harry potter - Is there a canon confirmation of why Dumbledore never gave Snape DADA teaching job?

We know from the books that Severus Snape always wanted DADA teaching position.

Is there any canon (books/interviews/pottermore) confirmation of why exactly Dumbledore didn't want that to happen in the first 5 years (or, for that matter, even before Harry went to Hogwarts, as the DADA teachers changed every year evers since before the First Wizarding war, when Voldemort came to seek the job)?

I can think of 4 possible reasons, but am interested in actual canon confirmation:

1. To help maintain illusion that Snape wasn't fully trusted, for Voldemort's sake




2. To help maintain illusion that Snape wasn't fully trusted to those who didn't trust an ex-DeathEater Snape, and would have made a lot of noise and complaints had that happened (I'm sure Barty Crouch Sr. would).




3. To avoid any risks to Snape as a chief Voldemort mole (as in, the 1-year-curse of the job could have caused Snape some damage, like it killed off Quirrell or permanently damaged Lockhart).




4. Because Dumbledore - just like he didn't trust himself with power of being a Minister of Magic - didn't trust Severus Snape who used to be "up to his ears in Dark Arts" to be too close to Dark Arts again. As in, he was worried that Snape may be seduced by the lure of the Dark Side.