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<?php

declare(strict_types=1);

namespace Brick\Math;

use Brick\Math\Exception\DivisionByZeroException;

use Brick\Math\Exception\MathException;

use Brick\Math\Exception\NumberFormatException;

use Brick\Math\Exception\RoundingNecessaryException;

/**

 * Common interface for arbitrary-precision rational numbers.

 *

 * @psalm-immutable

 */

abstract class BigNumber implements \Serializable, \JsonSerializable

{

    /**

     * The regular expression used to parse integer, decimal and rational numbers.

     */

    private const PARSE_REGEXP =

        '/^' .

            '(?<sign>[\-\+])?' .

            '(?:' .

                '(?:' .

                    '(?<integral>[0-9]+)?' .

                    '(?<point>\.)?' .

                    '(?<fractional>[0-9]+)?' .

                    '(?:[eE](?<exponent>[\-\+]?[0-9]+))?' .

                ')|(?:' .

                    '(?<numerator>[0-9]+)' .

                    '\/?' .

                    '(?<denominator>[0-9]+)' .

                ')' .

            ')' .

        '$/';

    /**

     * Creates a BigNumber of the given value.

     *

     * The concrete return type is dependent on the given value, with the following rules:

     *

     * - BigNumber instances are returned as is

     * - integer numbers are returned as BigInteger

     * - floating point numbers are converted to a string then parsed as such

     * - strings containing a `/` character are returned as BigRational

     * - strings containing a `.` character or using an exponential notation are returned as BigDecimal

     * - strings containing only digits with an optional leading `+` or `-` sign are returned as BigInteger

     *

     * @throws NumberFormatException   If the format of the number is not valid.

     * @throws DivisionByZeroException If the value represents a rational number with a denominator of zero.

     *

     * @psalm-pure

     */

    public static function of(BigNumber|int|float|string $value) : BigNumber

    {

        if ($value instanceof BigNumber) {

            return $value;

        }

        if (\is_int($value)) {

            return new BigInteger((string) $value);

        }

        $value = \is_float($value) ? self::floatToString($value) : $value;

        $throw = static function() use ($value) : void {

            throw new NumberFormatException(\sprintf(

                'The given value "%s" does not represent a valid number.',

                $value

            ));

        };

        if (\preg_match(self::PARSE_REGEXP, $value, $matches) !== 1) {

            $throw();

        }

        $getMatch = static fn(string $value): ?string => (($matches[$value] ?? '') !== '') ? $matches[$value] : null;

        $sign        = $getMatch('sign');

        $numerator   = $getMatch('numerator');

        $denominator = $getMatch('denominator');

        if ($numerator !== null) {

            assert($denominator !== null);

            if ($sign !== null) {

                $numerator = $sign . $numerator;

            }

            $numerator   = self::cleanUp($numerator);

            $denominator = self::cleanUp($denominator);

            if ($denominator === '0') {

                throw DivisionByZeroException::denominatorMustNotBeZero();

            }

            return new BigRational(

                new BigInteger($numerator),

                new BigInteger($denominator),

                false

            );

        }

        $point      = $getMatch('point');

        $integral   = $getMatch('integral');

        $fractional = $getMatch('fractional');

        $exponent   = $getMatch('exponent');

        if ($integral === null && $fractional === null) {

            $throw();

        }

        if ($integral === null) {

            $integral = '0';

        }

        if ($point !== null || $exponent !== null) {

            $fractional = ($fractional ?? '');

            $exponent = ($exponent !== null) ? (int) $exponent : 0;

            if ($exponent === PHP_INT_MIN || $exponent === PHP_INT_MAX) {

                throw new NumberFormatException('Exponent too large.');

            }

            $unscaledValue = self::cleanUp(($sign ?? ''). $integral . $fractional);

            $scale = \strlen($fractional) - $exponent;

            if ($scale < 0) {

                if ($unscaledValue !== '0') {

                    $unscaledValue .= \str_repeat('0', - $scale);

                }

                $scale = 0;

            }

            return new BigDecimal($unscaledValue, $scale);

        }

        $integral = self::cleanUp(($sign ?? '') . $integral);

        return new BigInteger($integral);

    }

    /**

     * Safely converts float to string, avoiding locale-dependent issues.

     *

     * @see https://github.com/brick/math/pull/20

     *

     * @psalm-pure

     * @psalm-suppress ImpureFunctionCall

     */

    private static function floatToString(float $float) : string

    {

        $currentLocale = \setlocale(LC_NUMERIC, '0');

        \setlocale(LC_NUMERIC, 'C');

        $result = (string) $float;

        \setlocale(LC_NUMERIC, $currentLocale);

        return $result;

    }

    /**

     * Proxy method to access BigInteger's protected constructor from sibling classes.

     *

     * @internal

     * @psalm-pure

     */

    protected function newBigInteger(string $value) : BigInteger

    {

        return new BigInteger($value);

    }

    /**

     * Proxy method to access BigDecimal's protected constructor from sibling classes.

     *

     * @internal

     * @psalm-pure

     */

    protected function newBigDecimal(string $value, int $scale = 0) : BigDecimal

    {

        return new BigDecimal($value, $scale);

    }

    /**

     * Proxy method to access BigRational's protected constructor from sibling classes.

     *

     * @internal

     * @psalm-pure

     */

    protected function newBigRational(BigInteger $numerator, BigInteger $denominator, bool $checkDenominator) : BigRational

    {

        return new BigRational($numerator, $denominator, $checkDenominator);

    }

    /**

     * Returns the minimum of the given values.

     *

     * @param BigNumber|int|float|string ...$values The numbers to compare. All the numbers need to be convertible

     *                                              to an instance of the class this method is called on.

     *

     * @throws \InvalidArgumentException If no values are given.

     * @throws MathException             If an argument is not valid.

     *

     * @psalm-suppress LessSpecificReturnStatement

     * @psalm-suppress MoreSpecificReturnType

     * @psalm-pure

     */

    public static function min(BigNumber|int|float|string ...$values) : static

    {

        $min = null;

        foreach ($values as $value) {

            $value = static::of($value);

            if ($min === null || $value->isLessThan($min)) {

                $min = $value;

            }

        }

        if ($min === null) {

            throw new \InvalidArgumentException(__METHOD__ . '() expects at least one value.');

        }

        return $min;

    }

    /**

     * Returns the maximum of the given values.

     *

     * @param BigNumber|int|float|string ...$values The numbers to compare. All the numbers need to be convertible

     *                                              to an instance of the class this method is called on.

     *

     * @throws \InvalidArgumentException If no values are given.

     * @throws MathException             If an argument is not valid.

     *

     * @psalm-suppress LessSpecificReturnStatement

     * @psalm-suppress MoreSpecificReturnType

     * @psalm-pure

     */

    public static function max(BigNumber|int|float|string ...$values) : static

    {

        $max = null;

        foreach ($values as $value) {

            $value = static::of($value);

            if ($max === null || $value->isGreaterThan($max)) {

                $max = $value;

            }

        }

        if ($max === null) {

            throw new \InvalidArgumentException(__METHOD__ . '() expects at least one value.');

        }

        return $max;

    }

    /**

     * Returns the sum of the given values.

     *

     * @param BigNumber|int|float|string ...$values The numbers to add. All the numbers need to be convertible

     *                                              to an instance of the class this method is called on.

     *

     * @throws \InvalidArgumentException If no values are given.

     * @throws MathException             If an argument is not valid.

     *

     * @psalm-pure

     */

    public static function sum(BigNumber|int|float|string ...$values) : static

    {

        /** @var static|null $sum */

        $sum = null;

        foreach ($values as $value) {

            $value = static::of($value);

            $sum = $sum === null ? $value : self::add($sum, $value);

        }

        if ($sum === null) {

            throw new \InvalidArgumentException(__METHOD__ . '() expects at least one value.');

        }

        return $sum;

    }

    /**

     * Adds two BigNumber instances in the correct order to avoid a RoundingNecessaryException.

     *

     * @todo This could be better resolved by creating an abstract protected method in BigNumber, and leaving to

     *       concrete classes the responsibility to perform the addition themselves or delegate it to the given number,

     *       depending on their ability to perform the operation. This will also require a version bump because we're

     *       potentially breaking custom BigNumber implementations (if any...)

     *

     * @psalm-pure

     */

    private static function add(BigNumber $a, BigNumber $b) : BigNumber

    {

        if ($a instanceof BigRational) {

            return $a->plus($b);

        }

        if ($b instanceof BigRational) {

            return $b->plus($a);

        }

        if ($a instanceof BigDecimal) {

            return $a->plus($b);

        }

        if ($b instanceof BigDecimal) {

            return $b->plus($a);

        }

        /** @var BigInteger $a */

        return $a->plus($b);

    }

    /**

     * Removes optional leading zeros and + sign from the given number.

     *

     * @param string $number The number, validated as a non-empty string of digits with optional leading sign.

     *

     * @psalm-pure

     */

    private static function cleanUp(string $number) : string

    {

        $firstChar = $number[0];

        if ($firstChar === '+' || $firstChar === '-') {

            $number = \substr($number, 1);

        }

        $number = \ltrim($number, '0');

        if ($number === '') {

            return '0';

        }

        if ($firstChar === '-') {

            return '-' . $number;

        }

        return $number;

    }

    /**

     * Checks if this number is equal to the given one.

     */

    public function isEqualTo(BigNumber|int|float|string $that) : bool

    {

        return $this->compareTo($that) === 0;

    }

    /**

     * Checks if this number is strictly lower than the given one.

     */

    public function isLessThan(BigNumber|int|float|string $that) : bool

    {

        return $this->compareTo($that) < 0;

    }

    /**

     * Checks if this number is lower than or equal to the given one.

     */

    public function isLessThanOrEqualTo(BigNumber|int|float|string $that) : bool

    {

        return $this->compareTo($that) <= 0;

    }

    /**

     * Checks if this number is strictly greater than the given one.

     */

    public function isGreaterThan(BigNumber|int|float|string $that) : bool

    {

        return $this->compareTo($that) > 0;

    }

    /**

     * Checks if this number is greater than or equal to the given one.

     */

    public function isGreaterThanOrEqualTo(BigNumber|int|float|string $that) : bool

    {

        return $this->compareTo($that) >= 0;

    }

    /**

     * Checks if this number equals zero.

     */

    public function isZero() : bool

    {

        return $this->getSign() === 0;

    }

    /**

     * Checks if this number is strictly negative.

     */

    public function isNegative() : bool

    {

        return $this->getSign() < 0;

    }

    /**

     * Checks if this number is negative or zero.

     */

    public function isNegativeOrZero() : bool

    {

        return $this->getSign() <= 0;

    }

    /**

     * Checks if this number is strictly positive.

     */

    public function isPositive() : bool

    {

        return $this->getSign() > 0;

    }

    /**

     * Checks if this number is positive or zero.

     */

    public function isPositiveOrZero() : bool

    {

        return $this->getSign() >= 0;

    }

    /**

     * Returns the sign of this number.

     *

     * @return int -1 if the number is negative, 0 if zero, 1 if positive.

     */

    abstract public function getSign() : int;

    /**

     * Compares this number to the given one.

     *

     * @return int [-1,0,1] If `$this` is lower than, equal to, or greater than `$that`.

     *

     * @throws MathException If the number is not valid.

     */

    abstract public function compareTo(BigNumber|int|float|string $that) : int;

    /**

     * Converts this number to a BigInteger.

     *

     * @throws RoundingNecessaryException If this number cannot be converted to a BigInteger without rounding.

     */

    abstract public function toBigInteger() : BigInteger;

    /**

     * Converts this number to a BigDecimal.

     *

     * @throws RoundingNecessaryException If this number cannot be converted to a BigDecimal without rounding.

     */

    abstract public function toBigDecimal() : BigDecimal;

    /**

     * Converts this number to a BigRational.

     */

    abstract public function toBigRational() : BigRational;

    /**

     * Converts this number to a BigDecimal with the given scale, using rounding if necessary.

     *

     * @param int $scale        The scale of the resulting `BigDecimal`.

     * @param int $roundingMode A `RoundingMode` constant.

     *

     * @throws RoundingNecessaryException If this number cannot be converted to the given scale without rounding.

     *                                    This only applies when RoundingMode::UNNECESSARY is used.

     */

    abstract public function toScale(int $scale, int $roundingMode = RoundingMode::UNNECESSARY) : BigDecimal;

    /**

     * Returns the exact value of this number as a native integer.

     *

     * If this number cannot be converted to a native integer without losing precision, an exception is thrown.

     * Note that the acceptable range for an integer depends on the platform and differs for 32-bit and 64-bit.

     *

     * @throws MathException If this number cannot be exactly converted to a native integer.

     */

    abstract public function toInt() : int;

    /**

     * Returns an approximation of this number as a floating-point value.

     *

     * Note that this method can discard information as the precision of a floating-point value

     * is inherently limited.

     *

     * If the number is greater than the largest representable floating point number, positive infinity is returned.

     * If the number is less than the smallest representable floating point number, negative infinity is returned.

     */

    abstract public function toFloat() : float;

    /**

     * Returns a string representation of this number.

     *

     * The output of this method can be parsed by the `of()` factory method;

     * this will yield an object equal to this one, without any information loss.

     */

    abstract public function __toString() : string;

    public function jsonSerialize() : string

    {

        return $this->__toString();

    }

}