src/services/oauth/crypto.ts

import { createHash, randomBytes } from 'crypto'

function base64URLEncode(buffer: Buffer): string {
  return buffer
    .toString('base64')
    .replace(/\+/g, '-')
    .replace(/\//g, '_')
    .replace(/=/g, '')
}

export function generateCodeVerifier(): string {
  return base64URLEncode(randomBytes(32))
}

export function generateCodeChallenge(verifier: string): string {
  const hash = createHash('sha256')
  hash.update(verifier)
  return base64URLEncode(hash.digest())
}

export function generateState(): string {
  return base64URLEncode(randomBytes(32))
}