From https://github.com/pret/pokeemerald/blob/master/data/battle_ai_scripts.s#L1519

WILL-O-WISP
- If target is resistant to Fire-type attacks, -10

SWAGGER
- If user has Psych Up and target's Attack stat is -2 or higher, -5

---------------------
HP THRESHOLDS - USER
---------------------
EXPLOSION: <50% (encourage), <30% (greatly encourage), otherwise discourage
RECOVER/MILK DRINK/SOFTBOILED/SLACK OFF: <50% (greatly encourage), <70% (no effect), otherwise discourage (might depend on Speed)
REST: <50% (encourage), 40% (greatly encourage), otherwise greatly discourage
STAT-BOOSTING MOVES: <70% (discourage), otherwise encourage
PARALYSIS (IF TIED/FASTER): <70% (discourage), otherwise no effect
TOXIC: <50% (greatly discourage), otherwise no effect

---------------------
HP THRESHOLDS - TARGET
---------------------
CONFUSE: <70% (discourage), 50% (dismiss), otherwise no effect
TOXIC: <50% (greatly discourage), otherwise no effect