using System.Collections.Generic;
using NUnit.Framework;
using BaseGames.Enemies.Abilities;

namespace BaseGames.Tests.EditMode.Enemies
{
    public class EnemyAttackSelectorTests
    {
        sealed class FakeCandidate : IAttackCandidate
        {
            public bool  CanUseV = true, InRange = true, ReqLOS = false, ReqGround = false, Executed;
            public float WeightV = 1f;
            public int   PriorityV = 0;
            public bool  CanUse => CanUseV;
            public bool  RequiresLineOfSight => ReqLOS;
            public bool  RequiresGrounded => ReqGround;
            public float Weight => WeightV;
            public int   Priority => PriorityV;
            public bool  InAttackRange() => InRange;
            public bool  Execute() { Executed = true; return true; }
        }

        static EnemyAttackSelector Sel(params IAttackCandidate[] cs)
            => new EnemyAttackSelector(new List<IAttackCandidate>(cs));

        [Test]
        public void Empty_NoEligible()
        {
            var s = Sel();
            Assert.IsFalse(s.HasEligible(true, true));
            Assert.IsNull(s.Select(true, true, AttackSelectionMode.Priority));
        }

        [Test]
        public void ExcludesOnCooldown()
        {
            var c = new FakeCandidate { CanUseV = false };
            Assert.IsFalse(Sel(c).HasEligible(true, true));
        }

        [Test]
        public void ExcludesOutOfRange()
        {
            var c = new FakeCandidate { InRange = false };
            Assert.IsFalse(Sel(c).HasEligible(true, true));
        }

        [Test]
        public void ExcludesWhenNeedsLOS_ButNoLOS()
        {
            var c = new FakeCandidate { ReqLOS = true };
            Assert.IsFalse(Sel(c).HasEligible(false, true));
            Assert.IsTrue (Sel(c).HasEligible(true,  true));
        }

        [Test]
        public void ExcludesWhenNeedsGrounded_ButAirborne()
        {
            var c = new FakeCandidate { ReqGround = true };
            Assert.IsFalse(Sel(c).HasEligible(true, false));
            Assert.IsTrue (Sel(c).HasEligible(true, true));
        }

        [Test]
        public void Priority_PicksHighest()
        {
            var lo = new FakeCandidate { PriorityV = 1 };
            var hi = new FakeCandidate { PriorityV = 5 };
            var pick = Sel(lo, hi).Select(true, true, AttackSelectionMode.Priority);
            Assert.AreSame(hi, pick);
        }

        [Test]
        public void Priority_TieTakesFirstInList()
        {
            var a = new FakeCandidate { PriorityV = 3 };
            var b = new FakeCandidate { PriorityV = 3 };
            var pick = Sel(a, b).Select(true, true, AttackSelectionMode.Priority);
            Assert.AreSame(a, pick);
        }

        [Test]
        public void Priority_SkipsIneligible()
        {
            var blocked = new FakeCandidate { PriorityV = 9, InRange = false };
            var ok      = new FakeCandidate { PriorityV = 1 };
            var pick = Sel(blocked, ok).Select(true, true, AttackSelectionMode.Priority);
            Assert.AreSame(ok, pick);
        }

        [Test]
        public void Weighted_SingleEligible_AlwaysThatOne()
        {
            var only = new FakeCandidate { WeightV = 2f };
            for (int i = 0; i < 20; i++)
                Assert.AreSame(only, Sel(only).Select(true, true, AttackSelectionMode.WeightedRandom));
        }

        [Test]
        public void Weighted_NeverPicksIneligible()
        {
            var bad = new FakeCandidate { WeightV = 100f, InRange = false };
            var ok  = new FakeCandidate { WeightV = 1f };
            for (int i = 0; i < 50; i++)
                Assert.AreSame(ok, Sel(bad, ok).Select(true, true, AttackSelectionMode.WeightedRandom));
        }

        // ── WeightedRandomAntiRepeat ─────────────────────────────────────────

        static EnemyAttackSelector SelAntiRepeat(float factor, params IAttackCandidate[] cs)
            => new EnemyAttackSelector(new List<IAttackCandidate>(cs), factor);

        [Test]
        public void AntiRepeat_ZeroFactor_NeverPicksSameTwiceWhenAlternativeExists()
        {
            var a = new FakeCandidate { WeightV = 1f };
            var b = new FakeCandidate { WeightV = 1f };
            var s = SelAntiRepeat(0f, a, b);

            var prev = s.Select(true, true, AttackSelectionMode.WeightedRandomAntiRepeat);
            for (int i = 0; i < 100; i++)
            {
                var cur = s.Select(true, true, AttackSelectionMode.WeightedRandomAntiRepeat);
                Assert.AreNotSame(prev, cur, "系数为 0 时不应连续选中同一招");
                prev = cur;
            }
        }

        [Test]
        public void AntiRepeat_ZeroFactor_SingleCandidate_StillReturnsIt()
        {
            // 只有一招时折扣会把权重压到 0，WeightedPick 返回 -1；
            // 必须退化为 Priority 路径把它选出来，否则敌人永远不出手。
            var only = new FakeCandidate { WeightV = 1f };
            var s = SelAntiRepeat(0f, only);

            for (int i = 0; i < 10; i++)
                Assert.AreSame(only, s.Select(true, true, AttackSelectionMode.WeightedRandomAntiRepeat));
        }

        [Test]
        public void AntiRepeat_DiscountsPreviousPick_ButDoesNotBanIt()
        {
            // 系数 0.5：a 被选过后权重折半，但仍有机会再被选中。
            var a = new FakeCandidate { WeightV = 1f };
            var b = new FakeCandidate { WeightV = 1f };
            var s = SelAntiRepeat(0.5f, a, b);

            s.Select(true, true, AttackSelectionMode.WeightedRandomAntiRepeat);
            int repeats = 0;
            var prev = s.LastPicked;
            for (int i = 0; i < 400; i++)
            {
                var cur = s.Select(true, true, AttackSelectionMode.WeightedRandomAntiRepeat);
                if (ReferenceEquals(cur, prev)) repeats++;
                prev = cur;
            }
            // 统计断言（无固定随机种子）：系数 0.5 → 每次重复概率 0.5/1.5≈1/3，
            // 400 次期望≈133，标准差≈9.4；下面的边界约 ±5σ，正确实现下几乎不可能红。
            const string msg = "系数 0.5 → 每次重复概率 0.5/1.5≈1/3，400 次期望≈133（±5σ 约 [90,180]）";
            Assert.Greater(repeats, 90,  "折扣不应等于禁用。" + msg);
            Assert.Less   (repeats, 180, "重复率明显高于预期，折扣可能未生效。" + msg);
        }

        [Test]
        public void AntiRepeat_IneligiblePrevious_DoesNotBlockOthers()
        {
            // 用系数 0.5 而非 0：若实现把折扣错误地施加在「资格归零」之前
            // （c.Weight * factor 而非 w * factor），冷却中的上一招会拿到 0.5 的权重而可能被选中。
            // 系数为 0 时那个 bug 也会算出 0，测试将永远通过、失去意义。
            var a = new FakeCandidate { WeightV = 1f };
            var b = new FakeCandidate { WeightV = 1f };
            var s = SelAntiRepeat(0.5f, a, b);

            var first = s.Select(true, true, AttackSelectionMode.WeightedRandomAntiRepeat);
            ((FakeCandidate)first).CanUseV = false;    // 上一招进冷却

            for (int i = 0; i < 20; i++)
            {
                var second = s.Select(true, true, AttackSelectionMode.WeightedRandomAntiRepeat);
                Assert.IsNotNull(second);
                Assert.AreNotSame(first, second, "冷却中的招不得因防重复折扣路径被选中");
            }
        }

        [Test]
        public void ResetRepeatMemory_RestoresUndiscountedWeights()
        {
            // 确定性用例：a 权重 1 / 优先级 0，b 权重 0 / 优先级 5。
            // 选中 a 后若不清记忆，a 被折扣到 0 → 全零 → 走 Priority 退化路径选出 b。
            // 清了记忆则 a 恢复权重 1，仍应选 a。因此该用例精确地在重置失效时变红。
            var a = new FakeCandidate { WeightV = 1f, PriorityV = 0 };
            var b = new FakeCandidate { WeightV = 0f, PriorityV = 5 };
            var s = SelAntiRepeat(0f, a, b);

            Assert.AreSame(a, s.Select(true, true, AttackSelectionMode.WeightedRandomAntiRepeat));
            s.ResetRepeatMemory();
            Assert.AreSame(a, s.Select(true, true, AttackSelectionMode.WeightedRandomAntiRepeat),
                           "清除防重复记忆后应恢复未折扣的权重分布");
        }

        [Test]
        public void AntiRepeat_FactorOne_AppliesNoPenalty()
        {
            // 系数 1.0 是 [Range] 的上界，语义为「不惩罚」：重复率应回到约 50%
            var a = new FakeCandidate { WeightV = 1f };
            var b = new FakeCandidate { WeightV = 1f };
            var s = SelAntiRepeat(1f, a, b);

            s.Select(true, true, AttackSelectionMode.WeightedRandomAntiRepeat);
            int repeats = 0;
            var prev = s.LastPicked;
            for (int i = 0; i < 400; i++)
            {
                var cur = s.Select(true, true, AttackSelectionMode.WeightedRandomAntiRepeat);
                if (ReferenceEquals(cur, prev)) repeats++;
                prev = cur;
            }
            Assert.Greater(repeats, 150,
                "系数 1.0 应无惩罚：重复概率≈50%，400 次期望≈200（σ≈10，150 约为 -5σ）");
        }

        [Test]
        public void AntiRepeat_ThreeCandidates_NoImmediateRepeat_AndAllReachable()
        {
            // 三候选：既验证折扣循环的下标没写错，也验证除上一招外其余候选都仍可达
            var a = new FakeCandidate { WeightV = 1f };
            var b = new FakeCandidate { WeightV = 1f };
            var c = new FakeCandidate { WeightV = 1f };
            var s = SelAntiRepeat(0f, a, b, c);

            var seen = new HashSet<IAttackCandidate>();
            var prev = s.Select(true, true, AttackSelectionMode.WeightedRandomAntiRepeat);
            seen.Add(prev);
            for (int i = 0; i < 200; i++)
            {
                var cur = s.Select(true, true, AttackSelectionMode.WeightedRandomAntiRepeat);
                Assert.AreNotSame(prev, cur, "系数为 0 时不应连续选中同一招");
                seen.Add(cur);
                prev = cur;
            }
            Assert.AreEqual(3, seen.Count, "三个等权候选应都能被选到");
        }

        [Test]
        public void PlainWeighted_DoesNotApplyAntiRepeat()
        {
            // WeightedRandom 模式下唯一候选恒被选中（回归：折扣不得泄漏到旧模式）
            var only = new FakeCandidate { WeightV = 1f };
            var s = SelAntiRepeat(0f, only);
            for (int i = 0; i < 10; i++)
                Assert.AreSame(only, s.Select(true, true, AttackSelectionMode.WeightedRandom));
        }
    }
}