// The evaluation layer must be well-behaved: every world gets a finite,
// clamped score, coupling and residual are separable, and the fitness
// discriminates between songs (in the sense that the spread across songs is
// clearly larger than the spread across seeds).

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 { Run } from '../src/film.js';
import { evaluate, fingerprint, divergence } from '../src/metrics.js';

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

function grow(name, seed, seconds = 45) {
    const wav = decodeWav(readFileSync(resolve(BANK, `${name}.wav`)));
    const song = buildSong(analyse(mono(wav.channels), wav.sampleRate), seed);
    const run = new Run(song, { fps: 30, seed, width: 240, height: 135 });
    run.simulate();
    return { world: run.world, song };
}

test('evaluation returns finite, clamped numbers', () => {
    for (const name of ['drone', 'runner', 'dusk']) {
        const { world, song } = grow(name, 12345);
        const m = evaluate(world, song);
        assert.ok(Number.isFinite(m.coupling), `${name} coupling`);
        assert.ok(Number.isFinite(m.residual), `${name} residual`);
        assert.ok(Number.isFinite(m.fitness), `${name} fitness`);
        assert.ok(m.coupling >= 0 && m.coupling <= 1);
        assert.ok(m.residual >= 0 && m.residual <= 1);
    }
});

test('fitness is stable across seeds of one song', () => {
    const songs = ['drone', 'runner', 'dusk'].map((n) => grow(n, 12345).song);
    for (const song of songs) {
        const s1 = evaluate(growSong(song, 111).world, growSong(song, 111).song);
        const s2 = evaluate(growSong(song, 222).world, growSong(song, 222).song);
        assert.ok(Math.abs(s1.fitness - s2.fitness) < 0.05, `${song.name}: ${s1.fitness} vs ${s2.fitness}`);
    }
});

test('fingerprint distances: songs farther than seeds', () => {
    const a = fingerprint(grow('drone', 12345).world);
    const b = fingerprint(grow('runner', 12345).world);
    const within = divergence(a, fingerprint(grow('drone', 42).world));
    assert.ok(divergence(a, b) > within);
});

function growSong(song, seed) {
    const run = new Run(song, { fps: 30, seed, width: 240, height: 135 });
    run.simulate();
    return { world: run.world, song };
}