Extend and clean up monster skill DB code

src/map/mob.c

@@ -1520,7 +1520,7 @@ static int mob_unlocktarget(struct mob_data *md, int64 tick)
  FALLTHROUGH
  case MSS_IDLE:
  // Idle skill.
- if (!(++md->ud.walk_count%IDLE_SKILL_INTERVAL) && mob->skill_use(md, tick, -1))
+ if ((++md->ud.walk_count % IDLE_SKILL_INTERVAL) == 0 && mob->skill_use(md, tick, -1) == 0)
  break;
  //Random walk.
  if (!md->master_id &&
@@ -1700,7 +1700,7 @@ static bool mob_ai_sub_hard(struct mob_data *md, int64 tick)
  || !mob->can_reach(md, tbl, md->min_chase, MSS_RUSH)
  )
  && md->state.attacked_count++ >= RUDE_ATTACKED_COUNT
- && !mob->skill_use(md, tick, MSC_RUDEATTACKED) // If can't rude Attack
+ && mob->skill_use(md, tick, MSC_RUDEATTACKED) == 0 // If can't rude Attack
  && can_move && unit->escape(&md->bl, tbl, rnd()%10 +1) // Attempt escape
  ) {
  //Escaped
@@ -1728,7 +1728,7 @@ static bool mob_ai_sub_hard(struct mob_data *md, int64 tick)
  ) {
  // Rude attacked
  if (md->state.attacked_count++ >= RUDE_ATTACKED_COUNT
- && !mob->skill_use(md, tick, MSC_RUDEATTACKED) && can_move
+ && mob->skill_use(md, tick, MSC_RUDEATTACKED) == 0 && can_move != 0
  && !tbl && unit->escape(&md->bl, abl, rnd()%10 +1)
  ) {
  //Escaped.
@@ -3465,7 +3465,7 @@ static struct block_list *mob_getfriendstatus(struct mob_data *md, int cond1, in
  * @param md The monster which tries to cast a skill.
  * @param tick The timestamp of skill execution.
  * @param event The MSC_* flag which triggered the skill execution. (-1 for non-event skill conditions.)
- * @return 1 on success, 0 on failure.
+ * @return 0 on success, 1 on failure.
  *
  **/
 static int mob_skill_use(struct mob_data *md, int64 tick, int event)
@@ -3477,10 +3477,10 @@ static int mob_skill_use(struct mob_data *md, int64 tick, int event)
  nullpo_ret(ms);
 
  if (battle_config.mob_skill_rate == 0 || md->ud.skilltimer != INVALID_TIMER || md->db->maxskill == 0)
- return 0;
+ return 1;
 
  if (event == -1 && DIFF_TICK(md->ud.canact_tick, tick) > 0)
- return 0; // Skill act delay only affects non-event skill conditions.
+ return 1; // Skill act delay only affects non-event skill conditions.
 
  // Pick a starting position and loop from that.
  int skill_idx = ((battle_config.mob_ai & 0x100) != 0) ? rnd() % md->db->maxskill : 0;
@@ -3718,12 +3718,12 @@ static int mob_skill_use(struct mob_data *md, int64 tick, int event)
  }
 
  map->freeblock_unlock();
- return 1;
+ return 0;
  }
 
  // No skill was used.
  md->skill_idx = -1;
- return 0;
+ return 1;
 }
 
 /*==========================================
@@ -3736,7 +3736,7 @@ static int mobskill_event(struct mob_data *md, struct block_list *src, int64 tic
  nullpo_ret(md);
  nullpo_ret(src);
  if(md->bl.prev == NULL || md->status.hp <= 0)
- return 0;
+ return 1;
 
  if (md->special_state.ai == AI_SPHERE) {//LOne WOlf explained that ANYONE can trigger the marine countdown skill. [Skotlex]
  md->state.alchemist = 1;
@@ -3756,7 +3756,7 @@ static int mobskill_event(struct mob_data *md, struct block_list *src, int64 tic
  else if (flag&BF_LONG && !(flag&BF_MAGIC)) //Long-attacked should not include magic.
  res = mob->skill_use(md, tick, MSC_LONGRANGEATTACKED);
 
- if (!res)
+ if (res != 0)
  //Restore previous target only if skill condition failed to trigger. [Skotlex]
  md->target_id = target_id;
  //Otherwise check if the target is an enemy, and unlock if needed.

src/map/unit.c

@@ -436,7 +436,7 @@ static int unit_walk_toxy_timer(int tid, int64 tick, int id, intptr_t data)
  // Walk skills are triggered regardless of target due to the idle-walk mob state.
  // But avoid triggering on stop-walk calls.
  if (tid != INVALID_TIMER && (ud->walk_count % WALK_SKILL_INTERVAL) == 0
- && map->list[bl->m].users > 0 && mob->skill_use(md, tick, -1) == 1) {
+ && map->list[bl->m].users > 0 && mob->skill_use(md, tick, -1) == 0) {
  // Walk skills are supposed to be used while walking
  if (!(ud->skill_id == NPC_SELFDESTRUCTION && ud->skilltimer != INVALID_TIMER)
  && md->state.skillstate != MSS_WALK) {
@@ -2345,7 +2345,7 @@ static int unit_attack_timer_sub(struct block_list *src, int tid, int64 tick)
  if(md) {
  //First attack is always a normal attack
  if(md->state.skillstate == MSS_ANGRY || md->state.skillstate == MSS_BERSERK) {
- if (mob->skill_use(md,tick,-1)) {
+ if (mob->skill_use(md, tick, -1) == 0) {
  map->freeblock_unlock();
  return 1;
  }