tbd-station-14/Content.Shared/Trigger/Systems/ScramOnTriggerSystem.cs

using System.Numerics;
using Content.Shared.Movement.Pulling.Components;
using Content.Shared.Movement.Pulling.Systems;
using Content.Shared.Physics;
using Content.Shared.Trigger.Components.Effects;
using Robust.Shared.Map;
using Robust.Shared.Map.Components;
using Robust.Shared.Network;
using Robust.Shared.Physics;
using Robust.Shared.Physics.Components;
using Robust.Shared.Audio.Systems;
using Robust.Shared.Collections;
using Robust.Shared.Random;

namespace Content.Shared.Trigger.Systems;

public sealed class ScramOnTriggerSystem : EntitySystem
{
    [Dependency] private readonly PullingSystem _pulling = default!;
    [Dependency] private readonly EntityLookupSystem _lookup = default!;
    [Dependency] private readonly SharedTransformSystem _transform = default!;
    [Dependency] private readonly IRobustRandom _random = default!;
    [Dependency] private readonly SharedMapSystem _map = default!;
    [Dependency] private readonly SharedAudioSystem _audio = default!;
    [Dependency] private readonly INetManager _net = default!;

    private EntityQuery<PhysicsComponent> _physicsQuery;
    private HashSet<Entity<MapGridComponent>> _targetGrids = new();

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

        SubscribeLocalEvent<ScramOnTriggerComponent, TriggerEvent>(OnTrigger);

        _physicsQuery = GetEntityQuery<PhysicsComponent>();
    }

    private void OnTrigger(Entity<ScramOnTriggerComponent> ent, ref TriggerEvent args)
    {
        if (args.Key != null && !ent.Comp.KeysIn.Contains(args.Key))
            return;

        var target = ent.Comp.TargetUser ? args.User : ent.Owner;

        if (target == null)
            return;

        // We need stop the user from being pulled so they don't just get "attached" with whoever is pulling them.
        // This can for example happen when the user is cuffed and being pulled.
        if (TryComp<PullableComponent>(target, out var pull) && _pulling.IsPulled(target.Value, pull))
            _pulling.TryStopPull(ent, pull);

        // Check if the user is pulling anything, and drop it if so.
        if (TryComp<PullerComponent>(target, out var puller) && TryComp<PullableComponent>(puller.Pulling, out var pullable))
            _pulling.TryStopPull(puller.Pulling.Value, pullable);

        _audio.PlayPredicted(ent.Comp.TeleportSound, ent, args.User);

        // Can't predict picking random grids and the target location might be out of PVS range.
        if (_net.IsClient)
            return;

        var xform = Transform(target.Value);
        var targetCoords = SelectRandomTileInRange(xform, ent.Comp.TeleportRadius);

        if (targetCoords != null)
        {
            _transform.SetCoordinates(target.Value, targetCoords.Value);
            args.Handled = true;
        }
    }

    private EntityCoordinates? SelectRandomTileInRange(TransformComponent userXform, float radius)
    {
        var userCoords = _transform.ToMapCoordinates(userXform.Coordinates);
        _targetGrids.Clear();
        _lookup.GetEntitiesInRange(userCoords, radius, _targetGrids);
        Entity<MapGridComponent>? targetGrid = null;

        if (_targetGrids.Count == 0)
            return null;

        // Give preference to the grid the entity is currently on.
        // This does not guarantee that if the probability fails that the owner's grid won't be picked.
        // In reality the probability is higher and depends on the number of grids.
        if (userXform.GridUid != null && TryComp<MapGridComponent>(userXform.GridUid, out var gridComp))
        {
            var userGrid = new Entity<MapGridComponent>(userXform.GridUid.Value, gridComp);
            if (_random.Prob(0.5f))
            {
                _targetGrids.Remove(userGrid);
                targetGrid = userGrid;
            }
        }

        if (targetGrid == null)
            targetGrid = _random.GetRandom().PickAndTake(_targetGrids);

        EntityCoordinates? targetCoords = null;

        do
        {
            var valid = false;

            var range = (float)Math.Sqrt(radius);
            var box = Box2.CenteredAround(userCoords.Position, new Vector2(range, range));
            var tilesInRange = _map.GetTilesEnumerator(targetGrid.Value.Owner, targetGrid.Value.Comp, box, false);
            var tileList = new ValueList<Vector2i>();

            while (tilesInRange.MoveNext(out var tile))
            {
                tileList.Add(tile.GridIndices);
            }

            while (tileList.Count != 0)
            {
                var tile = tileList.RemoveSwap(_random.Next(tileList.Count));
                valid = true;
                foreach (var entity in _map.GetAnchoredEntities(targetGrid.Value.Owner, targetGrid.Value.Comp,
                             tile))
                {
                    if (!_physicsQuery.TryGetComponent(entity, out var body))
                        continue;

                    if (body.BodyType != BodyType.Static ||
                        !body.Hard ||
                        (body.CollisionLayer & (int)CollisionGroup.MobMask) == 0)
                        continue;

                    valid = false;
                    break;
                }

                if (valid)
                {
                    targetCoords = new EntityCoordinates(targetGrid.Value.Owner,
                        _map.TileCenterToVector(targetGrid.Value, tile));
                    break;
                }
            }

            if (valid || _targetGrids.Count == 0) // if we don't do the check here then PickAndTake will blow up on an empty set.
                break;

            targetGrid = _random.GetRandom().PickAndTake(_targetGrids);
        } while (true);

        return targetCoords;
    }
}