wikimedia/mediawiki-extensions-CirrusSearch

<?php

namespace CirrusSearch\Maintenance;

/**
 * Simple set implementation so it's clear what the array
 * is being used for when values are only stored as keys.
 */
class Set implements \Countable {
    /** @var true[] */
    private $elements = [];

    public function __construct( array $elements = [] ) {
        $this->addAll( $elements );
    }

    /**
     * @return int Number of elements in the set
     */
    public function count(): int {
        return count( $this->elements );
    }

    /**
     * @param string $element Element to add to set
     * @return self
     */
    public function add( $element ) {
        $this->elements[$element] = true;
        return $this;
    }

    /**
     * @param string[] $elements Elements to add to set
     * @return self
     */
    public function addAll( array $elements ) {
        foreach ( $elements as $element ) {
            $this->add( $element );
        }
        return $this;
    }

    /**
     * @param Set $other Set to union into this one
     * @return self
     */
    public function union( Set $other ) {
        $this->elements += $other->elements;
        return $this;
    }

    /**
     * @param string $element Value to test
     * @return bool True when the set contains $element
     */
    public function contains( $element ) {
        return array_key_exists( $element, $this->elements );
    }

    /**
     * @return string[] Elements of the set
     */
    public function values() {
        return array_keys( $this->elements );
    }
}