAIST'] = 6,
    ['INVTYPE_LEGS'] = 7,
    ['INVTYPE_FEET'] = 8,
    ['INVTYPE_WRIST'] = 9,
    ['INVTYPE_HAND'] = 10,
    ['INVTYPE_CLOAK'] = 15,
    ['INVTYPE_WEAPON'] = 16,
    ['INVTYPE_SHIELD'] = 17,
    ['INVTYPE_2HWEAPON'] = 16,
    ['INVTYPE_WEAPONMAINHAND'] = 16,
    ['INVTYPE_RANGED'] = 16,
    ['INVTYPE_RANGEDRIGHT'] = 16,
    ['INVTYPE_WEAPONOFFHAND'] = 17,
    ['INVTYPE_HOLDABLE'] = 17,
    -- ['INVTYPE_TABARD'] = 19,
}
 
local model = CreateFrame('DressUpModel')
function GetItemAppearance(itemLink)
    local itemID, _, _, slotName = GetItemInfoInstant(itemLink)
    if itemLink == itemID then
        itemLink = 'item:' .. itemID
    end
    local slot = InventorySlots[slotName]
    if not slot or not IsDressableItem(itemLink) then return end
    model:SetUnit('player')
    model:Undress()
    model:TryOn(itemLink, slot)
    local sourceID = model:GetSlotTransmogSources(slot)
    if sourceID then
        local categoryID, appearanceID, canEnchant, texture, isCollected, itemLink = C_TransmogCollection.GetAppearanceSourceInfo(sourceID)
        return appearanceID, isCollected, sourceID
    end
end
 
function PlayerHasAppearance(appearanceID)
    local sources = C_TransmogCollection.GetAppearanceSources(appearanceID)
    if sources then
        for i, source in pairs(sources) do
            if source.isCollected then
                return true
            end
        end
    end
end
 
function PlayerCanCollectAppearance(appearanceID)
    local sources = C_TransmogCollection.GetAppearanceSources(appearanceID)
    if sources then
        for i, source in pairs(sources) do
            if C_TransmogCollection.PlayerCanCollectSource(source.sourceID) then
                return true
            end
        end
    end
end
 
function CanTransmogItem(itemLink)
    local itemID = GetItemInfoInstant(itemLink)
    if itemID then
        local canBeChanged, noChangeReason, canBeSource, noSourceReason = C_Transmog.GetItemInfo(itemID)
        return canBeSource, noSourceReason
    end
end