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 LIFE layer (Phase 1.5b bundle 4 — critters + weather beats, zero netcode). Sibling of
    /// <see cref="AmbientMotionSystem"/>: an observe-only <see cref="SystemBase"/> in
    /// <see cref="PresentationSystemGroup"/> that never touches the sim. Three cosmetic beats, all camera-following,
    /// scene-gated to "Game", biome-keyed off the same camera-X + replicated <see cref="RunInfo.CurrentBiome"/>
    /// switch <see cref="AmbientMotionSystem"/>/<see cref="WorldAtmosphereSystem"/> use:
    ///   - CRITTERS: a small pool of ground bugs (+ a few airborne birds) that idle-wander near the camera and
    ///     DART away when the local player closes in (the "scatter" beat), biome-tinted, recycled at the ring edge;
    ///   - CLOUD SHADOWS: soft dark feathered discs drifting slowly across the ground, recycled off the far edge;
    ///   - BLIGHT LIGHTNING: in Blight rooms only, a periodic double-blink directional-light flash + delayed
    ///     procedural thunder (a dedicated flash light, so it never fights WorldAtmosphereSystem's RenderSettings).
    /// Pooled GameObjects live under a private DontDestroyOnLoad root; wall-clock time is fine (presentation).
    /// Knobs live in <see cref="AmbientLifeConfig"/>.
    /// </summary>
    [WorldSystemFilter(WorldSystemFilterFlags.ClientSimulation)]
    [UpdateInGroup(typeof(PresentationSystemGroup))]
    public partial class AmbientLifeSystem : SystemBase
    {
        struct Critter { public GameObject Go; public Vector3 Pos; public Vector3 Vel; public bool IsBird; public float Phase; }
        struct Cloud { public GameObject Go; public Vector3 Pos; }

        static readonly Color[] CritterTint =
        {
            new Color(0.9f, 0.95f, 0.7f, 0.95f),  // 0 meadow — pale mote/butterfly
            new Color(0.8f, 0.66f, 0.42f, 0.95f), // 1 arid — tan
            new Color(0.6f, 0.72f, 1f, 0.95f),    // 2 cavern — pale blue
            new Color(0.7f, 0.45f, 0.85f, 0.95f), // 3 blight — sickly purple
        };
        static readonly int ColorId = Shader.PropertyToID("_Color");

        Camera _cam;
        GameObject _root;
        Mesh _critterMesh, _cloudMesh;
        Material _critterMat, _cloudMat;
        Light _flashLight;
        AudioClip _thunderClip;
        MaterialPropertyBlock _mpb;

        readonly List<Critter> _critters = new();
        readonly List<Cloud> _clouds = new();
        int _biomeKey = -1;

        // lightning schedule
        float _nextStrike = -1f;
        float _strikeStart = -1f;
        bool _thunderQueued;
        float _thunderAt = -1f;

        protected override void OnCreate()
        {
            _mpb = new MaterialPropertyBlock();
            _thunderClip = FeedbackFx.MakeClip("thunder", 70f, 30f, 0.9f, 0.6f, noise: true, decay: 3.5f);
        }

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

        protected override void OnUpdate()
        {
            if (UnityEngine.SceneManagement.SceneManager.GetActiveScene().name != "Game") { Hide(); return; }
            if (_cam == null) _cam = Camera.main;
            if (_cam == null) return;
            if (!AmbientLifeConfig.Enabled) { Hide(); return; }

            if (_root == null)
            {
                _root = new GameObject("~AmbientLife");
                Object.DontDestroyOnLoad(_root);
                _critterMesh = FeedbackFx.BuildDisc(7);          // tiny speck
                _cloudMesh = FeedbackFx.BuildScorchMesh(28, 0.22f, 3); // soft feathered shadow blob
                _critterMat = FeedbackFx.MakeParticleMaterial("AmbientCritter");
                _cloudMat = FeedbackFx.MakeDecalMaterial("CloudShadow");
            }

            int key = BiomeKey();
            if (key != _biomeKey)
            {
                _biomeKey = key;
                _critterMat.color = CritterTint[key];
            }

            Vector3 cam = _cam.transform.position;
            float dt = Mathf.Min(0.05f, UnityEngine.Time.deltaTime); // clamp so a hitch can't teleport critters
            float now = UnityEngine.Time.time;

            UpdateCritters(cam, dt, now);
            UpdateClouds(cam, dt);
            UpdateLightning(key == 3, now);
        }

        int BiomeKey()
        {
            int key = 0; // meadow / base hub
            if (_cam.transform.position.x > 500f)
            {
                key = 1; // arid default in the expedition region
                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;
                    }
            }
            return key;
        }

        // ---------- critters (bugs + birds) ----------

        void UpdateCritters(Vector3 cam, float dt, float now)
        {
            if (!AmbientLifeConfig.CrittersEnabled) { for (int i = 0; i < _critters.Count; i++) SetActive(_critters[i].Go, false); return; }

            // local player position (flee source); missing -> far away so nothing flees
            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);

            int want = Mathf.Clamp(AmbientLifeConfig.CritterCount, 0, 64);
            while (_critters.Count < want) SpawnCritter(cam);
            for (int i = _critters.Count - 1; i >= want; i--) { if (_critters[i].Go != null) Object.Destroy(_critters[i].Go); _critters.RemoveAt(i); }

            float radius = AmbientLifeConfig.CritterRadius;
            float fleeR2 = AmbientLifeConfig.CritterFleeRadius * AmbientLifeConfig.CritterFleeRadius;
            float idle = AmbientLifeConfig.CritterIdleSpeed, flee = AmbientLifeConfig.CritterFleeSpeed;

            for (int i = 0; i < _critters.Count; i++)
            {
                var c = _critters[i];
                if (c.Go == null) { c.Go = MakeCritterGo(c.IsBird); }
                SetActive(c.Go, true);

                float birdY = c.IsBird ? 2.6f : 0.06f;
                Vector3 flat = new Vector3(c.Pos.x, 0f, c.Pos.z);
                float dxp = flat.x - playerPos.x, dzp = flat.z - playerPos.z;
                Vector3 target;
                if (dxp * dxp + dzp * dzp < fleeR2)
                {
                    // DART away from the player (birds also rise a touch)
                    var away = new Vector3(dxp, 0f, dzp);
                    if (away.sqrMagnitude < 0.001f) away = new Vector3(Mathf.Cos(c.Phase), 0f, Mathf.Sin(c.Phase));
                    target = away.normalized * flee;
                }
                else
                {
                    // gentle wander: a slowly rotating heading per critter
                    float a = now * 0.35f + c.Phase;
                    target = new Vector3(Mathf.Cos(a), 0f, Mathf.Sin(a)) * idle * (c.IsBird ? 1.8f : 1f);
                }
                c.Vel = Vector3.Lerp(c.Vel, target, 1f - Mathf.Exp(-6f * dt));
                c.Pos += c.Vel * dt;

                // recycle when it wanders past the ring
                float dxc = c.Pos.x - cam.x, dzc = c.Pos.z - cam.z;
                if (dxc * dxc + dzc * dzc > radius * radius)
                {
                    float ang = UnityEngine.Random.value * 6.2831f;
                    float r = radius * 0.7f;
                    c.Pos = new Vector3(cam.x + Mathf.Cos(ang) * r, 0f, cam.z + Mathf.Sin(ang) * r);
                    c.Vel = Vector3.zero;
                }

                c.Go.transform.position = new Vector3(c.Pos.x, birdY, c.Pos.z);
                float s = c.IsBird ? 0.22f : 0.14f;
                c.Go.transform.localScale = new Vector3(s, 1f, s);
                _critters[i] = c;
            }
        }

        void SpawnCritter(Vector3 cam)
        {
            bool bird = UnityEngine.Random.value < Mathf.Clamp01(AmbientLifeConfig.BirdFraction);
            float ang = UnityEngine.Random.value * 6.2831f;
            float r = UnityEngine.Random.Range(3f, Mathf.Max(4f, AmbientLifeConfig.CritterRadius * 0.9f));
            _critters.Add(new Critter
            {
                Go = MakeCritterGo(bird),
                Pos = new Vector3(cam.x + Mathf.Cos(ang) * r, 0f, cam.z + Mathf.Sin(ang) * r),
                Vel = Vector3.zero,
                IsBird = bird,
                Phase = UnityEngine.Random.value * 6.2831f,
            });
        }

        GameObject MakeCritterGo(bool bird)
        {
            var go = new GameObject(bird ? "Bird" : "Bug");
            go.transform.SetParent(_root.transform, false);
            go.AddComponent<MeshFilter>().sharedMesh = _critterMesh;
            var mr = go.AddComponent<MeshRenderer>();
            mr.sharedMaterial = _critterMat;
            mr.shadowCastingMode = UnityEngine.Rendering.ShadowCastingMode.Off;
            mr.receiveShadows = false;
            mr.lightProbeUsage = UnityEngine.Rendering.LightProbeUsage.Off;
            return go;
        }

        // ---------- cloud-shadow drifts ----------

        void UpdateClouds(Vector3 cam, float dt)
        {
            if (!AmbientLifeConfig.CloudsEnabled) { for (int i = 0; i < _clouds.Count; i++) SetActive(_clouds[i].Go, false); return; }

            int want = Mathf.Clamp(AmbientLifeConfig.CloudCount, 0, 16);
            while (_clouds.Count < want)
            {
                var go = new GameObject("CloudShadow");
                go.transform.SetParent(_root.transform, false);
                go.AddComponent<MeshFilter>().sharedMesh = _cloudMesh;
                var mr = go.AddComponent<MeshRenderer>();
                mr.sharedMaterial = _cloudMat;
                mr.shadowCastingMode = UnityEngine.Rendering.ShadowCastingMode.Off;
                mr.receiveShadows = false;
                mr.lightProbeUsage = UnityEngine.Rendering.LightProbeUsage.Off;
                float sp = AmbientLifeConfig.CritterRadius; // reuse a spread
                _clouds.Add(new Cloud { Go = go, Pos = new Vector3(cam.x + UnityEngine.Random.Range(-sp, sp), 0f, cam.z + UnityEngine.Random.Range(-sp, sp)) });
            }
            for (int i = _clouds.Count - 1; i >= want; i--) { if (_clouds[i].Go != null) Object.Destroy(_clouds[i].Go); _clouds.RemoveAt(i); }

            _cloudMat.color = new Color(0.02f, 0.02f, 0.04f, Mathf.Clamp01(AmbientLifeConfig.CloudAlpha));
            float size = AmbientLifeConfig.CloudSize;
            float drift = AmbientLifeConfig.CloudDriftSpeed;
            float span = size * 2.2f;
            for (int i = 0; i < _clouds.Count; i++)
            {
                var cl = _clouds[i];
                SetActive(cl.Go, true);
                var p = cl.Pos;
                p.x += drift * dt; // drift along +X (a light prevailing wind)
                // recycle once it drifts a span past the camera downwind edge
                if (p.x > cam.x + size + span) { p.x = cam.x - size - span; p.z = cam.z + UnityEngine.Random.Range(-size, size); }
                cl.Pos = p;
                cl.Go.transform.position = new Vector3(p.x, 0.04f, p.z);
                cl.Go.transform.localScale = new Vector3(size, 1f, size);
                cl.Go.GetComponent<MeshRenderer>().SetPropertyBlock(null); // uses shared material color
                _clouds[i] = cl;
            }
        }

        // ---------- Blight lightning flicker ----------

        void UpdateLightning(bool inBlight, float now)
        {
            if (!AmbientLifeConfig.LightningEnabled || !inBlight)
            {
                if (_flashLight != null) _flashLight.intensity = 0f;
                _strikeStart = -1f; _nextStrike = -1f;
                return;
            }
            if (_flashLight == null)
            {
                var lgo = new GameObject("~BlightLightning");
                lgo.transform.SetParent(_root.transform, false);
                lgo.transform.rotation = Quaternion.Euler(52f, -28f, 0f);
                _flashLight = lgo.AddComponent<Light>();
                _flashLight.type = LightType.Directional;
                _flashLight.shadows = LightShadows.None;
                _flashLight.intensity = 0f;
            }
            _flashLight.color = AmbientLifeConfig.LightningColor;

            if (_nextStrike < 0f) _nextStrike = now + UnityEngine.Random.Range(AmbientLifeConfig.LightningMinInterval, AmbientLifeConfig.LightningMaxInterval);

            // begin a strike
            if (_strikeStart < 0f && now >= _nextStrike)
            {
                _strikeStart = now;
                _nextStrike = now + UnityEngine.Random.Range(AmbientLifeConfig.LightningMinInterval, AmbientLifeConfig.LightningMaxInterval);
                _thunderAt = now + UnityEngine.Random.Range(0.3f, 0.8f); // thunder trails the flash
                _thunderQueued = true;
            }

            // drive the double-blink envelope
            if (_strikeStart >= 0f)
            {
                float t = now - _strikeStart;
                float peak = AmbientLifeConfig.LightningIntensity;
                float e;
                if (t < 0.06f) e = peak;
                else if (t < 0.11f) e = peak * 0.15f;
                else if (t < 0.20f) e = peak;                       // brighter second blink
                else if (t < 0.5f) e = peak * (1f - (t - 0.20f) / 0.30f);
                else { e = 0f; _strikeStart = -1f; }
                _flashLight.intensity = Mathf.Max(0f, e);
            }

            if (_thunderQueued && now >= _thunderAt)
            {
                _thunderQueued = false;
                var p = _cam != null ? _cam.transform.position : Vector3.zero;
                FeedbackFx.PlayClip(_thunderClip, p, AmbientLifeConfig.ThunderVolume);
            }
        }

        // ---------- helpers ----------

        static void SetActive(GameObject go, bool on) { if (go != null && go.activeSelf != on) go.SetActive(on); }

        void Hide()
        {
            for (int i = 0; i < _critters.Count; i++) SetActive(_critters[i].Go, false);
            for (int i = 0; i < _clouds.Count; i++) SetActive(_clouds[i].Go, false);
            if (_flashLight != null) _flashLight.intensity = 0f;
            _strikeStart = -1f; _nextStrike = -1f;
        }
    }
}