<?php

namespace Matomo\Dependencies;

/**
 * Encode / Decode Base64 VLQ.
 *
 * @private
 */
class Less_SourceMap_Base64VLQ
{
    /**
     * Shift
     *
     * @var int
     */
    private $shift = 5;
    /**
     * Mask
     *
     * @var int
     */
    private $mask = 0x1f;
    // == (1 << shift) == 0b00011111
    /**
     * Continuation bit
     *
     * @var int
     */
    private $continuationBit = 0x20;
    // == (mask - 1 ) == 0b00100000
    /**
     * Char to integer map
     *
     * @var array
     */
    private $charToIntMap = ['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, 'a' => 26, 'b' => 27, 'c' => 28, 'd' => 29, 'e' => 30, 'f' => 31, 'g' => 32, 'h' => 33, 'i' => 34, 'j' => 35, 'k' => 36, 'l' => 37, 'm' => 38, 'n' => 39, 'o' => 40, 'p' => 41, 'q' => 42, 'r' => 43, 's' => 44, 't' => 45, 'u' => 46, 'v' => 47, 'w' => 48, 'x' => 49, 'y' => 50, 'z' => 51, 0 => 52, 1 => 53, 2 => 54, 3 => 55, 4 => 56, 5 => 57, 6 => 58, 7 => 59, 8 => 60, 9 => 61, '+' => 62, '/' => 63];
    /**
     * Integer to char map
     *
     * @var array
     */
    private $intToCharMap = [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 => 'a', 27 => 'b', 28 => 'c', 29 => 'd', 30 => 'e', 31 => 'f', 32 => 'g', 33 => 'h', 34 => 'i', 35 => 'j', 36 => 'k', 37 => 'l', 38 => 'm', 39 => 'n', 40 => 'o', 41 => 'p', 42 => 'q', 43 => 'r', 44 => 's', 45 => 't', 46 => 'u', 47 => 'v', 48 => 'w', 49 => 'x', 50 => 'y', 51 => 'z', 52 => '0', 53 => '1', 54 => '2', 55 => '3', 56 => '4', 57 => '5', 58 => '6', 59 => '7', 60 => '8', 61 => '9', 62 => '+', 63 => '/'];
    /**
     * Constructor
     */
    public function __construct()
    {
        // I leave it here for future reference
        // foreach(str_split('ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/') as $i => $char)
        // {
        //	 $this->charToIntMap[$char] = $i;
        //	 $this->intToCharMap[$i] = $char;
        // }
    }
    /**
     * Convert from a two-complement value to a value where the sign bit is
     * is placed in the least significant bit.	For example, as decimals:
     *	 1 becomes 2 (10 binary), -1 becomes 3 (11 binary)
     *	 2 becomes 4 (100 binary), -2 becomes 5 (101 binary)
     * We generate the value for 32 bit machines, hence -2147483648 becomes 1, not 4294967297,
     * even on a 64 bit machine.
     * @param int $aValue
     */
    public function toVLQSigned($aValue)
    {
        return 0xffffffff & ($aValue < 0 ? (-$aValue << 1) + 1 : ($aValue << 1) + 0);
    }
    /**
     * Convert to a two-complement value from a value where the sign bit is
     * is placed in the least significant bit. For example, as decimals:
     *	 2 (10 binary) becomes 1, 3 (11 binary) becomes -1
     *	 4 (100 binary) becomes 2, 5 (101 binary) becomes -2
     * We assume that the value was generated with a 32 bit machine in mind.
     * Hence
     *	 1 becomes -2147483648
     * even on a 64 bit machine.
     * @param int $aValue
     */
    public function fromVLQSigned($aValue)
    {
        return $aValue & 1 ? $this->zeroFill(~$aValue + 2, 1) | -1 - 0x7fffffff : $this->zeroFill($aValue, 1);
    }
    /**
     * Return the base 64 VLQ encoded value.
     *
     * @param int $aValue The value to encode
     * @return string The encoded value
     */
    public function encode($aValue)
    {
        $encoded = '';
        $vlq = $this->toVLQSigned($aValue);
        do {
            $digit = $vlq & $this->mask;
            $vlq = $this->zeroFill($vlq, $this->shift);
            if ($vlq > 0) {
                $digit |= $this->continuationBit;
            }
            $encoded .= $this->base64Encode($digit);
        } while ($vlq > 0);
        return $encoded;
    }
    /**
     * Return the value decoded from base 64 VLQ.
     *
     * @param string $encoded The encoded value to decode
     * @return int The decoded value
     */
    public function decode($encoded)
    {
        $vlq = 0;
        $i = 0;
        do {
            $digit = $this->base64Decode($encoded[$i]);
            $vlq |= ($digit & $this->mask) << $i * $this->shift;
            $i++;
        } while ($digit & $this->continuationBit);
        return $this->fromVLQSigned($vlq);
    }
    /**
     * Right shift with zero fill.
     *
     * @param int $a number to shift
     * @param int $b number of bits to shift
     * @return int
     */
    public function zeroFill($a, $b)
    {
        return $a >= 0 ? $a >> $b : $a >> $b & \PHP_INT_MAX >> $b - 1;
    }
    /**
     * Encode single 6-bit digit as base64.
     *
     * @param int $number
     * @return string
     * @throws Exception If the number is invalid
     */
    public function base64Encode($number)
    {
        if ($number < 0 || $number > 63) {
            throw new \Exception(\sprintf('Invalid number "%s" given. Must be between 0 and 63.', (string) $number));
        }
        return $this->intToCharMap[$number];
    }
    /**
     * Decode single 6-bit digit from base64
     *
     * @param string $char
     * @return int
     * @throws Exception If the number is invalid
     */
    public function base64Decode($char)
    {
        if (!\array_key_exists($char, $this->charToIntMap)) {
            throw new \Exception(\sprintf('Invalid base 64 digit "%s" given.', $char));
        }
        return $this->charToIntMap[$char];
    }
}
