crystall-punk-14/Content.Shared/Physics/Controllers/SharedTileFrictionController.cs

using System;
using Content.Shared.GameObjects.Components.Mobs.State;
using Content.Shared.GameObjects.Components.Movement;
using Content.Shared.GameObjects.EntitySystems.ActionBlocker;
using JetBrains.Annotations;
using Robust.Shared;
using Robust.Shared.Configuration;
using Robust.Shared.GameObjects;
using Robust.Shared.IoC;
using Robust.Shared.Map;
using Robust.Shared.Physics;
using Robust.Shared.Physics.Broadphase;
using Robust.Shared.Physics.Controllers;
using Robust.Shared.Physics.Dynamics;

#nullable enable

namespace Content.Shared.Physics.Controllers
{
    public sealed class SharedTileFrictionController : VirtualController
    {
        [Dependency] private readonly IConfigurationManager _configManager = default!;
        [Dependency] private readonly IMapManager _mapManager = default!;
        [Dependency] private readonly IPhysicsManager _physicsManager = default!;
        [Dependency] private readonly ITileDefinitionManager _tileDefinitionManager = default!;

        private SharedBroadPhaseSystem _broadPhaseSystem = default!;

        private float _stopSpeed;

        private float _frictionModifier;

        public override void Initialize()
        {
            base.Initialize();
            _broadPhaseSystem = EntitySystem.Get<SharedBroadPhaseSystem>();

            _frictionModifier = _configManager.GetCVar(CCVars.TileFrictionModifier);
            _configManager.OnValueChanged(CCVars.TileFrictionModifier, value => _frictionModifier = value);

            _stopSpeed = _configManager.GetCVar(CCVars.StopSpeed);
            _configManager.OnValueChanged(CCVars.StopSpeed, value => _stopSpeed = value);
        }

        public override void UpdateBeforeMapSolve(bool prediction, PhysicsMap map, float frameTime)
        {
            base.UpdateBeforeMapSolve(prediction, map, frameTime);

            foreach (var body in map.AwakeBodies)
            {
                var speed = body.LinearVelocity.Length;

                if (speed <= 0.0f || body.BodyStatus == BodyStatus.InAir) continue;

                // This is the *actual* amount that speed will drop by, we just do some multiplication around it to be easier.
                var drop = 0.0f;
                float control;

                // Only apply friction when it's not a mob (or the mob doesn't have control).
                if (SharedMoverController.UseMobMovement(_broadPhaseSystem, body, _physicsManager)) continue;

                var surfaceFriction = GetTileFriction(body);
                var bodyModifier = body.Owner.GetComponentOrNull<SharedTileFrictionModifier>()?.Modifier ?? 1.0f;
                var friction = _frictionModifier * surfaceFriction * bodyModifier;

                if (friction > 0.0f)
                {
                    // TBH I can't really tell if this makes a difference, player movement is fucking hard.
                    if (!prediction)
                    {
                        control = speed < _stopSpeed ? _stopSpeed : speed;
                    }
                    else
                    {
                        control = speed;
                    }

                    drop += control * friction * frameTime;
                }

                var newSpeed = MathF.Max(0.0f, speed - drop);

                newSpeed /= speed;
                body.LinearVelocity *= newSpeed;
            }
        }

        [Pure]
        private float GetTileFriction(IPhysBody body)
        {
            if (body.BodyStatus == BodyStatus.InAir || !_mapManager.TryGetGrid(body.Owner.Transform.GridID, out var grid))
                return 0.0f;

            var tile = grid.GetTileRef(body.Owner.Transform.Coordinates);
            var tileDef = _tileDefinitionManager[tile.Tile.TypeId];
            return tileDef.Friction;
        }
    }
}