using BaseGames.AI;

namespace BaseGames.Enemies
{
    /// <summary>
    /// 可复用的"待机/警觉/追击/巡逻"感知状态机（统一规则，见 spec《敌人感知↔状态》）。
    /// 纯决策：AI 只决定"进哪个状态 / 转换条件 / 每状态的移动意图或攻击能力"；
    /// 移动/朝向/动画/伤害的实现全部在 EnemyLocomotion 或攻击能力里（AI 不 actuate）。
    /// 规则：
    ///   待机/巡逻: 在追逐区→追击(优先); 否则 有警觉且在视野→警觉; 否则保持。
    ///   警觉:      在追逐区→追击; 否则 脱离视野→R; 否则保持警觉(朝向玩家)。
    ///   追击:      脱离全部感知(追逐区且视野区都不在)→R（永不回警觉）。
    /// 缺省自动降级：无警觉(HasAlert=false)→警觉分支不触发。
    /// 交战风格(Engagement)：默认 ChaseAbility=单一冲锋能力节点；
    ///   ApproachAttack=把追击换成 Approach(寻路逼近)↔Attack(到射程选招攻击、攻击时停逼近) 两态子机，
    ///   打完回逼近重判、脱离全部感知区→R。
    /// </summary>
    public static class PerceptionStateMachine
    {
        /// <summary>交战风格：单一冲锋能力，或"寻路逼近 + 选招攻击"两态子机。</summary>
        public enum EngagementStyle { ChaseAbility, ApproachAttack }

        public sealed class Config
        {
            public string Idle   = "Idle";
            public string Patrol = "Patrol";
            public string Alert  = "Alert";
            public string Chase  = "Chase";
            public string Death  = "Death";
            public string Entry  = "Idle";    // 初始态
            public string Rest   = "Patrol";  // R：降级(退出追击/警觉丢失)回到的静止态
            // 待机/巡逻/警觉的移动意图（由 EnemyLocomotion 执行）
            public LocomotionMode IdleMode   = LocomotionMode.Idle;
            public LocomotionMode PatrolMode = LocomotionMode.Patrol;
            public LocomotionMode AlertMode  = LocomotionMode.Face;  // 停 + 朝向玩家
            // 追击/死亡走能力（追击=接触伤害等战斗语义）
            public string ChaseAbilityId;
            public string DeathAbilityId;

            // 追击=带冷却的冲刺能力时开启（opt-in）：冲刺打完→巡逻(CD 期)，冷却结束且仍在追逐区→再冲刺。
            // 由冷却门控 Patrol→Chase，避免"CD 期在追逐区每帧 Chase↔Patrol 来回抖"。
            public bool PatrolBetweenChases = false;

            // 交战风格（默认冲锋能力，保持现状）；ApproachAttack 时启用 Approach↔Attack 两态子机。
            public EngagementStyle Engagement = EngagementStyle.ChaseAbility;
            public string ApproachState = "Approach";
            public string AttackState   = "Attack";
        }

        public static void Add(BrainBuilder b, Config c)
        {
            b.Entry(c.Entry);
            b.Global().To(c.Death).OnEvent(AiSignal.Died); // 受击致死 → 死亡（全局最高优先）

            // 进追击的条件：默认"在追逐区"。PatrolBetweenChases 时加冷却门——CD 中不回追击，
            // 使 Chase(冲刺)→Patrol(CD 巡逻)→Chase 循环不抖动。冷却门仅在冲锋能力风格下生效。
            string chaseId = c.ChaseAbilityId;
            System.Func<IAiContext, bool> canChase;
            string chaseLabel;
            if (c.Engagement == EngagementStyle.ChaseAbility && c.PatrolBetweenChases)
            {
                canChase   = x => x.Sensor.InChaseZone() && x.Combat.CanUseAbility(chaseId);
                chaseLabel = "InChaseZone+offCD";
            }
            else
            {
                canChase   = x => x.Sensor.InChaseZone();
                chaseLabel = "InChaseZone";
            }

            // 交战入口态：冲锋风格=Chase；逼近风格=Approach
            string combatEntry = c.Engagement == EngagementStyle.ApproachAttack ? c.ApproachState : c.Chase;

            // 待机 / 巡逻：未发现态，升级转换相同（追逐优先、其次警觉）
            AddLocomotionState(b, c.Idle, c.IdleMode)
                .To(combatEntry).When(canChase, chaseLabel)
                .To(c.Alert).When(x => HasAlert(x) && x.Sensor.InVisionZone(), "InVision+HasAlert");
            AddLocomotionState(b, c.Patrol, c.PatrolMode)
                .To(combatEntry).When(canChase, chaseLabel)
                .To(c.Alert).When(x => HasAlert(x) && x.Sensor.InVisionZone(), "InVision+HasAlert");

            // 警觉（仅升级路径出现）：进追逐区→追击；脱离视野→R；在视野内保持(朝向玩家)
            AddLocomotionState(b, c.Alert, c.AlertMode)
                .To(combatEntry).When(canChase, chaseLabel)
                .To(c.Rest).When(x => !x.Sensor.InVisionZone(), "leftVision");

            if (c.Engagement == EngagementStyle.ApproachAttack)
            {
                // Approach：寻路逼近；有招够得着→Attack；脱离全部感知→R
                b.State(c.ApproachState)
                    .OnEnter(x => x.Locomotion.Pursue(x.Sensor.LastKnown))
                    .Tick(x => x.Locomotion.Pursue(x.Sensor.LastKnown))
                    .OnExit(x => x.Locomotion.Stop())
                    .To(c.AttackState).When(x => x.Combat.HasEligibleAttack(), "attackInRange")
                    .To(c.Rest).When(x => !x.Sensor.InChaseZone() && !x.Sensor.InVisionZone(), "leftAllZones");

                // Attack：停逼近 + 选招攻击；打完回 Approach；脱离感知→R
                b.State(c.AttackState)
                    .OnEnter(x => { x.Locomotion.Stop(); x.Combat.UseBestAttack(); })
                    .OnExit(x => x.Combat.InterruptAbilities())
                    .To(c.ApproachState).When(x => !x.Combat.IsAbilityRunning(), "attackDone")
                    .To(c.Rest).When(x => !x.Sensor.InChaseZone() && !x.Sensor.InVisionZone(), "leftAllZones");
            }
            else
            {
                // 追击退出：
                //   PatrolBetweenChases: 冲刺打完(能力结束)→R(CD 期巡逻)；committed 冲锋不被感知丢失中途打断，
                //     是否再冲刺交由 Patrol 侧冷却门控。
                //   默认: 脱离全部感知(追逐区且视野区都不在)→R（永不回警觉）。
                var chase = AddAbilityState(b, c.Chase, chaseId);
                if (c.PatrolBetweenChases)
                    chase.To(c.Rest).When(x => !x.Combat.IsAbilityRunning(chaseId), "dashDone→CD");
                else
                    chase.To(c.Rest).When(x => !x.Sensor.InChaseZone() && !x.Sensor.InVisionZone(), "leftAllZones");
            }

            // 死亡：终态（无转出）；死亡演出走物理状态机
            AddAbilityState(b, c.Death, c.DeathAbilityId);
        }

        /// <summary>
        /// 一个"由 EnemyLocomotion 驱动"的状态：进入/每帧声明移动意图，离开时停。
        /// Face 模式每帧朝向最后已知玩家位置（Sensor.LastKnown 由 EnemyBrainContext.Refresh 维护）。
        /// </summary>
        static BrainBuilder.StateBuilder AddLocomotionState(BrainBuilder b, string state, LocomotionMode mode)
        {
            return b.State(state)
                .OnEnter(x => ApplyLocomotion(x, mode))
                .Tick(x => ApplyLocomotion(x, mode))
                .OnExit(x => x.Locomotion.Stop());
        }

        static void ApplyLocomotion(IAiContext x, LocomotionMode mode)
        {
            if (mode == LocomotionMode.Face) x.Locomotion.Face(x.Sensor.LastKnown);
            else x.Locomotion.SetMode(mode);
        }

        /// <summary>一个"由攻击能力驱动"的状态：进入/每帧确保能力运行(受击打断后重触发)，离开中断。</summary>
        static BrainBuilder.StateBuilder AddAbilityState(BrainBuilder b, string state, string abilityId)
        {
            return b.State(state)
                .OnEnter(x => EnsureAbility(x, abilityId))
                .Tick(x => EnsureAbility(x, abilityId))
                .OnExit(x => x.Combat.InterruptAbilities());
        }

        static void EnsureAbility(IAiContext x, string abilityId)
        {
            if (!string.IsNullOrEmpty(abilityId) && !x.Combat.IsAbilityRunning(abilityId))
                x.Combat.UseAbility(abilityId);
        }

        static bool HasAlert(IAiContext x) => x is IEnemyActor a && a.HasAlertState;
    }
}