Snapshot

Type

interface Snapshot {
  getResponse(endpoint, ...args)​ => { data, expiryStatus, expiresAt };
  getError(endpoint, ...args)​ => ErrorTypes | undefined;
  fetchedAt: number;
}

With Generics

import type { ErrorTypes } from './ErrorTypes.js';
import type { EndpointInterface } from './interface.js';
import type { DenormalizeNullable } from './normal.js';

export interface SnapshotInterface {
  getResponse: <
    E extends Pick<EndpointInterface, 'key' | 'schema' | 'invalidIfStale'>,
    Args extends readonly [...Parameters<E['key']>],
  >(
    endpoint: E,
    ...args: Args
  ) => {
    data: DenormalizeNullable<E['schema']>;
    expiryStatus: ExpiryStatusInterface;
    expiresAt: number;
  };

  getError: <
    E extends Pick<EndpointInterface, 'key'>,
    Args extends readonly [...Parameters<E['key']>],
  >(
    endpoint: E,
    ...args: Args
  ) => ErrorTypes | undefined;

  readonly fetchedAt: number;
}

// looser version to allow for cross-package version compatibility
export type ExpiryStatusInterface = 1 | 2 | 3;

tip

Use Controller.snapshot() to construct a snapshot

Snapshots passed to user-defined function that are used to compute state updates. These allow safe and performant access to the denormalized data based on the current state.

getResponse(endpoint, ...args)

returns

{
  data: DenormalizeNullable<E['schema']>;
  expiryStatus: ExpiryStatus;
  expiresAt: number;
}

Gets the (globally referentially stable) response for a given endpoint/args pair from state given.

data

The denormalize response data. Guarantees global referential stability for all members.

expiryStatus

export enum ExpiryStatus {
  Invalid = 1,
  InvalidIfStale,
  Valid,
}

Valid

• Will never suspend.
• Might fetch if data is stale

InvalidIfStale

• Will suspend if data is stale.
• Might fetch if data is stale

Invalid

• Will always suspend
• Will always fetch

expiresAt

A number representing time when it expires. Compare to Date.now().

getError(endpoint, ...args)

Gets the error, if any, for a given endpoint. Returns undefined for no errors.

fetchedAt

When the fetch was called that resulted in this snapshot.