Legally distinct gravity gun (#8114)

Content.Server/Weapon/Ranged/TetherGunSystem.cs

@@ -0,0 +1,153 @@
+using Content.Shared.Administration;
+using Content.Shared.Weapons.Ranged;
+using Robust.Server.Console;
+using Robust.Server.Player;
+using Robust.Shared.Containers;
+using Robust.Shared.Map;
+using Robust.Shared.Physics;
+using Robust.Shared.Physics.Dynamics.Joints;
+using Robust.Shared.Players;
+using Robust.Shared.Timing;
+using Robust.Shared.Utility;
+
+namespace Content.Server.Weapon.Ranged;
+
+public sealed class TetherGunSystem : SharedTetherGunSystem
+{
+    [Dependency] private readonly IConGroupController _admin = default!;
+    [Dependency] private readonly IPlayerManager _playerManager = default!;
+    [Dependency] private readonly SharedContainerSystem _container = default!;
+    [Dependency] private readonly SharedJointSystem _joints = default!;
+
+    private Dictionary<ICommonSession, (EntityUid Entity, EntityUid Tether, Joint Joint)> _tethered = new();
+
+    private const string JointId = "tether-joint";
+
+    public override void Initialize()
+    {
+        base.Initialize();
+        SubscribeNetworkEvent<StartTetherEvent>(OnStartTether);
+        SubscribeNetworkEvent<StopTetherEvent>(OnStopTether);
+        SubscribeNetworkEvent<TetherMoveEvent>(OnMoveTether);
+
+        _playerManager.PlayerStatusChanged += OnStatusChange;
+    }
+
+    private void OnStatusChange(object? sender, SessionStatusEventArgs e)
+    {
+        StopTether(e.Session);
+    }
+
+    public override void Shutdown()
+    {
+        base.Shutdown();
+
+        _playerManager.PlayerStatusChanged -= OnStatusChange;
+    }
+
+    private void OnStartTether(StartTetherEvent msg, EntitySessionEventArgs args)
+    {
+        if (args.SenderSession is not IPlayerSession playerSession ||
+            !_admin.CanCommand(playerSession, CommandName) ||
+            !Exists(msg.Entity) ||
+            Deleted(msg.Entity) ||
+            msg.Coordinates == MapCoordinates.Nullspace ||
+            _tethered.ContainsKey(args.SenderSession) ||
+            _container.IsEntityInContainer(msg.Entity)) return;
+
+        var tether = Spawn("TetherEntity", msg.Coordinates);
+
+        if (!TryComp<PhysicsComponent>(tether, out var bodyA) ||
+            !TryComp<PhysicsComponent>(msg.Entity, out var bodyB))
+        {
+            Del(tether);
+            return;
+        }
+
+        EnsureComp<AdminFrozenComponent>(msg.Entity);
+
+        if (TryComp<TransformComponent>(msg.Entity, out var xform))
+        {
+            xform.Anchored = false;
+        }
+
+        if (TryComp<PhysicsComponent>(msg.Entity, out var body))
+        {
+            body.BodyStatus = BodyStatus.InAir;
+        }
+
+        var joint = _joints.CreateMouseJoint(bodyA.Owner, bodyB.Owner, id: JointId);
+
+        SharedJointSystem.LinearStiffness(5f, 0.7f, bodyA.Mass, bodyB.Mass, out var stiffness, out var damping);
+        joint.Stiffness = stiffness;
+        joint.Damping = damping;
+        joint.MaxForce = 5000f * bodyB.Mass;
+
+        _tethered.Add(playerSession, (msg.Entity, tether, joint));
+    }
+
+    private void OnStopTether(StopTetherEvent msg, EntitySessionEventArgs args)
+    {
+        StopTether(args.SenderSession);
+    }
+
+    private void StopTether(ICommonSession session)
+    {
+        if (!_tethered.TryGetValue(session, out var weh))
+            return;
+
+        RemComp<AdminFrozenComponent>(weh.Entity);
+
+        if (TryComp<PhysicsComponent>(weh.Entity, out var body))
+        {
+            Timer.Spawn(1000, () =>
+            {
+                if (Deleted(body.Owner)) return;
+                body.BodyStatus = BodyStatus.OnGround;
+            });
+        }
+
+        _joints.RemoveJoint(weh.Joint);
+        Del(weh.Tether);
+        _tethered.Remove(session);
+    }
+
+    private void OnMoveTether(TetherMoveEvent msg, EntitySessionEventArgs args)
+    {
+        if (!_tethered.TryGetValue(args.SenderSession, out var tether) ||
+            !TryComp<TransformComponent>(tether.Tether, out var xform) ||
+            xform.MapID != msg.Coordinates.MapId) return;
+
+        xform.WorldPosition = msg.Coordinates.Position;
+    }
+
+    public override void Update(float frameTime)
+    {
+        base.Update(frameTime);
+
+        var toRemove = new RemQueue<ICommonSession>();
+        var bodyQuery = GetEntityQuery<PhysicsComponent>();
+
+        foreach (var (session, entity) in _tethered)
+        {
+            if (Deleted(entity.Entity) ||
+                Deleted(entity.Tether) ||
+                !entity.Joint.Enabled)
+            {
+                toRemove.Add(session);
+                continue;
+            }
+
+            // Force it awake, always
+            if (bodyQuery.TryGetComponent(entity.Entity, out var body))
+            {
+                body.WakeBody();
+            }
+        }
+
+        foreach (var session in toRemove)
+        {
+            StopTether(session);
+        }
+    }
+}