Advent of Typescript 2023

day24.ts

type Santa = "🎅";
type Alley = "  ";
type MazeMatrix = MazeItem[][];
type MazeItem = "🎄" | "🎅" | "  ";
type Directions = "up" | "down" | "left" | "right";

type FindSantaCol<
	T extends MazeItem[],
	A extends any[] = [],
	AL extends number = A["length"],
> = AL extends T["length"] ? never : T[AL] extends Santa ? AL : FindSantaCol<T, ["", ...A]>;
type FindSanta<
	M extends MazeMatrix,
	R extends any[] = [],
	C extends any[] = [],
> = Santa extends M[R["length"]][number]
	? [R["length"], FindSantaCol<M[R["length"]]>]
	: FindSanta<M, ["", ...R], C>;

type GetCol<
	B extends any[][],
	C extends number,
	A extends any[] = [],
> = A["length"] extends B["length"] ? A : GetCol<B, C, [...A, B[A["length"]][C]]>;

type CheckPathR<R extends MazeItem[], A extends any[] = []> = R extends [
	infer F1 extends MazeItem,
	infer F2 extends MazeItem,
	...infer R extends MazeItem[],
]
	? [F1, F2] extends [Santa, Alley]
		? ["", ...A]["length"]
		: CheckPathR<[F2, ...R], ["", ...A]>
	: null;
type CheckPathL<R extends MazeItem[], A extends any[] = []> = R extends [
	infer F1 extends MazeItem,
	infer F2 extends MazeItem,
	...infer R extends MazeItem[],
]
	? [F1, F2] extends [Alley, Santa]
		? A["length"]
		: CheckPathL<[F2, ...R], ["", ...A]>
	: null;

type CheckDir<
	R extends MazeItem[],
	C extends MazeItem[],
	D extends Directions,
	RI extends number,
	CI extends number,
> = D extends "left"
	? [RI, CheckPathL<R>]
	: D extends "up"
		? [CheckPathL<C>, CI]
		: D extends "right"
			? [RI, CheckPathR<R>]
			: D extends "down"
				? [CheckPathR<C>, CI]
				: null;

type FillRow<
	R extends any[],
	C extends number,
	M extends string,
	A extends any[] = [],
	I extends number = A["length"],
> = I extends R["length"] ? A : FillRow<R, C, M, [...A, I extends C ? M : R[I]]>;

type MoveSanta<
	M extends MazeMatrix,
	R extends number,
	C extends number,
	S extends MazeItem,
	A extends MazeMatrix = [],
> = M extends [infer F extends MazeItem[], ...infer L extends MazeMatrix]
	? A["length"] extends R
		? [...A, FillRow<F, C, S>, ...L]
		: MoveSanta<L, R, C, S, [...A, F]>
	: never;

type CR<L extends number, A extends "🍪"[] = []> = A["length"] extends L ? A : CR<L, ["🍪", ...A]>;
type MakeCookies<M extends MazeMatrix, A extends "🍪"[][] = []> = A["length"] extends M["length"]
	? A
	: MakeCookies<M, [...A, CR<M[0]["length"]>]>;

type Move<M extends MazeMatrix, D extends Directions> = FindSanta<M> extends [
	infer R extends number,
	infer C extends number,
]
	? [R, C] extends [5, 0]
		? MakeCookies<M>
		: CheckDir<M[R], GetCol<M, C>, D, R, C> extends [
					infer R1 extends number,
					infer C1 extends number,
			  ]
			? MoveSanta<MoveSanta<M, R, C, "  ">, R1, C1, Santa>
			: M
	: never;