/* eslint-disable @typescript-eslint/no-unsafe-function-type, @typescript-eslint/no-explicit-any, @typescript-eslint/no-unsafe-return */
type ValidFlow< Fns > = Fns extends []
	? []
	: Fns extends [ ( i: infer I ) => infer R ]
	? [ ( i: I ) => R ]
	: Fns extends [ ( i: infer I1 ) => infer O1, ...infer Rest1 ]
	? Rest1 extends [ ( i: infer I2 ) => any, ...infer Rest2 ]
		? [ O1 ] extends [ I2 ]
			? [ ( i: I1 ) => O1, ...ValidFlow< Rest1 > ]
			: [ ( i: I1 ) => O1, ( i: O1 ) => unknown, ...ValidFlow< Rest2 > ]
		: [ never ]
	: [ never ];

type Input< Fns extends Function[] > = Fns extends [
	( i: infer I ) => any,
	...Function[],
]
	? I
	: never;

type Output< Fns extends Function[] > = Fns extends [
	( i: any ) => infer R,
	...infer Rest,
]
	? Rest extends []
		? R
		: Rest extends Function[]
		? Output< Rest >
		: never
	: never;

export function flow< Fns extends Function[] >(
	...fns: Fns extends ValidFlow< Fns > ? Fns : ValidFlow< Fns >
): ( input: Input< Fns > ) => Output< Fns > {
	return ( input: Input< Fns > ) =>
		( fns as Array< ( i: any ) => any > ).reduce(
			( r, f ) => f( r ),
			input as any
		) as Output< Fns >;
}