Yii\EventDispatcher\Provider\Provider

Complexity

Total Complexity

24

Size/Duplication

Total Lines	166
Duplicated Lines	0 %

Coupling/Cohesion

Components	1
Dependencies	0

Importance

Changes

0

9 Methods

Rating	Name	Duplication	Size	Complexity
B	getListenersForEvent()	0	21	6
A	attach()	0	4	1
A	detach()	0	4	1
B	getParameterType()	0	39	8
A	isFunctionCallable()	0	5	1
A	isClosureCallable()	0	4	1
A	isObjectCallable()	0	4	2
A	isClassCallable()	0	4	3
A	isInvokable()	0	4	1

<?php
namespace Yii\EventDispatcher\Provider;

use Psr\EventDispatcher\ListenerProviderInterface;

/**
 * Provider is a listener provider that registers event listeners for interfaces used in callable type-hints
 * and gives out a list of handlers by event interface provided for further use with Dispatcher.
 */
final class Provider implements ListenerProviderInterface
{
    private $listeners = [];

    public function getListenersForEvent(object $event): iterable
    {
        $className = get_class($event);
        if (isset($this->listeners[$className])) {
            return $this->listeners[$className];
        }

        foreach (class_parents($event) as $parent) {
            if (isset($this->listeners[$parent])) {
                return $this->listeners[$parent];
            }
        }

        foreach (class_implements($event) as $interface) {
            if (isset($this->listeners[$interface])) {
                return $this->listeners[$interface];
            }
        }

        return [];
    }

    /**
     * Attaches listener to corresponding event based on the type-hint used for the event argument.
     *
     * Method signature should be the following:
     *
     * ```
     *  function (MyEvent $event): void
     * ```
     *
     * Any callable could be used be it a closure, invokable object or array referencing a class or object.
     *
     * @param callable $listener
     */
    public function attach(callable $listener): void
    {
        $this->listeners[$this->getParameterType($listener)][] = $listener;
    }

    /**
     * Detach all event handlers registered for an interface
     *
     * @param string $interface
     */
    public function detach(string $interface): void
    {
        unset($this->listeners[$interface]);
    }

    /**
     * Derives the class type of the first argument of a callable.
     *
     * @param callable $callable The callable for which we want the parameter type.
     * @return string The class the parameter is type hinted on.
     */
    private function getParameterType($callable): string
    {
        // We can't type hint $callable as it could be an array, and arrays are not callable. Sometimes. Bah, PHP.

        // This try-catch is only here to keep OCD linters happy about uncaught reflection exceptions.
        try {
            switch (true) {
                // See note on isClassCallable() for why this must be the first case.
                case $this->isClassCallable($callable):
                    $reflect = new \ReflectionClass($callable[0]);
                    $params = $reflect->getMethod($callable[1])->getParameters();
                    break;
                case $this->isFunctionCallable($callable):
                case $this->isClosureCallable($callable):
                    $reflect = new \ReflectionFunction($callable);
                    $params = $reflect->getParameters();
                    break;
                case $this->isObjectCallable($callable):
                    $reflect = new \ReflectionObject($callable[0]);
                    $params = $reflect->getMethod($callable[1])->getParameters();
                    break;
                case $this->isInvokable($callable):
                    $params = (new \ReflectionMethod($callable, '__invoke'))->getParameters();
                    break;
                default:
                    throw new \InvalidArgumentException('Not a recognized type of callable');
            }

            $rType = $params[0]->getType();
            if ($rType === null) {
                throw new \InvalidArgumentException('Listeners must declare an object type they can accept.');
            }
            $type = $rType->getName();
        } catch (\ReflectionException $e) {
            throw new \RuntimeException('Type error registering listener.', 0, $e);
        }

        return $type;
    }

    /**
     * Determines if a callable represents a function.
     *
     * Or at least a reasonable approximation, since a function name may not be defined yet.
     *
     * @param callable $callable
     * @return True if the callable represents a function, false otherwise.
     */
    private function isFunctionCallable(callable $callable): bool
    {
        // We can't check for function_exists() because it may be included later by the time it matters.
        return is_string($callable);
    }

    /**
     * Determines if a callable represents a closure/anonymous function.
     *
     * @param callable $callable
     * @return True if the callable represents a closure object, false otherwise.
     */
    private function isClosureCallable(callable $callable): bool
    {
        return $callable instanceof \Closure;
    }

    /**
     * @param callable $callable
     * @return True if the callable represents an invokable object, false otherwise.
     */
    private function isInvokable(callable $callable): bool
    {
        return is_object($callable);
    }

    /**
     * Determines if a callable represents a method on an object.
     *
     * @param callable $callable
     * @return True if the callable represents a method object, false otherwise.
     */
    private function isObjectCallable(callable $callable): bool
    {
        return (is_array($callable) && is_object($callable[0]));
    }

    /**
     * Determines if a callable represents a static class method.
     *
     * The parameter here is untyped so that this method may be called with an
     * array that represents a class name and a non-static method.  The routine
     * to determine the parameter type is identical to a static method, but such
     * an array is still not technically callable.  Omitting the parameter type here
     * allows us to use this method to handle both cases.
     *
     * Note that this method must therefore be the first in the switch statement
     * above, or else subsequent calls will break as the array is not going to satisfy
     * the callable type hint but it would pass `is_callable()`.  Because PHP.
     *
     * @param callable $callable
     * @return True if the callable represents a static method, false otherwise.
     */
    private function isClassCallable($callable): bool
    {
        return (is_array($callable) && is_string($callable[0]) && class_exists($callable[0]));
    }
}