Detecting casts with a casting time?

[Mizaru]

Hi there, I am currently looking into developing an addon which replicates a swing timer, and as such for the Paladin and Shaman class, thier swing timer resets on spells with a casting time, but not instant casts. I've been looking into using:

CHAT_MSG_SPELL_SELF_DAMAGE

However this does not include healing spells, and while looking at wowwiki I stumbled upon:

CHAT_MSG_SPELL_SELF_BUFF

however the examples of this were not so clear, these would work if I i were to heal myself, but what if I were to cast a healing spell on an ally, it wouldnt be counted, and then my swing timer addon wouldnt reset the timer while the game has.

(sorry for the lack of clarity)

Does anyone know anything about detecting casts with a casting time, hostile/friendly type spells? (Ex: Healing Wave and Lightning Bolt or Flash of Light and Holy Wrath or Avenger's shield.)