<?php
/*************************************************************
# 076 License

Copyright (c) テクニカル諏訪子

Permission is hereby granted to any person obtaining a copy of the software
Little Beast (the "Software") to use, modify, merge, copy, publish, distribute,
sublicense, and/or sell copies of the Software, subject to the following conditions:

    1. **Origin Attribution**:
       - You must not misrepresent the origin of the Software; you must not claim
         you created the original Software.
       - If the Software is used in a product, you must either:
         a. Provide clear attribution in the product's documentation, user interface,
            or other visible areas, **OR**
         b. Pay the original developers a fee they specify in writing.
    2. **Usage Restriction**:
       - The Software, or any derivative works, dependencies, or libraries
         incorporating it, must not be used for censorship or to suppress freedom of
         speech, expression, or creativity. Prohibited uses include, but are not
         limited to:
         - Censorship of so-called "hate speech", visuals, non-mainstream opinions,
           ideas, or objective reality.
         - Tools or systems designed to restrict access to information or
           artistic works.
    3. **Notice Preservation**:
       - This license and the above copyright notice must remain intact in all copies
         of the source code.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE
OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
namespace Std\Lib;

/**
 * Base32とBase64（RFC 4648）
 *
 * Base32は二段階認証の秘密鍵（大文字・小文字、空白、ハイフン、パディングの有無は問わずに読む）、
 * Base64はURL用の変種（「-」と「_」）も使える。
 */
final class BaseN {
  private const B32 = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567';
  private const B64 = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
  private const B64URL = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_';

  public static function encode32(string $data, bool $pad = true): string {
    return self::encode($data, self::B32, 5, $pad ? 8 : 1);
  }

  /**
   * @throws \InvalidArgumentException  Base32ではない文字、又は有り得ない長さ
   */
  public static function decode32(string $text): string {
    $text = rtrim(strtoupper(str_replace([' ', '-', "\t", "\r", "\n"], '', $text)), '=');
    // 8文字（40ビット）の内、1・3・6文字で終わる事は無い
    if (in_array(strlen($text) % 8, [1, 3, 6], true)) throw new \InvalidArgumentException('Base32の長さが不正です。');
    return self::decode($text, self::B32, 5);
  }

  /**
   * @param bool $url  URL用（「+/」の代わりに「-_」）
   */
  public static function encode64(string $data, bool $url = false, bool $pad = true): string {
    return self::encode($data, $url ? self::B64URL : self::B64, 6, $pad ? 4 : 1);
  }

  /**
   * @throws \InvalidArgumentException  Base64ではない文字、又は有り得ない長さ
   */
  public static function decode64(string $text, bool $url = false): string {
    $text = rtrim(str_replace([' ', "\t", "\r", "\n"], '', $text), '=');
    if (strlen($text) % 4 === 1) throw new \InvalidArgumentException('Base64の長さが不正です。');
    return self::decode($text, $url ? self::B64URL : self::B64, 6);
  }

  /**
   * @param int $bits  1文字のビット数
   * @param int $block  パディングで揃える文字数（1なら付けない）
   */
  private static function encode(string $data, string $alphabet, int $bits, int $block): string {
    $out = '';
    $acc = 0;
    $n = 0;
    $mask = (1 << $bits) - 1;
    for ($i = 0, $len = strlen($data); $i < $len; $i++) {
      $acc = (($acc << 8) | ord($data[$i])) & 0xffff;
      $n += 8;
      while ($n >= $bits) {
        $n -= $bits;
        $out .= $alphabet[($acc >> $n) & $mask];
      }
    }
    if ($n > 0) $out .= $alphabet[($acc << ($bits - $n)) & $mask];
    $rest = strlen($out) % $block;
    return $rest ? $out.str_repeat('=', $block - $rest) : $out;
  }

  private static function decode(string $text, string $alphabet, int $bits): string {
    $out = '';
    $acc = 0;
    $n = 0;
    for ($i = 0, $len = strlen($text); $i < $len; $i++) {
      $v = strpos($alphabet, $text[$i]);
      if ($v === false) throw new \InvalidArgumentException('不正な文字があります。');
      $acc = (($acc << $bits) | $v) & 0xffff;
      $n += $bits;
      if ($n >= 8) {
        $n -= 8;
        $out .= chr(($acc >> $n) & 0xff);
      }
    }
    return $out;
  }
}