library NegateDamageLib
globals
    private constant group Group = CreateGroup()
    private constant timer Timer = CreateTimer()

    public keyword MaxLifeBonusAbility
    public keyword MaxLifeBonus
endglobals

native UnitAlive takes unit id returns boolean

function GetUnitMaxLife takes unit u returns real
    return GetUnitState(u, UNIT_STATE_MAX_LIFE) - GetUnitAbilityLevel(u, MaxLifeBonusAbility) * MaxLifeBonus
endfunction

private function ProcessUnits takes nothing returns nothing
    local unit u
    local real life2set

    loop
        set u = FirstOfGroup(Group)
        exitwhen u == null
        call GroupRemoveUnit(Group, u)

        if UnitAlive(u) then
            set life2set = GetWidgetLife(u)
            call UnitRemoveAbility(u, MaxLifeBonusAbility)
            call SetWidgetLife(u, life2set)
        else
            call UnitRemoveAbility(u, MaxLifeBonusAbility)
        endif
    endloop
endfunction

function NegateDamage takes unit u, real negated returns nothing
    local real life2set = GetWidgetLife(u) + negated
    local boolean add_ability = life2set > GetUnitState(u, UNIT_STATE_MAX_LIFE)

    if add_ability then
        call GroupAddUnit(Group, u)
        call UnitAddAbility(u, MaxLifeBonusAbility)
    endif

    call SetWidgetLife(u, life2set)

    if add_ability then
        call TimerStart(Timer, 0., false, function ProcessUnits)
    endif
endfunction

endlibrary