type-fest/source/readonly-deep.d.ts

import {Primitive} from './basic';

/**
Convert `object`s, `Map`s, `Set`s, and `Array`s and all of their keys/elements into immutable structures recursively.

This is useful when a deeply nested structure needs to be exposed as completely immutable, for example, an imported JSON module or when receiving an API response that is passed around.

Please upvote [this issue](https://github.com/microsoft/TypeScript/issues/13923) if you want to have this type as a built-in in TypeScript.

@example
```
// data.json
{
	"foo": ["bar"]
}

// main.ts
import {ReadonlyDeep} from 'type-fest';
import dataJson = require('./data.json');

const data: ReadonlyDeep<typeof dataJson> = dataJson;

export default data;

// test.ts
import data from './main';

data.foo.push('bar');
//=> error TS2339: Property 'push' does not exist on type 'readonly string[]'
```
*/
export type ReadonlyDeep<T> = T extends Primitive | ((...arguments: any[]) => unknown)
	? T
	: T extends ReadonlyMap<infer KeyType, infer ValueType>
	? ReadonlyMapDeep<KeyType, ValueType>
	: T extends ReadonlySet<infer ItemType>
	? ReadonlySetDeep<ItemType>
	: T extends object
	? ReadonlyObjectDeep<T>
	: unknown;

/**
Same as `ReadonlyDeep`, but accepts only `ReadonlyMap`s as inputs. Internal helper for `ReadonlyDeep`.
*/
interface ReadonlyMapDeep<KeyType, ValueType>
	extends ReadonlyMap<ReadonlyDeep<KeyType>, ReadonlyDeep<ValueType>> {}

/**
Same as `ReadonlyDeep`, but accepts only `ReadonlySet`s as inputs. Internal helper for `ReadonlyDeep`.
*/
interface ReadonlySetDeep<ItemType>
	extends ReadonlySet<ReadonlyDeep<ItemType>> {}

/**
Same as `ReadonlyDeep`, but accepts only `object`s as inputs. Internal helper for `ReadonlyDeep`.
*/
type ReadonlyObjectDeep<ObjectType extends object> = {
	readonly [KeyType in keyof ObjectType]: ReadonlyDeep<ObjectType[KeyType]>
};