wikimedia/mediawiki-extensions-Wikibase

<?php

namespace Wikibase\Lib\Units;

use DataValues\DecimalMath;
use DataValues\DecimalValue;
use DataValues\UnboundedQuantityValue;
use MediaWiki\Logger\LoggerFactory;
use Psr\Log\LoggerInterface;

/**
 * Convert quantities to other units.
 *
 * @license GPL-2.0-or-later
 * @author Stas Malyshev
 */
class UnitConverter {

    /**
     * @var UnitStorage
     */
    private $store;

    /**
     * @var DecimalMath
     */
    private $math;

    /**
     * @var LoggerInterface
     */
    private $logger;

    /**
     * Prefix of the data entity (concept URI)
     * @var string
     */
    private $prefix;

    public function __construct( UnitStorage $store, $entityPrefix ) {
        $this->store = $store;
        $this->prefix = $entityPrefix;
        $this->math = new DecimalMath();
        // TODO: Inject
        $this->logger = LoggerFactory::getInstance( 'Wikibase' );
    }

    /**
     * Convert QuantityValue to standard units
     * @param UnboundedQuantityValue $value
     * @return UnboundedQuantityValue|null Converted value in standard units, or null if no conversion
     *      possible. If the value is already in standard units, returns the original value.
     */
    public function toStandardUnits( UnboundedQuantityValue $value ) {
        $fromUnit = $value->getUnit();

        if ( $fromUnit === '1' ) {
            // Won't convert unitless values
            return null;
        }

        if ( substr( $fromUnit, 0, strlen( $this->prefix ) ) === $this->prefix ) {
            // Cut off prefix
            $fromUnit = substr( $fromUnit, strlen( $this->prefix ) );
        }

        if ( $this->store->isPrimaryUnit( $fromUnit ) ) {
            // no conversion needed
            return $value;
        }

        $toUnits = $this->store->getConversion( $fromUnit );
        if ( !$toUnits ) {
            return null;
        }

        $targetUnit = $toUnits['unit'];
        if ( $targetUnit === $fromUnit ) {
            // if target is the same as source, do not touch the value
            return $value;
        }
        if ( substr( $targetUnit, 0, strlen( $this->prefix ) ) !== $this->prefix ) {
            $targetUnit = $this->prefix . $targetUnit;
        }
        if ( $targetUnit === $fromUnit ) {
            // if target is the same as source, do not touch the value
            return $value;
        }
        $mult = $this->makeDecimalValue( $toUnits['factor'] );

        if ( $mult->getSign() === '-' || $mult->isZero() ) {
            // We do not support negative conversion factors, and zero factor makes no sense
            $this->logger->debug(
                'Bad factor for {fromUnit}: {factor}',
                [
                    'fromUnit' => $fromUnit,
                    'factor' => $toUnits['factor'],
                ]
            );
            return null;
        }

        return $value->transform( $targetUnit, [ $this->math, 'product' ], $mult );
    }

    /**
     * Create DecimalValue from regular numeric string or value.
     * @param int|float|string $number
     * FIXME: replace with DecimalValue method from https://github.com/DataValues/Number/pull/67
     * @return DecimalValue
     */
    private function makeDecimalValue( $number ) {
        if ( is_string( $number ) && $number !== '' ) {
            if ( $number[0] !== '-' && $number[0] !== '+' ) {
                $number = '+' . $number;
            }
        }

        return new DecimalValue( $number );
    }

}