Project-M/Assets/_Project/Scripts/Client/Presentation/AmbientAudioSystem.cs

using ProjectM.Simulation;
using Unity.Entities;
using Unity.NetCode;
using UnityEngine;

namespace ProjectM.Client
{
    /// <summary>
    /// Client-only AMBIENT audio bed + run cues. A managed presentation <see cref="SystemBase"/>
    /// (<see cref="PresentationSystemGroup"/>, main thread, no Burst) that plays a low, seamless-looping
    /// procedural drone (asset-free, <c>AudioClip.Create</c> like <c>CombatFeedbackSystem.MakeClip</c>) plus
    /// launch-countdown beeps and the boss-arrival roar — replicated-state observations only. Lives only in the
    /// client world, so the server never creates audio and nothing here affects determinism. Volumes are
    /// deliberately conservative. (The cycle-phase stingers + Core alarm retired with the siege loop — LANTERN purge.)
    /// </summary>
    [WorldSystemFilter(WorldSystemFilterFlags.ClientSimulation)]
    [UpdateInGroup(typeof(PresentationSystemGroup))]
    public partial class AmbientAudioSystem : SystemBase
    {
        AudioSource _ambient;
        AudioClip _ambientClip;
        GameObject _root;

        AudioClip _stingBeep, _stingRoar;
        int _lastCountdownSec = -1;
        bool _bossRoared;

        const float AmbientBaseVolume = 0.10f; // low ambient bed

        protected override void OnCreate()
        {
            _ambientClip = MakeDrone();
            _stingBeep = MakeSting(880f, 880f, 0.09f, 0.30f);       // countdown tick
            _stingRoar = MakeSting(90f, 38f, 0.90f, 0.60f);         // boss-arrival roar (low falling growl)
        }

        protected override void OnStartRunning()
        {
            if (_root != null) return;
            _root = new GameObject("~AmbientAudio");
            _ambient = _root.AddComponent<AudioSource>();
            _ambient.clip = _ambientClip;
            _ambient.loop = true;
            _ambient.playOnAwake = false;
            _ambient.spatialBlend = 0f; // 2D bed
            _ambient.volume = AmbientBaseVolume * GameVolume.Music;
            _ambient.Play();
        }

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

        protected override void OnUpdate()
        {
            if (_ambient == null) return;

            _ambient.volume = Mathf.MoveTowards(_ambient.volume, AmbientBaseVolume * GameVolume.Music, SystemAPI.Time.DeltaTime * 0.25f);

            // Launch countdown beeps (3-2-1) + the boss-arrival roar — replicated-state observations only.
            if (SystemAPI.TryGetSingleton<RunInfo>(out var runAudio))
            {
                int sec = -1;
                if (runAudio.Lifecycle == RunLifecycle.Launching && runAudio.LaunchTick != 0
                    && SystemAPI.TryGetSingleton<NetworkTime>(out var antime) && antime.ServerTick.IsValid)
                {
                    int tl = new NetworkTick(runAudio.LaunchTick).TicksSince(antime.ServerTick);
                    if (tl > 0) sec = tl / 60 + 1;
                }
                if (sec > 0 && sec != _lastCountdownSec && sec <= 3)
                    _ambient.PlayOneShot(_stingBeep, 0.5f * GameVolume.Sfx);
                _lastCountdownSec = sec;

                bool inBossRoom = runAudio.Lifecycle == RunLifecycle.InRoom
                    && runAudio.CurrentRoomType == RoomTypeId.Boss;
                if (!inBossRoom)
                {
                    _bossRoared = false; // re-arm for the next boss room
                }
                else if (!_bossRoared)
                {
                    foreach (var _ in SystemAPI.Query<RefRO<Health>>().WithAll<EnemyTag>())
                    {
                        _ambient.PlayOneShot(_stingRoar, 0.9f * GameVolume.Sfx);
                        _bossRoared = true;
                        break;
                    }
                }
            }
        }

        // ---- Procedural audio (asset-free; mirrors CombatFeedbackSystem.MakeClip) ----

        // A low, seamless-looping pad: each partial completes an integer number of cycles over the buffer
        // (freq snapped to k/duration) so the loop point has no click. A slow tremolo adds motion.
        static AudioClip MakeDrone()
        {
            const int rate = 44100;
            const float dur = 4f;
            int len = (int)(dur * rate);
            var clip = AudioClip.Create("ambient_drone", len, 1, rate, false);
            var data = new float[len];
            float f0 = Snap(55f, dur);     // sub
            float f1 = Snap(110f, dur);    // root
            float f2 = Snap(164.81f, dur); // fifth-ish
            float f3 = Snap(220f, dur);
            float trem = Snap(0.5f, dur);  // slow amplitude wobble
            for (int i = 0; i < len; i++)
            {
                float t = i / (float)rate;
                float s = 0.50f * Mathf.Sin(2f * Mathf.PI * f0 * t)
                        + 0.35f * Mathf.Sin(2f * Mathf.PI * f1 * t)
                        + 0.18f * Mathf.Sin(2f * Mathf.PI * f2 * t)
                        + 0.10f * Mathf.Sin(2f * Mathf.PI * f3 * t);
                float amp = 0.75f + 0.25f * Mathf.Sin(2f * Mathf.PI * trem * t);
                data[i] = s * amp * 0.5f; // peak ~0.57, no clipping
            }
            clip.SetData(data, 0);
            return clip;
        }

        // freq snapped so freq*dur is an integer -> the waveform closes seamlessly at the loop point.
        static float Snap(float freq, float dur)
        {
            float cycles = Mathf.Max(1f, Mathf.Round(freq * dur));
            return cycles / dur;
        }

        // Short one-shot tone sweeping f0->f1 with an exponential decay envelope.
        static AudioClip MakeSting(float f0, float f1, float dur, float vol) => FeedbackFx.MakeClip("sting", f0, f1, dur, vol, decay: 3.5f);
    }
}