Lua transmogrification

local NPCENTRY = 123123 -- Your NPC's entry

-- Warning! Executes quite some code. Delay in milliseconds. (applies transmogs)
local DELAY = 500 -- 500 (best visual update, very low population), 1000 (good visual update, very low population), 2000+ (slow visual update, medium  to high population)

-- DO NOT TOUCH ANYTHING BELOW!

-- Transmog table and functions.
local Transmogs, Hello, Select, AddTransmog, RemoveTransmog, GetValidSources, LoadTransmogs, ApplyTransmogs

-- Key0 is the key for inv_slots table, which contains the slotID. Key0 is also used for the inv_slot_names table
local inv_slots =       {0,         2,              4,          5,          6,      7,      8,          9,          14,     15,             16,         17}
local inv_slot_names =  {"Head",    "Shoulders",    "Chest",    "Waist",    "Legs", "Feet", "Wrists",   "Hands",    "Back", "Main hand",    "Off hand", "Ranged"}

local INV_BAG, INV_START, INV_END = 255, 1, #inv_slots
local VISIBLE_ITEM_ENTRY_0 = 283
local BAGS =
{
    {BAG = INV_BAG, START = 23, END = 38},
    {BAG = 19, START = 0, END = 35},
    {BAG = 20, START = 0, END = 35},
    {BAG = 21, START = 0, END = 35},
    {BAG = 22, START = 0, END = 35},
}

-- bags -1 inventory and backpack, 19-22 other bags
-- slots 0-18 equipment
-- slots 19-22 bags
-- slots 23-38 backpack
-- slots 0-35 other bags

local space = 20
local opt_space = 100
local opt_amount = 13 -- Warning! Do not use over 30

local Data = {}

function Hello(unit, event, player)
    Data[tostring(player:GetGUID())] = nil
    unit:GossipCreateMenu(100, player, 0)
    for Key0 = INV_START, INV_END do
        unit:GossipMenuAddItem(3, inv_slot_names[Key0], Key0+space, 0, "", 0)
    end
    unit:GossipMenuAddItem(4, "Remove all transmogrifications", 0, 0, "Remove transmogrifications from equipped items?", 0)
    unit:GossipSendMenu(player)
end

function Select(unit, event, player, id, intid, code)
    local pGUID = tostring(player:GetGUID())
    if(intid == 0) then -- remove all transmogs
        for Key0 = INV_START, INV_END do
            RemoveTransmog(inv_slots[Key0], player)
        end
        player:SendAreaTriggerMessage("Transmogrifications removed")
        Hello(unit, event, player)
    elseif(intid == 1) then
        Hello(unit, event, player)
    elseif(intid > INV_START and intid <= INV_END+1) then -- remove one transmog
        RemoveTransmog(inv_slots[intid-1], player)
        player:SendAreaTriggerMessage("Transmogrification removed from "..inv_slot_names[intid-1])
        Select(unit, event, player, id, intid+space-1, code)
    elseif(intid >= INV_START+space and intid <= INV_END+space) then
        local Key0 = intid-space
        local sources = GetValidSources(inv_slots[Key0], player)
        if(not sources) then
            player:SendAreaTriggerMessage("No item in that slot")
            Hello(unit, event, player)
        elseif(#sources < 2) then
            player:SendAreaTriggerMessage("No suitable items in bags")
            Hello(unit, event, player)
        else
            Data[pGUID] = {Key0, sources}
            unit:GossipCreateMenu(100, player, 0)
            for k = 1, #sources-1 do
                unit:GossipMenuAddItem(4, sources[k]:GetName(), k+INV_END+space, 0, "", 0)
            end
            unit:GossipMenuAddItem(4, "Remove transmogrification from "..inv_slot_names[Key0], Key0+1, 0, "Remove transmogrif ication from "..inv_slot_names[Key0].."?", 0)
            unit:GossipMenuAddItem(7, "Back..", 1, 0, "", 0)
            unit:GossipSendMenu(player)
        end
    elseif(intid > INV_END+space and intid <= INV_END+space+opt_amount) then
        local slot = inv_slots[Data[pGUID][1]]
        local target = player:GetInventoryItem(INV_BAG, slot)
        local origGUID = Data[pGUID][2][#Data[pGUID][2]] -- no cheating with swapping items on the fly
        if(target and tostring(target:GetGUID()) == origGUID) then
            local source = Data[pGUID][2][intid-INV_END-space]
            if(source and source:GetOwner():IsInWorld() and pGUID == tostring(source:GetOwner():GetGUID())) then
                AddTransmog(slot, player, source:GetEntryId())
                player:SendAreaTriggerMessage(inv_slot_names[Data[pGUID][1]].." transmogrified")
            else
                player:SendAreaTriggerMessage("Source item is not in bags")
            end
        else
            player:SendAreaTriggerMessage("Target item was unequipped")
        end
        Select(unit, event, player, id, Data[pGUID][1]+space, code)
    end
end

function AddTransmog(slot, player, fake)
    local item = player:GetInventoryItem(INV_BAG, slot)
    if (item) then
        local pGUID, iGUID = tostring(player:GetGUID()), tostring(item:GetGUID())
        player:SetUInt32Value(VISIBLE_ITEM_ENTRY_0+(slot * 2), fake)
        if (not Transmogs[pGUID]) then
            Transmogs[pGUID] = {}
        end
        if (not Transmogs[pGUID][slot]) then
            Transmogs[pGUID][slot] = {}
        end
        Transmogs[pGUID][slot][iGUID] = fake
        CharDBQuery('REPLACE INTO Transmog_items (player_GUID, item_GUID, slot, fake) VALUES ("'..pGUID..'", "'..iGUID..'", '..slot..', '..fake..')')
        return true
    end
    return false
end

function RemoveTransmog(slot, player)
    local pGUID = tostring(player:GetGUID())
    if (Transmogs[pGUID] and Transmogs[pGUID][slot]) then
        local item = player:GetInventoryItem(INV_BAG, slot)
        if (item) then
            local iGUID = tostring(item:GetGUID())
            if (Transmogs[pGUID][slot][iGUID]) then
                player:SetUInt32Value(VISIBLE_ITEM_ENTRY_0+(slot * 2), item:GetEntryId())
                Transmogs[pGUID][slot][iGUID] = nil
                CharDBQuery('DELETE FROM Transmog_items WHERE item_GUID = "'..iGUID..'"')
                return true
            end
        end
    end
    return false
end

function GetValidSources(inv_slot, player) -- returns nil or a table containing the items (can be empty)
    local item = player:GetInventoryItem(INV_BAG, inv_slot)
    if (not item) then return nil end
    local items = {}
    local entries = {}
    local hasitems = false
    for k, DATA in ipairs(BAGS) do
        if (DATA.BAG == INV_BAG or player:GetInventoryItem(INV_BAG, DATA.BAG)) then -- skip nonexistant bags
            for slot = DATA.START, DATA.END do
                local item = player:GetInventoryItem(DATA.BAG, slot)
                if(item) then
                    table.insert(entries, item:GetEntryId())
                    items[item:GetEntryId()] = item
                    if (not hasitems) then hasitems = true end
                end
            end
        end
    end
    if (hasitems) then
        local Q = WorldDBQuery("SELECT inventorytype FROM items WHERE entry = "..item:GetEntryId())
        if (Q) then
            local Q = WorldDBQuery("SELECT entry FROM items WHERE entry IN("..table.concat(entries, ',')..") and inventorytype = "..Q:GetColumn(0):GetULong().." LIMIT "..opt_amount)
            if (Q) then
                local suitable = {}
                for i = 1, Q:GetRowCount() do
                    table.insert(suitable, items[Q:GetColumn(0):GetULong()]) -- Could possibly add performance if we let this security off
                    Q:NextRow()
                end
                table.insert(suitable, tostring(item:GetGUID()))
                return suitable
            end
        end
    end
    return {}
end

function LoadTransmogs()
    local Time = os.time()
    print("Loading transmogrifications..")
    Transmogs = {}
    -- CharDBQuery("DELETE FROM transmog_items WHERE NOT EXISTS (SELECT 1 FROM playeritems WHERE item_GUID = guid) OR NOT EXISTS (SELECT 1 FROM characters WHERE player_GUID = guid)") -- cleanup before load
    local Q = CharDBQuery("SELECT player_GUID, item_GUID, slot, fake FROM Transmog_items")
    if (Q) then
        for i = 1, Q:GetRowCount() do
            local pGUID, iGUID, slot, fake = Q:GetColumn(0):GetString(), Q:GetColumn(1):GetString(), Q:GetColumn(2):GetULong(), Q:GetColumn(3):GetULong()
            if (not Transmogs[pGUID]) then
                Transmogs[pGUID] = {}
            end
            if (not Transmogs[pGUID][slot]) then
                Transmogs[pGUID][slot] = {}
            end
            Transmogs[pGUID][slot][iGUID] = fake
            Q:NextRow()
        end
    end
    print("Transmogrifications loaded in "..(os.time()-Time).." seconds")
end

function ApplyTransmogs() -- minimum looping and checking
    local players = GetPlayersInWorld()
    for k, player in ipairs(players) do -- loop players
        if (player and player:IsInWorld()) then -- player exists
            local pGUID = tostring(player:GetGUID())
            if (Transmogs[pGUID]) then -- has transmogs
                for slot, Data in pairs(Transmogs[pGUID]) do -- looop transmog slots
                    local item = player:GetInventoryItem(INV_BAG, slot)
                    if (item) then -- has item in slot
                        local iGUID = tostring(item:GetGUID())
                        if(Data[iGUID]) then -- check if item has transmog saved
                            player:SetUInt32Value(283+(slot * 2), Data[iGUID]) -- apply transmog
                        end
                    end
                end
            end
        end
    end
end

RegisterUnitGossipEvent(NPCENTRY, 1, Hello)
RegisterUnitGossipEvent(NPCENTRY, 2, Select)
LoadTransmogs()
CreateLuaEvent(ApplyTransmogs, DELAY, 0)