/**
 * Loads the config manifest and every JSON file it references.
 *
 *   data/manifest.json:  { "files": ["game.json", "menu.json", "ship.json"] }
 *
 * Adding a config file = drop the .json in /data + one line in the manifest.
 * Each file becomes a section keyed by its file name (without .json), so
 * `ship.json` is available as `config.get('ship.thrust')`.
 */
export class ConfigLoader {
  static async load(manifestPath = 'data/manifest.json') {
    const manifest = await this.fetchJson(manifestPath);
    const files = Array.isArray(manifest?.files) ? manifest.files : [];
    // Resolve config files relative to the manifest's own location,
    // so this works with relative or absolute manifest paths.
    const base = manifestPath.replace(/[^/]*$/, '');

    const data = {};
    for (const file of files) {
      const name = file.split('/').pop().replace(/\.json$/i, '');
      data[name] = await this.fetchJson(base + file);
    }
    return data;
  }

  static async fetchJson(path) {
    const res = await fetch(path);
    if (!res.ok) {
      throw new Error(`Could not load config "${path}" (${res.status} ${res.statusText})`);
    }
    return res.json();
  }
}