export interface ParsedAssetSpec {
  id: string;
  kind: 'image' | 'video' | 'audio' | 'subtitle' | 'other';
  path: string;
  sceneIndex?: number;
  backend?: string;
}

const ALLOWED_KINDS = new Set(['image', 'video', 'audio', 'subtitle', 'other']);
// A URI/URL scheme prefix (http://, https://, Asset://, gobananas://, gs://, s3://, …)
// — its internal `://` and any `:port` would be shredded by a naive split(':').
const SCHEME_RE = /^[a-zA-Z][a-zA-Z0-9+.\-]*:\/\//;
// For a scheme path, peel an optional trailing `:sceneIndex[:backend]` from the END
// so the URL (which may itself contain colons) is preserved intact.
const TRAILING_RE = /^(.*?)(?::(\d+)(?::([^:]+))?)?$/;

/**
 * Parse a `--asset kind:path[:sceneIndex][:backend]` spec. The path may be a
 * local file path OR a URL / `Asset://` URI whose internal colons must survive.
 * Local paths keep the original positional split (byte-identical behavior);
 * scheme paths peel the trailing `:sceneIndex[:backend]` from the end instead.
 */
export function parseAssetSpec(raw: string): ParsedAssetSpec {
  const firstColon = raw.indexOf(':');
  const kindRaw = firstColon >= 0 ? raw.slice(0, firstColon) : '';
  const remainder = firstColon >= 0 ? raw.slice(firstColon + 1) : '';
  if (!kindRaw || !remainder) {
    throw new Error(`Invalid --asset value: "${raw}". Expected kind:path[:sceneIndex][:backend]`);
  }

  let path: string;
  let sceneIndexRaw: string | undefined;
  let backend: string | undefined;

  if (SCHEME_RE.test(remainder)) {
    const match = TRAILING_RE.exec(remainder);
    path = match?.[1] ?? remainder;
    sceneIndexRaw = match?.[2];
    backend = match?.[3];
  } else {
    [path, sceneIndexRaw, backend] = remainder.split(':');
  }

  const kind = (ALLOWED_KINDS.has(kindRaw) ? kindRaw : 'other') as ParsedAssetSpec['kind'];
  const sceneIndex = sceneIndexRaw !== undefined && sceneIndexRaw !== '' ? Number(sceneIndexRaw) : undefined;
  return {
    id: `${kind}-${path}`,
    kind,
    path,
    ...(Number.isFinite(sceneIndex) ? { sceneIndex } : {}),
    ...(backend ? { backend } : {}),
  };
}