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

namespace ProjectM.Client
{
    /// <summary>
    /// Client-only AMBIENT MOTION layer (Phase 1.5 "world alive" — the anti-static beat, zero netcode):
    ///   - per-biome DRIFT particles (meadow motes / arid wind-blown dust / cavern motes / blight spores) from
    ///     one world-space emitter that follows the camera; palette keys on camera-X region + the replicated
    ///     per-room biome, mirroring <see cref="WorldAtmosphereSystem"/>'s switch
    ///   - idle SWAY on the cosmetic flora prop roots near the camera (Game.unity classic layer; probed
    ///     2026-07-09: 212 flora roots, none static-batched, LOD children follow the root)
    ///   - walk-through RUSTLE: flora brushed by the LOCAL player (the GhostOwnerIsLocal idiom) gets an
    ///     energy pulse that shakes and decays
    /// Observe-only <see cref="SystemBase"/> in <see cref="PresentationSystemGroup"/>; wall-clock time is fine
    /// (presentation). Rotations write around a cached base so the layer is lossless when toggled off.
    /// Knobs live in <see cref="AmbientMotionConfig"/> (defaults when absent).
    /// </summary>
    [WorldSystemFilter(WorldSystemFilterFlags.ClientSimulation)]
    [UpdateInGroup(typeof(PresentationSystemGroup))]
    public partial class AmbientMotionSystem : SystemBase
    {
        static readonly System.Text.RegularExpressions.Regex FloraName = new System.Text.RegularExpressions.Regex(
            "bush|grass|flower|fern|groundcover|ground_cover|wildflower|clover|reed|succulent|cactus",
            System.Text.RegularExpressions.RegexOptions.IgnoreCase);

        struct Flora
        {
            public Transform T;
            public Vector3 Pos;
            public Quaternion BaseRot;
            public float Phase;
            public float RustleEnergy;
        }

        readonly List<Flora> _flora = new List<Flora>(256);
        bool _floraCached;
        string _sceneKey;
        Camera _cam;
        GameObject _root;
        ParticleSystem _drift;
        int _biomeKey = -1;

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

        protected override void OnUpdate()
        {
            var scene = UnityEngine.SceneManagement.SceneManager.GetActiveScene();
            if (scene.name != "Game") { RestoreFlora(); _floraCached = false; return; }
            if (_cam == null) _cam = Camera.main;
            if (_cam == null) return;

            var cfg = AmbientMotionConfig.Instance;
            bool enabled = cfg == null || cfg.Enabled;
            if (!enabled)
            {
                RestoreFlora();
                if (_drift != null && _drift.isPlaying) _drift.Stop();
                return;
            }

            if (!_floraCached || _sceneKey != scene.path) CacheFlora(scene);

            UpdateDrift(cfg);
            UpdateSwayAndRustle(cfg);
        }

        // ---------- flora cache ----------

        void CacheFlora(UnityEngine.SceneManagement.Scene scene)
        {
            RestoreFlora();
            _flora.Clear();
            foreach (var root in scene.GetRootGameObjects())
            {
                if (root.name != "BaseBiome" && !root.name.StartsWith("ExpeditionBiome")) continue;
                foreach (var t in root.GetComponentsInChildren<Transform>(false))
                {
                    if (!FloraName.IsMatch(t.gameObject.name)) continue;
                    if (t.gameObject.name.Contains("LOD")) continue; // prop roots only; LOD children follow
                    if (t.GetComponent<LODGroup>() == null && t.GetComponent<MeshRenderer>() == null) continue;
                    var p = t.position;
                    _flora.Add(new Flora
                    {
                        T = t,
                        Pos = p,
                        BaseRot = t.localRotation,
                        Phase = (p.x * 12.9898f + p.z * 78.233f) % 6.2831f,
                        RustleEnergy = 0f,
                    });
                }
            }
            _floraCached = true;
            _sceneKey = scene.path;
        }

        void RestoreFlora()
        {
            for (int i = 0; i < _flora.Count; i++)
                if (_flora[i].T != null) _flora[i].T.localRotation = _flora[i].BaseRot;
        }

        // ---------- biome drift particles ----------

        void UpdateDrift(AmbientMotionConfig cfg)
        {
            bool driftOn = cfg == null || cfg.DriftEnabled;
            if (!driftOn)
            {
                if (_drift != null && _drift.isPlaying) _drift.Stop();
                return;
            }
            if (_root == null)
            {
                _root = new GameObject("~AmbientMotion");
                Object.DontDestroyOnLoad(_root);
            }
            if (_drift == null)
            {
                var mat = FeedbackFx.MakeParticleMaterial("AmbientDrift");
                _drift = FeedbackFx.MakeBurst(_root.transform, "Drift", mat, Color.white,
                    0.09f, 0.15f, 9f, 600, gravity: 0f, shapeRadius: 1f, sizeTail: 0.9f);
                var main = _drift.main;
                main.simulationSpace = ParticleSystemSimulationSpace.World;
                main.startLifetime = 9f;
                var shape = _drift.shape;
                shape.enabled = true;
                shape.shapeType = ParticleSystemShapeType.Box;
                shape.scale = new Vector3(36f, 7f, 24f);
                var noise = _drift.noise;
                noise.enabled = true;
                noise.strength = 0.45f;
                noise.frequency = 0.25f;
                var emission = _drift.emission;
                emission.enabled = true;
            }

            // palette key: base hub vs the replicated per-room biome (WorldAtmosphereSystem's switch shape)
            int key = 0; // 0 = meadow/base
            if (_cam.transform.position.x > 500f)
            {
                key = 1; // arid default
                if (SystemAPI.TryGetSingleton<RunInfo>(out var ri) && ri.Lifecycle != RunLifecycle.Staging)
                {
                    switch (ri.CurrentBiome)
                    {
                        case RoomBiomeId.Meadow: key = 0; break;
                        case RoomBiomeId.Cavern: key = 2; break;
                        case RoomBiomeId.Blight: key = 3; break;
                    }
                }
            }
            if (key != _biomeKey)
            {
                _biomeKey = key;
                var main = _drift.main;
                main.startSize = cfg != null ? cfg.DriftSize : 0.09f;
                Color c;
                Vector3 wind;
                switch (key)
                {
                    case 1: c = cfg != null ? cfg.AridDustColor : new Color(0.85f, 0.68f, 0.45f, 0.28f); wind = cfg != null ? cfg.AridWind : new Vector3(2.2f, -0.15f, 0.5f); break;
                    case 2: c = cfg != null ? cfg.CavernMoteColor : new Color(0.55f, 0.65f, 0.95f, 0.33f); wind = new Vector3(0f, 0.18f, 0f); break;
                    case 3: c = cfg != null ? cfg.BlightSporeColor : new Color(0.72f, 0.50f, 0.85f, 0.33f); wind = new Vector3(0f, 0.28f, 0f); break;
                    default: c = cfg != null ? cfg.MeadowMoteColor : new Color(0.62f, 0.85f, 0.60f, 0.35f); wind = new Vector3(0f, 0.22f, 0f); break;
                }
                main.startColor = c;
                var vel = _drift.velocityOverLifetime;
                vel.enabled = true;
                vel.space = ParticleSystemSimulationSpace.World;
                vel.x = wind.x; vel.y = wind.y; vel.z = wind.z;
                var emission = _drift.emission;
                emission.rateOverTime = cfg != null ? cfg.DriftRate : 28f;
            }
            if (!_drift.isPlaying) _drift.Play();
            // follow the camera's ground focus so the volume always blankets the view
            var camPos = _cam.transform.position;
            _drift.transform.position = new Vector3(camPos.x, 3.5f, camPos.z);
        }

        // ---------- sway + rustle ----------

        void UpdateSwayAndRustle(AmbientMotionConfig cfg)
        {
            bool swayOn = cfg == null || cfg.SwayEnabled;
            bool rustleOn = cfg == null || cfg.RustleEnabled;
            if (!swayOn && !rustleOn) { RestoreFlora(); return; }

            float swayRadius = cfg != null ? cfg.SwayRadius : 30f;
            float swayAmp = cfg != null ? cfg.SwayAmpDeg : 1.4f;
            float swayHz = cfg != null ? cfg.SwayHz : 0.8f;
            float rustleRadius = cfg != null ? cfg.RustleRadius : 1.7f;
            float rustleAmp = cfg != null ? cfg.RustleAmpDeg : 7f;
            float rustleHz = cfg != null ? cfg.RustleHz : 9f;
            float rustleDecay = cfg != null ? cfg.RustleDecay : 2.5f;

            // local player position (rustle source); missing (menu/no ghost yet) -> far away
            Vector3 playerPos = new Vector3(1e9f, 0f, 1e9f);
            foreach (var lt in SystemAPI.Query<RefRO<LocalTransform>>().WithAll<GhostOwnerIsLocal, PlayerTag>())
                playerPos = new Vector3(lt.ValueRO.Position.x, 0f, lt.ValueRO.Position.z);

            float t = UnityEngine.Time.time;
            float dt = UnityEngine.Time.deltaTime;
            var camPos = _cam.transform.position;
            float swayR2 = swayRadius * swayRadius;
            float rustleR2 = rustleRadius * rustleRadius;

            for (int i = 0; i < _flora.Count; i++)
            {
                var f = _flora[i];
                if (f.T == null) continue;

                float dxc = f.Pos.x - camPos.x, dzc = f.Pos.z - camPos.z;
                bool nearCam = dxc * dxc + dzc * dzc < swayR2;

                if (rustleOn)
                {
                    float dxp = f.Pos.x - playerPos.x, dzp = f.Pos.z - playerPos.z;
                    if (dxp * dxp + dzp * dzp < rustleR2) f.RustleEnergy = 1f;
                    else if (f.RustleEnergy > 0f) f.RustleEnergy = Mathf.Max(0f, f.RustleEnergy - rustleDecay * dt);
                }

                if (!nearCam && f.RustleEnergy <= 0f)
                {
                    _flora[i] = f;
                    continue;
                }

                float ax = 0f, az = 0f;
                if (swayOn && nearCam)
                {
                    ax += swayAmp * Mathf.Sin(t * swayHz * 6.2831f + f.Phase);
                    az += swayAmp * 0.8f * Mathf.Sin(t * swayHz * 5.5f + f.Phase * 1.7f);
                }
                if (f.RustleEnergy > 0f)
                {
                    float e = f.RustleEnergy;
                    ax += rustleAmp * e * Mathf.Sin(t * rustleHz * 6.2831f + f.Phase);
                    az += rustleAmp * 0.7f * e * Mathf.Sin(t * rustleHz * 5.1f + f.Phase * 2.3f);
                }
                f.T.localRotation = f.BaseRot * Quaternion.Euler(ax, 0f, az);
                _flora[i] = f;
            }
        }
    }
}