export type SyncEngineMode = "legacy" | "shadow" | "livestore-read-pilot" | "livestore";

const VALID_SYNC_ENGINE_MODES: ReadonlySet<SyncEngineMode> = new Set([
  "legacy",
  "shadow",
  "livestore-read-pilot",
  "livestore",
]);

export function resolveSyncEngineMode(raw: string | undefined): SyncEngineMode {
  if (!raw || raw.trim().length === 0) {
    return "livestore";
  }
  const normalized = raw.trim().toLowerCase();
  if (VALID_SYNC_ENGINE_MODES.has(normalized as SyncEngineMode)) {
    return normalized as SyncEngineMode;
  }
  throw new Error(
    `Invalid T3CODE_SYNC_ENGINE_MODE: ${raw}. Expected "legacy", "shadow", "livestore-read-pilot", or "livestore".`,
  );
}

export function assertSyncEngineModeAllowed(
  syncEngineMode: SyncEngineMode,
  options: { enforceLiveStoreOnly?: boolean } = {},
): void {
  if (!options.enforceLiveStoreOnly) {
    return;
  }
  if (syncEngineMode === "legacy" || syncEngineMode === "shadow") {
    throw new Error(
      `Sync engine mode "${syncEngineMode}" is disabled because T3CODE_LIVESTORE_ENFORCE_MODE is enabled.`,
    );
  }
}