Lag compensation for melee (#11885)

Co-authored-by: metalgearsloth <metalgearsloth@gmail.com>

Content.Server/Movement/Components/ActiveLagCompensationComponent.cs

@@ -0,0 +1,10 @@
+namespace Content.Server.Movement.Components;
+
+/// <summary>
+/// Track lag compensation components that may need to have their data culled for memory reasons.
+/// </summary>
+[RegisterComponent]
+public sealed class ActiveLagCompensationComponent : Component
+{
+
+}

Content.Server/Movement/Components/LagCompensationComponent.cs

@@ -0,0 +1,10 @@
+using Robust.Shared.Map;
+
+namespace Content.Server.Movement.Components;
+
+[RegisterComponent]
+public sealed class LagCompensationComponent : Component
+{
+    [ViewVariables]
+    public readonly Queue<ValueTuple<TimeSpan, EntityCoordinates, Angle>> Positions = new();
+}

Content.Server/Movement/Systems/LagCompensationSystem.cs

@@ -0,0 +1,113 @@
+using Content.Server.Movement.Components;
+using Robust.Server.Player;
+using Robust.Shared.Map;
+using Robust.Shared.Timing;
+
+namespace Content.Server.Movement.Systems;
+
+/// <summary>
+/// Stores a buffer of previous positions of the relevant entity.
+/// Can be used to check the entity's position at a recent point in time.
+/// </summary>
+public sealed class LagCompensationSystem : EntitySystem
+{
+    [Dependency] private readonly IGameTiming _timing = default!;
+
+    // I figured 500 ping is max, so 1.5 is 750.
+    // Max ping I've had is 350ms from aus to spain.
+    public static readonly TimeSpan BufferTime = TimeSpan.FromMilliseconds(750);
+
+    private ISawmill _sawmill = Logger.GetSawmill("lagcomp");
+
+    public override void Initialize()
+    {
+        base.Initialize();
+        _sawmill.Level = LogLevel.Info;
+        SubscribeLocalEvent<LagCompensationComponent, MoveEvent>(OnLagMove);
+    }
+
+    public override void Update(float frameTime)
+    {
+        base.Update(frameTime);
+
+        var curTime = _timing.CurTime;
+        var earliestTime = curTime - BufferTime;
+
+        // Cull any old ones from active updates
+        // Probably fine to include ignored.
+        foreach (var (_, comp) in EntityQuery<ActiveLagCompensationComponent, LagCompensationComponent>(true))
+        {
+            while (comp.Positions.TryPeek(out var pos))
+            {
+                if (pos.Item1 < earliestTime)
+                {
+                    comp.Positions.Dequeue();
+                    continue;
+                }
+
+                break;
+            }
+
+            if (comp.Positions.Count == 0)
+            {
+                RemComp<ActiveLagCompensationComponent>(comp.Owner);
+            }
+        }
+    }
+
+    private void OnLagMove(EntityUid uid, LagCompensationComponent component, ref MoveEvent args)
+    {
+        EnsureComp<ActiveLagCompensationComponent>(uid);
+        component.Positions.Enqueue((_timing.CurTime, args.NewPosition, args.NewRotation));
+    }
+
+    public (EntityCoordinates Coordinates, Angle Angle) GetCoordinatesAngle(EntityUid uid, IPlayerSession pSession,
+        TransformComponent? xform = null)
+    {
+        if (!Resolve(uid, ref xform))
+            return (EntityCoordinates.Invalid, Angle.Zero);
+
+        if (!TryComp<LagCompensationComponent>(uid, out var lag) || lag.Positions.Count == 0)
+            return (xform.Coordinates, xform.LocalRotation);
+
+        var angle = Angle.Zero;
+        var coordinates = EntityCoordinates.Invalid;
+        var ping = pSession.Ping;
+        // Use 1.5 due to the trip buffer.
+        var sentTime = _timing.CurTime - TimeSpan.FromMilliseconds(ping * 1.5);
+
+        foreach (var pos in lag.Positions)
+        {
+            coordinates = pos.Item2;
+            angle = pos.Item3;
+
+            if (pos.Item1 >= sentTime)
+                break;
+        }
+
+        if (coordinates == default)
+        {
+            _sawmill.Debug($"No long comp coords found, using {xform.Coordinates}");
+            coordinates = xform.Coordinates;
+            angle = xform.LocalRotation;
+        }
+        else
+        {
+            _sawmill.Debug($"Actual coords is {xform.Coordinates} and got {coordinates}");
+        }
+
+        return (coordinates, angle);
+    }
+
+    public Angle GetAngle(EntityUid uid, IPlayerSession pSession, TransformComponent? xform = null)
+    {
+        var (_, angle) = GetCoordinatesAngle(uid, pSession, xform);
+        return angle;
+    }
+
+    public EntityCoordinates GetCoordinates(EntityUid uid, IPlayerSession pSession, TransformComponent? xform = null)
+    {
+        var (coordinates, _) = GetCoordinatesAngle(uid, pSession, xform);
+        return coordinates;
+    }
+}

Content.Server/Weapons/Melee/MeleeWeaponSystem.cs

@@ -12,6 +12,7 @@ using Content.Server.Contests;
 using Content.Server.Damage.Systems;
 using Content.Server.Examine;
 using Content.Server.Hands.Components;
+using Content.Server.Movement.Systems;
 using Content.Server.Weapons.Melee.Components;
 using Content.Server.Weapons.Melee.Events;
 using Content.Shared.CombatMode;
@@ -24,11 +25,13 @@ using Content.Shared.Physics;
 using Content.Shared.Verbs;
 using Content.Shared.Weapons.Melee;
 using Content.Shared.Weapons.Melee.Events;
+using Robust.Server.Player;
 using Robust.Shared.Audio;
 using Robust.Shared.Map;
 using Robust.Shared.Physics;
 using Robust.Shared.Physics.Systems;
 using Robust.Shared.Player;
+using Robust.Shared.Players;
 using Robust.Shared.Prototypes;
 using Robust.Shared.Random;
 
@@ -43,6 +46,7 @@ public sealed class MeleeWeaponSystem : SharedMeleeWeaponSystem
     [Dependency] private readonly ContestsSystem _contests = default!;
     [Dependency] private readonly DamageableSystem _damageable = default!;
     [Dependency] private readonly ExamineSystem _examine = default!;
+    [Dependency] private readonly LagCompensationSystem _lag = default!;
     [Dependency] private readonly SharedInteractionSystem _interaction = default!;
     [Dependency] private readonly SharedPhysicsSystem _physics = default!;
     [Dependency] private readonly SolutionContainerSystem _solutions = default!;
@@ -106,9 +110,9 @@ public sealed class MeleeWeaponSystem : SharedMeleeWeaponSystem
         PopupSystem.PopupEntity(message, uid.Value, Filter.Pvs(uid.Value, entityManager: EntityManager).RemoveWhereAttachedEntity(e => e == user));
     }
 
-    protected override void DoLightAttack(EntityUid user, LightAttackEvent ev, MeleeWeaponComponent component)
+    protected override void DoLightAttack(EntityUid user, LightAttackEvent ev, MeleeWeaponComponent component, ICommonSession? session)
     {
-        base.DoLightAttack(user, ev, component);
+        base.DoLightAttack(user, ev, component, session);
 
         // Can't attack yourself
         // Not in LOS.
@@ -122,7 +126,7 @@ public sealed class MeleeWeaponSystem : SharedMeleeWeaponSystem
             return;
         }
 
-        if (!_interaction.InRangeUnobstructed(user, ev.Target.Value, component.Range))
+        if (!InRange(user, ev.Target.Value, component.Range, session))
             return;
 
         var damage = component.Damage * GetModifier(component, true);
@@ -191,9 +195,9 @@ public sealed class MeleeWeaponSystem : SharedMeleeWeaponSystem
         }
     }
 
-    protected override void DoHeavyAttack(EntityUid user, HeavyAttackEvent ev, MeleeWeaponComponent component)
+    protected override void DoHeavyAttack(EntityUid user, HeavyAttackEvent ev, MeleeWeaponComponent component, ICommonSession? session)
     {
-        base.DoHeavyAttack(user, ev, component);
+        base.DoHeavyAttack(user, ev, component, session);
 
         // TODO: This is copy-paste as fuck with DoPreciseAttack
         if (!TryComp<TransformComponent>(user, out var userXform))
@@ -303,9 +307,9 @@ public sealed class MeleeWeaponSystem : SharedMeleeWeaponSystem
         }
     }
 
-    protected override bool DoDisarm(EntityUid user, DisarmAttackEvent ev, MeleeWeaponComponent component)
+    protected override bool DoDisarm(EntityUid user, DisarmAttackEvent ev, MeleeWeaponComponent component, ICommonSession? session)
     {
-        if (!base.DoDisarm(user, ev, component))
+        if (!base.DoDisarm(user, ev, component, session))
             return false;
 
         if (!TryComp<CombatModeComponent>(user, out var combatMode) ||
@@ -322,7 +326,7 @@ public sealed class MeleeWeaponSystem : SharedMeleeWeaponSystem
             return false;
         }
 
-        if (!_interaction.InRangeUnobstructed(user, ev.Target.Value, component.Range + 0.1f))
+        if (!InRange(user, ev.Target.Value, component.Range, session))
         {
             return false;
         }
@@ -377,6 +381,25 @@ public sealed class MeleeWeaponSystem : SharedMeleeWeaponSystem
         return true;
     }
 
+    private bool InRange(EntityUid user, EntityUid target, float range, ICommonSession? session)
+    {
+        EntityCoordinates targetCoordinates;
+        Angle targetLocalAngle;
+
+        if (session is IPlayerSession pSession)
+        {
+            (targetCoordinates, targetLocalAngle) = _lag.GetCoordinatesAngle(target, pSession);
+        }
+        else
+        {
+            var xform = Transform(target);
+            targetCoordinates = xform.Coordinates;
+            targetLocalAngle = xform.LocalRotation;
+        }
+
+        return _interaction.InRangeUnobstructed(user, target, targetCoordinates, targetLocalAngle, range);
+    }
+
     private float CalculateDisarmChance(EntityUid disarmer, EntityUid disarmed, EntityUid? inTargetHand, SharedCombatModeComponent disarmerComp)
     {
         if (HasComp<DisarmProneComponent>(disarmer))