using System;
using Cielonos.MainGame.Buffs.Character;
using Cielonos.MainGame.Characters;
using SLSUtilities.General;

namespace Cielonos.MainGame.Inventory.Collections
{
    /// <summary>
    /// 时空乱流 / Spacetime Turbulence
    /// 降低直接攻击伤害，并将被降低的部分转化为 Decay。
    /// </summary>
    public class SpacetimeTurbulence : PassiveEquipmentBase
    {
        private const string EventKey = nameof(SpacetimeTurbulence);
        private const string DamageReductionAttribute = "DamageReduction";
        private const string DecayMultiplierAttribute = "DecayMultiplier";

        // 数值越高越先执行；减伤应处于 onBeforeDamageApplied 的末端。
        private const int BeforeDamagePriority = -100;
        // 让 Decay 在攻击完成后尽早施加，供后续攻击完成事件和受击事件读取。
        private const int FinishAttackPriority = 100;

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

            Action<AttackAreaBase, CharacterBase, Attack.Result> onBeforeDamageApplied = OnBeforeDamageApplied;
            player.eventSm.onBeforeDamageApplied.InsertByPriority(
                EventKey, onBeforeDamageApplied.ToPrioritized(BeforeDamagePriority));

            Action<AttackAreaBase, CharacterBase, Attack.Result> onFinishAttack = OnFinishAttack;
            player.eventSm.onFinishAttack.InsertByPriority(
                EventKey, onFinishAttack.ToPrioritized(FinishAttackPriority));
        }

        public override void OnDiscarded()
        {
            player.eventSm.onBeforeDamageApplied.Remove(EventKey);
            player.eventSm.onFinishAttack.Remove(EventKey);
            base.OnDiscarded();
        }

        private void OnBeforeDamageApplied(AttackAreaBase attackArea, CharacterBase target, Attack.Result result)
        {
            if (target is not Enemy)
            {
                return;
            }

            result.value.damageMultiplier *= (1 - passiveAttributeSm.GetItemAttribute(DamageReductionAttribute));
        }

        private void OnFinishAttack(AttackAreaBase attackArea, CharacterBase target, Attack.Result result)
        {
            if (target is not Enemy || result.causedDeath)
            {
                return;
            }

            float reducedDamage = result.finalDamage + result.shieldBlockedDamage;
            if (reducedDamage <= 0f)
            {
                return;
            }

            float damageMultiplier = (1 - passiveAttributeSm.GetItemAttribute(DamageReductionAttribute));
            if (damageMultiplier <= 0f)
            {
                return;
            }

            // 当前直接伤害为原伤害的 damageMultiplier，反推被降低部分后再乘 Decay 系数。
            float decayDamage = reducedDamage * (1f - damageMultiplier) / damageMultiplier;
            decayDamage *= passiveAttributeSm.GetItemAttribute(DecayMultiplierAttribute);
            if (decayDamage <= 0f)
            {
                return;
            }

            new Decay(decayDamage).Apply(target, player, this);
        }
    }
}