escape-string-literals-typescript.ts

// Splits `T` at the first occurrence of `S`.
type SplitBy<T extends string, S extends string> =
	T extends `${infer A}${S}${infer B}`
	? { before: A, split: S, after: B }
	: never;

type SplitInfo = { before: string, split: string, after: string };

type UseShorter<A extends SplitInfo, B extends SplitInfo> =
	A["before"] extends `${B["before"]}${infer R}` ? B : A;

// Given a tuple of `SplitInfo`, returns the one which has a `before` that is a
// prefix of all others.
type UseShortest<A extends SplitInfo[]> =
	A extends [infer Only]
	? Only & SplitInfo
	: A extends [infer First, ...infer Rest]
	? UseShorter<First & SplitInfo, UseShortest<Rest extends SplitInfo[] ? Rest : never>>
	: never;

// Performs `SplitBy` on each splitter in `R`, and returns the shortest `before`
// split using `UseShortest`.
type ShortestSplit<T extends string, R extends [... string[]]> = UseShortest<{ [K in keyof R]: SplitBy<T, R[K] extends string ? R[K] : never> }>;

// Leaves `before` alone.
// Wraps each `split` in parentheses.
// Recursively invokes `Escaping` on the `after`.
type ExpandEscaping<T extends SplitInfo, Splitters extends [...string[]]> =
	`${T["before"]}(${T["split"]})${Escaping<T["after"], Splitters>}`;

// Wrap each occurrence of any of the `Splitters` within `T` in parentheses.
type Escaping<T extends string, Splitters extends [...string[]]> =
	T extends `${infer _1}${Splitters[number]}${infer _2}`
	? ExpandEscaping<ShortestSplit<T, Splitters>, Splitters>
	: T;

// type z = "alpha(,)beta(@)gamma(,)delta(@)banana"
type z = Escaping<"alpha,beta@gamma,delta@banana", [",", "@"]>;