/* @flow */

export type Base64String = string;

export type ResolvedGlobalId = {
  type: string,
  id: string,
};

export function base64(i: string): Base64String {
  return Buffer.from(i, 'ascii').toString('base64');
}

export function unbase64(i: Base64String): string {
  return Buffer.from(i, 'base64').toString('ascii');
}

/**
 * Takes a type name and an ID specific to that type name, and returns a
 * "global ID" that is unique among all types.
 */
export function toGlobalId(type: string, id: string | number): string {
  return base64([type, id].join(':'));
}

/**
 * Takes the "global ID" created by toGlobalID, and returns the type name and ID
 * used to create it.
 */
export function fromGlobalId(globalId: string): ResolvedGlobalId {
  const unbasedGlobalId = unbase64(globalId);
  const delimiterPos = unbasedGlobalId.indexOf(':');
  return {
    type: unbasedGlobalId.substring(0, delimiterPos),
    id: unbasedGlobalId.substring(delimiterPos + 1),
  };
}