automode.ts

// SPDX-License-Identifier: Apache-2.0
import { weightedRandom } from "@thi.ng/random";
import { map, range } from "@thi.ng/transducers";
import { updateAudio } from "./audio";
import { NUM_BINS } from "./config";
import { DB, updateSpectrumBin } from "./state";

const weights = [
	0,
	...map(
		(x) => 1 - Math.pow((x - 1) / NUM_BINS, 0.15) * 0.99,
		range(1, NUM_BINS)
	),
];

const rnd = weightedRandom([...range(0, NUM_BINS)], weights);

const startAutoMode = () => {
	let i = 0;
	DB.resetIn(
		["auto"],
		setInterval(() => {
			let { decay, attenuate, interval } = DB.value;
			attenuate = 1 + attenuate;
			DB.swapIn(["bins"], (buf: number[]) =>
				buf.map((x, i) => (x * decay) / attenuate ** i)
			);
			if (i % interval === 0) {
				const bin = rnd();
				updateSpectrumBin(
					bin,
					Math.random() * (1 - Math.pow((bin - 1) / NUM_BINS, 0.8))
				);
			}
			updateAudio();
			i++;
		}, 16)
	);
};

const stopAutoMode = () => {
	clearInterval(DB.value.auto);
	DB.resetIn(["auto"], null);
};

export const toggleAutoMode = () =>
	DB.value.auto == null ? startAutoMode() : stopAutoMode();