tests/unit/detector.test.js

import { describe, it, expect } from "vitest";
import { detectTransientOnsets, highpass, energyFlux } from "../../lib/detector.js";
import { textToSchedule, decodeOnsets } from "../../lib/wire.js";
import { makeTiming } from "../../lib/timing.js";

const SR = 48000;
const T = makeTiming(120);

/**
 * Render an onset schedule (ms) into a synthetic mono buffer.
 * Each impulse is a short decaying ~4 kHz burst (sharp click, energy well
 * above the 2 kHz highpass). Optionally add a low 60 Hz hum + deterministic
 * pseudo-noise to prove the highpass + flux stages are doing real work.
 */
function renderClicks(onsetsMs, { leadMs = 60, tailMs = 300, hum = 0, noise = 0 } = {}) {
    // Lead-in silence: a real listener is already recording before the
    // sender starts, so the very first click has a low-energy window before
    // it for the rising-edge detector to key off.
    const durMs = leadMs + (onsetsMs.length ? onsetsMs[onsetsMs.length - 1] : 0) + tailMs;
    const n = Math.ceil((durMs / 1000) * SR);
    const buf = new Float32Array(n);
    const clickLen = Math.round(0.01 * SR); // 10 ms
    const tau = 0.0015; // 1.5 ms decay
    for (const t0 of onsetsMs) {
        const start = Math.round(((t0 + leadMs) / 1000) * SR);
        for (let j = 0; j < clickLen && start + j < n; j++) {
            const tt = j / SR;
            buf[start + j] += 0.6 * Math.exp(-tt / tau) * Math.sin(2 * Math.PI * 4000 * tt);
        }
    }
    if (hum || noise) {
        for (let i = 0; i < n; i++) {
            const tt = i / SR;
            if (hum) buf[i] += hum * Math.sin(2 * Math.PI * 60 * tt);
            // deterministic low-level "noise": sum of a few incommensurate tones
            if (noise) {
                buf[i] += noise * (
                    Math.sin(2 * Math.PI * 137 * tt) +
                    Math.sin(2 * Math.PI * 311 * tt)
                ) * 0.5;
            }
        }
    }
    return buf;
}

describe("highpass + energyFlux primitives", () => {
    it("highpass removes a strong 60 Hz hum", () => {
        const n = SR; // 1 s
        const hum = new Float32Array(n);
        for (let i = 0; i < n; i++) hum[i] = Math.sin(2 * Math.PI * 60 * (i / SR));
        const filtered = highpass(hum, SR, 2000);
        let rmsIn = 0, rmsOut = 0;
        for (let i = 0; i < n; i++) { rmsIn += hum[i] ** 2; rmsOut += filtered[i] ** 2; }
        expect(Math.sqrt(rmsOut / n)).toBeLessThan(Math.sqrt(rmsIn / n) * 0.05);
    });

    it("energyFlux returns positive spikes around clicks", () => {
        const buf = renderClicks([100, 500]);
        const { flux } = energyFlux(highpass(buf, SR, 2000), SR, 5);
        let maxFlux = 0;
        for (const f of flux) if (f > maxFlux) maxFlux = f;
        expect(maxFlux).toBeGreaterThan(0);
    });
});

describe("detectTransientOnsets — count + timing", () => {
    it("finds all 12 impulses of SOS within 25 ms", () => {
        const { onsets } = textToSchedule("SOS", T);
        const detected = detectTransientOnsets(renderClicks(onsets), SR);
        expect(detected.length).toBe(onsets.length);
        // Compare spacing relative to the first onset (absorbs the constant
        // lead-in offset + any fixed detection latency).
        for (let i = 0; i < onsets.length; i++) {
            const exp = onsets[i] - onsets[0];
            const got = detected[i] - detected[0];
            expect(Math.abs(got - exp)).toBeLessThan(25);
        }
    });
});

describe("end-to-end: text -> clicks -> detect -> decode", () => {
    const phrases = ["SOS", "HI", "HELLO WORLD", "CQ CQ"];
    for (const text of phrases) {
        it(`recovers "${text}" from clean synthetic audio`, () => {
            const { onsets } = textToSchedule(text, T);
            const detected = detectTransientOnsets(renderClicks(onsets), SR);
            expect(decodeOnsets(detected, T).text).toBe(text);
        });

        it(`recovers "${text}" through 60 Hz hum + tonal noise`, () => {
            const { onsets } = textToSchedule(text, T);
            const buf = renderClicks(onsets, { hum: 0.15, noise: 0.03 });
            const detected = detectTransientOnsets(buf, SR);
            expect(decodeOnsets(detected, T).text).toBe(text);
        });
    }
});