class Link

class Link {
    public const TYPE_REQUIRE = 'requires';
    public const TYPE_DEV_REQUIRE = 'devRequires';
    public const TYPE_PROVIDE = 'provides';
    public const TYPE_CONFLICT = 'conflicts';
    public const TYPE_REPLACE = 'replaces';
    
    /**
     * Special type
     * @internal
     */
    public const TYPE_DOES_NOT_REQUIRE = 'does not require';
    private const TYPE_UNKNOWN = 'relates to';
    
    /**
     * Will be converted into a constant once the min PHP version allows this
     *
     * @internal
     * @var string[]
     * @phpstan-var array<self::TYPE_REQUIRE|self::TYPE_DEV_REQUIRE|self::TYPE_PROVIDE|self::TYPE_CONFLICT|self::TYPE_REPLACE>
     */
    public static $TYPES = [
        self::TYPE_REQUIRE,
        self::TYPE_DEV_REQUIRE,
        self::TYPE_PROVIDE,
        self::TYPE_CONFLICT,
        self::TYPE_REPLACE,
    ];
    
    /**
     * @var string
     */
    protected $source;
    
    /**
     * @var string
     */
    protected $target;
    
    /**
     * @var ConstraintInterface
     */
    protected $constraint;
    
    /**
     * @var string
     * @phpstan-var string $description
     */
    protected $description;
    
    /**
     * @var ?string
     */
    protected $prettyConstraint;
    
    /**
     * Creates a new package link.
     *
     * @param ConstraintInterface $constraint       Constraint applying to the target of this link
     * @param self::TYPE_*        $description      Used to create a descriptive string representation
     */
    public function __construct(string $source, string $target, ConstraintInterface $constraint, $description = self::TYPE_UNKNOWN, ?string $prettyConstraint = null) {
        $this->source = strtolower($source);
        $this->target = strtolower($target);
        $this->constraint = $constraint;
        $this->description = self::TYPE_DEV_REQUIRE === $description ? 'requires (for development)' : $description;
        $this->prettyConstraint = $prettyConstraint;
    }
    public function getDescription() : string {
        return $this->description;
    }
    public function getSource() : string {
        return $this->source;
    }
    public function getTarget() : string {
        return $this->target;
    }
    public function getConstraint() : ConstraintInterface {
        return $this->constraint;
    }
    
    /**
     * @throws \UnexpectedValueException If no pretty constraint was provided
     */
    public function getPrettyConstraint() : string {
        if (null === $this->prettyConstraint) {
            throw new \UnexpectedValueException(sprintf('Link %s has been misconfigured and had no prettyConstraint given.', $this));
        }
        return $this->prettyConstraint;
    }
    public function __toString() : string {
        return $this->source . ' ' . $this->description . ' ' . $this->target . ' (' . $this->constraint . ')';
    }
    public function getPrettyString(PackageInterface $sourcePackage) : string {
        return $sourcePackage->getPrettyString() . ' ' . $this->description . ' ' . $this->target . ' ' . $this->constraint
            ->getPrettyString();
    }

}