tbd-station-14/Content.Server/Hands/Systems/HandsSystem.cs

using System.Numerics;
using Content.Server.Inventory;
using Content.Server.Stack;
using Content.Server.Stunnable;
using Content.Shared.ActionBlocker;
using Content.Shared.Body.Part;
using Content.Shared.CombatMode;
using Content.Shared.Damage.Systems;
using Content.Shared.Explosion;
using Content.Shared.Hands.Components;
using Content.Shared.Hands.EntitySystems;
using Content.Shared.Input;
using Content.Shared.Inventory.VirtualItem;
using Content.Shared.Movement.Pulling.Components;
using Content.Shared.Movement.Pulling.Events;
using Content.Shared.Movement.Pulling.Systems;
using Content.Shared.Stacks;
using Content.Shared.Standing;
using Content.Shared.Throwing;
using Robust.Shared.GameStates;
using Robust.Shared.Input.Binding;
using Robust.Shared.Map;
using Robust.Shared.Physics.Components;
using Robust.Shared.Player;
using Robust.Shared.Random;
using Robust.Shared.Timing;
using Robust.Shared.Utility;

namespace Content.Server.Hands.Systems
{
    public sealed class HandsSystem : SharedHandsSystem
    {
        [Dependency] private readonly IGameTiming _timing = default!;
        [Dependency] private readonly IRobustRandom _random = default!;
        [Dependency] private readonly StackSystem _stackSystem = default!;
        [Dependency] private readonly VirtualItemSystem _virtualItemSystem = default!;
        [Dependency] private readonly ActionBlockerSystem _actionBlockerSystem = default!;
        [Dependency] private readonly SharedTransformSystem _transformSystem = default!;
        [Dependency] private readonly PullingSystem _pullingSystem = default!;
        [Dependency] private readonly ThrowingSystem _throwingSystem = default!;

        private EntityQuery<PhysicsComponent> _physicsQuery;

        /// <summary>
        /// Items dropped when the holder falls down will be launched in
        /// a direction offset by up to this many degrees from the holder's
        /// movement direction.
        /// </summary>
        private const float DropHeldItemsSpread = 45;

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

            SubscribeLocalEvent<HandsComponent, DisarmedEvent>(OnDisarmed, before: new[] {typeof(StunSystem), typeof(StaminaSystem)});

            SubscribeLocalEvent<HandsComponent, PullStartedMessage>(HandlePullStarted);
            SubscribeLocalEvent<HandsComponent, PullStoppedMessage>(HandlePullStopped);

            SubscribeLocalEvent<HandsComponent, BodyPartAddedEvent>(HandleBodyPartAdded);
            SubscribeLocalEvent<HandsComponent, BodyPartRemovedEvent>(HandleBodyPartRemoved);

            SubscribeLocalEvent<HandsComponent, ComponentGetState>(GetComponentState);

            SubscribeLocalEvent<HandsComponent, BeforeExplodeEvent>(OnExploded);

            SubscribeLocalEvent<HandsComponent, DropHandItemsEvent>(OnDropHandItems);

            CommandBinds.Builder
                .Bind(ContentKeyFunctions.ThrowItemInHand, new PointerInputCmdHandler(HandleThrowItem))
                .Register<HandsSystem>();

            _physicsQuery = GetEntityQuery<PhysicsComponent>();
        }

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

            CommandBinds.Unregister<HandsSystem>();
        }

        private void GetComponentState(EntityUid uid, HandsComponent hands, ref ComponentGetState args)
        {
            args.State = new HandsComponentState(hands);
        }


        private void OnExploded(Entity<HandsComponent> ent, ref BeforeExplodeEvent args)
        {
            if (ent.Comp.DisableExplosionRecursion)
                return;

            foreach (var hand in ent.Comp.Hands.Values)
            {
                if (hand.HeldEntity is { } uid)
                    args.Contents.Add(uid);
            }
        }

        private void OnDisarmed(EntityUid uid, HandsComponent component, DisarmedEvent args)
        {
            if (args.Handled)
                return;

            // Break any pulls
            if (TryComp(uid, out PullerComponent? puller) && TryComp(puller.Pulling, out PullableComponent? pullable))
                _pullingSystem.TryStopPull(puller.Pulling.Value, pullable);

            var offsetRandomCoordinates = _transformSystem.GetMoverCoordinates(args.Target).Offset(_random.NextVector2(1f, 1.5f));
            if (!ThrowHeldItem(args.Target, offsetRandomCoordinates))
                return;

            args.PopupPrefix = "disarm-action-";

            args.Handled = true; // no shove/stun.
        }

        private void HandleBodyPartAdded(EntityUid uid, HandsComponent component, ref BodyPartAddedEvent args)
        {
            if (args.Part.Comp.PartType != BodyPartType.Hand)
                return;

            // If this annoys you, which it should.
            // Ping Smugleaf.
            var location = args.Part.Comp.Symmetry switch
            {
                BodyPartSymmetry.None => HandLocation.Middle,
                BodyPartSymmetry.Left => HandLocation.Left,
                BodyPartSymmetry.Right => HandLocation.Right,
                _ => throw new ArgumentOutOfRangeException(nameof(args.Part.Comp.Symmetry))
            };

            AddHand(uid, args.Slot, location);
        }

        private void HandleBodyPartRemoved(EntityUid uid, HandsComponent component, ref BodyPartRemovedEvent args)
        {
            if (args.Part.Comp.PartType != BodyPartType.Hand)
                return;

            RemoveHand(uid, args.Slot);
        }

        #region pulling

        private void HandlePullStarted(EntityUid uid, HandsComponent component, PullStartedMessage args)
        {
            if (args.PullerUid != uid)
                return;

            if (TryComp<PullerComponent>(args.PullerUid, out var pullerComp) && !pullerComp.NeedsHands)
                return;

            if (!_virtualItemSystem.TrySpawnVirtualItemInHand(args.PulledUid, uid))
            {
                DebugTools.Assert("Unable to find available hand when starting pulling??");
            }
        }

        private void HandlePullStopped(EntityUid uid, HandsComponent component, PullStoppedMessage args)
        {
            if (args.PullerUid != uid)
                return;

            // Try find hand that is doing this pull.
            // and clear it.
            foreach (var hand in component.Hands.Values)
            {
                if (hand.HeldEntity == null
                    || !TryComp(hand.HeldEntity, out VirtualItemComponent? virtualItem)
                    || virtualItem.BlockingEntity != args.PulledUid)
                {
                    continue;
                }

                TryDrop(args.PullerUid, hand, handsComp: component);
                break;
            }
        }

        #endregion

        #region interactions

        private bool HandleThrowItem(ICommonSession? playerSession, EntityCoordinates coordinates, EntityUid entity)
        {
            if (playerSession?.AttachedEntity is not {Valid: true} player || !Exists(player) || !coordinates.IsValid(EntityManager))
                return false;

            return ThrowHeldItem(player, coordinates);
        }

        /// <summary>
        /// Throw the player's currently held item.
        /// </summary>
        public bool ThrowHeldItem(EntityUid player, EntityCoordinates coordinates, float minDistance = 0.1f)
        {
            if (ContainerSystem.IsEntityInContainer(player) ||
                !TryComp(player, out HandsComponent? hands) ||
                hands.ActiveHandEntity is not { } throwEnt ||
                !_actionBlockerSystem.CanThrow(player, throwEnt))
                return false;

            if (_timing.CurTime < hands.NextThrowTime)
                return false;
            hands.NextThrowTime = _timing.CurTime + hands.ThrowCooldown;

            if (EntityManager.TryGetComponent(throwEnt, out StackComponent? stack) && stack.Count > 1 && stack.ThrowIndividually)
            {
                var splitStack = _stackSystem.Split(throwEnt, 1, EntityManager.GetComponent<TransformComponent>(player).Coordinates, stack);

                if (splitStack is not {Valid: true})
                    return false;

                throwEnt = splitStack.Value;
            }

            var direction = _transformSystem.ToMapCoordinates(coordinates).Position - _transformSystem.GetWorldPosition(player);
            if (direction == Vector2.Zero)
                return true;

            var length = direction.Length();
            var distance = Math.Clamp(length, minDistance, hands.ThrowRange);
            direction *= distance / length;

            var throwSpeed = hands.BaseThrowspeed;

            // Let other systems change the thrown entity (useful for virtual items)
            // or the throw strength.
            var ev = new BeforeThrowEvent(throwEnt, direction, throwSpeed, player);
            RaiseLocalEvent(player, ref ev);

            if (ev.Cancelled)
                return true;

            // This can grief the above event so we raise it afterwards
            if (IsHolding(player, throwEnt, out _, hands) && !TryDrop(player, throwEnt, handsComp: hands))
                return false;

            _throwingSystem.TryThrow(ev.ItemUid, ev.Direction, ev.ThrowSpeed, ev.PlayerUid, compensateFriction: !HasComp<LandAtCursorComponent>(ev.ItemUid));

            return true;
        }

        private void OnDropHandItems(Entity<HandsComponent> entity, ref DropHandItemsEvent args)
        {
            // If the holder doesn't have a physics component, they ain't moving
            var holderVelocity = _physicsQuery.TryComp(entity, out var physics) ? physics.LinearVelocity : Vector2.Zero;
            var spreadMaxAngle = Angle.FromDegrees(DropHeldItemsSpread);

            var fellEvent = new FellDownEvent(entity);
            RaiseLocalEvent(entity, fellEvent, false);

            foreach (var hand in entity.Comp.Hands.Values)
            {
                if (hand.HeldEntity is not EntityUid held)
                    continue;

                var throwAttempt = new FellDownThrowAttemptEvent(entity);
                RaiseLocalEvent(hand.HeldEntity.Value, ref throwAttempt);

                if (throwAttempt.Cancelled)
                    continue;

                if (!TryDrop(entity, hand, null, checkActionBlocker: false, handsComp: entity.Comp))
                    continue;

                // Rotate the item's throw vector a bit for each item
                var angleOffset = _random.NextAngle(-spreadMaxAngle, spreadMaxAngle);
                // Rotate the holder's velocity vector by the angle offset to get the item's velocity vector
                var itemVelocity = angleOffset.RotateVec(holderVelocity);
                // Decrease the distance of the throw by a random amount
                itemVelocity *= _random.NextFloat(1f);
                // Heavier objects don't get thrown as far
                // If the item doesn't have a physics component, it isn't going to get thrown anyway, but we'll assume infinite mass
                itemVelocity *= _physicsQuery.TryComp(held, out var heldPhysics) ? heldPhysics.InvMass : 0;
                // Throw at half the holder's intentional throw speed and
                // vary the speed a little to make it look more interesting
                var throwSpeed = entity.Comp.BaseThrowspeed * _random.NextFloat(0.45f, 0.55f);

                _throwingSystem.TryThrow(held,
                    itemVelocity,
                    throwSpeed,
                    entity,
                    pushbackRatio: 0,
                    compensateFriction: false
                );
            }
        }

        #endregion
    }
}