@youneed/cli-middleware-oscillator

A synthetic spectrum source and a cava-style bar renderer for @youneed/cli. The middleware adds this.oscillator — a deterministic, dependency-free signal (a sum of sines, bass-biased) whose sample(time) returns per-band magnitudes (0..1) — and spectrumBars() turns those magnitudes into multi-row block bars. It's not a real FFT, it's a stylised visualiser: perfect for a demo, a loading screen, or a music-player UI, and testable because the same time always yields the same frame.

import { Application, Command, task, text } from "@youneed/cli";
import { oscillator, spectrumBars } from "@youneed/cli-middleware-oscillator";

class Vis extends Command("vis", { middleware: [oscillator({ bands: 32, speed: 1.5 })] }) {
  t = 0;

  execute() {
    // animate: bump `t` on a timer and repaint via a task/render loop
    task(this, async () => {
      for (let i = 0; i < 300; i++) {
        this.t = i / 30;
        this.requestUpdate?.();
        await new Promise((r) => setTimeout(r, 33));
      }
    }).run();
  }

  render() {
    return text`${spectrumBars(this.oscillator.sample(this.t), { height: 10 })}`;
  }
}

const app = Application({ name: "demo", commands: [Vis] });
app.run(["vis"]);

Exports

• oscillator(opts?) — middleware. Contributes this.oscillator, an Oscillator built from createOscillator(opts).
• createOscillator(opts?) — build a standalone Oscillator (no middleware; handy for tests).
• spectrumBars(values, opts?) — render an array of 0..1 magnitudes as vertical block bars, top row first, returned as a multi-line string.

Options

• OscillatorOptions — { bands?, speed? }. bands is the number of columns (default 24); speed is the animation multiplier (default 1).
• Oscillator — { bands, sample(time) }. sample(time) returns the per-band magnitudes for time in seconds.
• SpectrumOptions — { height?, color? }. height is the bar height in rows (default 8); color(cell, value, row) transforms each non-blank glyph (e.g. to add ANSI colour).