Fixed the half-done hunger implementation, fixed lots of bugs related to hunger

- Fixed starvation doesn't deal any damage at all (Human->getFood() returns a float, not an int, === 0 won't work so great)
- Added exhaustion for sprinting, walking, jumping and sprint-jumping as per MCPE (these use MCPE values, and yes MCPE does walking exhaustion!)
- Fixed attributes don't get reset after player death
- Added food and hunger regeneration in peaceful difficulty
- Added API methods Living->jump() (motion isn't updated yet, so this won't actually do much if plugins try to use it) and Living->getJumpVelocity()

TODO: implement exhaustion for swimming

src/pocketmine/entity/Attribute.php

@@ -165,6 +165,10 @@ class Attribute{
 		return $this;
 	}
 
+	public function resetToDefault(){
+		$this->setValue($this->getDefaultValue());
+	}
+
 	public function getValue(){
 		return $this->currentValue;
 	}

src/pocketmine/entity/AttributeMap.php

@@ -38,6 +38,9 @@ class AttributeMap implements \ArrayAccess{
 		return $this->attributes[$id] ?? null;
 	}
 
+	/**
+	 * @return Attribute[]
+	 */
 	public function getAll(): array{
 		return $this->attributes;
 	}

src/pocketmine/entity/Human.php

@@ -99,6 +99,15 @@ class Human extends Creature implements ProjectileSource, InventoryHolder{
 		$this->skinId = $skinId;
 	}
 
+	public function jump(){
+		parent::jump();
+		if($this->isSprinting()){
+			$this->exhaust(0.8, PlayerExhaustEvent::CAUSE_SPRINT_JUMPING);
+		}else{
+			$this->exhaust(0.2, PlayerExhaustEvent::CAUSE_JUMPING);
+		}
+	}
+
 	public function getFood() : float{
 		return $this->attributeMap->getAttribute(Attribute::HUNGER)->getValue();
 	}
@@ -355,31 +364,35 @@ class Human extends Creature implements ProjectileSource, InventoryHolder{
 		if($this->isAlive()){
 			$food = $this->getFood();
 			$health = $this->getHealth();
-			if($food >= 18){
-				$this->foodTickTimer++;
-				if($this->foodTickTimer >= 80 and $health < $this->getMaxHealth()){
-					$this->heal(1, new EntityRegainHealthEvent($this, 1, EntityRegainHealthEvent::CAUSE_SATURATION));
-					$this->exhaust(3.0, PlayerExhaustEvent::CAUSE_HEALTH_REGEN);
-					$this->foodTickTimer = 0;
+			$difficulty = $this->server->getDifficulty();
 
+			$this->foodTickTimer++;
+			if($this->foodTickTimer >= 80){
+				$this->foodTickTimer = 0;
+			}
+
+			if($difficulty === 0 and $this->foodTickTimer % 10 === 0){ //Peaceful
+				if($food < 20){
+					$this->addFood(1.0);
 				}
-			}elseif($food === 0){
-				$this->foodTickTimer++;
-				if($this->foodTickTimer >= 80){
-					$diff = $this->server->getDifficulty();
-					$can = false;
-					if($diff === 1){
-						$can = $health > 10;
-					}elseif($diff === 2){
-						$can = $health > 1;
-					}elseif($diff === 3){
-						$can = true;
+				if($this->foodTickTimer % 20 === 0 and $health < $this->getMaxHealth()){
+					$this->heal(1, new EntityRegainHealthEvent($this, 1, EntityRegainHealthEvent::CAUSE_SATURATION));
+				}
+			}
+
+			if($this->foodTickTimer === 0){
+				if($food >= 18){
+					if($health < $this->getMaxHealth()){
+						$this->heal(1, new EntityRegainHealthEvent($this, 1, EntityRegainHealthEvent::CAUSE_SATURATION));
+						$this->exhaust(3.0, PlayerExhaustEvent::CAUSE_HEALTH_REGEN);
 					}
-					if($can){
+				}elseif($food <= 0){
+					if(($difficulty === 1 and $health > 10) or ($difficulty === 2 and $health > 1) or $difficulty === 3){
 						$this->attack(1, new EntityDamageEvent($this, EntityDamageEvent::CAUSE_STARVATION, 1));
 					}
 				}
 			}
+
 			if($food <= 6){
 				if($this->isSprinting()){
 					$this->setSprinting(false);

src/pocketmine/entity/Living.php

@@ -43,6 +43,8 @@ abstract class Living extends Entity implements Damageable{
 
 	protected $invisible = false;
 
+	protected $jumpVelocity = 0.42;
+
 	protected function initEntity(){
 		parent::initEntity();
 
@@ -115,6 +117,23 @@ abstract class Living extends Entity implements Damageable{
 		$this->attackTime = 0;
 	}
 
+	/**
+	 * Returns the initial upwards velocity of a jumping entity in blocks/tick, including additional velocity due to effects.
+	 * @return float
+	 */
+	public function getJumpVelocity() : float{
+		return $this->jumpVelocity + ($this->hasEffect(Effect::JUMP) ? (($this->getEffect(Effect::JUMP)->getAmplifier() + 1) / 10) : 0);
+	}
+
+	/**
+	 * Called when the entity jumps from the ground. This method adds upwards velocity to the entity.
+	 */
+	public function jump(){
+		if($this->onGround){
+			$this->motionY = $this->getJumpVelocity(); //Y motion should already be 0 if we're jumping from the ground.
+		}
+	}
+
 	public function attack($damage, EntityDamageEvent $source){
 		if($this->attackTime > 0 or $this->noDamageTicks > 0){
 			$lastCause = $this->getLastDamageCause();
@@ -183,6 +202,10 @@ abstract class Living extends Entity implements Damageable{
 			return;
 		}
 		parent::kill();
+		$this->callDeathEvent();
+	}
+
+	protected function callDeathEvent(){
 		$this->server->getPluginManager()->callEvent($ev = new EntityDeathEvent($this, $this->getDrops()));
 		foreach($ev->getDrops() as $item){
 			$this->getLevel()->dropItem($this, $item);