Lofi_Generator/lib/audio/chordEngine.ts

import * as Tone from 'tone';
import { ChordProgression } from '@/types/audio';
import { getRandomProgression } from './patterns';

export class ChordEngine {
  private synth: Tone.PolySynth;
  private sequence: Tone.Sequence | null = null;
  private progression: ChordProgression;
  private output: Tone.Gain;
  private filter: Tone.Filter;
  private reverb: Tone.Reverb;
  private chorus: Tone.Chorus;

  constructor(destination: Tone.InputNode) {
    this.output = new Tone.Gain(0.6);

    // Warm lofi filter
    this.filter = new Tone.Filter({
      frequency: 2000,
      type: 'lowpass',
      rolloff: -24,
    });

    // Dreamy reverb
    this.reverb = new Tone.Reverb({
      decay: 3,
      wet: 0.4,
    });

    // Subtle chorus for width
    this.chorus = new Tone.Chorus({
      frequency: 0.5,
      delayTime: 3.5,
      depth: 0.5,
      wet: 0.3,
    }).start();

    // FM Synth for warm, evolving pad sound
    this.synth = new Tone.PolySynth(Tone.FMSynth, {
      harmonicity: 2,
      modulationIndex: 1.5,
      oscillator: {
        type: 'sine',
      },
      envelope: {
        attack: 0.3,
        decay: 0.3,
        sustain: 0.8,
        release: 1.5,
      },
      modulation: {
        type: 'sine',
      },
      modulationEnvelope: {
        attack: 0.5,
        decay: 0.2,
        sustain: 0.5,
        release: 0.5,
      },
    });

    // Lower the overall synth volume to prevent clipping
    this.synth.volume.value = -12;

    // Chain: synth -> filter -> chorus -> reverb -> output -> destination
    this.synth.connect(this.filter);
    this.filter.connect(this.chorus);
    this.chorus.connect(this.reverb);
    this.reverb.connect(this.output);
    this.output.connect(destination);

    // Initialize with a random progression
    this.progression = getRandomProgression();
  }

  createSequence(): void {
    if (this.sequence) {
      this.sequence.dispose();
    }

    const steps = Array.from({ length: this.progression.chords.length }, (_, i) => i);

    this.sequence = new Tone.Sequence(
      (time, step) => {
        const chord = this.progression.chords[step];
        const duration = this.progression.durations[step];

        // Release previous notes and play new chord
        this.synth.releaseAll(time);
        this.synth.triggerAttackRelease(chord, duration, time, 0.5);
      },
      steps,
      '2n'
    );

    this.sequence.start(0);
  }

  setProgression(progression: ChordProgression): void {
    this.progression = progression;
    // Recreate sequence with new progression
    if (this.sequence) {
      this.createSequence();
    }
  }

  randomize(): ChordProgression {
    this.progression = getRandomProgression();
    if (this.sequence) {
      this.createSequence();
    }
    return this.progression;
  }

  setVolume(volume: number): void {
    this.output.gain.rampTo(volume, 0.1);
  }

  mute(muted: boolean): void {
    this.output.gain.rampTo(muted ? 0 : 0.6, 0.1);
  }

  setFilterFrequency(freq: number): void {
    this.filter.frequency.rampTo(freq, 0.1);
  }

  getProgression(): ChordProgression {
    return this.progression;
  }

  dispose(): void {
    this.sequence?.dispose();
    this.synth.dispose();
    this.filter.dispose();
    this.reverb.dispose();
    this.chorus.dispose();
    this.output.dispose();
  }
}