using System.Collections.Generic;
using ProjectM.Simulation;
using Unity.Entities;
using Unity.NetCode;
using Unity.Transforms;
using UnityEngine;

namespace ProjectM.Client
{
    /// <summary>
    /// Client-only DYNAMIC LIGHT layer (Phase 1.5 lighting pass — dark ambient, dynamic-light-first): pooled
    /// point lights that follow projectile ghosts, a pulsing portal light during the RoomExplore loot window
    /// (same <see cref="RegionMath.ExpeditionPortalPos"/> authority the beacon + HUD prompt use), a soft glow
    /// on resource nodes, and short impact FLASHES fed by CombatFeedbackSystem's burst funnel via
    /// <see cref="RequestFlash"/>. Observe-only <see cref="SystemBase"/> in
    /// <see cref="PresentationSystemGroup"/> (once per frame, no rollback double-fire); never mutates the sim;
    /// Entity keys are pruned every frame (a pruned ghost = despawn); lights are pooled GameObjects under a
    /// private root, NEVER scene-saved. Knobs live in <see cref="DynamicLightConfig"/> (defaults when absent).
    /// Wall-clock time is fine here (presentation only). URP: point lights, shadows off.
    /// </summary>
    [WorldSystemFilter(WorldSystemFilterFlags.ClientSimulation)]
    [UpdateInGroup(typeof(PresentationSystemGroup))]
    public partial class DynamicLightSystem : SystemBase
    {
        struct FlashRequest { public Vector3 Pos; public Color Color; public float Scale; }
        struct ActiveFlash { public Light Light; public float EndTime; public float BaseIntensity; public float Duration; }

        // Static request queue: CombatFeedbackSystem (same thread, PresentationSystemGroup) enqueues, we drain.
        static readonly List<FlashRequest> Pending = new List<FlashRequest>();

        [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.SubsystemRegistration)]
        static void ResetStatics() { Pending.Clear(); }

        /// <summary>Queue a short impact flash. <paramref name="color"/> with a==0 means "use the config
        /// default colour"; <paramref name="scale"/> scales intensity+range (clamped by the drainer).</summary>
        public static void RequestFlash(Vector3 pos, Color color, float scale)
        {
            if (Pending.Count < 64) Pending.Add(new FlashRequest { Pos = pos, Color = color, Scale = scale });
        }

        GameObject _root;
        readonly Dictionary<Entity, Light> _projectileLights = new Dictionary<Entity, Light>();
        readonly Dictionary<Entity, Light> _nodeLights = new Dictionary<Entity, Light>();
        readonly HashSet<Entity> _seen = new HashSet<Entity>();
        readonly List<Entity> _dead = new List<Entity>();
        readonly Stack<Light> _pool = new Stack<Light>();
        readonly List<ActiveFlash> _flashes = new List<ActiveFlash>();
        Light _portalLight;

        protected override void OnDestroy()
        {
            if (_root != null) Object.Destroy(_root);
        }

        protected override void OnUpdate()
        {
            if (UnityEngine.SceneManagement.SceneManager.GetActiveScene().name != "Game") return;
            var cfg = DynamicLightConfig.Instance;
            bool enabled = cfg == null || cfg.Enabled;
            if (!enabled)
            {
                Pending.Clear();
                if (_root != null && _root.activeSelf) _root.SetActive(false);
                return;
            }
            if (_root == null)
            {
                _root = new GameObject("~DynamicLights");
                Object.DontDestroyOnLoad(_root);
            }
            if (!_root.activeSelf) _root.SetActive(true);

            // ---- projectile lights (pooled follow-lights) ----
            int projCap = cfg != null ? cfg.MaxProjectileLights : 24;
            Color projColor = cfg != null ? cfg.ProjectileColor : new Color(0.45f, 0.85f, 1f, 1f);
            float projIntensity = cfg != null ? cfg.ProjectileIntensity : 2.6f;
            float projRange = cfg != null ? cfg.ProjectileRange : 7f;
            Color enemyProjColor = cfg != null ? cfg.EnemyProjectileColor : new Color(0.55f, 1f, 0.35f, 1f);
            _seen.Clear();
            foreach (var (lt, entity) in SystemAPI.Query<RefRO<LocalTransform>>().WithAll<Projectile>().WithEntityAccess())
            {
                _seen.Add(entity);
                if (!_projectileLights.TryGetValue(entity, out var light))
                {
                    if (_projectileLights.Count >= projCap) continue;
                    light = Rent();
                    _projectileLights[entity] = light;
                }
                // Attack-distinctness: owned shots glow the player cyan; un-owned (enemy spit) glows toxic green.
                light.color = EntityManager.HasComponent<GhostOwner>(entity) ? projColor : enemyProjColor;
                light.intensity = projIntensity;
                light.range = projRange;
                var p = lt.ValueRO.Position;
                light.transform.position = new Vector3(p.x, p.y + 0.4f, p.z);
            }
            PruneUnseen(_projectileLights);

            // ---- resource-node glow ----
            bool nodeGlow = cfg == null || cfg.NodeGlow;
            int nodeCap = cfg != null ? cfg.MaxNodeLights : 12;
            Color nodeColor = cfg != null ? cfg.NodeColor : new Color(0.40f, 1f, 0.75f, 1f);
            float nodeIntensity = cfg != null ? cfg.NodeIntensity : 1.3f;
            float nodeRange = cfg != null ? cfg.NodeRange : 4.5f;
            _seen.Clear();
            if (nodeGlow)
            {
                foreach (var (lt, entity) in SystemAPI.Query<RefRO<LocalTransform>>().WithAll<ResourceNode>().WithEntityAccess())
                {
                    _seen.Add(entity);
                    if (!_nodeLights.TryGetValue(entity, out var light))
                    {
                        if (_nodeLights.Count >= nodeCap) continue;
                        light = Rent();
                        _nodeLights[entity] = light;
                    }
                    light.color = nodeColor;
                    // scale the glow with the node's harvest-shrink so it fades as the node depletes
                    light.intensity = nodeIntensity * Mathf.Clamp01(lt.ValueRO.Scale);
                    light.range = nodeRange;
                    var p = lt.ValueRO.Position;
                    light.transform.position = new Vector3(p.x, p.y + 1.1f, p.z);
                }
            }
            PruneUnseen(_nodeLights);

            // ---- portal light (RoomExplore only) ----
            bool portalOn = false;
            if (SystemAPI.TryGetSingleton<RunInfo>(out var runInfo)
                && runInfo.Lifecycle == RunLifecycle.RoomExplore
                && SystemAPI.TryGetSingleton<BaseAnchor>(out var anchor))
            {
                portalOn = true;
                var pos = RegionMath.ExpeditionPortalPos(BaseGridMath.PlotCenter(anchor), (byte)(runInfo.CurrentRoom & 1));
                if (_portalLight == null) _portalLight = Rent();
                float baseI = cfg != null ? cfg.PortalIntensity : 3.5f;
                float amp = cfg != null ? cfg.PortalPulseAmp : 1.2f;
                _portalLight.color = cfg != null ? cfg.PortalColor : new Color(0.55f, 0.95f, 1f, 1f);
                _portalLight.range = cfg != null ? cfg.PortalRange : 13f;
                _portalLight.intensity = baseI + amp * Mathf.Sin(UnityEngine.Time.time * 4f);
                _portalLight.transform.position = new Vector3(pos.x, pos.y + 2.2f, pos.z);
            }
            if (!portalOn && _portalLight != null) { Return(_portalLight); _portalLight = null; }

            // ---- impact flashes ----
            float now = UnityEngine.Time.time;
            int flashCap = cfg != null ? cfg.MaxFlashLights : 8;
            Color flashDefault = cfg != null ? cfg.FlashDefaultColor : new Color(1f, 0.85f, 0.55f, 1f);
            float flashIntensity = cfg != null ? cfg.FlashIntensity : 3.2f;
            float flashRange = cfg != null ? cfg.FlashRange : 6.5f;
            float flashDur = cfg != null ? cfg.FlashDuration : 0.18f;
            for (int i = 0; i < Pending.Count; i++)
            {
                if (_flashes.Count >= flashCap) break;
                var req = Pending[i];
                float scale = Mathf.Clamp(req.Scale, 0.3f, 1.6f);
                var light = Rent();
                light.color = req.Color.a > 0f ? req.Color : flashDefault;
                light.intensity = flashIntensity * scale;
                light.range = flashRange * Mathf.Sqrt(scale);
                light.transform.position = req.Pos + new Vector3(0f, 0.6f, 0f);
                _flashes.Add(new ActiveFlash { Light = light, EndTime = now + flashDur, BaseIntensity = light.intensity, Duration = flashDur });
            }
            Pending.Clear();
            for (int i = _flashes.Count - 1; i >= 0; i--)
            {
                var f = _flashes[i];
                float remain = f.EndTime - now;
                if (remain <= 0f) { Return(f.Light); _flashes.RemoveAt(i); continue; }
                f.Light.intensity = f.BaseIntensity * (remain / f.Duration);
            }
        }

        void PruneUnseen(Dictionary<Entity, Light> map)
        {
            _dead.Clear();
            foreach (var kv in map)
                if (!_seen.Contains(kv.Key)) _dead.Add(kv.Key);
            for (int i = 0; i < _dead.Count; i++)
            {
                Return(map[_dead[i]]);
                map.Remove(_dead[i]);
            }
        }

        Light Rent()
        {
            while (_pool.Count > 0)
            {
                var pooled = _pool.Pop();
                if (pooled == null) continue; // scene reload can null pooled objects
                pooled.gameObject.SetActive(true);
                return pooled;
            }
            var go = new GameObject("PointLight");
            go.transform.SetParent(_root.transform, false);
            var light = go.AddComponent<Light>();
            light.type = LightType.Point;
            light.shadows = LightShadows.None;
            return light;
        }

        void Return(Light light)
        {
            if (light == null) return;
            light.gameObject.SetActive(false);
            _pool.Push(light);
        }
    }
}