tbd-station-14/Content.Shared/Slippery/SlipperySystem.cs

using Content.Shared.Administration.Logs;
using Content.Shared.Database;
using Content.Shared.Inventory;
using Content.Shared.StatusEffect;
using Content.Shared.StepTrigger.Systems;
using Content.Shared.Stunnable;
using JetBrains.Annotations;
using Robust.Shared.Audio;
using Robust.Shared.Containers;
using Robust.Shared.GameStates;
using Robust.Shared.Physics.Components;
using Robust.Shared.Physics.Systems;

namespace Content.Shared.Slippery;

[UsedImplicitly]
public sealed class SlipperySystem : EntitySystem
{
    [Dependency] private readonly ISharedAdminLogManager _adminLogger = default!;
    [Dependency] private readonly SharedAudioSystem _audio = default!;
    [Dependency] private readonly SharedStunSystem _stun = default!;
    [Dependency] private readonly StatusEffectsSystem _statusEffects = default!;
    [Dependency] private readonly SharedContainerSystem _container = default!;
    [Dependency] private readonly SharedPhysicsSystem _physics = default!;

    public override void Initialize()
    {
        base.Initialize();

        SubscribeLocalEvent<SlipperyComponent, StepTriggerAttemptEvent>(HandleAttemptCollide);
        SubscribeLocalEvent<SlipperyComponent, StepTriggeredEvent>(HandleStepTrigger);
        SubscribeLocalEvent<NoSlipComponent, SlipAttemptEvent>(OnNoSlipAttempt);
        // as long as slip-resistant mice are never added, this should be fine (otherwise a mouse-hat will transfer it's power to the wearer).
        SubscribeLocalEvent<NoSlipComponent, InventoryRelayedEvent<SlipAttemptEvent>>((e, c, ev) => OnNoSlipAttempt(e, c, ev.Args));
        SubscribeLocalEvent<SlipperyComponent, ComponentGetState>(OnSlipperyGetState);
        SubscribeLocalEvent<SlipperyComponent, ComponentHandleState>(OnSlipperyHandleState);
    }

    private void OnSlipperyHandleState(EntityUid uid, SlipperyComponent component, ref ComponentHandleState args)
    {
        if (args.Current is not SlipperyComponentState state) return;

        component.ParalyzeTime = state.ParalyzeTime;
        component.LaunchForwardsMultiplier = state.LaunchForwardsMultiplier;
        component.SlipSound = new SoundPathSpecifier(state.SlipSound);
    }

    private void OnSlipperyGetState(EntityUid uid, SlipperyComponent component, ref ComponentGetState args)
    {
        args.State = new SlipperyComponentState(component.ParalyzeTime, component.LaunchForwardsMultiplier, _audio.GetSound(component.SlipSound));
    }

    private void HandleStepTrigger(EntityUid uid, SlipperyComponent component, ref StepTriggeredEvent args)
    {
        TrySlip(uid, component, args.Tripper);
    }

    private void HandleAttemptCollide(
        EntityUid uid,
        SlipperyComponent component,
        ref StepTriggerAttemptEvent args)
    {
        args.Continue |= CanSlip(uid, args.Tripper);
    }

    private static void OnNoSlipAttempt(EntityUid uid, NoSlipComponent component, SlipAttemptEvent args)
    {
        args.Cancel();
    }

    private bool CanSlip(EntityUid uid, EntityUid toSlip)
    {
        return !_container.IsEntityInContainer(uid)
                && _statusEffects.CanApplyEffect(toSlip, "Stun"); //Should be KnockedDown instead?
    }

    private void TrySlip(EntityUid uid, SlipperyComponent component, EntityUid other)
    {
        if (HasComp<KnockedDownComponent>(other))
            return;

        var attemptEv = new SlipAttemptEvent();
        RaiseLocalEvent(other, attemptEv);
        if (attemptEv.Cancelled)
            return;

        var ev = new SlipEvent(other);
        RaiseLocalEvent(uid, ref ev);

        if (TryComp(other, out PhysicsComponent? physics))
            _physics.SetLinearVelocity(other, physics.LinearVelocity * component.LaunchForwardsMultiplier, body: physics);

        var playSound = !_statusEffects.HasStatusEffect(other, "KnockedDown");

        _stun.TryParalyze(other, TimeSpan.FromSeconds(component.ParalyzeTime), true);

        // Preventing from playing the slip sound when you are already knocked down.
        if (playSound)
        {
            _audio.PlayPredicted(component.SlipSound, other, other);
        }

        _adminLogger.Add(LogType.Slip, LogImpact.Low,
            $"{ToPrettyString(other):mob} slipped on collision with {ToPrettyString(uid):entity}");
    }

    public void CopyConstruct(EntityUid destUid, SlipperyComponent srcSlip)
    {
        var destEvaporation = EntityManager.EnsureComponent<SlipperyComponent>(destUid);
        destEvaporation.SlipSound = srcSlip.SlipSound;
        destEvaporation.ParalyzeTime = srcSlip.ParalyzeTime;
        destEvaporation.LaunchForwardsMultiplier = srcSlip.LaunchForwardsMultiplier;
    }
}

/// <summary>
///     Raised on an entity to determine if it can slip or not.
/// </summary>
public sealed class SlipAttemptEvent : CancellableEntityEventArgs, IInventoryRelayEvent
{
    public SlotFlags TargetSlots { get; } = SlotFlags.FEET;
}

[ByRefEvent]
public readonly record struct SlipEvent(EntityUid Slipped);