ComputationOptions

import type { ComputationOptions } from "@shadow-js/core/extend";

interface ComputationOptions {
  /**
   * `"memo"` creates a cached value that readers pull with {@link readComputation}; `"effect"`
   * creates a side effect that the scheduler runs.
   */
  kind: "memo" | "effect";
  /**
   * The computation. It is tracked: every source it reads becomes a dependency. It receives the
   * previous value (a memo's last value, or an effect's last computed value when `apply` is set;
   * `undefined` otherwise). A memo stores its result; an effect without `apply` may return a
   * cleanup function.
   */
  fn: (previous: never) => unknown;
  /**
   * Memos: decides whether a recomputation changed the value; readers are notified only when it
   * returns `false`, and `false` always propagates. Ignored for effects.
   * @default Object.is
   */
  equals?: Equals<unknown>;
  /**
   * Label shown by devtools and diagnostics.
   * @default undefined (the node is unnamed)
   */
  name?: string;
  /**
   * Effects: run in the render phase, synchronously at creation and before user effects in each
   * flush. Ignored for memos.
   * @default false
   */
  render?: boolean;
  /**
   * Effects with `apply`: skip the first call of `apply`; `fn` still runs and tracks.
   * @default false
   */
  defer?: boolean;
  /**
   * Memos: do not compute until the first read.
   * @default false (the memo computes once at creation)
   */
  lazy?: boolean;
  /**
   * Memos that run component setup (such as a hot-reload wrapper): writing signals inside is
   * legitimate there, so the dev-mode write guard stays off.
   * @default false
   */
  allowWrites?: boolean;
  /**
   * Effects: second stage, run untracked with the value `fn` computed and the previous one. It may
   * return a cleanup function.
   * @default undefined (`fn` is the whole effect)
   */
  apply?: (value: never, previous: never) => unknown;
  /**
   * Owner to attach to. `null` creates a node that no owner disposes.
   * @default the current owner
   */
  owner?: Owner | null;
  /**
   * Effects: always run in the transition lane (the watcher behind `useDeferredValue`).
   * @default false
   */
  lane?: boolean;
}