[console] Add GenerateCommand Base class. (#334)

* [console] Add  GenerateCommand Base class.

* [console] Fix dockblock.

src/Command/GenerateCommand.php

@@ -0,0 +1,84 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Console\Core\Command\GenerateCommand.
+ */
+
+namespace Drupal\Console\Core\Command;
+
+use Symfony\Component\Filesystem\Filesystem;
+use Webmozart\PathUtil\Path;
+
+/**
+ * Class GenerateCommand
+ *
+ * @package Drupal\Console\Core\Command
+ */
+abstract class GenerateCommand extends Command
+{
+    protected function validateFileExists(
+        Filesystem $fs,
+        $sourceFiles,
+        $stopOnException = true
+    ) {
+        $notFound = [];
+        if (!is_array($sourceFiles)) {
+            $sourceFiles = [$sourceFiles];
+        }
+        foreach ($sourceFiles as $sourceFile) {
+            if ($fs->exists($sourceFile)) {
+                return $sourceFile;
+            }
+
+            $notFound[] = Path::makeRelative(
+                $sourceFile,
+                $this->drupalFinder->getComposerRoot()
+            );
+        }
+
+        if ($stopOnException) {
+            $this->createException(
+                'File(s): ' . implode(', ', $notFound) . ' not found.'
+            );
+        }
+
+        return null;
+    }
+
+    protected function backUpFile(Filesystem $fs, $fileName)
+    {
+        $fileNameBackup = $fileName.'.original';
+        if ($fs->exists($fileName)) {
+            if ($fs->exists($fileNameBackup)) {
+                $fs->remove($fileName);
+                return;
+            }
+
+            $fs->rename(
+                $fileName,
+                $fileNameBackup,
+                TRUE
+            );
+
+            $fileNameBackup = Path::makeRelative(
+                $fileNameBackup,
+                $this->drupalFinder->getComposerRoot()
+            );
+
+            $this->getIo()->success(
+                'File ' . $fileNameBackup . ' created.'
+            );
+
+        }
+    }
+
+    protected function showFileCreatedMessage($fileName) {
+        $fileName = Path::makeRelative(
+            $fileName,
+            $this->drupalFinder->getComposerRoot()
+        );
+
+        $this->getIo()->success('File: ' . $fileName . ' created.');
+    }
+}