// Copyright: © 2026 TWWIM UG. All rights reserved. (www.twwim.com)
//
// UTF-8-safe wrappers around atob. Vanilla atob() returns Latin-1 bytes, which
// JSON.parse then mis-decodes for any non-ASCII payload (em-dashes, umlauts).
// `base64UrlToUtf8` additionally normalises base64url -> base64 for JWT parts.

export function base64ToUtf8(input: string): string {
  const binary = atob(input);
  const bytes = new Uint8Array(binary.length);
  for (let i = 0; i < binary.length; i++) {
    bytes[i] = binary.charCodeAt(i);
  }
  return new TextDecoder().decode(bytes);
}

export function base64UrlToUtf8(input: string): string {
  let normalised = input.replace(/-/g, '+').replace(/_/g, '/');
  const padding = normalised.length % 4;
  if (padding) {
    normalised += '='.repeat(4 - padding);
  }
  return base64ToUtf8(normalised);
}