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

namespace ProjectM.Client
{
    /// <summary>
    /// EB-1 — client-only WORLD JUICE for player-built structures taking damage + dying ("loses have weight"). A
    /// managed <see cref="SystemBase"/> in <see cref="PresentationSystemGroup"/> that OBSERVES replicated state and
    /// never mutates the sim: it edge-detects each structure ghost's [GhostField] <c>Health.Current</c> — a decrease
    /// spawns a small amber chip (camera-SILENT so a siege's many hits never clamp the shake), and a destruction
    /// (an HP&lt;=0 edge OR a despawn) spawns a LOUD red-orange burst + camera punch. A PROXIMITY GATE suppresses the
    /// destruction burst unless the structure was near the local player, so the base->expedition RegionRelevancy
    /// despawn (every base structure drops from this client at once) stays SILENT. De-duped: a structure fires its
    /// death burst AT MOST once (the HP&lt;=0 edge sets DeathFired so the prune-cleanup skips it; the server destroys
    /// a structure the same tick it hits 0, so the prune is usually the path that fires). CombatFeedbackSystem
    /// suppresses structures, so this is the SOLE structure cue. Procedural particles + SFX (mirrors
    /// WorldFeedbackSystem; self-contained). Never destroys a ghost (GhostDespawnSystem owns despawn); prunes the
    /// cache EVERY frame (no <c>[RequireMatchingQueriesForUpdate]</c> — else a cache entry leaks per kill).
    /// </summary>
    [WorldSystemFilter(WorldSystemFilterFlags.ClientSimulation)]
    [UpdateInGroup(typeof(PresentationSystemGroup))]
    public partial class StructureFeedbackSystem : SystemBase
    {
        struct Cache { public float Hp; public float3 Pos; public bool DeathFired; }

        readonly Dictionary<Entity, Cache> _cache = new();
        readonly HashSet<Entity> _seen = new();
        readonly List<Entity> _stale = new();

        Transform _fxRoot;
        ParticleSystem _chipFx;
        ParticleSystem _deathFx;
        AudioClip _chipClip;
        AudioClip _deathClip;

        protected override void OnCreate()
        {
            _chipClip = MakeClip("struct_chip", 700f, 500f, 0.05f, 0.30f);
            _deathClip = MakeClip("struct_death", 220f, 60f, 0.35f, 0.55f);
        }

        protected override void OnStartRunning()
        {
            if (_fxRoot != null) return;
            _fxRoot = new GameObject("~StructureFeedbackFX").transform;
            var mat = MakeParticleMaterial();
            _chipFx = MakeBurst("StructChips", mat, StructureFeelConfig.DamageTint, 0.12f, 5f, 0.30f, 256);
            _deathFx = MakeBurst("StructDeath", mat, StructureFeelConfig.DeathTint, 0.20f, 8f, 0.55f, 512);
        }

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

        protected override void OnUpdate()
        {
            if (!StructureFeelConfig.Enabled) { _cache.Clear(); return; }

            EntityManager.CompleteDependencyBeforeRO<Health>();
            EntityManager.CompleteDependencyBeforeRO<PlacedStructure>();
            EntityManager.CompleteDependencyBeforeRO<LocalTransform>();

            bool haveLocal = false;
            float3 localPos = default;
            foreach (var xf in SystemAPI.Query<RefRO<LocalTransform>>().WithAll<GhostOwnerIsLocal, PlayerTag>())
            {
                localPos = xf.ValueRO.Position;
                haveLocal = true;
            }
            float rangeSq = StructureFeelConfig.ProximityRange * StructureFeelConfig.ProximityRange;

            _seen.Clear();
            foreach (var (health, xf, e) in
                     SystemAPI.Query<RefRO<Health>, RefRO<LocalTransform>>().WithAll<PlacedStructure>().WithEntityAccess())
            {
                _seen.Add(e);
                float cur = health.ValueRO.Current;
                float3 pos = xf.ValueRO.Position;
                bool nearby = haveLocal && math.distancesq(pos, localPos) <= rangeSq;

                if (_cache.TryGetValue(e, out var prev))
                {
                    if (cur <= 0f && prev.Hp > 0f && !prev.DeathFired)
                    {
                        if (nearby) FireDeath(pos);
                        _cache[e] = new Cache { Hp = cur, Pos = pos, DeathFired = true };
                        continue;
                    }
                    if (cur < prev.Hp - 0.001f && cur > 0f && nearby)
                    {
                        EmitTinted(_chipFx, (Vector3)pos + Vector3.up * 0.7f, StructureFeelConfig.ChipBurstCount, StructureFeelConfig.DamageTint);
                        PlayClip(_chipClip, (Vector3)pos, StructureFeelConfig.ChipSfxVolume);
                    }
                }
                _cache[e] = new Cache { Hp = cur, Pos = pos, DeathFired = _cache.TryGetValue(e, out var c2) && c2.DeathFired };
            }

            // Prune: a despawn = destroyed (or a region-transit drop). Proximity-gated so the +1000 base->expedition
            // despawn stays silent; de-duped against an HP<=0 edge that already fired this structure's death.
            if (_cache.Count != _seen.Count)
            {
                _stale.Clear();
                foreach (var kv in _cache)
                    if (!_seen.Contains(kv.Key)) _stale.Add(kv.Key);
                for (int i = 0; i < _stale.Count; i++)
                {
                    var c = _cache[_stale[i]];
                    if (!c.DeathFired && haveLocal && math.distancesq(c.Pos, localPos) <= rangeSq)
                        FireDeath(c.Pos);
                    _cache.Remove(_stale[i]);
                }
            }
        }

        void FireDeath(float3 pos)
        {
            EmitTinted(_deathFx, (Vector3)pos + Vector3.up * 0.6f, StructureFeelConfig.DeathBurstCount, StructureFeelConfig.DeathTint);
            PlayClip(_deathClip, (Vector3)pos, StructureFeelConfig.DeathSfxVolume);
            PrototypeCameraRig.PunchFov(StructureFeelConfig.DeathFovKick, 110f);
            PrototypeCameraRig.AddShake(StructureFeelConfig.DeathShake);
        }

        // ---- procedural particles + SFX (mirrors WorldFeedbackSystem; self-contained) ----

        static void EmitTinted(ParticleSystem ps, Vector3 pos, int count, Color tint)
        {
            if (ps == null) return;
            var main = ps.main;
            main.startColor = tint;
            ps.transform.position = pos;
            ps.Emit(count);
        }

        static Material MakeParticleMaterial()
        {
            Shader sh = Shader.Find("Sprites/Default");
            if (sh == null) sh = Shader.Find("Universal Render Pipeline/Particles/Unlit");
            if (sh == null) sh = Shader.Find("Unlit/Color");
            return new Material(sh) { name = "StructureFeedbackParticle" };
        }

        ParticleSystem MakeBurst(string name, Material mat, Color color, float size, float speed, float life, int max)
        {
            var go = new GameObject(name);
            go.transform.SetParent(_fxRoot, false);
            var ps = go.AddComponent<ParticleSystem>();

            var main = ps.main;
            main.loop = false;
            main.playOnAwake = false;
            main.startLifetime = life;
            main.startSpeed = speed;
            main.startSize = size;
            main.startColor = color;
            main.maxParticles = max;
            main.gravityModifier = 0.3f;
            main.simulationSpace = ParticleSystemSimulationSpace.World;

            var emission = ps.emission;
            emission.enabled = false; // manual Emit(count)

            var shape = ps.shape;
            shape.enabled = true;
            shape.shapeType = ParticleSystemShapeType.Sphere;
            shape.radius = 0.18f;

            var colOverLife = ps.colorOverLifetime;
            colOverLife.enabled = true;
            var grad = new Gradient();
            grad.SetKeys(
                new[] { new GradientColorKey(Color.white, 0f), new GradientColorKey(Color.white, 1f) },
                new[] { new GradientAlphaKey(1f, 0f), new GradientAlphaKey(0f, 1f) });
            colOverLife.color = new ParticleSystem.MinMaxGradient(grad);

            var sizeOverLife = ps.sizeOverLifetime;
            sizeOverLife.enabled = true;
            sizeOverLife.size = new ParticleSystem.MinMaxCurve(1f, AnimationCurve.Linear(0f, 1f, 1f, 0.15f));

            var renderer = ps.GetComponent<ParticleSystemRenderer>();
            renderer.material = mat;
            renderer.renderMode = ParticleSystemRenderMode.Billboard;
            return ps;
        }

        static AudioClip MakeClip(string name, float f0, float f1, float dur, float vol)
        {
            const int rate = 44100;
            int len = Mathf.Max(16, (int)(dur * rate));
            var clip = AudioClip.Create(name, len, 1, rate, false);
            var data = new float[len];
            float phase = 0f;
            for (int i = 0; i < len; i++)
            {
                float t = i / (float)len;
                float env = Mathf.Exp(-5f * t);
                float freq = Mathf.Lerp(f0, f1, t);
                phase += 2f * Mathf.PI * freq / rate;
                data[i] = Mathf.Sin(phase) * env * vol;
            }
            clip.SetData(data, 0);
            return clip;
        }

        static void PlayClip(AudioClip clip, Vector3 pos, float vol)
        {
            if (clip == null) return;
            AudioSource.PlayClipAtPoint(clip, pos, vol * GameVolume.Sfx);
        }
    }
}