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

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

namespace ProjectM.Client
{
    /// <summary>
    /// Client-only PROCEDURAL MUSIC — four synchronized loop layers (bass / chord pad / arpeggio / percussion
    /// pulse), all generated over the SAME 4-bar buffer (100 BPM, Am–F–C–G) so they stay phase-locked forever:
    /// every AudioSource starts the same frame with loop=true and identical clip length, and per-bar amplitude
    /// envelopes reach ~zero at each bar boundary so both the chord changes and the loop point are click-free
    /// (the <c>AmbientAudioSystem.Snap</c> trick generalized to enveloped segments). The MIX is the state
    /// machine: layer volumes ease toward targets chosen from replicated state only — the <see cref="RunInfo"/>
    /// lifecycle (staging / launch / combat / boss / reward lull / return). Observe-only presentation
    /// system: no sim writes, no determinism surface; asset-free per the project convention. Sits under SFX at
    /// <see cref="MasterVolume"/> × <see cref="GameVolume.Music"/>; the low <c>AmbientAudioSystem</c> drone
    /// (vol 0.10) remains as texture beneath it.
    /// </summary>
    [WorldSystemFilter(WorldSystemFilterFlags.ClientSimulation)]
    [UpdateInGroup(typeof(PresentationSystemGroup))]
    public partial class MusicSystem : SystemBase
    {
        const float MasterVolume = 0.45f;
        const float FadePerSecond = 0.30f;

        // ---- shared musical grid: 100 BPM, 4/4, one chord per bar, 4 bars ----
        const int SampleRate = 44100;
        const float BarSeconds = 2.4f;   // 4 beats @ 0.6 s
        const int Bars = 4;
        const float LoopSeconds = BarSeconds * Bars; // 9.6 s

        // Am – F – C – G (natural-minor loop; index = bar): root/third/fifth per chord.
        static readonly float[][] ChordHz =
        {
            new[] { 110.00f, 130.81f, 164.81f }, // Am: A2 C3 E3
            new[] { 87.31f, 110.00f, 130.81f },  // F:  F2 A2 C3
            new[] { 130.81f, 164.81f, 196.00f }, // C:  C3 E3 G3
            new[] { 98.00f, 123.47f, 146.83f },  // G:  G2 B2 D3
        };

        GameObject _root;
        AudioSource _bass, _pad, _arp, _pulse;
        float _vBass, _vPad, _vArp, _vPulse;      // current smoothed volumes (pre-master)

        protected override void OnStartRunning()
        {
            if (_root != null) return;
            _root = new GameObject("~Music");
            _bass = MakeSource(BuildBassLoop());
            _pad = MakeSource(BuildPadLoop());
            _arp = MakeSource(BuildArpLoop());
            _pulse = MakeSource(BuildPulseLoop());
            // Same frame, same length, loop=true -> phase-locked for the whole session.
            _bass.Play(); _pad.Play(); _arp.Play(); _pulse.Play();
        }

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

        AudioSource MakeSource(AudioClip clip)
        {
            var src = _root.AddComponent<AudioSource>();
            src.clip = clip;
            src.loop = true;
            src.playOnAwake = false;
            src.spatialBlend = 0f;
            src.volume = 0f;
            return src;
        }

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

            // ---- pick the mix from replicated state (defaults = quiet staging bed) ----
            float tBass = 0.50f, tPad = 0.55f, tArp = 0.12f, tPulse = 0f;

            // 2026-08-07 audit purge: the mix used to key off RunInfo.Lifecycle (staging / launching / in-room /
            // boss / returning). With the run FSM deleted the bed holds its defaults; re-key it off LANTERN's
            // descent state when Phase 2 lands.

            float dt = SystemAPI.Time.DeltaTime * FadePerSecond;
            _vBass = Mathf.MoveTowards(_vBass, tBass, dt);
            _vPad = Mathf.MoveTowards(_vPad, tPad, dt);
            _vArp = Mathf.MoveTowards(_vArp, tArp, dt);
            _vPulse = Mathf.MoveTowards(_vPulse, tPulse, dt);

            float master = MasterVolume * GameVolume.Music;
            _bass.volume = _vBass * master;
            _pad.volume = _vPad * master;
            _arp.volume = _vArp * master;
            _pulse.volume = _vPulse * master;
        }



        // ================= clip builders (deterministic, asset-free) =================

        static AudioClip NewLoopClip(string name, out float[] data)
        {
            int len = (int)(LoopSeconds * SampleRate);
            data = new float[len];
            return AudioClip.Create(name, len, 1, SampleRate, false);
        }

        /// <summary>Bar-local envelope that is ~0 at both bar edges (click-free chord changes + loop point).</summary>
        static float BarEnv(float tInBar, float attack, float release)
        {
            float up = Mathf.Clamp01(tInBar / attack);
            float down = Mathf.Clamp01((BarSeconds - tInBar) / release);
            return up * up * down;
        }

        static AudioClip BuildBassLoop()
        {
            var clip = NewLoopClip("music_bass", out var data);
            for (int i = 0; i < data.Length; i++)
            {
                float t = i / (float)SampleRate;
                int bar = Mathf.Min(Bars - 1, (int)(t / BarSeconds));
                float tb = t - bar * BarSeconds;
                float f = ChordHz[bar][0] * 0.5f; // root, an octave down
                float s = Mathf.Sin(2f * Mathf.PI * f * t) * 0.8f
                        + Mathf.Sin(2f * Mathf.PI * f * 2f * t) * 0.2f;
                data[i] = s * BarEnv(tb, 0.03f, 0.12f) * 0.50f;
            }
            clip.SetData(data, 0);
            return clip;
        }

        static AudioClip BuildPadLoop()
        {
            var clip = NewLoopClip("music_pad", out var data);
            for (int i = 0; i < data.Length; i++)
            {
                float t = i / (float)SampleRate;
                int bar = Mathf.Min(Bars - 1, (int)(t / BarSeconds));
                float tb = t - bar * BarSeconds;
                var chord = ChordHz[bar];
                float s = 0f;
                for (int n = 0; n < chord.Length; n++)
                    s += Mathf.Sin(2f * Mathf.PI * chord[n] * t + n * 1.7f);
                float trem = 0.85f + 0.15f * Mathf.Sin(2f * Mathf.PI * 0.8f * t);
                data[i] = s / 3f * BarEnv(tb, 0.45f, 0.50f) * trem * 0.34f;
            }
            clip.SetData(data, 0);
            return clip;
        }

        static AudioClip BuildArpLoop()
        {
            var clip = NewLoopClip("music_arp", out var data);
            const float noteLen = BarSeconds / 8f; // 8th notes
            for (int i = 0; i < data.Length; i++)
            {
                float t = i / (float)SampleRate;
                int bar = Mathf.Min(Bars - 1, (int)(t / BarSeconds));
                float tb = t - bar * BarSeconds;
                int step = Mathf.Min(7, (int)(tb / noteLen));
                float tn = tb - step * noteLen;
                var chord = ChordHz[bar];
                // up-and-over pattern: root, fifth, octave, tenth, back down
                float f = step switch
                {
                    0 => chord[0] * 2f,
                    1 => chord[2] * 2f,
                    2 => chord[0] * 4f,
                    3 => chord[1] * 4f,
                    4 => chord[2] * 4f,
                    5 => chord[0] * 4f,
                    6 => chord[2] * 2f,
                    _ => chord[1] * 2f,
                };
                float env = Mathf.Exp(-9f * tn);
                data[i] = Mathf.Sin(2f * Mathf.PI * f * tn) * env * 0.32f;
            }
            clip.SetData(data, 0);
            return clip;
        }

        static AudioClip BuildPulseLoop()
        {
            var clip = NewLoopClip("music_pulse", out var data);
            const float beat = BarSeconds / 4f;
            uint rng = 0x5EED5EEDu; // deterministic hat noise
            for (int i = 0; i < data.Length; i++)
            {
                float t = i / (float)SampleRate;
                float tBeat = t % beat;
                // Low thump on every beat: 55->38 Hz sweep, tight decay.
                float thump = 0f;
                if (tBeat < 0.14f)
                {
                    float f = Mathf.Lerp(55f, 38f, tBeat / 0.14f);
                    thump = Mathf.Sin(2f * Mathf.PI * f * tBeat) * Mathf.Exp(-22f * tBeat) * 0.85f;
                }
                // Off-beat hat: a 30 ms noise tick halfway through each beat.
                float tHat = (t + beat * 0.5f) % beat;
                float hat = 0f;
                if (tHat < 0.03f)
                {
                    rng ^= rng << 13; rng ^= rng >> 17; rng ^= rng << 5; // xorshift
                    float n = (rng & 0xFFFF) / 32768f - 1f;
                    hat = n * Mathf.Exp(-120f * tHat) * 0.22f;
                }
                data[i] = thump + hat;
            }
            clip.SetData(data, 0);
            return clip;
        }


    }
}