// Song serialization — the prepare step (EVOLUTION.md).
//
// The whole analysis is deterministic, so a song's *processed* form can be
// written out once and loaded instead of re-derived from the WAV. This module
// is the single serializer for both sides: node's tools/prepare.js writes the
// artifact, the browser deserializes it. `deserializeSong` rebuilds the song
// through the SAME buildSong call the live path uses, so a prepared song is
// bit-identical to one analysed from the WAV — prepare is a cache, never a
// parallel pipeline.

import { buildSong } from './song.js';

const VERSION = 1;

/** Compact everything downstream (world, camera, metrics) needs. */
export function serializeSong(song) {
    const a = song.analysis;
    return {
        version: VERSION,
        seed: song.seed,
        fps: a.fps,
        frames: a.frames,
        duration: a.duration,
        sampleRate: a.sampleRate,
        energy: Array.from(a.energy),
        flux: Array.from(a.flux),
        dominantHz: Array.from(a.dominantHz),
        flatness: Array.from(a.flatness),
        onsets: a.onsets,
        sections: a.sections,
        summary: a.summary,
    };
}

/** Rebuild the analysis object the pipeline expects. */
export function deserializeAnalysis(obj) {
    return {
        fps: obj.fps,
        frames: obj.frames,
        duration: obj.duration,
        sampleRate: obj.sampleRate,
        energy: Float32Array.from(obj.energy),
        flux: Float32Array.from(obj.flux),
        dominantHz: Float32Array.from(obj.dominantHz),
        flatness: Float32Array.from(obj.flatness),
        onsets: obj.onsets,
        sections: obj.sections,
        summary: obj.summary,
    };
}

/**
 * Rebuild a song from a prepared artifact. Same code path as the live WAV
 * pipeline (buildSong over a reconstructed analysis), so the world, the camera
 * and the metrics cannot drift from it.
 * @param {object} obj serializedSong() output
 */
export function deserializeSong(obj) {
    if (obj.version !== VERSION) throw new Error(`prepared song version mismatch: ${obj.version}`);
    return buildSong(deserializeAnalysis(obj), obj.seed);
}