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| 1 | <?php |
| 2 | |
| 3 | namespace TonyBogdanov\Alphabase; |
| 4 | |
| 5 | use TonyBogdanov\Alphabase\Exception\InvalidAlphabetException; |
| 6 | use TonyBogdanov\Alphabase\Exception\InvalidInputException; |
| 7 | |
| 8 | /** |
| 9 | * Class Converter |
| 10 | * |
| 11 | * @package TonyBogdanov\Alphabase |
| 12 | */ |
| 13 | class Converter { |
| 14 | |
| 15 | /** @var array[] */ |
| 16 | protected static array $alphabets = []; |
| 17 | |
| 18 | /** |
| 19 | * @param string $symbols |
| 20 | * @return array |
| 21 | * @throws InvalidAlphabetException |
| 22 | */ |
| 23 | protected static function createAlphabet( string $symbols ): array { |
| 24 | |
| 25 | if ( ! isset( static::$alphabets[ $symbols ] ) ) { |
| 26 | |
| 27 | $alphabet = str_split( $symbols ); |
| 28 | $unique = array_unique( $alphabet ); |
| 29 | |
| 30 | if ( count( $unique ) !== count( $alphabet ) ) { |
| 31 | throw new InvalidAlphabetException( 'The alphabet must contain only unique characters.' ); |
| 32 | } |
| 33 | |
| 34 | if ( 2 > count( $unique ) ) { |
| 35 | throw new InvalidAlphabetException( sprintf( |
| 36 | 'The alphabet must contain at least 2 characters, got: %d.', |
| 37 | count( $unique ), |
| 38 | ) ); |
| 39 | } |
| 40 | |
| 41 | static::$alphabets[ $symbols ] = [ $unique, array_flip( $unique ) ]; |
| 42 | |
| 43 | } |
| 44 | |
| 45 | return static::$alphabets[ $symbols ]; |
| 46 | |
| 47 | } |
| 48 | |
| 49 | /** |
| 50 | * @param string $input |
| 51 | * @param string $inputAlphabet |
| 52 | * @param string $outputAlphabet |
| 53 | * @return string |
| 54 | * @throws InvalidAlphabetException |
| 55 | * @throws InvalidInputException |
| 56 | */ |
| 57 | public static function convert( string $input, string $inputAlphabet, string $outputAlphabet ): string { |
| 58 | |
| 59 | if ( '' === $input ) { |
| 60 | return ''; |
| 61 | } |
| 62 | |
| 63 | [ $is, $isf ] = static::createAlphabet( $inputAlphabet ); |
| 64 | [ $os ] = static::createAlphabet( $outputAlphabet ); |
| 65 | |
| 66 | $invalid = array_diff( array_unique( str_split( $input ) ), $is ); |
| 67 | if ( 0 < count( $invalid ) ) { |
| 68 | throw new InvalidInputException( sprintf( |
| 69 | 'The input string contains characters outside of the input alphabet: %s.', |
| 70 | json_encode( array_values( $invalid ) ), |
| 71 | ) ); |
| 72 | } |
| 73 | |
| 74 | $ib = count( $is ); |
| 75 | $ob = count( $os ); |
| 76 | |
| 77 | $carry = preg_match( '/^' . preg_quote( $is[0], '/' ) . '+/', $input, $match ) ? strlen( $match[0] ) : 0; |
| 78 | if ( $carry === strlen( $input ) ) { |
| 79 | return str_repeat( $os[0], $carry ); |
| 80 | } |
| 81 | |
| 82 | $value = '0'; |
| 83 | foreach ( array_reverse( str_split( substr( $input, $carry ) ) ) as $index => $symbol ) { |
| 84 | $value = bcadd( $value, bcmul( $isf[ $symbol ], bcpow( $ib, $index ) ) ); |
| 85 | } |
| 86 | |
| 87 | $result = []; |
| 88 | while ( -1 === bccomp( 0, $value ) ) { |
| 89 | array_unshift( $result, $os[ (int) bcmod( $value, $ob ) ] ); |
| 90 | $value = bcdiv( $value, $ob ); |
| 91 | } |
| 92 | |
| 93 | return ( 0 < $carry ? str_repeat( $os[0], $carry ) : '' ) . implode( '', $result ); |
| 94 | |
| 95 | } |
| 96 | |
| 97 | } |