interface key-value {
  // A handle to an open key-value store
  type store = u32;

  // The set of errors which may be raised by functions in this interface
  variant error {
    // Too many stores have been opened simultaneously. Closing one or more
    // stores prior to retrying may address this.
    store-table-full,

    // The host does not recognize the store name requested.  Defining and
    // configuring a store with that name in a runtime configuration file
    // may address this.
    no-such-store,

    // The requesting component does not have access to the specified store
    // (which may or may not exist).
    access-denied,

    // The store handle provided is not recognized, i.e. it was either never
    // opened or has been closed.
    invalid-store,

    // No key-value tuple exists for the specified key in the specified
    // store.
    no-such-key,

    // Some implementation-specific error has occurred (e.g. I/O)
    io(string)
  }

  // Open the store with the specified name.
  //
  // If `name` is "default", the default store is opened.  Otherwise,
  // `name` must refer to a store defined and configured in a runtime
  // configuration file supplied with the application.
  //
  // `error::no-such-store` will be raised if the `name` is not recognized.
  open: func(name: string) -> result<store, error>;

  // Get the value associated with the specified `key` from the specified
  // `store`.
  //
  // `error::invalid-store` will be raised if `store` is not a valid handle
  // to an open store, and `error::no-such-key` will be raised if there is no
  // tuple for `key` in `store`.
  get: func(store: store, key: string) -> result<list<u8>, error>;

  // Set the `value` associated with the specified `key` in the specified
  // `store`, overwriting any existing value.
  //
  // `error::invalid-store` will be raised if `store` is not a valid handle
  // to an open store.
  set: func(store: store, key: string, value: list<u8>) -> result<_, error>;

  // Delete the tuple with the specified `key` from the specified `store`.
  //
  // `error::invalid-store` will be raised if `store` is not a valid handle
  // to an open store.  No error is raised if a tuple did not previously
  // exist for `key`.
  delete: func(store: store, key: string) -> result<_, error>;

  // Return whether a tuple exists for the specified `key` in the specified
  // `store`.
  //
  // `error::invalid-store` will be raised if `store` is not a valid handle
  // to an open store.
  exists: func(store: store, key: string) -> result<bool, error>;

  // Return a list of all the keys in the specified `store`.
  //
  // `error::invalid-store` will be raised if `store` is not a valid handle
  // to an open store.
  get-keys: func(store: store) -> result<list<string>, error>;

  // Close the specified `store`.
  //
  // This has no effect if `store` is not a valid handle to an open store.
  close: func(store: store);
}