cirnogodot/Scripts/Components/Actors/DamageReceiver3D.cs

using System.Linq;
using Cirno.Scripts.Resources;
using Cirno.Scripts.Utils;
using Cirno.Scripts.Weapons;
using Cirno.Scripts.Components.FSM.Enemy._3D;
using Godot;
using Godot.Collections;

namespace Cirno.Scripts.Components.Actors;

public partial class DamageReceiver3D : Area3D, IHittable
{
    [Export] public ActorResourceProvider HealthProvider { get; private set; }

    [Export] public bool Invulnerable { get; private set; } = false;

    [Export] public BulletOwner BulletGroup { get; set; } = BulletOwner.None;

    [Export] public PackedScene Debris { get; set; }

    [Export] public Array<DamageResistance> DamageResistances { get; set; } = [];

    [Export] public bool DeleteParentOnDeath { get; private set; } = true;

    [Signal]
    public delegate void ShieldHitEventHandler();

    [Signal]
    public delegate void BulletHitEventHandler(Bullet3D bullet, Vector3 position, Vector3 direction);

    //[Signal] public delegate void DeathEventHandler();

    private Node3D _parent;

    public bool Enabled { get; private set; } = true;

    public override void _Ready()
    {
        _parent = GetParent<Node3D>();
        HealthProvider.FillResource();
        HealthProvider.ResourceDepleted += OnDeath;
    }

    public void ChangeState(bool enabled)
    {
        Enabled = enabled;
    }

    private void _on_damage_hitbox_area_entered(Area3D area)
    {
        if (!Enabled) return;
        if (area is not Bullet3D bullet) return;
        if (Invulnerable)
        {
            EmitSignalShieldHit();
            return;
        }

        if (BulletGroup is BulletOwner.None)
        {
            this.Hit(bullet.Damage, bullet.DamageType);

            EmitSignalBulletHit(bullet, area.GlobalPosition, (this.GlobalPosition - area.GlobalPosition).Normalized());

            // Attribute XP if this hit was lethal
            if (HealthProvider.CurrentResource <= 0 && bullet.BulletInfo?.SourceWeapon != null)
            {
                int xp = 0;
                if (GetParent() is EnemyProxy3D enemyProxy && enemyProxy.EnemyResource is not null)
                {
                    xp = (int)System.Math.Round(enemyProxy.EnemyResource.MotivationReward);
                }

                bullet.BulletInfo.SourceWeapon.GainExperience(xp);
            }

            bullet.RequestCollisionDestruction();
            return;
        }

        if (bullet.BulletInfo.Owner == BulletGroup) return;

        this.Hit(bullet.Damage, bullet.DamageType);

        EmitSignalBulletHit(bullet, area.GlobalPosition, (this.GlobalPosition - area.GlobalPosition).Normalized());

        // Attribute XP on lethal hit
        if (HealthProvider.CurrentResource <= 0 && bullet.BulletInfo?.SourceWeapon != null)
        {
            int xp = 0;
            if (GetParent() is EnemyProxy3D enemyProxy && enemyProxy.EnemyResource is not null)
            {
                xp = (int)System.Math.Round(enemyProxy.EnemyResource.MotivationReward);
            }

            bullet.BulletInfo.SourceWeapon.GainExperience(xp);
        }

        bullet.RequestCollisionDestruction();
    }

    public void Hit(float damage, DamageType damageType = DamageType.Neutral)
    {
        if (!Enabled) return;
        if (Invulnerable) return;

        // Change value based on difficulty
        float difficultyReducedDmg = damage * GlobalState.Instance.SessionSettings.DifficultyDamageMultiplier;

        var dmg = DamageResistances.Aggregate(difficultyReducedDmg,
            (current, resistance) => current * resistance.CalculateDamage(current, damageType));

        HealthProvider.CurrentResource -= dmg;
    }

    private void OnDeath()
    {
        if (Debris is not null)
        {
            _parent.CreateSibling<Node3D>(Debris);
        }

        // Not needed because the health provider is accessible
        //EmitSignal(SignalName.Death);

        if (DeleteParentOnDeath)
        {
            _parent.QueueFree();
        }
    }
}