Ensure that the directory doesn't already exist

src/Command/GenerateDrupal7Command.php

@@ -0,0 +1,51 @@
+<?php
+
+namespace Opdavies\DrupalModuleGenerator\Command;
+
+use Opdavies\DrupalModuleGenerator\Exception\CannotCreateModuleException;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Input\InputArgument;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Output\OutputInterface;
+
+class GenerateDrupal7Command extends Command
+{
+    private $moduleName;
+
+    /**
+     * {@inheritdoc}
+     */
+    protected static $defaultName = 'generate-drupal-7-module';
+
+    /**
+     * {@inheritDoc}
+     */
+    protected function configure()
+    {
+        $this
+            ->setDescription('Generate a new Drupal 7 module.')
+            ->addArgument('module-name', InputArgument::REQUIRED, 'The name of the module to create');
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    protected function execute(InputInterface $input, OutputInterface $output)
+    {
+        $this->moduleName = $input->getArgument('module-name');
+
+        $this->ensureDirectoryDoesNotExist();
+
+        return 0;
+    }
+
+    /**
+     * Ensure that the directory name for the module doesn't already exist.
+     */
+    private function ensureDirectoryDoesNotExist()
+    {
+        if (is_dir($this->moduleName)) {
+            throw CannotCreateModuleException::directoryAlreadyExists();
+        }
+    }
+}

src/Exception/CannotCreateModuleException.php

@@ -0,0 +1,11 @@
+<?php
+
+namespace Opdavies\DrupalModuleGenerator\Exception;
+
+class CannotCreateModuleException extends \RuntimeException
+{
+    public static function directoryAlreadyExists()
+    {
+        return new static('The given directory name for the module already exists.');
+    }
+}