import {Primitive} from './basic';

/**
Create a type from another type with all keys and nested keys set to optional.

Use-cases:
- Merging a default settings/config object with another object, the second object would be a deep partial of the default object.
- Mocking and testing complex entities, where populating an entire object with its keys would be redundant in terms of the mock or test.

@example
```
import {PartialDeep} from 'type-fest';

const settings: Settings = {
	textEditor: {
		fontSize: 14;
		fontColor: '#000000';
		fontWeight: 400;
	}
	autocomplete: false;
	autosave: true;
};

const applySavedSettings = (savedSettings: PartialDeep) => {
	return {...settings, ...savedSettings};
}

settings = applySavedSettings({textEditor: {fontWeight: 500}});
```
*/
export type PartialDeep = T extends Primitive
	? Partial
	: T extends Map
	? PartialMapDeep
	: T extends Set
	? PartialSetDeep
	: T extends ReadonlyMap
	? PartialReadonlyMapDeep
	: T extends ReadonlySet
	? PartialReadonlySetDeep
	: T extends ((...arguments: any[]) => unknown)
	? T | undefined
	: T extends object
	? PartialObjectDeep
	: unknown;

/**
Same as `PartialDeep`, but accepts only `Map`s and  as inputs. Internal helper for `PartialDeep`.
*/
interface PartialMapDeep extends Map, PartialDeep> {}

/**
Same as `PartialDeep`, but accepts only `Set`s as inputs. Internal helper for `PartialDeep`.
*/
interface PartialSetDeep extends Set> {}

/**
Same as `PartialDeep`, but accepts only `ReadonlyMap`s as inputs. Internal helper for `PartialDeep`.
*/
interface PartialReadonlyMapDeep extends ReadonlyMap, PartialDeep> {}

/**
Same as `PartialDeep`, but accepts only `ReadonlySet`s as inputs. Internal helper for `PartialDeep`.
*/
interface PartialReadonlySetDeep extends ReadonlySet> {}

/**
Same as `PartialDeep`, but accepts only `object`s as inputs. Internal helper for `PartialDeep`.
*/
type PartialObjectDeep = {
	[KeyType in keyof ObjectType]?: PartialDeep
};