Type-Level String Reversal in TypeScript

This challenge focuses on leveraging TypeScript's advanced type system to perform string manipulation at compile time. You will create a type that can reverse a given string literal. This is a valuable exercise for understanding the power and expressiveness of TypeScript's template literal types and conditional types.

Problem Description

Your task is to create a TypeScript type called ReverseString that accepts a string literal type as input and returns a new string literal type that is the reverse of the input.

Key Requirements

1. Type-Level Operation: The reversal must happen entirely at the type level. No runtime JavaScript code should be involved.
2. Template Literal Types: You should primarily use TypeScript's template literal types for string manipulation.
3. Recursive or Iterative Approach: You will likely need a recursive or iterative type-level pattern to process the string character by character.

Expected Behavior

The ReverseString type should correctly reverse any valid string literal it's applied to.

Edge Cases to Consider

• Empty String: How should ReverseString<""> behave?
• Single Character String: How should ReverseString<"a"> behave?
• Strings with Spaces and Special Characters: The reversal should handle these correctly.

Examples

Example 1:

type Original = "hello";
type Reversed = ReverseString<Original>;

Output:

"olleh"

Explanation: The type Reversed should resolve to the string literal "olleh".

Example 2:

type Original = "TypeScript";
type Reversed = ReverseString<Original>;

Output:

"tpircSepyT"

Explanation: The type Reversed should resolve to the string literal "tpircSepyT".

Example 3:

type Original = "";
type Reversed = ReverseString<Original>;

Output:

""

Explanation: An empty string reversed is still an empty string.

Example 4:

type Original = "a";
type Reversed = ReverseString<Original>;

Output:

"a"

Explanation: A single character string reversed is itself.

Constraints

• The solution must be a pure TypeScript type definition.
• No runtime code execution is allowed.
• The solution should be reasonably efficient for typical string lengths (e.g., up to 100 characters). Extremely long strings might hit TypeScript's recursion depth limits, but this is generally not a primary concern for this type of challenge unless explicitly stated.

Notes

• Consider how you can break down a string literal into its constituent characters at the type level.
• Think about how you can build the reversed string progressively.
• You may need to use conditional types and inferential types to achieve this.
• This problem is an excellent way to practice recursive type definitions in TypeScript.