<?php

/**
 * Pure-PHP arbitrary precision integer arithmetic library.
 *
 * Supports base-2, base-10, base-16, and base-256 numbers.  Uses the GMP or BCMath extensions, if available,
 * and an internal implementation, otherwise.
 *
 * PHP version 5 and 7
 *
 * Here's an example of how to use this library:
 * <code>
 * <?php
 *    $a = new \phpseclib\Math\BigInteger(2);
 *    $b = new \phpseclib\Math\BigInteger(3);
 *
 *    $c = $a->add($b);
 *
 *    echo $c->toString(); // outputs 5
 * ?>
 * </code>
 *
 * @category  Math
 * @package   BigInteger
 * @author    Jim Wigginton <terrafrost@php.net>
 * @copyright 2017 Jim Wigginton
 * @license   http://www.opensource.org/licenses/mit-license.html  MIT License
 */

namespace phpseclib\Math;

use phpseclib\Exception\BadConfigurationException;

/**
 * Pure-PHP arbitrary precision integer arithmetic library. Supports base-2, base-10, base-16, and base-256
 * numbers.
 *
 * @package BigInteger
 * @author  Jim Wigginton <terrafrost@php.net>
 * @access  public
 */
class BigInteger implements \Serializable
{
    /**
     * Main Engine
     *
     * @var string
     */
    private static $mainEngine;

    /**
     * Modular Exponentiation Engine
     *
     * @var string
     */
    private static $modexpEngine;

    /**
     * Selected Engines
     *
     * @var array
     */
    private static $engines;

    /**
     * The actual BigInteger object
     *
     * @var object
     */
    private $value;

    /**
     * Sets engine type.
     *
     * Throws an exception if the type is invalid
     *
     * @param string $main
     * @param array $modexps optional
     */
    public static function setEngine($main, $modexps = ['DefaultEngine'])
    {
        self::$engines = [];

        $fqmain = 'phpseclib\\Math\\BigInteger\\Engines\\' . $main;
        if (!class_exists($fqmain) || !method_exists($fqmain, 'isValidEngine')) {
            throw new \InvalidArgumentException("$main is not a valid engine");
        }
        if (!$fqmain::isValidEngine()) {
            throw new BadConfigurationException("$main is not setup correctly on this system");
        }
        self::$mainEngine = $fqmain;

        if (!in_array('Default', $modexps)) {
            $modexps[] = 'DefaultEngine';
        }

        $found = false;
        foreach ($modexps as $modexp) {
            try {
                $fqmain::setModExpEngine($modexp);
                $found = true;
                break;
            } catch (\Exception $e) {
            }
        }

        if (!$found) {
            throw new BadConfigurationException("No valid modular exponentiation engine found for $main");
        }

        self::$modexpEngine = $modexp;

        self::$engines = [$main, $modexp];
    }

    /**
     * Returns the engine type
     *
     * @return string[]
     */
    public static function getEngine()
    {
        self::initialize_static_variables();

        return self::$engines;
    }

    /**
     * Initialize static variables
     */
    private static function initialize_static_variables()
    {
        if (!isset(self::$mainEngine)) {
            $engines = [
                ['GMP'],
                ['PHP64', ['OpenSSL']],
                ['BCMath', ['OpenSSL']],
                ['PHP32', ['OpenSSL']]
            ];
            foreach ($engines as $engine) {
                try {
                    self::setEngine($engine[0], isset($engine[1]) ? $engine[1] : []);
                    break;
                } catch (\Exception $e) {
                }
            }
        }
    }

    /**
     * Converts base-2, base-10, base-16, and binary strings (base-256) to BigIntegers.
     *
     * If the second parameter - $base - is negative, then it will be assumed that the number's are encoded using
     * two's compliment.  The sole exception to this is -10, which is treated the same as 10 is.
     *
     * @param $x integer|BigInteger\Engines\Engine Base-10 number or base-$base number if $base set.
     * @param int $base
     * @return BigInteger
     */
    public function __construct($x = 0, $base = 10)
    {
        self::initialize_static_variables();

        if ($x instanceof self::$mainEngine) {
            $this->value = clone $x;
        } elseif ($x instanceof BigInteger\Engines\Engine) {
            $this->value = new static("$x");
            $this->value->setPrecision($x->getPrecision());
        } else {
            $this->value = new self::$mainEngine($x, $base);
        }
    }

    /**
     * Converts a BigInteger to a base-10 number.
     *
     * @return string
     */
    public function toString()
    {
        return $this->value->toString();
    }

    /**
     *  __toString() magic method
     */
    public function __toString()
    {
        return (string) $this->value;
    }

    /**
     *  __debugInfo() magic method
     *
     * Will be called, automatically, when print_r() or var_dump() are called
     */
    public function __debugInfo()
    {
        return $this->value->__debugInfo();
    }

    /**
     * Converts a BigInteger to a byte string (eg. base-256).
     *
     * @param bool $twos_compliment
     * @return string
     */
    public function toBytes($twos_compliment = false)
    {
        return $this->value->toBytes($twos_compliment);
    }

    /**
     * Converts a BigInteger to a hex string (eg. base-16).
     *
     * @param bool $twos_compliment
     * @return string
     */
    public function toHex($twos_compliment = false)
    {
        return $this->value->toHex($twos_compliment);
    }

    /**
     * Converts a BigInteger to a bit string (eg. base-2).
     *
     * Negative numbers are saved as positive numbers, unless $twos_compliment is set to true, at which point, they're
     * saved as two's compliment.
     *
     * @param bool $twos_compliment
     * @return string
     */
    function toBits($twos_compliment = false)
    {
        return $this->value->toBits();
    }

    /**
     * Adds two BigIntegers.
     *
     * @param BigInteger $y
     * @return BigInteger
     */
    public function add(BigInteger $y)
    {
        return new static($this->value->add($y->value));
    }

    /**
     * Subtracts two BigIntegers.
     *
     * @param BigInteger $y
     * @return BigInteger
     */
    function subtract(BigInteger $y)
    {
        return new static($this->value->subtract($y->value));
    }

    /**
     * Multiplies two BigIntegers
     *
     * @param BigInteger $x
     * @return BigInteger
     */
    public function multiply(BigInteger $x)
    {
        return new static($this->value->multiply($x->value));
    }

    /**
     * Divides two BigIntegers.
     *
     * Returns an array whose first element contains the quotient and whose second element contains the
     * "common residue".  If the remainder would be positive, the "common residue" and the remainder are the
     * same.  If the remainder would be negative, the "common residue" is equal to the sum of the remainder
     * and the divisor (basically, the "common residue" is the first positive modulo).
     *
     * Here's an example:
     * <code>
     * <?php
     *    $a = new \phpseclib\Math\BigInteger('10');
     *    $b = new \phpseclib\Math\BigInteger('20');
     *
     *    list($quotient, $remainder) = $a->divide($b);
     *
     *    echo $quotient->toString(); // outputs 0
     *    echo "\r\n";
     *    echo $remainder->toString(); // outputs 10
     * ?>
     * </code>
     *
     * @param BigInteger $y
     * @return BigInteger[]
     */
    public function divide(BigInteger $y)
    {
        list($q, $r) = $this->value->divide($y->value);
        return [
            new static($q),
            new static($r)
        ];
    }

    /**
     * Calculates modular inverses.
     *
     * Say you have (30 mod 17 * x mod 17) mod 17 == 1.  x can be found using modular inverses.
     * @return BigInteger
     * @param BigInteger $n
     */
    public function modInverse(BigInteger $n)
    {
        return new static($this->value->modInverse($n->value));
    }

    /**
     * Calculates modular inverses.
     *
     * Say you have (30 mod 17 * x mod 17) mod 17 == 1.  x can be found using modular inverses.
     * @return BigInteger[]
     * @param BigInteger $n
     */
    public function extendedGCD(BigInteger $n)
    {
        extract($this->value->extendedGCD($n->value));
        /**
         * @var BigInteger $gcd
         * @var BigInteger $x
         * @var BigInteger $y
         */
        return [
            'gcd' => new static($gcd),
            'x' => new static($x),
            'y' => new static($y)
        ];
    }

    /**
     * Calculates the greatest common divisor
     *
     * Say you have 693 and 609.  The GCD is 21.
     *
     * @param BigInteger $n
     * @return BigInteger
     */
    public function gcd(BigInteger $n)
    {
        return new static($this->value->gcd($n->value));
    }

    /**
     * Absolute value.
     *
     * @return BigInteger
     * @access public
     */
    public function abs()
    {
         return new static($this->value->abs());
    }

    /**
     * Set Precision
     *
     * Some bitwise operations give different results depending on the precision being used.  Examples include left
     * shift, not, and rotates.
     *
     * @param int $bits
     */
    public function setPrecision($bits)
    {
        $this->value->setPrecision($bits);
    }

    /**
     * Get Precision
     *
     * Returns the precision if it exists, false if it doesn't
     *
     * @return int|bool
     */
    public function getPrecision()
    {
        return $this->value->getPrecision();
    }

    /**
     * Serialize
     *
     * Will be called, automatically, when serialize() is called on a BigInteger object.
     *
     * phpseclib 1.0 serialized strings look like this:
     * O:15:"Math_BigInteger":1:{s:3:"hex";s:18:"00ab54a98ceb1f0ad2";}
     *
     * phpseclib 3.0 serialized strings look like this:
     * C:25:"phpseclib\Math\BigInteger":42:{a:1:{s:3:"hex";s:18:"00ab54a98ceb1f0ad2";}}
     *
     * @return string
     */
    public function serialize()
    {
        $val = ['hex' => $this->toHex(true)];
        $precision = $this->value->getPrecision();
        if ($precision > 0) {
            $val['precision'] = $precision;
        }
        return serialize($val);
    }

    /**
     * Serialize
     *
     * Will be called, automatically, when unserialize() is called on a BigInteger object.
     *
     * @param string $serialized
     */
    public function unserialize($serialized)
    {
        $r = unserialize($serialized);
        $temp = new static($r['hex'], -16);
        $this->value = $temp->value;
        if (isset($r['precision'])) {
            // recalculate $this->bitmask
            $this->setPrecision($r['precision']);
        }
    }

    /**
     * Performs modular exponentiation.
     *
     * @param BigInteger $e
     * @param BigInteger $n
     * @return BigInteger
     */
    public function powMod(BigInteger $e, BigInteger $n)
    {
        return new static($this->value->powMod($e->value, $n->value));
    }

    /**
     * Performs modular exponentiation.
     *
     * @param BigInteger $e
     * @param BigInteger $n
     * @return BigInteger
     */
    public function modPow(BigInteger $e, BigInteger $n)
    {
        return new static($this->value->modPow($e->value, $n->value));
    }

    /**
     * Compares two numbers.
     *
     * Although one might think !$x->compare($y) means $x != $y, it, in fact, means the opposite.  The reason for this is
     * demonstrated thusly:
     *
     * $x  > $y: $x->compare($y)  > 0
     * $x  < $y: $x->compare($y)  < 0
     * $x == $y: $x->compare($y) == 0
     *
     * Note how the same comparison operator is used.  If you want to test for equality, use $x->equals($y).
     *
     * @param BigInteger $y
     * @return int < 0 if $this is less than $y; > 0 if $this is greater than $y, and 0 if they are equal.
     * @access public
     * @see self::equals()
     * @internal Could return $this->subtract($x), but that's not as fast as what we do do.
     */
    public function compare(BigInteger $y)
    {
        return $this->value->compare($y->value);
    }

    /**
     * Tests the equality of two numbers.
     *
     * If you need to see if one number is greater than or less than another number, use BigInteger::compare()
     *
     * @param BigInteger $x
     * @return bool
     */
    public function equals(BigInteger $x)
    {
        return $this->value->equals($x->value);
    }

    /**
     * Logical Not
     *
     * @return BigInteger
     */
    public function bitwise_not()
    {
        return new static($this->value->bitwise_not());
    }

    /**
     * Logical And
     *
     * @param BigInteger $x
     * @return BigInteger
     */
    public function bitwise_and(BigInteger $x)
    {
        return new static($this->value->bitwise_and($x->value));
    }

    /**
     * Logical Or
     *
     * @param BigInteger $x
     * @return BigInteger
     */
    public function bitwise_or(BigInteger $x)
    {
        return new static($this->value->bitwise_or($x->value));
    }

    /**
     * Logical Exclusive Or
     *
     * @param BigInteger $x
     * @return BigInteger
     */
    public function bitwise_xor(BigInteger $x)
    {
        return new static($this->value->bitwise_xor($x->value));
    }

    /**
     * Logical Right Shift
     *
     * Shifts BigInteger's by $shift bits, effectively dividing by 2**$shift.
     *
     * @param int $shift
     * @return BigInteger
     */
    public function bitwise_rightShift($shift)
    {
        return new static($this->value->bitwise_rightShift($shift));
    }

    /**
     * Logical Left Shift
     *
     * Shifts BigInteger's by $shift bits, effectively multiplying by 2**$shift.
     *
     * @param int $shift
     * @return BigInteger
     */
    public function bitwise_leftShift($shift)
    {
        return new static($this->value->bitwise_leftShift($shift));
    }

    /**
     * Logical Left Rotate
     *
     * Instead of the top x bits being dropped they're appended to the shifted bit string.
     *
     * @param int $shift
     * @return BigInteger
     */
    public function bitwise_leftRotate($shift)
    {
        return new static($this->value->bitwise_leftRotate($shift));
    }

    /**
     * Logical Right Rotate
     *
     * Instead of the bottom x bits being dropped they're prepended to the shifted bit string.
     *
     * @param int $shift
     * @return BigInteger
     */
    public function bitwise_rightRotate($shift)
    {
        return new static($this->value->bitwise_rightRotate($shift));
    }

    /**
     * Returns the smallest and largest n-bit number
     *
     * @param int $bits
     * @return BigInteger[]
     */
    public static function minMaxBits($bits)
    {
        self::initialize_static_variables();

        $class = self::$mainEngine;
        extract($class::minMaxBits($bits));
        /** @var BigInteger $min
         *  @var BigInteger $max
         */
        return [
            'min' => new static($min),
            'max' => new static($max)
        ];
    }

    /**
     * Return the size of a BigInteger in bits
     *
     * @return int
     */
    public function getLength()
    {
        return $this->value->getLength();
    }

    /**
     * Return the size of a BigInteger in bytes
     *
     * @return int
     */
    public function getLengthInBytes()
    {
        return $this->value->getLengthInBytes();
    }

    /**
     * Generates a random number of a certain size
     *
     * Bit length is equal to $size
     *
     * @param int $size
     * @return BigInteger
     */
    public static function random($size)
    {
        self::initialize_static_variables();

        $class = self::$mainEngine;
        return new static($class::random($size));
    }

    /**
     * Generates a random prime number of a certain size
     *
     * Bit length is equal to $size
     *
     * @param int $size
     * @return BigInteger
     */
    public static function randomPrime($size)
    {
        self::initialize_static_variables();

        $class = self::$mainEngine;
        return new static($class::randomPrime($size));
    }

    /**
     * Generate a random prime number between a range
     *
     * If there's not a prime within the given range, false will be returned.
     *
     * @param BigInteger $min
     * @param BigInteger $max
     * @return false|BigInteger
     */
    public static function randomRangePrime(BigInteger $min, BigInteger $max)
    {
        $class = self::$mainEngine;
        return new static($class::randomRangePrime($min->value, $max->value));
    }

    /**
     * Generate a random number between a range
     *
     * Returns a random number between $min and $max where $min and $max
     * can be defined using one of the two methods:
     *
     * BigInteger::randomRange($min, $max)
     * BigInteger::randomRange($max, $min)
     *
     * @param BigInteger $min
     * @param BigInteger $max
     * @return BigInteger
     */
    public static function randomRange(BigInteger $min, BigInteger $max)
    {
        $class = self::$mainEngine;
        return new static($class::randomRange($min->value, $max->value));
    }

    /**
     * Checks a numer to see if it's prime
     *
     * Assuming the $t parameter is not set, this function has an error rate of 2**-80.  The main motivation for the
     * $t parameter is distributability.  BigInteger::randomPrime() can be distributed across multiple pageloads
     * on a website instead of just one.
     *
     * @param int|bool $t
     * @return bool
     */
    public function isPrime($t = false)
    {
        return $this->value->isPrime($t);
    }

    /**
     * Calculates the nth root of a biginteger.
     *
     * Returns the nth root of a positive biginteger, where n defaults to 2
     *
     * @param int $n optional
     * @return BigInteger
     */
    public function root($n = 2)
    {
        return new static($this->value->root($n));
    }

    /**
     * Performs exponentiation.
     *
     * @param BigInteger $n
     * @return BigInteger
     */
    public function pow(BigInteger $n)
    {
        return new static($this->value->pow($n->value));
    }

    /**
     * Return the minimum BigInteger between an arbitrary number of BigIntegers.
     *
     * @param BigInteger[] $nums
     * @return BigInteger
     */
    public static function min(BigInteger ...$nums)
    {
        $class = self::$mainEngine;
        $nums = array_map(function($num) { return $num->value; }, $nums);
        return new static($class::min(...$nums));
    }

    /**
     * Return the maximum BigInteger between an arbitrary number of BigIntegers.
     *
     * @param BigInteger[] $nums
     * @return BigInteger
     */
    public static function max(BigInteger ...$nums)
    {
        $class = self::$mainEngine;
        $nums = array_map(function($num) { return $num->value; }, $nums);
        return new static($class::max(...$nums));
    }

    /**
     * Tests BigInteger to see if it is between two integers, inclusive
     *
     * @param BigInteger $min
     * @param BigInteger $max
     * @return bool
     */
    public function between(BigInteger $min, BigInteger $max)
    {
        return $this->value->between($min->value, $max->value);
    }

    /**
     * Clone
     */
    public function __clone()
    {
        $this->value = clone $this->value;
    }

    /**
     * Is Odd?
     *
     * @return boolean
     */
    public function isOdd()
    {
        return $this->value->isOdd();
    }

    /**
     * Tests if a bit is set
     *
     * @param int $x
     * @return boolean
     */
    public function testBit($x)
    {
        return $this->value->testBit($x);
    }

    /**
     * Is Negative?
     *
     * @return boolean
     */
    public function isNegative()
    {
        return $this->value->isNegative();
    }

    /**
     * Negate
     *
     * Given $k, returns -$k
     *
     * @return BigInteger
     */
    public function negate()
    {
        return new static($this->value->negate());
    }

    /**
     * Scan for 1 and right shift by that amount
     *
     * ie. $s = gmp_scan1($n, 0) and $r = gmp_div_q($n, gmp_pow(gmp_init('2'), $s));
     *
     * @param BigInteger $r
     * @return int
     */
    public static function scan1divide(BigInteger $r)
    {
        $class = self::$mainEngine;
        return $class::scan1divide($r->value);
    }

    /**
     * Create Recurring Modulo Function
     *
     * Sometimes it may be desirable to do repeated modulos with the same number outside of
     * modular exponentiation
     *
     * @return callable
     */
    public function createRecurringModuloFunction()
    {
        $func = $this->value->createRecurringModuloFunction();
        return function(BigInteger $x) use ($func) {
            return new static($func($x->value));
        };
    }

    /**
     * Bitwise Split
     *
     * Splits BigInteger's into chunks of $split bits
     *
     * @param int $split
     * @return \phpseclib\Math\BigInteger[]
     */
    public function bitwise_split($split)
    {
        return array_map(function($val) {
            return new static($val);
        }, $this->value->bitwise_split($split));
    }
}