Type-Level SQL Parser in TypeScript

This challenge asks you to build a rudimentary SQL parser at the type level in TypeScript. Type-level programming allows us to perform computations and validations during compile time, leading to more robust and safer code. This parser will focus on extracting table and column names from a simplified SELECT statement, demonstrating the power of TypeScript's type system.

Problem Description

You are tasked with creating a type-level function parseSelectStatement that takes a string representing a simplified SELECT statement and extracts the table and column names. The input string will follow a specific format: "SELECT column1, column2 FROM table_name;". The function should return a type representing an object with two properties: table (a string) and columns (a tuple of strings).

Key Requirements:

• Input: A string representing a SELECT statement in the format "SELECT column1, column2 FROM table_name;".
• Output: A type representing an object with the following structure: { table: string; columns: [string, ...string]; }.
• Error Handling: If the input string does not match the expected format, the function should return never. This signifies a parsing error at compile time.
• Column Extraction: The columns property should be a tuple containing all the column names listed in the SELECT clause, in the order they appear.
• Table Extraction: The table property should contain the table name specified in the FROM clause.

Expected Behavior:

The function should leverage TypeScript's type manipulation capabilities to parse the string and construct the desired type. It should not involve runtime parsing or string manipulation. The parsing should be entirely performed at compile time.

Edge Cases to Consider:

• Empty SELECT clause (e.g., "SELECT FROM table_name;"). Should return never.
• No FROM clause (e.g., "SELECT column1, column2;"). Should return never.
• Multiple spaces around commas or keywords. The parser should be robust enough to handle these variations.
• Invalid characters in column or table names. While not strictly required, consider how you might represent this (e.g., by returning never).
• Statements with more than one table (e.g., "SELECT column1 FROM table1, table2;"). This challenge focuses on a single table. Returning never is acceptable.

Examples

Example 1:

Input: "SELECT column1, column2 FROM table_name;"
Output: { table: "table_name", columns: ["column1", "column2"] }
Explanation: The function correctly extracts "table_name" as the table and ["column1", "column2"] as the columns.

Example 2:

Input: "SELECT column1 FROM table_name;"
Output: { table: "table_name", columns: ["column1"] }
Explanation: The function correctly extracts "table_name" as the table and ["column1"] as the columns.

Example 3:

Input: "SELECT  column1 , column2 FROM table_name ;"
Output: { table: "table_name", columns: ["column1", "column2"] }
Explanation: The function handles extra spaces correctly.

Example 4:

Input: "SELECT FROM table_name;"
Output: never
Explanation:  Missing columns, so parsing fails.

Example 5:

Input: "SELECT column1, column2;"
Output: never
Explanation: Missing FROM clause, so parsing fails.

Constraints

• Input String Length: The input string will be no longer than 256 characters.
• Column/Table Name Length: Column and table names will be no longer than 32 characters.
• Number of Columns: The SELECT statement can contain a maximum of 10 columns.
• Type Safety: The solution must be type-safe and leverage TypeScript's type system for parsing. Runtime parsing is not allowed.
• Performance: While not a primary concern, the solution should be reasonably efficient in terms of compile time. Excessively complex type manipulations could lead to long compilation times.

Notes

• This is a challenging problem that requires a good understanding of TypeScript's advanced type features, including conditional types, tuple types, and mapped types.
• Consider breaking down the problem into smaller, more manageable steps. For example, you could first create a type to represent a single column, then a type to represent a list of columns, and finally a type to represent the entire SELECT statement.
• The goal is to demonstrate the possibility of type-level parsing, not to create a fully functional SQL parser. This is a simplified scenario.
• Think about how you can use TypeScript's type inference capabilities to your advantage.
• The use of string literal types can be helpful for defining the expected input format.
• Remember that the parser should fail (return never) if the input string does not conform to the expected format. This is crucial for type safety.