using System;
using System.Collections.Generic;
using Cielonos.MainGame.Characters;
using UnityEngine;

namespace Cielonos.MainGame
{
    public partial class CombatManager
    {
        public partial class EnemySubmodule
        {
            /// <summary>
            /// 索敌评分结果。保留各分项，方便调试面板和后续权重调参。
            /// </summary>
            public struct TargetingScore
            {
                public Enemy target;
                public float totalScore;
                public float baseScore;
                public float bonusScore;
                public float distanceScore;
                public float inputDirScore;
                public float cameraFacingScore;
                public float stickyScore;
                public float lockOnScore;
            }

            private CharacterBase _lastHitTarget;
            private float _lastHitTime;

            private readonly TargetingScoreConfig _targetingConfig = new();

            /// <summary>
            /// 索敌评分配置。这里控制距离、输入方向、镜头朝向、粘滞目标、锁定目标等评分权重。
            /// </summary>
            public TargetingScoreConfig TargetingConfig => _targetingConfig;

            /// <summary>
            /// 记录最近命中的目标，用于让连续攻击在短时间内更倾向同一个敌人。
            /// </summary>
            public void SetLastHitTarget(CharacterBase target)
            {
                _lastHitTarget = target;
                _lastHitTime = Time.time;
            }

            /// <summary>
            /// 创建一条索敌查询链。默认从玩家位置出发，候选范围为全部活跃敌人。
            /// </summary>
            public TargetingQuery Query(TargetingScorePreset preset = TargetingScorePreset.Default)
            {
                return new TargetingQuery(this).UsePreset(preset);
            }

            /// <summary>
            /// 创建指定半径内的索敌查询链。
            /// </summary>
            public TargetingQuery Query(float radius, TargetingScorePreset preset = TargetingScorePreset.Default)
            {
                return new TargetingQuery(this).WithinRadius(radius).UsePreset(preset);
            }

            /// <summary>
            /// 创建基于已有候选列表的索敌查询链。
            /// </summary>
            public TargetingQuery Query(List<Enemy> candidates, TargetingScorePreset preset = TargetingScorePreset.Default)
            {
                return new TargetingQuery(this).FromCandidates(candidates).UsePreset(preset);
            }

            private List<TargetingScore> ScoreEnemies(List<Enemy> candidates, Vector3 origin, TargetingScoreConfig config = null)
            {
                if (candidates == null || candidates.Count == 0)
                {
                    return new List<TargetingScore>();
                }

                config ??= _targetingConfig;

                Camera camera = MainGameManager.Player.viewSc.playerCamera;
                Vector2 moveInput = MainGameManager.Player.inputSc.Move;
                bool hasInput = MainGameManager.Player.inputSc.IsMoving;

                // 将移动输入转成世界方向；有输入时，摇杆方向会成为强索敌意图。
                Vector3 inputWorldDir = Vector3.zero;
                if (hasInput)
                {
                    float cameraYaw = camera.transform.eulerAngles.y;
                    inputWorldDir = Quaternion.Euler(0f, cameraYaw, 0f) *
                                    new Vector3(moveInput.x, 0f, moveInput.y).normalized;
                }

                Vector3 cameraForward = camera.transform.forward;
                cameraForward.y = 0f;
                cameraForward.Normalize();

                CharacterBase lockTarget = MainGameManager.Player.viewSc.lockTargetModule.isLocking
                    ? MainGameManager.Player.viewSc.lockTargetModule.lockTarget
                    : null;

                // 最近命中目标会随时间衰减，避免攻击链在多敌人中频繁抖动换目标。
                float stickyFactor = 0f;
                if (_lastHitTarget != null && !_lastHitTarget.statusSm.isDead)
                {
                    float elapsed = Time.time - _lastHitTime;
                    stickyFactor = Mathf.Clamp01(1f - elapsed / config.stickyDecayTime);
                }

                float totalWeight = config.TotalWeight;
                if (totalWeight <= 0f)
                {
                    totalWeight = 1f;
                }

                float maxDist = 0f;
                for (int i = 0; i < candidates.Count; i++)
                {
                    Enemy enemy = candidates[i];
                    if (enemy == null || enemy.statusSm.isDead) continue;

                    float dist = GetSurfaceDistance(origin, enemy);
                    if (dist > maxDist)
                    {
                        maxDist = dist;
                    }
                }
                if (maxDist <= 0f)
                {
                    maxDist = 1f;
                }

                float inputCosThreshold = Mathf.Cos(config.inputConeHalfAngle * Mathf.Deg2Rad);
                float cameraCosThreshold = Mathf.Cos(config.cameraConeHalfAngle * Mathf.Deg2Rad);

                List<TargetingScore> results = new List<TargetingScore>(candidates.Count);

                for (int i = 0; i < candidates.Count; i++)
                {
                    Enemy enemy = candidates[i];
                    if (enemy == null || enemy.statusSm.isDead) continue;

                    Vector3 toEnemy = enemy.transform.position - origin;
                    toEnemy.y = 0f;
                    float centerDistance = toEnemy.magnitude;
                    float distance = GetSurfaceDistance(origin, enemy);
                    Vector3 toEnemyDir = centerDistance > 0.01f ? toEnemy / centerDistance : Vector3.zero;

                    TargetingScore score = new TargetingScore { target = enemy };

                    // 1. 距离分：越近越高。
                    score.distanceScore = 1f - Mathf.Clamp01(distance / maxDist);

                    // 2. 输入方向分：有移动输入时，优先选玩家指向的敌人；无输入时不惩罚任何目标。
                    if (hasInput && toEnemyDir.sqrMagnitude > 0f)
                    {
                        float dot = Vector3.Dot(inputWorldDir, toEnemyDir);
                        score.inputDirScore = dot >= inputCosThreshold
                            ? Mathf.InverseLerp(inputCosThreshold, 1f, dot)
                            : 0f;
                    }
                    else
                    {
                        score.inputDirScore = 1f;
                    }

                    // 3. 镜头朝向分：用于辅助无输入或弱输入时的自然索敌。
                    if (cameraForward.sqrMagnitude > 0f && toEnemyDir.sqrMagnitude > 0f)
                    {
                        float dot = Vector3.Dot(cameraForward, toEnemyDir);
                        score.cameraFacingScore = dot >= cameraCosThreshold
                            ? Mathf.InverseLerp(cameraCosThreshold, 1f, dot)
                            : 0f;
                    }
                    else
                    {
                        score.cameraFacingScore = 0f;
                    }

                    // 4. 粘滞分：短时间内维持攻击目标，减少目标跳变。
                    score.stickyScore = enemy == _lastHitTarget ? stickyFactor : 0f;

                    // 5. 锁定分：锁定目标在常规评分中获得额外倾向，但不会强制覆盖所有查询。
                    score.lockOnScore = lockTarget != null && enemy == lockTarget ? 1f : 0f;

                    score.baseScore =
                        (config.distanceWeight * score.distanceScore
                         + config.inputDirectionWeight * score.inputDirScore
                         + config.cameraFacingWeight * score.cameraFacingScore
                         + config.stickyWeight * score.stickyScore
                         + config.lockOnWeight * score.lockOnScore)
                        / totalWeight;
                    score.bonusScore = 0f;
                    score.totalScore = score.baseScore;

                    results.Add(score);
                }

                results.Sort((a, b) => b.totalScore.CompareTo(a.totalScore));
                return results;
            }

            private Enemy GetValidLockonTarget(Vector3 origin, float radius, List<Enemy> candidates)
            {
                var lockModule = MainGameManager.Player.viewSc.lockTargetModule;
                if (!lockModule.isLocking || lockModule.lockTarget == null)
                {
                    return null;
                }

                Enemy lockTarget = lockModule.lockTarget;
                if (candidates != null && !candidates.Contains(lockTarget))
                {
                    return null;
                }

                return IsEnemyInRadius(lockTarget, origin, radius) ? lockTarget : null;
            }

            /// <summary>
            /// 链式索敌查询。调用侧应尽量通过这套 API 表达索敌意图：
            /// CombatManager.EnemySm.Query(4f).PreferDisruptable().Best();
            /// Query 会缓存候选列表和评分结果，仅建议在一次决策中临时使用，不要跨帧保存为字段。
            /// </summary>
            public sealed class TargetingQuery
            {
                private readonly EnemySubmodule _enemySm;
                private readonly List<Predicate<Enemy>> _filters = new List<Predicate<Enemy>>();
                private readonly List<ScoreModifier> _scoreModifiers = new List<ScoreModifier>();
                private readonly List<Enemy> _excludedTargets = new List<Enemy>();

                private Transform _originTransform;
                private Vector3 _originPosition;
                private bool _hasOriginPosition;
                private float _radius = float.MaxValue;
                private SortingType _sortingType = SortingType.Nearest;
                private TargetingScoreConfig _scoreConfig;
                private List<Enemy> _sourceCandidates;

                private List<Enemy> _cachedCandidates;
                private List<TargetingScore> _cachedScores;
                private Vector3 _cachedOrigin;
                private bool _hasCachedOrigin;
                private int _cachedFrame = -1;
                private int _cachedTargetingVersion = -1;

                public TargetingQuery(EnemySubmodule enemySm)
                {
                    _enemySm = enemySm;
                }

                /// <summary>
                /// 设置索敌原点为某个 Transform。评分和半径都会使用它的当前位置。
                /// </summary>
                public TargetingQuery From(Transform origin)
                {
                    _originTransform = origin;
                    _hasOriginPosition = false;
                    Invalidate();
                    return this;
                }

                /// <summary>
                /// 设置索敌原点为固定世界坐标，适合爆炸、弹体、攻击区域等非角色来源。
                /// </summary>
                public TargetingQuery From(Vector3 origin)
                {
                    _originPosition = origin;
                    _originTransform = null;
                    _hasOriginPosition = true;
                    Invalidate();
                    return this;
                }

                /// <summary>
                /// 限制候选目标半径。
                /// </summary>
                public TargetingQuery WithinRadius(float radius)
                {
                    _radius = radius;
                    Invalidate();
                    return this;
                }

                /// <summary>
                /// 使用外部已经筛好的候选列表继续索敌。
                /// </summary>
                public TargetingQuery FromCandidates(List<Enemy> candidates)
                {
                    _sourceCandidates = candidates != null ? new List<Enemy>(candidates) : null;
                    Invalidate();
                    return this;
                }

                /// <summary>
                /// 设置候选列表的基础排序，主要用于 Candidates/Nearest。
                /// </summary>
                public TargetingQuery SortBy(SortingType sortingType)
                {
                    _sortingType = sortingType;
                    Invalidate();
                    return this;
                }

                public TargetingQuery UsePreset(TargetingScorePreset preset)
                {
                    _scoreConfig = TargetingScoreConfig.CreatePreset(preset);
                    InvalidateScores();
                    return this;
                }
                
                /// <summary>
                /// 从候选目标中排除单个敌人。
                /// </summary>
                public TargetingQuery Exclude(Enemy target)
                {
                    if (target != null && !_excludedTargets.Contains(target))
                    {
                        _excludedTargets.Add(target);
                        Invalidate();
                    }

                    return this;
                }

                /// <summary>
                /// 从候选目标中排除一组敌人。
                /// </summary>
                public TargetingQuery Exclude(IEnumerable<Enemy> targets)
                {
                    if (targets == null)
                    {
                        return this;
                    }

                    foreach (Enemy target in targets)
                    {
                        if (target != null && !_excludedTargets.Contains(target))
                        {
                            _excludedTargets.Add(target);
                        }
                    }

                    Invalidate();
                    return this;
                }

                /// <summary>
                /// 硬过滤候选目标。不符合条件的敌人会直接从 Candidates/Scores/Best 中移除。
                /// </summary>
                public TargetingQuery Where(Predicate<Enemy> match)
                {
                    if (match == null)
                    {
                        return this;
                    }

                    _filters.Add(match);
                    Invalidate();
                    return this;
                }

                /// <summary>
                /// 只保留存活敌人。默认候选列表已做该过滤，显式调用可增强复杂查询的语义。
                /// </summary>
                public TargetingQuery OnlyAlive()
                {
                    return Where(enemy => enemy != null && !enemy.statusSm.isDead);
                }

                /// <summary>
                /// 只保留屏幕内可见的敌人。
                /// </summary>
                public TargetingQuery OnlyInScreen()
                {
                    return Where(IsInScreen);
                }

                /// <summary>
                /// 只保留当前索敌系统认为可见的敌人。目前等同于屏幕内目标，后续可扩展遮挡判定。
                /// </summary>
                public TargetingQuery OnlyVisible()
                {
                    return OnlyInScreen();
                }

                /// <summary>
                /// 只保留可被指定 Breakthrough 类型打断的敌人。
                /// </summary>
                public TargetingQuery OnlyDisruptable(Breakthrough.Type breakthroughType = Breakthrough.Type.Disruption)
                {
                    return Where(enemy => _enemySm.IsDisruptable(enemy, breakthroughType));
                }

                /// <summary>
                /// 对符合条件的目标施加额外评分。offset 是固定加分，amplifier 是按基础分放大。
                /// </summary>
                public TargetingQuery Prefer(Predicate<Enemy> match, float offset = 1f, float amplifier = 0f)
                {
                    if (match == null)
                    {
                        return this;
                    }

                    _scoreModifiers.Add(new ScoreModifier(match, amplifier, offset));
                    InvalidateScores();
                    return this;
                }

                /// <summary>
                /// 提高可被 Breakthrough 打断目标的优先级。
                /// </summary>
                public TargetingQuery PreferDisruptable(float offset = 1f,
                    Breakthrough.Type breakthroughType = Breakthrough.Type.Disruption, float amplifier = 0f)
                {
                    return Prefer(enemy => _enemySm.IsDisruptable(enemy, breakthroughType), offset, amplifier);
                }

                /// <summary>
                /// 锁定目标优先的终端查询：如果锁定目标在本次候选范围内则直接返回，否则返回 Best()。
                /// </summary>
                public Enemy LockonFirst()
                {
                    Enemy lockTarget = _enemySm.GetValidLockonTarget(Origin, _radius, ResolveCandidates());
                    return lockTarget != null ? lockTarget : Best();
                }

                /// <summary>
                /// 返回当前查询的候选敌人列表。列表按 SortBy 指定规则排序，默认最近优先。
                /// </summary>
                public List<Enemy> Candidates()
                {
                    return new List<Enemy>(ResolveCandidates());
                }

                /// <summary>
                /// 返回完整评分结果，按 totalScore 从高到低排序。
                /// </summary>
                public List<TargetingScore> Scores()
                {
                    return new List<TargetingScore>(ResolveScores());
                }

                /// <summary>
                /// 返回综合评分最高的敌人。
                /// </summary>
                public Enemy Best()
                {
                    return ResolveScores().BestEnemy();
                }

                /// <summary>
                /// 返回综合评分最高的前 count 个敌人。
                /// </summary>
                public List<Enemy> Best(int count)
                {
                    return ResolveScores().BestEnemies(count);
                }

                /// <summary>
                /// 返回距离原点最近的敌人，不进行综合评分。
                /// </summary>
                public Enemy Nearest()
                {
                    List<Enemy> candidates = ResolveCandidates();
                    return candidates.Count > 0 ? candidates[0] : null;
                }

                /// <summary>
                /// 返回距离原点最近的前 count 个敌人，不进行综合评分。
                /// </summary>
                public List<Enemy> Nearest(int count)
                {
                    List<Enemy> candidates = ResolveCandidates();
                    List<Enemy> result = new List<Enemy>(Mathf.Min(count, candidates.Count));
                    for (int i = 0; i < candidates.Count && i < count; i++)
                    {
                        result.Add(candidates[i]);
                    }

                    return result;
                }

                /// <summary>
                /// 当前候选列表中是否存在可被 Breakthrough 打断的敌人。
                /// </summary>
                public bool AnyDisruptable(Breakthrough.Type breakthroughType = Breakthrough.Type.Disruption)
                {
                    List<Enemy> candidates = ResolveCandidates();
                    for (int i = 0; i < candidates.Count; i++)
                    {
                        if (_enemySm.IsDisruptable(candidates[i], breakthroughType))
                        {
                            return true;
                        }
                    }

                    return false;
                }

                private Vector3 Origin
                {
                    get
                    {
                        if (_hasOriginPosition)
                        {
                            return _originPosition;
                        }

                        return _originTransform != null ? _originTransform.position : MainGameManager.Player.transform.position;
                    }
                }

                private List<Enemy> ResolveCandidates()
                {
                    InvalidateIfStale();
                    if (_cachedCandidates != null)
                    {
                        return _cachedCandidates;
                    }

                    Vector3 origin = Origin;
                    List<Enemy> candidates = _sourceCandidates == null
                        ? _enemySm.CollectEnemiesInRadius(origin, _radius, _sortingType)
                        : FilterSourceCandidates(origin);

                    if (_excludedTargets.Count > 0)
                    {
                        for (int i = candidates.Count - 1; i >= 0; i--)
                        {
                            if (_excludedTargets.Contains(candidates[i]))
                            {
                                candidates.RemoveAt(i);
                            }
                        }
                    }

                    ApplyFilters(candidates);

                    SortCandidates(candidates, origin);
                    _cachedCandidates = candidates;
                    _cachedOrigin = origin;
                    _hasCachedOrigin = true;
                    _cachedFrame = Time.frameCount;
                    _cachedTargetingVersion = _enemySm.TargetingVersion;
                    return _cachedCandidates;
                }

                private List<TargetingScore> ResolveScores()
                {
                    InvalidateIfStale();
                    if (_cachedScores != null)
                    {
                        return _cachedScores;
                    }

                    List<TargetingScore> scores = _enemySm.ScoreEnemies(ResolveCandidates(), Origin, _scoreConfig);
                    foreach (ScoreModifier modifier in _scoreModifiers)
                    {
                        scores.ApplyScoreModifier(modifier.match, modifier.amplifier, modifier.offset);
                    }

                    _cachedScores = scores;
                    _cachedOrigin = Origin;
                    _hasCachedOrigin = true;
                    _cachedFrame = Time.frameCount;
                    _cachedTargetingVersion = _enemySm.TargetingVersion;
                    return _cachedScores;
                }

                private List<Enemy> FilterSourceCandidates(Vector3 origin)
                {
                    List<Enemy> candidates = new List<Enemy>(_sourceCandidates.Count);
                    for (int i = 0; i < _sourceCandidates.Count; i++)
                    {
                        Enemy enemy = _sourceCandidates[i];
                        if (enemy == null || enemy.statusSm.isDead)
                        {
                            continue;
                        }

                        if (_radius < float.MaxValue && !_enemySm.IsEnemyInRadius(enemy, origin, _radius))
                        {
                            continue;
                        }

                        candidates.Add(enemy);
                    }

                    return candidates;
                }

                private void ApplyFilters(List<Enemy> candidates)
                {
                    if (_filters.Count == 0)
                    {
                        return;
                    }

                    for (int i = candidates.Count - 1; i >= 0; i--)
                    {
                        Enemy enemy = candidates[i];
                        for (int j = 0; j < _filters.Count; j++)
                        {
                            if (!_filters[j](enemy))
                            {
                                candidates.RemoveAt(i);
                                break;
                            }
                        }
                    }
                }

                private void SortCandidates(List<Enemy> candidates, Vector3 origin)
                {
                    if (_sortingType == SortingType.Nearest)
                    {
                        candidates.Sort((a, b) =>
                            _enemySm.GetSurfaceDistance(origin, a)
                                .CompareTo(_enemySm.GetSurfaceDistance(origin, b)));
                    }
                    else if (_sortingType == SortingType.Farthest)
                    {
                        candidates.Sort((a, b) =>
                            _enemySm.GetSurfaceDistance(origin, b)
                                .CompareTo(_enemySm.GetSurfaceDistance(origin, a)));
                    }
                }

                private static bool IsInScreen(Enemy enemy)
                {
                    if (enemy == null || enemy.statusSm.isDead)
                    {
                        return false;
                    }

                    Vector3 screenPos = MainGameManager.Player.viewSc.playerCamera.WorldToScreenPoint(enemy.CenterPoint.position);
                    return screenPos.z > 0f &&
                           screenPos.x > 0f && screenPos.x < Screen.width &&
                           screenPos.y > 0f && screenPos.y < Screen.height;
                }

                private void Invalidate()
                {
                    _cachedCandidates = null;
                    _cachedScores = null;
                    _hasCachedOrigin = false;
                    _cachedFrame = -1;
                    _cachedTargetingVersion = -1;
                }

                private void InvalidateScores()
                {
                    _cachedScores = null;
                }

                private void InvalidateIfStale()
                {
                    if (_cachedFrame < 0)
                    {
                        return;
                    }

                    if (_cachedFrame == Time.frameCount &&
                        _cachedTargetingVersion == _enemySm.TargetingVersion &&
                        (!_hasCachedOrigin || _cachedOrigin == Origin))
                    {
                        return;
                    }

                    _cachedCandidates = null;
                    _cachedScores = null;
                    _hasCachedOrigin = false;
                    _cachedFrame = -1;
                    _cachedTargetingVersion = -1;
                }

                private readonly struct ScoreModifier
                {
                    public readonly Predicate<Enemy> match;
                    public readonly float amplifier;
                    public readonly float offset;

                    public ScoreModifier(Predicate<Enemy> match, float amplifier, float offset)
                    {
                        this.match = match;
                        this.amplifier = amplifier;
                        this.offset = offset;
                    }
                }
            }
        }
    }

    public static class TargetingSystemExtensions
    {
        public static List<CombatManager.EnemySubmodule.TargetingScore> ApplyScoreModifier(
            this List<CombatManager.EnemySubmodule.TargetingScore> scores,
            List<Enemy> boostTargets, float amplifier, float offset = 0)
        {
            return scores.ApplyScoreModifier(Predicate, amplifier, offset);

            bool Predicate(Enemy target)
            {
                return boostTargets != null && boostTargets.Contains(target);
            }
        }

        public static List<CombatManager.EnemySubmodule.TargetingScore> ApplyScoreModifier(
            this List<CombatManager.EnemySubmodule.TargetingScore> scores,
            Predicate<Enemy> match, float amplifier, float offset = 0)
        {
            bool changed = false;
            for (int i = 0; i < scores.Count; i++)
            {
                if (!match(scores[i].target)) continue;

                CombatManager.EnemySubmodule.TargetingScore s = scores[i];
                s.bonusScore += s.baseScore * amplifier + offset;
                s.totalScore = s.baseScore + s.bonusScore;
                scores[i] = s;
                changed = true;
            }

            if (changed)
            {
                scores.Sort((a, b) => b.totalScore.CompareTo(a.totalScore));
            }

            return scores;
        }

        public static Enemy BestEnemy(this List<CombatManager.EnemySubmodule.TargetingScore> scores)
        {
            return scores.Count > 0 ? scores[0].target : null;
        }

        public static List<Enemy> BestEnemies(this List<CombatManager.EnemySubmodule.TargetingScore> scores, int count)
        {
            List<Enemy> result = new List<Enemy>(Mathf.Min(count, scores.Count));
            for (int i = 0; i < scores.Count && i < count; i++)
            {
                result.Add(scores[i].target);
            }

            return result;
        }
    }
}