<?php
//namespace Base32;

/**
 * Base32 encoder and decoder
 *
 * Last update: 2012-06-20
 *
 * RFC 4648 compliant
 * @link http://www.ietf.org/rfc/rfc4648.txt
 *
 * Some groundwork based on this class
 * https://github.com/NTICompass/PHP-Base32
 *
 * @author Christian Riesen <chris.riesen@gmail.com>
 * @link http://christianriesen.com
 * @license MIT License see LICENSE file
 */
class Base32
{
	/**
	 * Table for encoding base32
	 *
	 * @var array
	 */
	private static $encode = array(
        0 => 'A',
        1 => 'B',
        2 => 'C',
        3 => 'D',
        4 => 'E',
        5 => 'F',
        6 => 'G',
        7 => 'H',
        8 => 'I',
        9 => 'J',
        10 => 'K',
        11 => 'L',
        12 => 'M',
        13 => 'N',
        14 => 'O',
        15 => 'P',
        16 => 'Q',
        17 => 'R',
        18 => 'S',
        19 => 'T',
        20 => 'U',
        21 => 'V',
        22 => 'W',
        23 => 'X',
        24 => 'Y',
        25 => 'Z',
        26 => 2,
        27 => 3,
        28 => 4,
        29 => 5,
        30 => 6,
        31 => 7,
        32 => '=',
    );
	
	/**
	 * Table for decoding base32
	 *
	 * @var array
	 */
	private static $decode = array(
        'A' => 0,
        'B' => 1,
        'C' => 2,
        'D' => 3,
        'E' => 4,
        'F' => 5,
        'G' => 6,
        'H' => 7,
        'I' => 8,
        'J' => 9,
        'K' => 10,
        'L' => 11,
        'M' => 12,
        'N' => 13,
        'O' => 14,
        'P' => 15,
        'Q' => 16,
        'R' => 17,
        'S' => 18,
        'T' => 19,
        'U' => 20,
        'V' => 21,
        'W' => 22,
        'X' => 23,
        'Y' => 24,
        'Z' => 25,
        2 => 26,
        3 => 27,
        4 => 28,
        5 => 29,
        6 => 30,
        7 => 31,
        '=' => 32,
    );
	
	/**
	 * Creates an array from a binary string into a given chunk size
	 *
	 * @param string $binaryString String to chunk
	 * @param integer $bits Number of bits per chunk
	 * @return array
	 */
	private static function chunk($binaryString, $bits)
	{
		$binaryString = chunk_split($binaryString, $bits, ' ');
		
		if (substr($binaryString, (strlen($binaryString)) - 1)  == ' ') {
			$binaryString = substr($binaryString, 0, strlen($binaryString)-1);
		}
		
		return explode(' ', $binaryString);
	}
	
	/**
	 * Encodes into base32
	 *
	 * @param string $string Clear text string
	 * @return string Base32 encoded string
	 */
	public static function encode($string)
	{
		if (strlen($string) == 0) {
			// Gives an empty string
			return '';
		}
		
		// Convert string to binary
		$binaryString = '';
		
		foreach (str_split($string) as $s) {
			// Return each character as an 8-bit binary string
			$s = decbin(ord($s));
			$binaryString .= str_pad($s, 8, 0, STR_PAD_LEFT);
		}
		
		// Break into 5-bit chunks, then break that into an array
		$binaryArray = self::chunk($binaryString, 5);
		
		// Pad array to be divisible by 8
		while (count($binaryArray) % 8 !== 0) {
			$binaryArray[] = null;
		}
		
		$base32String = '';
		
		// Encode in base32
		foreach ($binaryArray as $bin) {
			$char = 32;
			
			if (!is_null($bin)) {
				// Pad the binary strings
				$bin = str_pad($bin, 5, 0, STR_PAD_RIGHT);
				$char = bindec($bin);
			}
			
			// Base32 character
			$base32String .= self::$encode[$char];
		}
		
		return $base32String;
	}
	
	/**
	 * Decodes base32
	 *
	 * @param string $base32String Base32 encoded string
	 * @return string Clear text string
	 */
	public static function decode($base32String)
	{
		if (strlen($base32String) == 0) {
			// Gives an empty string
			return '';
		}
		
		// Only work in upper cases
		$base32String = strtoupper($base32String);
		
		// Remove anything that is not base32 alphabet
		$pattern = '/[^A-Z2-7]/';
		$replacement = '';
		
		$base32String = preg_replace($pattern, '', $base32String);
		
		$base32Array = str_split($base32String);
		
		$binaryArray = array();
		$string = '';
		
		foreach ($base32Array as $str) {
			$char = self::$decode[$str];
			
			// Ignore the padding character
			if ($char !== 32) {
				$char = decbin($char);
				$string .= str_pad($char, 5, 0, STR_PAD_LEFT);
			}
		}
		
		while (strlen($string) %8 !== 0) {
			$string = substr($string, 0, strlen($string)-1);
		}
		
		$binaryArray = self::chunk($string, 8);
		
		$realString = '';
		
		foreach ($binaryArray as $bin) {
			// Pad each value to 8 bits
			$bin = str_pad($bin, 8, 0, STR_PAD_RIGHT);
			// Convert binary strings to ascii
			$realString .= chr(bindec($bin));
		}
		
		return $realString;
	}
}