import { createCapability } from './capabilities'

/**
 * Namespaced key/value store for app and middleware metadata.
 *
 * `(namespace, key)` is the composite identity. Keep both values separate;
 * joining them with a delimiter can create collisions.
 */
export interface MetadataStore {
  /** Return the value for `(namespace, key)`, or `null` when it is absent. */
  get: (namespace: string, key: string) => Promise<unknown | null>
  /** Insert or replace the value for `(namespace, key)`. */
  set: (namespace: string, key: string, value: unknown) => Promise<void>
  /** Delete `(namespace, key)`. Do nothing when it is absent. */
  delete: (namespace: string, key: string) => Promise<void>
}

export const MetadataCapability = createCapability<MetadataStore>()('metadata')

export const [getMetadata, provideMetadata] = MetadataCapability