TypeScript: Implement a Trim Utility Type

This challenge asks you to create a TypeScript utility type called Trim. This type should be able to remove leading and trailing whitespace from string literal types. This is a common task when dealing with user input or data from external sources, ensuring consistency and preventing unexpected behavior due to stray spaces.

Problem Description

Your task is to define a generic TypeScript type Trim<S> that accepts a string literal type S and returns a new string literal type with all leading and trailing whitespace characters removed.

Key Requirements:

• The Trim type should handle standard whitespace characters: space ( ), tab (\t), newline (\n), and carriage return (\r).
• It should only remove whitespace from the beginning and end of the string. Whitespace in the middle of the string should be preserved.
• The type should work with various string literal inputs, including empty strings, strings with only whitespace, and strings with no whitespace.

Expected Behavior:

• If the input string has leading whitespace, it should be removed.
• If the input string has trailing whitespace, it should be removed.
• If the input string has both leading and trailing whitespace, both should be removed.
• If the input string has no leading or trailing whitespace, it should remain unchanged.
• If the input string is an empty string, it should remain an empty string.
• If the input string consists entirely of whitespace, it should result in an empty string.

Edge Cases to Consider:

• Strings with only leading whitespace.
• Strings with only trailing whitespace.
• Strings with both leading and trailing whitespace.
• Strings with no whitespace.
• Empty strings.
• Strings composed entirely of whitespace.
• Strings with multiple types of whitespace (e.g., leading spaces and trailing tabs).

Examples

Example 1:

type Input1 = "  Hello World  ";
type Output1 = Trim<Input1>; // Expected: "Hello World"

Explanation: Leading and trailing spaces are removed from " Hello World ".

Example 2:

type Input2 = "\t\n   TypeScript   \r";
type Output2 = Trim<Input2>; // Expected: "TypeScript"

Explanation: Leading tabs, newlines, spaces, and trailing carriage return are removed from "\t\n TypeScript \r".

Example 3:

type Input3 = "NoSpaces";
type Output3 = Trim<Input3>; // Expected: "NoSpaces"

Explanation: The string "NoSpaces" has no leading or trailing whitespace, so it remains unchanged.

Example 4:

type Input4 = " ";
type Output4 = Trim<Input4>; // Expected: ""

Explanation: A string consisting only of a space is trimmed to an empty string.

Example 5:

type Input5 = "";
type Output5 = Trim<Input5>; // Expected: ""

Explanation: An empty string remains an empty string.

Constraints

• Your solution must be a single generic type alias in TypeScript.
• You cannot use any external libraries or JavaScript runtime features directly within the type definition. You must rely solely on TypeScript's type-level manipulation capabilities.
• The solution should be efficient and avoid overly complex recursive structures if a simpler approach exists.

Notes

Consider how TypeScript's conditional types and template literal types can be used to deconstruct and reconstruct string literal types. You might need to think about how to recursively check for and remove whitespace characters from both ends of the string.

Think about the base cases for your type's recursion. What happens when there's no more whitespace to remove, or when the string becomes empty?