/**
* generateServerId Utilities
*
* DESIGN PATTERNS:
* - Pure functions with no side effects
* - Single responsibility per function
* - Functional programming approach
*
* CODING STANDARDS:
* - Export individual functions, not classes
* - Use descriptive function names with verbs
* - Add JSDoc comments for complex logic
* - Keep functions small and focused
*
* AVOID:
* - Side effects (mutating external state)
* - Stateful logic (use services for state)
* - Complex external dependencies
*/
import { randomBytes } from 'node:crypto';
/**
* Character set for generating human-readable IDs.
* Excludes confusing characters: 0, O, 1, l, I
*/
const CHARSET = '23456789abcdefghjkmnpqrstuvwxyz';
/**
* Default length for generated server IDs (6 characters)
*/
const DEFAULT_ID_LENGTH = 6;
/**
* Generate a short, human-readable server ID.
*
* Uses Node.js crypto.randomBytes for cryptographically secure randomness
* with rejection sampling to avoid modulo bias.
*
* The generated ID:
* - Is 6 characters long by default
* - Uses only lowercase alphanumeric characters
* - Excludes confusing characters (0, O, 1, l, I)
*
* @param length - Length of the ID to generate (default: 6)
* @returns A random, human-readable ID
*
* @example
* generateServerId() // "abc234"
* generateServerId(4) // "x7mn"
*/
export function generateServerId(length: number = DEFAULT_ID_LENGTH): string {
const charsetLength = CHARSET.length;
// Compute the largest value we can safely accept without introducing modulo bias.
// For a single random byte (0-255), we only accept values up to the highest
// multiple of charsetLength that is <= 255.
const maxUnbiased = Math.floor(256 / charsetLength) * charsetLength - 1;
let result = '';
let remaining = length;
while (remaining > 0) {
const bytes = randomBytes(remaining);
for (let i = 0; i < bytes.length && remaining > 0; i++) {
const byte = bytes[i];
// Discard values that would introduce bias when using modulo.
if (byte > maxUnbiased) {
continue;
}
result += CHARSET[byte % charsetLength];
remaining--;
}
}
return result;
}
