civ14/Content.Client/_RMC14/Weapons/Ranged/Prediction/GunPredictionSystem.cs

using System.Linq;
using Content.Client.Projectiles;
using Content.Shared._RMC14.Weapons.Ranged.Prediction;
using Content.Shared.Projectiles;
using Content.Shared.Weapons.Ranged.Events;
using Content.Shared.Weapons.Ranged.Systems;
using Robust.Client.GameObjects;
using Robust.Client.Physics;
using Robust.Client.Player;
using Robust.Shared.Map;
using Robust.Shared.Physics.Components;
using Robust.Shared.Physics.Events;
using Robust.Shared.Physics.Systems;
using Robust.Shared.Timing;

namespace Content.Client._RMC14.Weapons.Ranged.Prediction;

public sealed class GunPredictionSystem : SharedGunPredictionSystem
{
    [Dependency] private readonly SharedGunSystem _gun = default!;
    [Dependency] private readonly PhysicsSystem _physics = default!;
    [Dependency] private readonly IPlayerManager _player = default!;
    [Dependency] private readonly ProjectileSystem _projectile = default!;
    [Dependency] private readonly IGameTiming _timing = default!;
    [Dependency] private readonly SharedTransformSystem _transform = default!;

    private EntityQuery<IgnorePredictionHideComponent> _ignorePredictionHideQuery;
    private EntityQuery<SpriteComponent> _spriteQuery;

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

        _ignorePredictionHideQuery = GetEntityQuery<IgnorePredictionHideComponent>();
        _spriteQuery = GetEntityQuery<SpriteComponent>();

        SubscribeLocalEvent<PhysicsUpdateBeforeSolveEvent>(OnBeforeSolve);
        SubscribeLocalEvent<PhysicsUpdateAfterSolveEvent>(OnAfterSolve);
        SubscribeLocalEvent<RequestShootEvent>(OnShootRequest);

        SubscribeLocalEvent<PredictedProjectileClientComponent, UpdateIsPredictedEvent>(OnClientProjectileUpdateIsPredicted);
        SubscribeLocalEvent<PredictedProjectileClientComponent, StartCollideEvent>(OnClientProjectileStartCollide);

        SubscribeLocalEvent<PredictedProjectileServerComponent, ComponentStartup>(OnServerProjectileStartup);

        UpdatesBefore.Add(typeof(TransformSystem));
    }

    private void OnBeforeSolve(ref PhysicsUpdateBeforeSolveEvent ev)
    {
        var query = EntityQueryEnumerator<PredictedProjectileClientComponent>();
        while (query.MoveNext(out var uid, out var predicted))
        {
            predicted.Coordinates = Transform(uid).Coordinates;
        }
    }

    private void OnAfterSolve(ref PhysicsUpdateAfterSolveEvent ev)
    {
        var query = EntityQueryEnumerator<PredictedProjectileClientComponent>();
        while (query.MoveNext(out var uid, out var predicted))
        {
            if (_timing.IsFirstTimePredicted)
                continue;

            if (predicted.Coordinates is { } coordinates)
                _transform.SetCoordinates(uid, coordinates);

            predicted.Coordinates = null;
        }
    }

    private void OnShootRequest(RequestShootEvent ev, EntitySessionEventArgs args)
    {
        if (_timing.IsFirstTimePredicted)
            return;

        _gun.ShootRequested(ev.Gun, ev.Coordinates, ev.Target, null, args.SenderSession);
    }

    private void OnClientProjectileUpdateIsPredicted(Entity<PredictedProjectileClientComponent> ent, ref UpdateIsPredictedEvent args)
    {
        args.IsPredicted = true;
    }

    private void OnClientProjectileStartCollide(Entity<PredictedProjectileClientComponent> ent, ref StartCollideEvent args)
    {
        if (ent.Comp.Hit)
            return;

        if (!TryComp(ent, out ProjectileComponent? projectile) ||
            !TryComp(ent, out PhysicsComponent? physics))
        {
            return;
        }

        var netEnt = GetNetEntity(args.OtherEntity);
        var pos = _transform.GetMapCoordinates(args.OtherEntity);
        var hit = new HashSet<(NetEntity, MapCoordinates)> { (netEnt, pos) };
        var ev = new PredictedProjectileHitEvent(ent.Owner.Id, hit);
        RaiseNetworkEvent(ev);

        _projectile.ProjectileCollide((ent, projectile, physics), args.OtherEntity);
    }

    private void OnServerProjectileStartup(Entity<PredictedProjectileServerComponent> ent, ref ComponentStartup args)
    {
        if (!GunPrediction)
            return;

        if (ent.Comp.ClientEnt != _player.LocalEntity)
            return;

        if (_ignorePredictionHideQuery.HasComp(ent))
            return;

        if (_spriteQuery.TryComp(ent, out var sprite))
            sprite.Visible = false;
    }

    public override void Update(float frameTime)
    {
        base.Update(frameTime);

        if (!_timing.IsFirstTimePredicted)
            return;

        // TODO gun prediction remove this once the client reliably detects collisions
        var projectiles = EntityQueryEnumerator<PredictedProjectileClientComponent, ProjectileComponent, PhysicsComponent>();
        while (projectiles.MoveNext(out var uid, out var predicted, out var projectile, out var physics))
        {
            if (predicted.Hit)
                continue;

            var contacts = _physics.GetContactingEntities(uid, physics, true);
            if (contacts.Count == 0)
                continue;

            var hit = new HashSet<(NetEntity, MapCoordinates)>();
            foreach (var contact in contacts)
            {
                var netEnt = GetNetEntity(contact);
                var pos = _transform.GetMapCoordinates(contact);
                hit.Add((netEnt, pos));
            }

            var ev = new PredictedProjectileHitEvent(uid.Id, hit);
            RaiseNetworkEvent(ev);

            _projectile.ProjectileCollide((uid, projectile, physics), contacts.First());
        }

        var predictedQuery = EntityQueryEnumerator<PredictedProjectileHitComponent, SpriteComponent, TransformComponent>();
        while (predictedQuery.MoveNext(out var hit, out var sprite, out var xform))
        {
            var origin = hit.Origin;
            var coordinates = xform.Coordinates;
            if (!origin.TryDistance(EntityManager, _transform, coordinates, out var distance) ||
                distance >= hit.Distance)
            {
                sprite.Visible = false;
            }
        }
    }

    public override void FrameUpdate(float frameTime)
    {
        base.FrameUpdate(frameTime);

        // TODO bullet prediction remove this when lerping doesnt make the client's entity slightly slower
        var projectiles = EntityQueryEnumerator<PredictedProjectileClientComponent, TransformComponent>();
        while (projectiles.MoveNext(out _, out var xform))
        {
            xform.ActivelyLerping = false;
        }
    }
}