ProjectileSystem.cs

using Content.Server.Administration.Logs;
using Content.Server.Effects;
using Content.Server.Weapons.Ranged.Systems;
using Content.Shared._CorvaxNext.Penetration;
using Content.Shared.Camera;
using Content.Shared.Damage;
using Content.Shared.Database;
using Content.Shared.Projectiles;
using Robust.Shared.Physics.Events;
using Robust.Shared.Player;
using Robust.Shared.Random;

namespace Content.Server.Projectiles;

public sealed class ProjectileSystem : SharedProjectileSystem
{
    [Dependency] private readonly IAdminLogManager _adminLogger = default!;
    [Dependency] private readonly ColorFlashEffectSystem _color = default!;
    [Dependency] private readonly DamageableSystem _damageableSystem = default!;
    [Dependency] private readonly GunSystem _guns = default!;
    [Dependency] private readonly SharedCameraRecoilSystem _sharedCameraRecoil = default!;
    [Dependency] private readonly IRobustRandom _random = default!;

    private EntityQuery<PenetratableComponent> _penetratableQuery;

    public override void Initialize()
    {
        base.Initialize();
        _penetratableQuery = GetEntityQuery<PenetratableComponent>();
        SubscribeLocalEvent<ProjectileComponent, StartCollideEvent>(OnStartCollide);
    }

    private void OnStartCollide(EntityUid uid, ProjectileComponent component, ref StartCollideEvent args)
    {
        // This is so entities that shouldn't get a collision are ignored.
        if (args.OurFixtureId != ProjectileFixture || !args.OtherFixture.Hard
            || component.DamagedEntity || component is { Weapon: null, OnlyCollideWhenShot: true })
            return;

        var target = args.OtherEntity;
        // it's here so this check is only done once before possible hit
        var attemptEv = new ProjectileReflectAttemptEvent(uid, component, false);
        RaiseLocalEvent(target, ref attemptEv);
        if (attemptEv.Cancelled)
        {
            SetShooter(uid, component, target);
            return;
        }

        var ev = new ProjectileHitEvent(component.Damage, target, component.Shooter);
        RaiseLocalEvent(uid, ref ev);

        var otherName = ToPrettyString(target);
        var direction = args.OurBody.LinearVelocity.Normalized();
        var modifiedDamage = _damageableSystem.TryChangeDamage(target, ev.Damage, component.IgnoreResistances, origin: component.Shooter);
        var deleted = Deleted(target);

        if (modifiedDamage is not null && EntityManager.EntityExists(component.Shooter))
        {
            if (modifiedDamage.AnyPositive() && !deleted)
            {
                _color.RaiseEffect(Color.Red, new List<EntityUid> { target }, Filter.Pvs(target, entityManager: EntityManager));
            }

            _adminLogger.Add(LogType.BulletHit,
                HasComp<ActorComponent>(target) ? LogImpact.Extreme : LogImpact.High,
                $"Projectile {ToPrettyString(uid):projectile} shot by {ToPrettyString(component.Shooter!.Value):user} hit {otherName:target} and dealt {modifiedDamage.GetTotal():damage} damage");
        }

        if (!deleted)
        {
            _guns.PlayImpactSound(target, modifiedDamage, component.SoundHit, component.ForceSound);
            _sharedCameraRecoil.KickCamera(target, direction);
        }

        // Corvax-Next-Penetration-Start
        if (component.PenetrationScore > 0
            && _penetratableQuery.TryGetComponent(target, out var penetratable)
            && _random.Next(component.PenetrationScore + penetratable.StoppingPower) >= penetratable.StoppingPower)
        {
            component.DamagedEntity = component.PenetrationScore < penetratable.StoppingPower;

            component.PenetrationScore -= penetratable.StoppingPower;
        }
        else
            component.DamagedEntity = true;

        if (component.DeleteOnCollide && component.DamagedEntity)
            QueueDel(uid);
        // Corvax-Next-Penetration-End

        if (component.ImpactEffect != null && TryComp(uid, out TransformComponent? xform))
        {
            RaiseNetworkEvent(new ImpactEffectEvent(component.ImpactEffect, GetNetCoordinates(xform.Coordinates)), Filter.Pvs(xform.Coordinates, entityMan: EntityManager));
        }
    }
}