music-video-gen/metabolism/test/world.test.js

// The world must be deterministic, bounded, and fundamentally unstable under
// seed change — while two DIFFERENT songs must grow clearly different worlds.

import { test } from 'node:test';
import assert from 'node:assert/strict';
import { readFileSync } from 'node:fs';
import { fileURLToPath } from 'node:url';
import { resolve, dirname } from 'node:path';
import { analyse } from '../src/audio/analyse.js';
import { decodeWav, mono } from '../src/audio/wav.js';
import { buildSong } from '../src/song/song.js';
import { World } from '../src/sim/world.js';
import { Run } from '../src/film.js';
import { fingerprint, divergence } from '../src/metrics.js';

const HERE = dirname(fileURLToPath(import.meta.url));
const BANK = resolve(HERE, '../..', 'flow-state/test/songs');

function load(name) {
    const wav = decodeWav(readFileSync(resolve(BANK, `${name}.wav`)));
    return buildSong(analyse(mono(wav.channels), wav.sampleRate), 12345);
}

/** Run `seconds` of the world for song `name` with a seed. Returns world. */
function grow(name, seed, seconds = 20) {
    const song = load(name);
    const run = new Run(song, { fps: 30, seed, width: 240, height: 135, field: 64, genesis: 0 });
    for (let f = 0; f < Math.floor(seconds * 30); f++) {
        run.world.step();
        run.camera.update(f);
    }
    return { world: run.world, song };
}

test('same seed reproduces identical history', () => {
    const { world: a } = grow('drone', 12345);
    const { world: b } = grow('drone', 12345);
    assert.deepEqual(Array.from(a.history.alive), Array.from(b.history.alive));
    assert.deepEqual(Array.from(a.history.movement), Array.from(b.history.movement));
    assert.deepEqual(Array.from(a.trail[0]), Array.from(b.trail[0]));
    assert.equal(a.frame, b.frame);
});

test('different seeds give different ecologies', () => {
    const { world: a } = grow('drone', 12345);
    const { world: b } = grow('drone', 99999);
    const moved = a.history.movement.some((v, i) => Math.abs(v - b.history.movement[i]) > 1e-3);
    assert.ok(moved, 'ecologies should diverge under a different seed');
});

test('population stays within bounds and alive', () => {
    const { world: w } = grow('runner', 12345, 30);
    for (const v of w.history.alive) {
        assert.ok(v <= w.cap + 40, `population exceeded cap: ${v}`);
    }
    assert.ok(w.history.alive.some((v) => v > 0), 'the dish should stay inhabited');
});

test('field and trail never go negative', () => {
    const { world: w } = grow('drone', 7, 25);
    for (const v of w.resource) assert.ok(v >= -1e-9, `negative resource ${v}`);
    for (let c = 0; c < 3; c++) {
        for (const v of w.trail[c]) assert.ok(v >= -1e-9, `negative trail ${v}`);
    }
});

test('trail mass reflects a busy vs sparse world', () => {
    const sparse = grow('drone', 12345, 25);
    const dense = grow('runner', 12345, 25);
    assert.ok(dense.world.count > sparse.world.count * 1.5);
});

test('three songs grow fingerprints further apart than seeds of one song', () => {
    const a = fingerprint(grow('drone', 12345).world);
    const b = fingerprint(grow('runner', 12345).world);
    const c = fingerprint(grow('dusk', 12345).world);
    const cross = Math.max(divergence(a, b), divergence(a, c), divergence(b, c));
    const a2 = fingerprint(grow('drone', 99).world);
    const within = divergence(a, a2);
    assert.ok(cross > within * 2, `cross ${cross} !> 2×within ${within}`);
});

test('genesis pre-simulates generations so frame 0 is already an ecosystem', () => {
    const song = load('drone');
    const withGenesis = new Run(song, { fps: 30, seed: 12345, width: 240, height: 135, field: 64 });
    const without = new Run(song, { fps: 30, seed: 12345, width: 240, height: 135, field: 64, genesis: 0 });

    assert.ok(withGenesis.world.genesisFrames > 0, 'song should demand a genesis epoch');
    // The world at frame 0 is more evolved (generations already lived)…
    assert.ok(withGenesis.world.count > without.world.count * 1.1,
        `genesis world should be more populated (${withGenesis.world.count} vs ${without.world.count})`);
    // …and the ground already carries history, where a fresh plate has none.
    assert.ok(withGenesis.world.sampleTrailMass() > 0.00003,
        `genesis world should already hold ink (${withGenesis.world.sampleTrailMass()})`);
    assert.equal(withGenesis.world.history.alive[0], 0, 'genesis must not record into the film');
    assert.equal(withGenesis.world.frame, -1, 'the film starts at frame 0');
});

test('the region pool is exact: parallel == serial, bit for bit', () => {
    const grow = (workers, { frames = 150, seed = 12345 } = {}) => {
        const song = load('drone');
        const run = new Run(song, { fps: 30, seed, width: 240, height: 135, field: 64, genesis: 0, workers });
        for (let f = 0; f < frames; f++) { run.world.step(); run.camera.update(f); }
        const history = Array.from(run.world.history.alive.slice(0, frames));
        const trail = Array.from(run.world.trail[0].slice(0, 4000));
        run.world.dispose?.();
        return { history, trail };
    };
    const serial = grow(0);
    const two = grow(2);
    const four = grow(4);
    const eq = (a, b) => a.history.every((v, i) => v === b.history[i]) &&
        a.trail.every((v, i) => v === b.trail[i]);
    assert.ok(eq(serial, two), '2 regions must match the serial world exactly');
    assert.ok(eq(serial, four), '4 regions must match the serial world exactly');

    // LONG: across a section boundary (drone's drop lands at frame 1545) and
    // with a seed distinct from song.seed (the workers must be told the same
    // seed — they seed their own jitter-noise fields). A 150-frame run inside
    // one section with the default seed passes even with both bugs present.
    const longSerial = grow(0, { frames: 1600, seed: 999 });
    const longTwo = grow(2, { frames: 1600, seed: 999 });
    const longEq = (a, b) => a.history.every((v, i) => v === b.history[i]) &&
        a.trail.every((v, i) => v === b.trail[i]);
    assert.ok(longEq(longSerial, longTwo),
        '2 regions must match the serial world exactly across the section boundary');
});

test('genesis is deterministic and song-scaled', () => {
    const a = new Run(load('drone'), { fps: 30, seed: 12345, width: 240, height: 135, field: 64 });
    const b = new Run(load('drone'), { fps: 30, seed: 12345, width: 240, height: 135, field: 64 });
    assert.equal(a.world.genesisFrames, b.world.genesisFrames);
    assert.deepEqual(Array.from(a.world.pop[0]), Array.from(b.world.pop[0]));

    const runner = new Run(load('runner'), { fps: 30, seed: 12345, width: 240, height: 135, field: 64 });
    assert.notEqual(a.world.genesisFrames, runner.world.genesisFrames,
        'the genesis amount should depend on the song');
});