wikimedia/mediawiki-extensions-Wikibase

<?php

namespace Wikibase\Lib\Units;

/**
 * Basic unit storage functionality.
 * Concrete classes need to fill in data loading.
 *
 * @license GPL-2.0-or-later
 * @author Stas Malyshev
 */
abstract class BaseUnitStorage implements UnitStorage {

    /**
     * @var array[]
     */
    private $storageData;

    /**
     * Load data from concrete storage.
     * The method should return array indexed by source unit.
     * Each row should be either [<factor>, <unit>] or
     * ['factor' => <factor>, 'unit' => <unit>]
     * @return array[]|null null when loading failed.
     */
    abstract protected function loadStorageData();

    /**
     * Load data from storage.
     */
    private function loadData() {
        if ( $this->storageData === null ) {
            $this->storageData = $this->loadStorageData();
            if ( $this->storageData === null ) {
                throw new \RuntimeException( "Failed to load unit storage" );
            }
        }
    }

    /**
     * Check if certain unit is primary.
     * @param string $unit
     * @return bool
     */
    public function isPrimaryUnit( $unit ) {
        if ( $this->storageData === null ) {
            $this->loadData();
        }
        if ( !isset( $this->storageData[$unit] ) ) {
            return false;
        }
        return ( $this->storageData[$unit]['unit'] ?? $this->storageData[$unit][1] ) === $unit;
    }

    /**
     * Get conversion from this unit to primary unit
     * @param string $unit
     * @return array|null 'factor' => factor from this unit to primary unit
     *                    'unit' => primary unit
     */
    public function getConversion( $unit ) {
        if ( $this->storageData === null ) {
            $this->loadData();
        }
        if ( !isset( $this->storageData[$unit] ) ) {
            return null;
        }
        if ( isset( $this->storageData[$unit]['factor'] ) ) {
            return $this->storageData[$unit];
        } else {
            return [
                'factor' => $this->storageData[$unit][0],
                'unit' => $this->storageData[$unit][1],
            ];
        }
    }

}