tbd-station-14/Content.Shared/Weapons/Reflect/SharedReflectSystem.cs

using System.Diagnostics.CodeAnalysis;
using System.Numerics;
using Content.Shared.Administration.Logs;
using Content.Shared.Audio;
using Content.Shared.Database;
using Content.Shared.Hands.Components;
using Content.Shared.Weapons.Ranged.Events;
using Content.Shared.Inventory;
using Content.Shared.Inventory.Events;
using Robust.Shared.Physics.Components;
using Content.Shared.Popups;
using Content.Shared.Projectiles;
using Content.Shared.Weapons.Ranged.Components;
using Robust.Shared.Network;
using Robust.Shared.Physics.Systems;
using Robust.Shared.Random;

namespace Content.Shared.Weapons.Reflect;

/// <summary>
/// This handles reflecting projectiles and hitscan shots.
/// </summary>
public abstract class SharedReflectSystem : EntitySystem
{
    [Dependency] private readonly INetManager _netManager = default!;
    [Dependency] private readonly IRobustRandom _random = default!;
    [Dependency] private readonly ISharedAdminLogManager _adminLogger = default!;
    [Dependency] private readonly SharedPopupSystem _popup = default!;
    [Dependency] private readonly SharedPhysicsSystem _physics = default!;
    [Dependency] private readonly SharedAudioSystem _audio = default!;
    [Dependency] private readonly SharedTransformSystem _transform = default!;
    [Dependency] private readonly InventorySystem _inventorySystem = default!;

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

        SubscribeLocalEvent<HandsComponent, ProjectileReflectAttemptEvent>(OnHandReflectProjectile);
        SubscribeLocalEvent<HandsComponent, HitScanReflectAttemptEvent>(OnHandsReflectHitscan);

        SubscribeLocalEvent<ReflectComponent, ProjectileReflectAttemptEvent>(OnReflectCollide);
        SubscribeLocalEvent<ReflectComponent, HitScanReflectAttemptEvent>(OnReflectHitscan);

        SubscribeLocalEvent<ReflectComponent, GotEquippedEvent>(OnReflectEquipped);
        SubscribeLocalEvent<ReflectComponent, GotUnequippedEvent>(OnReflectUnequipped);
    }

    private void OnReflectCollide(EntityUid uid, ReflectComponent component, ref ProjectileReflectAttemptEvent args)
    {
        if (args.Cancelled)
        {
            return;
        }

        if (TryReflectProjectile(uid, args.ProjUid, reflect: component))
            args.Cancelled = true;
    }

    private void OnHandReflectProjectile(EntityUid uid, HandsComponent hands, ref ProjectileReflectAttemptEvent args)
    {
        if (args.Cancelled)
            return;

        if (hands.ActiveHandEntity != null && TryReflectProjectile(hands.ActiveHandEntity.Value, args.ProjUid))
            args.Cancelled = true;
    }

    private bool TryReflectProjectile(EntityUid reflector, EntityUid projectile, ProjectileComponent? projectileComp = null, ReflectComponent? reflect = null)
    {
        if (!Resolve(reflector, ref reflect, false) ||
            !reflect.Enabled ||
            !TryComp<ReflectiveComponent>(projectile, out var reflective) ||
            (reflect.Reflects & reflective.Reflective) == 0x0 ||
            !_random.Prob(reflect.ReflectProb) ||
            !TryComp<PhysicsComponent>(projectile, out var physics))
        {
            return false;
        }

        var rotation = _random.NextAngle(-reflect.Spread / 2, reflect.Spread / 2).Opposite();
        var existingVelocity = _physics.GetMapLinearVelocity(projectile, component: physics);
        var relativeVelocity = existingVelocity - _physics.GetMapLinearVelocity(reflector);
        var newVelocity = rotation.RotateVec(relativeVelocity);

        // Have the velocity in world terms above so need to convert it back to local.
        var difference = newVelocity - existingVelocity;

        _physics.SetLinearVelocity(projectile, physics.LinearVelocity + difference, body: physics);

        var locRot = Transform(projectile).LocalRotation;
        var newRot = rotation.RotateVec(locRot.ToVec());
        _transform.SetLocalRotation(projectile, newRot.ToAngle());

        if (_netManager.IsServer)
        {
            _popup.PopupEntity(Loc.GetString("reflect-shot"), reflector);
            _audio.PlayPvs(reflect.SoundOnReflect, reflector, AudioHelpers.WithVariation(0.05f, _random));
        }

        if (Resolve(projectile, ref projectileComp, false))
        {
            _adminLogger.Add(LogType.BulletHit, LogImpact.Medium, $"{ToPrettyString(reflector)} reflected {ToPrettyString(projectile)} from {ToPrettyString(projectileComp.Weapon)} shot by {projectileComp.Shooter}");

            projectileComp.Shooter = reflector;
            projectileComp.Weapon = reflector;
            Dirty(projectileComp);
        }
        else
        {
            _adminLogger.Add(LogType.BulletHit, LogImpact.Medium, $"{ToPrettyString(reflector)} reflected {ToPrettyString(projectile)}");
        }

        return true;
    }

    private void OnHandsReflectHitscan(EntityUid uid, HandsComponent hands, ref HitScanReflectAttemptEvent args)
    {
        if (args.Reflected || hands.ActiveHandEntity == null)
            return;

        if (TryReflectHitscan(hands.ActiveHandEntity.Value, args.Shooter, args.SourceItem, args.Direction, out var dir))
        {
            args.Direction = dir.Value;
            args.Reflected = true;
        }
    }

    private void OnReflectHitscan(EntityUid uid, ReflectComponent component, ref HitScanReflectAttemptEvent args)
    {
        if (args.Reflected ||
            (component.Reflects & args.Reflective) == 0x0)
        {
            return;
        }

        if (TryReflectHitscan(uid, args.Shooter, args.SourceItem, args.Direction, out var dir))
        {
            args.Direction = dir.Value;
            args.Reflected = true;
        }
    }

    private bool TryReflectHitscan(EntityUid reflector, EntityUid? shooter, EntityUid shotSource, Vector2 direction,
        [NotNullWhen(true)] out Vector2? newDirection)
    {
        if (!TryComp<ReflectComponent>(reflector, out var reflect) ||
            !reflect.Enabled ||
            !_random.Prob(reflect.ReflectProb))
        {
            newDirection = null;
            return false;
        }

        if (_netManager.IsServer)
        {
            _popup.PopupEntity(Loc.GetString("reflect-shot"), reflector);
            _audio.PlayPvs(reflect.SoundOnReflect, reflector, AudioHelpers.WithVariation(0.05f, _random));
        }

        var spread = _random.NextAngle(-reflect.Spread / 2, reflect.Spread / 2);
        newDirection = -spread.RotateVec(direction);

        if (shooter != null)
            _adminLogger.Add(LogType.HitScanHit, LogImpact.Medium, $"{ToPrettyString(reflector)} reflected hitscan from {ToPrettyString(shotSource)} shot by {ToPrettyString(shooter.Value)}");
        else
            _adminLogger.Add(LogType.HitScanHit, LogImpact.Medium, $"{ToPrettyString(reflector)} reflected hitscan from {ToPrettyString(shotSource)}");

        return true;
    }

    private void OnReflectEquipped(EntityUid uid, ReflectComponent comp, GotEquippedEvent args)
    {

        if (!TryComp(args.Equipee, out ReflectComponent? reflection))
            return;

        reflection.Enabled = true;

        // reflection probability should be: (1 - old probability) * newly-equipped item probability + old probability
        // example: if entity has .25 reflection and newly-equipped item has .7, entity should have (1 - .25) * .7 + .25 = .775
        reflection.ReflectProb += (1 - reflection.ReflectProb) * comp.ReflectProb;

    }

    private void OnReflectUnequipped(EntityUid uid, ReflectComponent comp, GotUnequippedEvent args)
    {

        if (!TryComp(args.Equipee, out ReflectComponent? reflection))
            return;

        if (!_inventorySystem.TryGetSlots(args.Equipee, out var slotDef))
            return;

        // you could recalculate reflectprob with new = (old - component) / (1 - component), but component=1 introduces loss
        // still need to either maintain a counter or loop through all slots to determine reflection.enabled anyway?
        float newProb = 1;
        var reflecting = false;

        foreach (var slot in slotDef)
        {
            if (!_inventorySystem.TryGetSlotEntity(args.Equipee, slot.Name, out var slotEnt))
                continue;

            if (!TryComp(slotEnt, out ReflectComponent? refcomp))
                continue;

            reflecting = true;
            var prob = refcomp.ReflectProb;
            newProb -= newProb * prob;
        }

        reflection.ReflectProb = 1 - newProb;
        reflection.Enabled = reflecting;
    }
}