Detecting cast on me

[n00bsteam]

Hello guys! Can u help me with some code, it didnt work, i'm new in lua
Looks like table guids allways clear

local f = CreateFrame("Frame")
    local guids = {}
    f:RegisterEvent("NAME_PLATE_UNIT_ADDED")
    f:RegisterEvent("NAME_PLATE_UNIT_REMOVED")
    f:RegisterEvent("COMBAT_LOG_EVENT_UNFILTERED")
    f:SetScript("OnEvent", function(self, event, ...)
        if event == "NAME_PLATE_UNIT_ADDED" then
            local unit = ...
            guids[UnitGUID(unit)] = unit
          elseif event == "NAME_PLATE_UNIT_REMOVED" then
            local unit = ...
            guids[UnitGUID(unit)] = nil
        end
        local timestamp, subevent, _, sourceGUID, sourceName, sourceFlags, sourceRaidFlags, destGUID, destName, destFlags, destRaidFlags, spellId, spellName, spellSchool = CombatLogGetCurrentEventInfo()
        if subevent == "SPELL_CAST_START" then
            local unit = guids[sourceGUID]
            if unit and UnitIsUnit(unit.."target", "player") and bit.band(sourceFlags, COMBATLOG_OBJECT_REACTION_HOSTILE) > 0 then
                print( format("%s cast %s on me", sourceName, spellID) )
            end
        end
    end)