CatStation/Content.Server/EntityEffects/Effects/Smite/HomingRodEntityEffectSystem.cs

using System.Numerics;
using Content.Server.Physics.Components;
using Content.Shared.EntityEffects;
using Content.Shared.EntityEffects.Effects.Smite;
using Content.Shared.Movement.Components;
using Robust.Shared.Random;
using Robust.Shared.Spawners;

namespace Content.Server.EntityEffects.Effects.Smite;

/// <summary>
/// Spawns a rod at a distance and makes it chase this entity.
/// </summary>
/// <inheritdoc cref="EntityEffectSystem{T, TEffect}"/>
public sealed partial class HomingRodEntityEffectSystem : EntityEffectSystem<MetaDataComponent, HomingRod>
{
    [Dependency] private IRobustRandom _random = default!;
    [Dependency] private SharedTransformSystem _transform = default!;

    protected override void Effect(Entity<MetaDataComponent> entity, ref EntityEffectEvent<HomingRod> args)
    {
        var speed = args.Effect.Speed;
        if (args.Effect.MatchTargetSprintSpeed &&
            TryComp<MovementSpeedModifierComponent>(entity, out var movement))
            speed = movement.CurrentSprintSpeed + 0.001f;

        if (speed <= 0)
            return;

        var offset = _random.NextAngle().RotateVec(new Vector2(args.Effect.Distance, 0));
        var spawnCoords = _transform.GetMapCoordinates(entity).Offset(offset);
        var rod = Spawn(args.Effect.Prototype, spawnCoords);

        EnsureComp<ChasingWalkComponent>(rod, out var chasing);
        chasing.NextChangeVectorTime = TimeSpan.MaxValue;
        chasing.ChasingEntity = entity.Owner;
        chasing.ImpulseInterval = 0.1f;
        chasing.RotateWithImpulse = true;
        chasing.MaxSpeed = speed;
        chasing.Speed = speed;

        if (TryComp<TimedDespawnComponent>(rod, out var despawn))
            despawn.Lifetime = offset.Length() / speed * 3;
    }
}