<?php
// Version.php
// Created: 2021-04-29
// Updated: 2022-02-27

namespace Index;

use InvalidArgumentException;
use Stringable;

/**
 * A Semantic Versioning implementation. Following version 2.0.0 of the specification.
 *
 * @see https://semver.org/spec/v2.0.0.html
 */
class Version implements Stringable, IComparable, IEquatable {
    private int $major;
    private int $minor;
    private int $patch;
    private array $prerelease;
    private array $build;

    private ?string $versionString = null;

    private static ?Version $empty = null;

    /**
     * Constructor for Version.
     *
     * @param int $major A positive integer indicating the major version.
     * @param int $minor A positive integer indicating the minor version.
     * @param int $patch A positive integer indicating the patch version.
     * @param string $prerelease A dot separated string indicating prerelease information.
     * @param string $build A dot separated string indicating build information.
     * @throws InvalidArgumentException A negative integer was provided.
     * @return Version
     */
    public function __construct(int $major, int $minor = 0, int $patch = 0, string $prerelease = '', string $build = '') {
        if($major < 0 || $minor < 0 || $patch < 0)
            throw new InvalidArgumentException('$major, $minor and $patch should be positive integers.');

        $this->major      = $major;
        $this->minor      = $minor;
        $this->patch      = $patch;
        $this->prerelease = empty($prerelease) ? [] : explode('.', $prerelease);
        $this->build      = empty($build)      ? [] : explode('.', $build);
    }

    /**
     * Gets the value of the major version component.
     *
     * @return int Major version component.
     */
    public function getMajor(): int {
        return $this->major;
    }

    /**
     * Gets the value of the minor version component.
     *
     * @return int Minor version component.
     */
    public function getMinor(): int {
        return $this->minor;
    }

    /**
     * Gets the value of the patch version component.
     *
     * @return int Patch version component.
     */
    public function getPatch(): int {
        return $this->patch;
    }

    /**
     * Gets the split value of the prerelease component.
     *
     * @return array array containing the prerelease parts.
     */
    public function getPrerelease(): array {
        return $this->prerelease;
    }

    /**
     * Gets the split value of the build component.
     *
     * @return array array contains the build parts.
     */
    public function getBuild(): array {
        return $this->build;
    }

    /**
     * Tests if this Version instance represents a prerelease according to the SemVer spec.
     *
     * @return bool true if the version indicates a prerelease, false if not.
     */
    public function isPrerelease(): bool {
        return $this->major < 1 || !empty($this->prerelease);
    }

    /**
     * Creates a new instance of Version with the major component incremented.
     *
     * This will implicitly drop prerelease and build info and reset the minor and patch component.
     *
     * @return Version the newly created instance of Version.
     */
    public function incrementMajor(): Version {
        return new Version($this->major + 1, 0, 0);
    }

    /**
     * Creates a new instance of Version with the minor component incremented.
     *
     * This will implicitly drop the prerelease and build info and reset the patch component.
     *
     * @return Version the newly created instance of Version.
     */
    public function incrementMinor(): Version {
        return new Version($this->major, $this->minor + 1, 0);
    }

    /**
     * Creates a new instance of Version with the patch component incremented.
     *
     * This will implicitly drop the prerelease and build info.
     *
     * @return Version the newly created instance of Version.
     */
    public function incrementPatch(): Version {
        return new Version($this->major, $this->minor, $this->patch + 1);
    }

    /**
     * Checks this instance of Version with another for equality.
     *
     * The build component is ignored, as per the SemVer spec.
     *
     * @param mixed $other Another instance of Version.
     * @return bool true if the instances are equal, false if not.
     */
    public function equals(mixed $other): bool {
        return $other instanceof Version
            && $other->major === $this->major
            && $other->minor === $this->minor
            && $other->patch === $this->patch
            && XArray::sequenceEquals($this->prerelease, $other->prerelease);
    }

    /**
     * Compares this instance of Version with another.
     *
     * The build component is ignored and prerelease component is compared as per the SemVer spec.
     *
     * @param mixed $other Another instance of Version.
     */
    public function compare(mixed $other): int {
        if(!($other instanceof Version))
            return PHP_INT_MIN;

        $diff = $this->major <=> $other->major;
        if($diff) return $diff;

        $diff = $this->minor <=> $other->minor;
        if($diff) return $diff;

        $diff = $this->patch <=> $other->patch;
        if($diff) return $diff;

        $tpi = XArray::extractIterator($this->prerelease);
        $opi = XArray::extractIterator($other->prerelease);

        $tpi->rewind();
        $opi->rewind();
        $valid = $tpi->valid();
        $diff = $opi->valid() <=> $valid;
        if($diff) return $diff;

        while($valid) {
            $diff = $opi->current()->compare($tpi->current());
            if($diff) return $diff;

            $tpi->next();
            $opi->next();
            $valid = $tpi->valid();
            $diff = $opi->valid() <=> $valid;
            if($diff) return $diff;
        }

        return 0;
    }

    public function __toString(): string {
        if($this->versionString === null) {
            $string = $this->major . '.' . $this->minor . '.' . $this->patch;

            if(!empty($this->prerelease))
                $string .= '-' . implode('.', $this->prerelease);

            if(!empty($this->build))
                $string .= '+' . implode('.', $this->build);

            $this->versionString = $string;
        }

        return $this->versionString;
    }

    /**
     * Returns an empty Version instance.
     *
     * @return Version Instance of Version with all values set to 0.
     */
    public static function empty(): Version {
        if(self::$empty === null)
            self::$empty = new Version(0);
        return self::$empty;
    }

    /**
     * Parses a version string.
     *
     * Parses a version string with a regex adapted from SemVer's documentation. Modified to allow an optional v prefix.
     *
     * @see https://semver.org/spec/v2.0.0.html#is-there-a-suggested-regular-expression-regex-to-check-a-semver-string
     * @param string $versionString String containing a version number.
     * @throws InvalidArgumentException Provided string does not represent a valid version.
     * @return Version An instance of Version representing the provided version string.
     */
    public static function parse(string $versionString): Version {
        // Regex adapted from https://semver.org/spec/v2.0.0.html#is-there-a-suggested-regular-expression-regex-to-check-a-semver-string
        if(!preg_match('#^v?(?P<major>0|[1-9]\d*)\.(?P<minor>0|[1-9]\d*)\.(?P<patch>0|[1-9]\d*)(?:-(?P<prerelease>(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*)(?:\.(?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*))*))?(?:\+(?P<build>[0-9a-zA-Z-]+(?:\.[0-9a-zA-Z-]+)*))?$#', $versionString, $matches))
            throw new InvalidArgumentException('$versionString is not a valid version string.');

        return new Version($matches['major'], $matches['minor'], $matches['patch'], $matches['prerelease'] ?? '', $matches['build'] ?? '');
    }
}