types.ts

import type * as t from "@babel/types";
import { NodePath } from "./index";
import type { VirtualTypeAliases } from "./path/lib/virtual-types";

export type Visitor<S = {}> = VisitNodeObject<S, t.Node> & {
  [Type in t.Node["type"]]?: VisitNode<S, Extract<t.Node, { type: Type }>>;
} & {
  [K in keyof t.Aliases]?: VisitNode<S, t.Aliases[K]>;
} & {
  [K in keyof VirtualTypeAliases]?: VisitNode<S, VirtualTypeAliases[K]>;
} & {
  [K in keyof InternalVisitorFlags]?: InternalVisitorFlags[K];
} & {
  // Babel supports `NodeTypesWithoutComment | NodeTypesWithoutComment | ... ` but it is
  // too complex for TS. So we type it as a general visitor only if the key contains `|`
  // this is good enough for non-visitor traverse options e.g. `noScope`
  [k: `${string}|${string}`]: VisitNode<S, t.Node>;
};

/** @internal */
type InternalVisitorFlags = {
  _exploded?: boolean;
  _verified?: boolean;
};

export type VisitNode<S, P extends t.Node> =
  | VisitNodeFunction<S, P>
  | VisitNodeObject<S, P>;

export type VisitNodeFunction<S, P extends t.Node> = (
  this: S,
  path: NodePath<P>,
  state: S,
) => void;

export interface VisitNodeObject<S, P extends t.Node> {
  enter?: VisitNodeFunction<S, P>;
  exit?: VisitNodeFunction<S, P>;
}