Use wall time instead of ticks for several things. Fixes BUKKIT-4059

Currently furnace smelting and the item pickup delay timer use wall time
(aka actual time passed) to emulate a constant tick rate so run at the
same speed regardless of the server's actual tick rate. There are several
other places this makes sense so this commit converts them.

The item despawn timer is converted so now always takes 5 minutes. Users
know this 5 minute number well so keeping this constant helps to avoid
confusion. This also helps alleviate lag because if a large number of item
drops is the reason your server is running slowly having them stay around
longer just means your server is slow longer.

Potion brewing and the zombie villager conversion timer are now constant.
These match the furnace criteria of being useful for hiding lag and not
having a detrimental effect on gameplay.

Potion effects are now also using wall time. The client is told about effect
times in ticks and displays this information to the user as minutes and
seconds assuming a solid 20 ticks per second. The server does have
code for updating the client with the current time remaining to help
avoid skew due to differing tick rates but making this a constant makes
sense due to this display.

src/main/java/net/minecraft/server/EntityItem.java

@@ -10,7 +10,7 @@ public class EntityItem extends Entity {
     public int pickupDelay;
     private int d;
     public float c;
-    private int lastTick = (int) (System.currentTimeMillis() / 50); // CraftBukkit
+    private int lastTick = MinecraftServer.currentTick; // CraftBukkit
 
     public EntityItem(World world, double d0, double d1, double d2) {
         super(world);
@@ -55,10 +55,11 @@ public class EntityItem extends Entity {
 
     public void l_() {
         super.l_();
-        // CraftBukkit start
-        int currentTick = (int) (System.currentTimeMillis() / 50);
-        this.pickupDelay -= (currentTick - this.lastTick);
-        this.lastTick = currentTick;
+        // CraftBukkit start - Use wall time for pickup and despawn timers
+        int elapsedTicks = Math.max(1, MinecraftServer.currentTick - this.lastTick);
+        this.pickupDelay -= elapsedTicks;
+        this.age += elapsedTicks;
+        this.lastTick = MinecraftServer.currentTick;
         // CraftBukkit end
 
         this.lastX = this.locX;
@@ -100,7 +101,7 @@ public class EntityItem extends Entity {
             this.motY *= -0.5D;
         }
 
-        ++this.age;
+        // ++this.age; // CraftBukkit - Moved up
         if (!this.world.isStatic && this.age >= 6000) {
             // CraftBukkit start
             if (org.bukkit.craftbukkit.event.CraftEventFactory.callItemDespawnEvent(this).isCancelled()) {

src/main/java/net/minecraft/server/EntityZombie.java

@@ -10,6 +10,7 @@ import org.bukkit.event.entity.EntityCombustEvent;
 public class EntityZombie extends EntityMonster {
 
     private int d = 0;
+    private int lastTick = MinecraftServer.currentTick; // CraftBukkit
 
     public EntityZombie(World world) {
         super(world);
@@ -119,6 +120,12 @@ public class EntityZombie extends EntityMonster {
         if (!this.world.isStatic && this.o()) {
             int i = this.q();
 
+            // CraftBukkit start - Use wall time instead of ticks for villager conversion
+            int elapsedTicks = Math.max(1, MinecraftServer.currentTick - this.lastTick);
+            this.lastTick = MinecraftServer.currentTick;
+            i *= elapsedTicks;
+            // CraftBukkit end
+
             this.d -= i;
             if (this.d <= 0) {
                 this.p();

src/main/java/net/minecraft/server/MinecraftServer.java

@@ -78,7 +78,7 @@ public abstract class MinecraftServer implements ICommandListener, Runnable, IMo
     public org.bukkit.command.ConsoleCommandSender console;
     public org.bukkit.command.RemoteConsoleCommandSender remoteConsole;
     public ConsoleReader reader;
-    public static int currentTick;
+    public static int currentTick = (int) (System.currentTimeMillis() / 50);
     public final Thread primaryThread;
     public java.util.Queue<Runnable> processQueue = new java.util.concurrent.ConcurrentLinkedQueue<Runnable>();
     public int autosavePeriod;

src/main/java/net/minecraft/server/MobEffect.java

@@ -7,6 +7,7 @@ public class MobEffect {
     private int amplification;
     private boolean splash;
     private boolean ambient;
+    private int lastTick = MinecraftServer.currentTick; // CraftBukkit
 
     public MobEffect(int i, int j) {
         this(i, j, 0);
@@ -81,7 +82,13 @@ public class MobEffect {
     }
 
     private int h() {
-        return --this.duration;
+        // CraftBukkit start - Use wall time instead of ticks for potion effects
+        int elapsedTicks = Math.max(1, MinecraftServer.currentTick - this.lastTick);
+        this.lastTick = MinecraftServer.currentTick;
+        this.duration -= elapsedTicks;
+
+        return this.duration;
+        // CraftBukkit end
     }
 
     public void b(EntityLiving entityliving) {

src/main/java/net/minecraft/server/PlayerInteractManager.java

@@ -55,7 +55,7 @@ public class PlayerInteractManager {
     }
 
     public void a() {
-        this.currentTick = (int) (System.currentTimeMillis() / 50); // CraftBukkit
+        this.currentTick = MinecraftServer.currentTick; // CraftBukkit
         int i;
         float f;
         int j;
@@ -189,7 +189,7 @@ public class PlayerInteractManager {
 
     public void a(int i, int j, int k) {
         if (i == this.f && j == this.g && k == this.h) {
-            this.currentTick = (int) (System.currentTimeMillis() / 50); // CraftBukkit
+            this.currentTick = MinecraftServer.currentTick; // CraftBukkit
             int l = this.currentTick - this.lastDigTick;
             int i1 = this.world.getTypeId(i, j, k);
 

src/main/java/net/minecraft/server/TileEntityBrewingStand.java

@@ -17,6 +17,7 @@ public class TileEntityBrewingStand extends TileEntity implements IWorldInventor
     private int e;
     private int f;
     private String g;
+    private int lastTick = MinecraftServer.currentTick; // CraftBukkit
 
     public TileEntityBrewingStand() {}
 
@@ -62,9 +63,14 @@ public class TileEntityBrewingStand extends TileEntity implements IWorldInventor
     }
 
     public void h() {
+        // CraftBukkit start - Use wall time instead of ticks for brewing
+        int elapsedTicks = Math.max(1, MinecraftServer.currentTick - this.lastTick);
+        this.lastTick = MinecraftServer.currentTick;
+
         if (this.brewTime > 0) {
-            --this.brewTime;
-            if (this.brewTime == 0) {
+            this.brewTime -= elapsedTicks;
+            if (this.brewTime <= 0) { // == -> <=
+                // CraftBukkit end
                 this.u();
                 this.update();
             } else if (!this.l()) {

src/main/java/net/minecraft/server/TileEntityFurnace.java

@@ -22,7 +22,7 @@ public class TileEntityFurnace extends TileEntity implements IWorldInventory {
     private String h;
 
     // CraftBukkit start
-    private int lastTick = (int) (System.currentTimeMillis() / 50);
+    private int lastTick = MinecraftServer.currentTick;
     private int maxStack = MAX_STACK;
     public List<HumanEntity> transaction = new java.util.ArrayList<HumanEntity>();
 
@@ -165,10 +165,9 @@ public class TileEntityFurnace extends TileEntity implements IWorldInventory {
         boolean flag = this.burnTime > 0;
         boolean flag1 = false;
 
-        // CraftBukkit start
-        int currentTick = (int) (System.currentTimeMillis() / 50); // CraftBukkit
-        int elapsedTicks = currentTick - this.lastTick;
-        this.lastTick = currentTick;
+        // CraftBukkit start - Use wall time instead of ticks for cooking
+        int elapsedTicks = Math.max(1, MinecraftServer.currentTick - this.lastTick);
+        this.lastTick = MinecraftServer.currentTick;
 
         // CraftBukkit - moved from below
         if (this.isBurning() && this.canBurn()) {