using System.Collections.Generic;
using UnityEngine;

namespace BaseGames.Enemies.Abilities
{
    /// <summary>
    /// 多攻击选招器：从候选（category==Attack）里按"射程 + 冷却 + LOS + 着地"过滤，
    /// 再按 <see cref="AttackSelectionMode"/> 选一个。纯逻辑、无 MonoBehaviour 依赖，可单测。
    /// </summary>
    public sealed class EnemyAttackSelector
    {
        private readonly List<IAttackCandidate> _candidates;

        public EnemyAttackSelector(IEnumerable<IAttackCandidate> candidates)
            => _candidates = new List<IAttackCandidate>(candidates);

        public int Count => _candidates.Count;

        private static bool Eligible(IAttackCandidate c, bool hasLOS, bool grounded)
            => c != null && c.CanUse && c.InAttackRange()
               && (!c.RequiresLineOfSight || hasLOS)
               && (!c.RequiresGrounded    || grounded);

        public bool HasEligible(bool hasLOS, bool grounded)
        {
            for (int i = 0; i < _candidates.Count; i++)
                if (Eligible(_candidates[i], hasLOS, grounded)) return true;
            return false;
        }

        public IAttackCandidate Select(bool hasLOS, bool grounded, AttackSelectionMode mode)
            => mode == AttackSelectionMode.Priority
                ? SelectByPriority(hasLOS, grounded)
                : SelectByWeight(hasLOS, grounded);

        private IAttackCandidate SelectByPriority(bool hasLOS, bool grounded)
        {
            IAttackCandidate best = null;
            for (int i = 0; i < _candidates.Count; i++)
            {
                var c = _candidates[i];
                if (!Eligible(c, hasLOS, grounded)) continue;
                if (best == null || c.Priority > best.Priority) best = c; // 并列取首个
            }
            return best;
        }

        private IAttackCandidate SelectByWeight(bool hasLOS, bool grounded)
        {
            float total = 0f;
            for (int i = 0; i < _candidates.Count; i++)
            {
                var c = _candidates[i];
                if (Eligible(c, hasLOS, grounded)) total += Mathf.Max(0f, c.Weight);
            }
            if (total <= 0f) return SelectByPriority(hasLOS, grounded); // 权重全 0 → 退化为确定性取首个合格
            float roll = Random.value * total;
            for (int i = 0; i < _candidates.Count; i++)
            {
                var c = _candidates[i];
                if (!Eligible(c, hasLOS, grounded)) continue;
                roll -= Mathf.Max(0f, c.Weight);
                if (roll <= 0f) return c;
            }
            return null; // 理论不达（浮点边界兜底）
        }
    }
}