class EventDriver

final class EventDriver extends AbstractDriver {
    
    /** @var array<string, \Event>|null */
    private static ?array $activeSignals = null;
    public static function isSupported() : bool {
        return \extension_loaded("event");
    }
    private \EventBase $handle;
    
    /** @var array<string, \Event> */
    private array $events = [];
    private readonly \Closure $ioCallback;
    private readonly \Closure $timerCallback;
    private readonly \Closure $signalCallback;
    
    /** @var array<string, \Event> */
    private array $signals = [];
    public function __construct() {
        parent::__construct();
        
        /** @psalm-suppress TooFewArguments https://github.com/JetBrains/phpstorm-stubs/pull/763 */
        $this->handle = new \EventBase();
        if (self::$activeSignals === null) {
            self::$activeSignals =& $this->signals;
        }
        $this->ioCallback = function ($resource, $what, StreamCallback $callback) : void {
            $this->enqueueCallback($callback);
        };
        $this->timerCallback = function ($resource, $what, TimerCallback $callback) : void {
            $this->enqueueCallback($callback);
        };
        $this->signalCallback = function ($signo, $what, SignalCallback $callback) : void {
            $this->enqueueCallback($callback);
        };
    }
    
    /**
     * {@inheritdoc}
     */
    public function cancel(string $callbackId) : void {
        parent::cancel($callbackId);
        if (isset($this->events[$callbackId])) {
            $this->events[$callbackId]
                ->free();
            unset($this->events[$callbackId]);
        }
    }
    
    /**
     * @codeCoverageIgnore
     */
    public function __destruct() {
        foreach ($this->events as $event) {
            if ($event !== null) {
                // Events may have been nulled in extension depending on destruct order.
                $event->free();
            }
        }
        // Unset here, otherwise $event->del() fails with a warning, because __destruct order isn't defined.
        // See https://github.com/amphp/amp/issues/159.
        $this->events = [];
        // Manually free the loop handle to fully release loop resources.
        // See https://github.com/amphp/amp/issues/177.
        
        /** @psalm-suppress RedundantPropertyInitializationCheck */
        if (isset($this->handle)) {
            $this->handle
                ->free();
            unset($this->handle);
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function run() : void {
        $active = self::$activeSignals;
        \assert($active !== null);
        foreach ($active as $event) {
            $event->del();
        }
        self::$activeSignals =& $this->signals;
        foreach ($this->signals as $event) {
            
            /** @psalm-suppress TooFewArguments https://github.com/JetBrains/phpstorm-stubs/pull/763 */
            $event->add();
        }
        try {
            parent::run();
        } finally {
            foreach ($this->signals as $event) {
                $event->del();
            }
            self::$activeSignals =& $active;
            foreach ($active as $event) {
                
                /** @psalm-suppress TooFewArguments https://github.com/JetBrains/phpstorm-stubs/pull/763 */
                $event->add();
            }
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function stop() : void {
        $this->handle
            ->stop();
        parent::stop();
    }
    
    /**
     * {@inheritdoc}
     */
    public function getHandle() : \EventBase {
        return $this->handle;
    }
    protected function now() : float {
        return (double) \hrtime(true) / 1000000000;
    }
    
    /**
     * {@inheritdoc}
     */
    protected function dispatch(bool $blocking) : void {
        $this->handle
            ->loop($blocking ? \EventBase::LOOP_ONCE : \EventBase::LOOP_ONCE | \EventBase::LOOP_NONBLOCK);
    }
    
    /**
     * {@inheritdoc}
     */
    protected function activate(array $callbacks) : void {
        $now = $this->now();
        foreach ($callbacks as $callback) {
            if (!isset($this->events[$id = $callback->id])) {
                if ($callback instanceof StreamReadableCallback) {
                    \assert(\is_resource($callback->stream));
                    $this->events[$id] = new \Event($this->handle, $callback->stream, \Event::READ | \Event::PERSIST, $this->ioCallback, $callback);
                }
                elseif ($callback instanceof StreamWritableCallback) {
                    \assert(\is_resource($callback->stream));
                    $this->events[$id] = new \Event($this->handle, $callback->stream, \Event::WRITE | \Event::PERSIST, $this->ioCallback, $callback);
                }
                elseif ($callback instanceof TimerCallback) {
                    $this->events[$id] = new \Event($this->handle, -1, \Event::TIMEOUT, $this->timerCallback, $callback);
                }
                elseif ($callback instanceof SignalCallback) {
                    $this->events[$id] = new \Event($this->handle, $callback->signal, \Event::SIGNAL | \Event::PERSIST, $this->signalCallback, $callback);
                }
                else {
                    // @codeCoverageIgnoreStart
                    throw new \Error("Unknown callback type");
                    // @codeCoverageIgnoreEnd
                }
            }
            if ($callback instanceof TimerCallback) {
                $interval = \min(\max(0, $callback->expiration - $now), \PHP_INT_MAX / 2);
                $this->events[$id]
                    ->add($interval > 0 ? $interval : 0);
            }
            elseif ($callback instanceof SignalCallback) {
                $this->signals[$id] = $this->events[$id];
                
                /** @psalm-suppress TooFewArguments https://github.com/JetBrains/phpstorm-stubs/pull/763 */
                $this->events[$id]
                    ->add();
            }
            else {
                
                /** @psalm-suppress TooFewArguments https://github.com/JetBrains/phpstorm-stubs/pull/763 */
                $this->events[$id]
                    ->add();
            }
        }
    }
    
    /**
     * {@inheritdoc}
     */
    protected function deactivate(DriverCallback $callback) : void {
        if (isset($this->events[$id = $callback->id])) {
            $this->events[$id]
                ->del();
            if ($callback instanceof SignalCallback) {
                unset($this->signals[$id]);
            }
        }
    }

}