Gravity generator rewrite (#4828)

Co-authored-by: metalgearsloth <comedian_vs_clown@hotmail.com>

Content.Server/Gravity/EntitySystems/GravityShakeSystem.cs

@@ -0,0 +1,93 @@
+using System.Collections.Generic;
+using Content.Server.Camera;
+using Content.Shared.Gravity;
+using Robust.Server.Player;
+using Robust.Shared.Audio;
+using Robust.Shared.GameObjects;
+using Robust.Shared.IoC;
+using Robust.Shared.Map;
+using Robust.Shared.Maths;
+using Robust.Shared.Player;
+using Robust.Shared.Random;
+
+namespace Content.Server.Gravity.EntitySystems
+{
+    /// <summary>
+    /// Handles the grid shake effect used by the gravity generator.
+    /// </summary>
+    public sealed class GravityShakeSystem : EntitySystem
+    {
+        [Dependency] private readonly IPlayerManager _playerManager = default!;
+        [Dependency] private readonly IRobustRandom _random = default!;
+
+        private Dictionary<GridId, uint> _gridsToShake = new();
+
+        private const float GravityKick = 100.0f;
+        private const uint ShakeTimes = 10;
+
+        private float _internalTimer = 0.0f;
+
+        public override void Update(float frameTime)
+        {
+            if (_gridsToShake.Count > 0)
+            {
+                _internalTimer += frameTime;
+
+                if (_internalTimer > 0.2f)
+                {
+                    // TODO: Could just have clients do this themselves via event and save bandwidth.
+                    ShakeGrids();
+                    _internalTimer -= 0.2f;
+                }
+            }
+            else
+            {
+                _internalTimer = 0.0f;
+            }
+        }
+
+        public void ShakeGrid(GridId gridId, GravityComponent comp)
+        {
+            _gridsToShake[gridId] = ShakeTimes;
+
+            SoundSystem.Play(
+                Filter.BroadcastGrid(gridId),
+                comp.GravityShakeSound.GetSound(),
+                AudioParams.Default.WithVolume(-2f));
+        }
+
+        private void ShakeGrids()
+        {
+            // I have to copy this because C# doesn't allow changing collections while they're
+            // getting enumerated.
+            var gridsToShake = new Dictionary<GridId, uint>(_gridsToShake);
+            foreach (var gridId in _gridsToShake.Keys)
+            {
+                if (_gridsToShake[gridId] == 0)
+                {
+                    gridsToShake.Remove(gridId);
+                    continue;
+                }
+                ShakeGrid(gridId);
+                gridsToShake[gridId] -= 1;
+            }
+
+            _gridsToShake = gridsToShake;
+        }
+
+        private void ShakeGrid(GridId gridId)
+        {
+            foreach (var player in _playerManager.GetAllPlayers())
+            {
+                if (player.AttachedEntity == null
+                    || player.AttachedEntity.Transform.GridID != gridId
+                    || !player.AttachedEntity.TryGetComponent(out CameraRecoilComponent? recoil))
+                {
+                    continue;
+                }
+
+                recoil.Kick(new Vector2(_random.NextFloat(), _random.NextFloat()) * GravityKick);
+            }
+        }
+    }
+}