Cleaned up and added API for entity air supply, fixed oxygen being used in creative/spectator

this commit also includes respiration checks because it's cherry-picked
from api3/blocks, but respiration won't work until it's registered.

src/pocketmine/Player.php

@@ -1713,6 +1713,10 @@ class Player extends Human implements CommandSender, ChunkLoader, IPlayer{
 		return 0.0;
 	}
 
+	public function canBreathe() : bool{
+		return $this->isCreative() or parent::canBreathe();
+	}
+
 	public function checkNetwork(){
 		if(!$this->isOnline()){
 			return;

src/pocketmine/entity/Human.php

@@ -28,6 +28,9 @@ use pocketmine\event\entity\EntityRegainHealthEvent;
 use pocketmine\event\player\PlayerExhaustEvent;
 use pocketmine\inventory\InventoryHolder;
 use pocketmine\inventory\PlayerInventory;
+use pocketmine\item\Consumable;
+use pocketmine\item\enchantment\Enchantment;
+use pocketmine\item\FoodSource;
 use pocketmine\item\Item as ItemItem;
 use pocketmine\level\Level;
 use pocketmine\nbt\NBT;
@@ -454,6 +457,14 @@ class Human extends Creature implements ProjectileSource, InventoryHolder{
 		}
 	}
 
+	protected function doAirSupplyTick(int $tickDiff){
+		//TODO: allow this to apply to other mobs
+		if(($ench = $this->inventory->getHelmet()->getEnchantment(Enchantment::RESPIRATION)) === null or
+			lcg_value() <= (1 / ($ench->getLevel() + 1))){
+			parent::doAirSupplyTick($tickDiff);
+		}
+	}
+
 	public function getName() : string{
 		return $this->getNameTag();
 	}

src/pocketmine/entity/Living.php

@@ -422,7 +422,6 @@ abstract class Living extends Entity implements Damageable{
 
 	public function entityBaseTick(int $tickDiff = 1) : bool{
 		Timings::$timerLivingEntityBaseTick->startTiming();
-		$this->setGenericFlag(self::DATA_FLAG_BREATHING, !$this->isInsideOfWater());
 
 		$hasUpdate = parent::entityBaseTick($tickDiff);
 
@@ -435,34 +434,14 @@ abstract class Living extends Entity implements Damageable{
 				$this->attack($ev);
 			}
 
-			if(!$this->hasEffect(Effect::WATER_BREATHING) and $this->isInsideOfWater()){
-				if($this instanceof WaterAnimal){
-					$this->setDataProperty(self::DATA_AIR, self::DATA_TYPE_SHORT, 400);
-				}else{
-					$hasUpdate = true;
-					$airTicks = $this->getDataProperty(self::DATA_AIR) - $tickDiff;
-					if($airTicks <= -20){
-						$airTicks = 0;
-
-						$ev = new EntityDamageEvent($this, EntityDamageEvent::CAUSE_DROWNING, 2);
-						$this->attack($ev);
-					}
-					$this->setDataProperty(self::DATA_AIR, self::DATA_TYPE_SHORT, $airTicks);
-				}
-			}else{
-				if($this instanceof WaterAnimal){
-					$hasUpdate = true;
-					$airTicks = $this->getDataProperty(self::DATA_AIR) - $tickDiff;
-					if($airTicks <= -20){
-						$airTicks = 0;
-
-						$ev = new EntityDamageEvent($this, EntityDamageEvent::CAUSE_SUFFOCATION, 2);
-						$this->attack($ev);
-					}
-					$this->setDataProperty(self::DATA_AIR, self::DATA_TYPE_SHORT, $airTicks);
-				}else{
-					$this->setDataProperty(self::DATA_AIR, self::DATA_TYPE_SHORT, 400);
+			if(!$this->canBreathe()){
+				if($this->isBreathing()){
+					$this->setBreathing(false);
 				}
+				$this->doAirSupplyTick($tickDiff);
+			}elseif(!$this->isBreathing()){
+				$this->setBreathing(true);
+				$this->setAirSupplyTicks($this->getMaxAirSupplyTicks());
 			}
 		}
 
@@ -495,6 +474,90 @@ abstract class Living extends Entity implements Damageable{
 		}
 	}
 
+	/**
+	 * Ticks the entity's air supply when it cannot breathe.
+	 * @param int $tickDiff
+	 */
+	protected function doAirSupplyTick(int $tickDiff){
+		$ticks = $this->getAirSupplyTicks() - $tickDiff;
+
+		if($ticks <= -20){
+			$this->setAirSupplyTicks(0);
+			$this->onAirExpired();
+		}else{
+			$this->setAirSupplyTicks($ticks);
+		}
+	}
+
+	/**
+	 * Returns whether the entity can currently breathe.
+	 * @return bool
+	 */
+	public function canBreathe() : bool{
+		return $this->hasEffect(Effect::WATER_BREATHING) or !$this->isInsideOfWater();
+	}
+
+	/**
+	 * Returns whether the entity is currently breathing or not. If this is false, the entity's air supply will be used.
+	 * @return bool
+	 */
+	public function isBreathing() : bool{
+		return $this->getGenericFlag(self::DATA_FLAG_BREATHING);
+	}
+
+	/**
+	 * Sets whether the entity is currently breathing. If false, it will cause the entity's air supply to be used.
+	 * For players, this also shows the oxygen bar.
+	 *
+	 * @param bool $value
+	 */
+	public function setBreathing(bool $value = true){
+		$this->setGenericFlag(self::DATA_FLAG_BREATHING, $value);
+	}
+
+	/**
+	 * Returns the number of ticks remaining in the entity's air supply. Note that the entity may survive longer than
+	 * this amount of time without damage due to enchantments such as Respiration.
+	 *
+	 * @return int
+	 */
+	public function getAirSupplyTicks() : int{
+		return $this->getDataProperty(self::DATA_AIR);
+	}
+
+	/**
+	 * Sets the number of air ticks left in the entity's air supply.
+	 * @param int $ticks
+	 */
+	public function setAirSupplyTicks(int $ticks){
+		$this->setDataProperty(self::DATA_AIR, self::DATA_TYPE_SHORT, $ticks);
+	}
+
+	/**
+	 * Returns the maximum amount of air ticks the entity's air supply can contain.
+	 * @return int
+	 */
+	public function getMaxAirSupplyTicks() : int{
+		return $this->getDataProperty(self::DATA_MAX_AIR);
+	}
+
+	/**
+	 * Sets the maximum amount of air ticks the air supply can hold.
+	 * @param int $ticks
+	 */
+	public function setMaxAirSupplyTicks(int $ticks){
+		$this->setDataProperty(self::DATA_AIR, self::DATA_TYPE_SHORT, $ticks);
+	}
+
+	/**
+	 * Called when the entity's air supply ticks reaches -20 or lower. The entity will usually take damage at this point
+	 * and then the supply is reset to 0, so this method will be called roughly every second.
+	 */
+	public function onAirExpired(){
+		$ev = new EntityDamageEvent($this, EntityDamageEvent::CAUSE_DROWNING, 2);
+		$this->attack($ev);
+	}
+
 	/**
 	 * @return ItemItem[]
 	 */

src/pocketmine/entity/WaterAnimal.php

@@ -23,9 +23,20 @@ declare(strict_types=1);
 
 namespace pocketmine\entity;
 
+use pocketmine\event\entity\EntityDamageEvent;
+
 abstract class WaterAnimal extends Creature implements Ageable{
 
 	public function isBaby() : bool{
 		return $this->getGenericFlag(self::DATA_FLAG_BABY);
 	}
+
+	public function canBreathe() : bool{
+		return $this->isInsideOfWater();
+	}
+
+	public function onAirExpired(){
+		$ev = new EntityDamageEvent($this, EntityDamageEvent::CAUSE_SUFFOCATION, 2);
+		$this->attack($ev);
+	}
 }