How do I make a NPC cast some spell on his Summoner

[chaplisimo]

So, I wanna fix some bugs on NPC summoned by the player.
I need that the player, use some object, that object summons a NPC (you know, that kind of 'Minion of player'/'Guardian of player')
This part works like it should.

Now, I want that summoned NPC (i don't know if 'summoned' its the word i should use) cast a spell on the player who summoned it.

I tried several things, which didn't work at all.

First, I wrote a script and attached to the creature_template in 'ScriptName'. Did not work. (I've done some scripting on creatures that worked, but never summoned creatures).

This is my script

#include "ScriptPCH.h"

enum Spells
{
	SPELL_HEALTH = 139
};

class summoned_creature : public CreatureScript
{
    public:
        summoned_creature() : CreatureScript("summoned_creature") { }

        struct summoned_creatureAI : public CreatureAI
        {
			summoned_creatureAI(Creature* creature) : CreatureAI(creature)
            {
            }
			
            void EnterCombat(Unit* /*who*/) override
            {
            }
			
            void KilledUnit(Unit * /*victim*/) override
            {
            }
			
            void JustDied(Unit * /*victim*/) override
            {
            }
            
            void JustSummoned(Creature * Summoner/*summoner*/)
            {
				DoCast(Summoner, SPELL_HEALTH);
				me->DisappearAndDie();
			}

            void UpdateAI(uint32 diff) override
            {
                if (!UpdateVictim())
                    return;

                if (me->HasUnitState(UNIT_STATE_CASTING))
                    return;
            }
        };

        CreatureAI* GetAI(Creature* creature) const override
        {
            return new summoned_creatureAI(creature);
        }
};

void AddSC_summoned_creature()
{
	new summoned_creature();
}

Second, I tryed modifying the smart_scripts table, (erasing the ScriptName field) and with this link help, make the NPC do its work.

It didn't.

Luckily, you'll guide me to resolve this.
I hope I'd not make any mistakes, since I'm not an English expert

Thanks