Game_Input.php

<?php

namespace Game;

use \Game\Connection\Interfaces\Connection;
use Game\Module\Interfaces\Command;
use InvalidArgumentException;

/**
 * Game input handler
 *
 * @package Game
 * @author  Rian Orie <rian.orie@gmail.com>
 * @version 1.0
 * @created 2015-07-23
 */
class Input
{
    const PRIORITY_LOW = 1;

    const PRIORITY_NORMAL = 2;

    const PRIORITY_HIGH = 3;

    /**
     * List of the registered commands
     *
     * @var array
     */
    private $commands;

    /**
     * @var Event
     */
    private $event;

    /**
     * Construct the input class
     *
     * @param Event $event The event handler
     */
    public function __construct(Event $event)
    {
        $this->event = $event;
    }

    /**
     * Register a command in the system
     *
     * @param string   $command  The command to register
     * @param Command  $callback Callable handler that works with the given input
     * @param boolean  $priority Give the command priority, pushing it to the front of the command list
     *
     * @throws Exception
     */
    public function registerCommand(string $command, Command $callback, $priority = self::PRIORITY_NORMAL)
    {
        if ( ! preg_match('/^[a-z]+$/', $command)) {
            throw new Exception('Command ' . $command . ' contains invalid characters! Only use a-z');
        }

        // make sure we're not trying to register an already existing command
        if (in_array($command, $this->getCommands())) {
            throw new Exception('Command ' . $command . ' is already registered!');
        }

        // call some events
        $this->event->dispatch('input.before_register', ['command' => &$command, 'callback' => &$callback]);
        $this->event->dispatch('input.before_register.' . $command, ['command' => &$command, 'callback' => &$callback]);

        if ($callback instanceof Command) {
            $callback = [$callback, 'execute'];
        }

        // and register the command
        $this->commands[$priority][$command] = $callback;
        ksort($this->commands[$priority]);

        // and some events again
        $this->event->dispatch('input.after_register', ['command' => $command, 'callback' => $callback]);
        $this->event->dispatch('input.after_register.' . $command, ['command' => $command, 'callback' => $callback]);
    }

    /**
     * Register commands by an associative array
     *
     * @param array $commandList
     * @param bool  $priority
     *
     * @throws Exception
     */
    public function registerCommands(array $commandList, $priority = self::PRIORITY_NORMAL)
    {
        foreach($commandList as $command => $callback) {

            if ( ! $callback instanceof Command) {
                throw new InvalidArgumentException('Callback should implement the Command interface');
            }

            $this->registerCommand($command, $callback, $priority);
        }
    }

    /**
     * Process the input from a connection
     *
     * @param Connection $connection The connection that added the input
     * @param string     $input      The actual input
     */
    public function handle(Connection $connection, $input)
    {
        // clean off anything that shouldn't be at the start of the line and then separate the input
        $arguments = explode(' ', rtrim($input));

        $this->event->dispatch('input.before_process', ['connection' => $connection, 'input' => &$input, 'arguments' => &$arguments]);

        if (isset($arguments[0])) {
            // try and find the command
            $command = $this->findCommand(ltrim($arguments[0]));

            // if we can't find it, simply stop
            if ( ! $command) {

                if (trim($arguments[0]) == '') {
                    $this->event->dispatch('input.empty', ['connection' => $connection]);
                    return;
                }

                $this->event->dispatch('input.not_found', ['connection' => $connection, 'input' => $input]);
                return;
            }

            // but if we did find the command, let the command handle the input

            // clean the input. ltrim potential whitespaces, then ltrim the first argument then trim potential whitespaces again
            $cleaned = trim(ltrim(ltrim($input), $arguments[0]));

            // fire event handlers
            $this->event->dispatch('input.before_command', ['connection' => $connection, 'command' => $command, 'input' => $input, 'cleaned' => $cleaned]);
            $this->event->dispatch('input.before_command.' . $command, ['connection' => $connection, 'command' => $command, 'input' => $input, 'cleaned' => $cleaned]);

            // execute the command
            if (isset($this->commands[self::PRIORITY_HIGH][$command])) {
                call_user_func_array($this->commands[self::PRIORITY_HIGH][$command], [$connection, $cleaned, $command, $input]);

            } elseif (isset($this->commands[self::PRIORITY_NORMAL][$command])) {
                call_user_func_array($this->commands[self::PRIORITY_NORMAL][$command], [$connection, $cleaned, $command, $input]);

            } else {
                call_user_func_array($this->commands[self::PRIORITY_LOW][$command], [$connection, $cleaned, $command, $input]);
            }

            // fire event handlers
            $this->event->dispatch('input.after_command', ['connection' => $connection, 'command' => $command, 'input' => $input, 'cleaned' => $cleaned]);
            $this->event->dispatch('input.after_command.' . $command, ['connection' => $connection, 'command' => $command, 'input' => $input, 'cleaned' => $cleaned]);
        }
    }

    /**
     * Retrieve an array of the currently registered commands
     *
     * @return array
     */
    public function getCommands()
    {
        return array_merge(
            (isset($this->commands[self::PRIORITY_HIGH]) ? array_keys($this->commands[self::PRIORITY_HIGH]) : []),
            (isset($this->commands[self::PRIORITY_NORMAL]) ? array_keys($this->commands[self::PRIORITY_NORMAL]) : []),
            (isset($this->commands[self::PRIORITY_LOW]) ? array_keys($this->commands[self::PRIORITY_LOW]) : [])
        );
    }

    /**
     * Find the closest matching command in the array of commands
     *
     * @param string $input The given command
     *
     * @return string|bool
     */
    protected function findCommand($input)
    {
        // sanitize the input
        $input = strtolower(trim($input));

        // if the command is empty
        if (strlen($input) == 0) {
            return false;
        }

        foreach ($this->getCommands() as $command) {
            if (substr($command, 0, strlen($input)) == $input) {
                return $command;
            }
        }

        // if not, fail
        return false;
    }
}

Modules_CommandNotFound_Observer_NotFound.php

<?php

namespace Modules\CommandNotFound\Observer;

use Game\Module\Observer;
use stdClass;

class NotFound extends Observer
{
    public function fire(stdClass $data)
    {
        $output = [
            'Wait, what? I have no idea what that means.',
            'Soo.. that doesn\'t make any kind of sense.',
            'Command not found.',
            "I could not find that command.\nCheck your spelling and check the help files."
        ];

        $this->getOutput()->write($data->connection, ["%s\n", $output[rand(0, 3)]]);
    }
}