[console] Add Requirement checker/validator.

requirements.yml

@@ -0,0 +1,28 @@
+requirements:
+  php-version:
+    required: 5.5.9
+  configurations:
+    required:
+      - date.timezone: "America/Los_Angeles"
+      - memory_limit: 1024M
+    recomended:
+  extensions:
+    required:
+      - date
+      - dom
+      - filter
+      - gd
+      - hash
+      - json
+      - pcre
+      - pdo
+      - session
+      - SimpleXML
+      - SPL
+      - tokenizer
+      - xml
+      - curl
+    recommended:
+      - mysql
+      - sqlite3
+      - ssh2

src/Application.php

@@ -166,6 +166,7 @@ public function getLongVersion()
     public function doRun(InputInterface $input, OutputInterface $output)
     {
         $output = new DrupalStyle($input, $output);
+
         $root = null;
         $config = $this->getConfig();
         $target = $input->getParameterOption(['--target'], null);

src/Utils/RequirementChecker.php

@@ -0,0 +1,89 @@
+<?php
+
+namespace Drupal\Console\Utils;
+
+/**
+ * Class RequirementChecker
+ * @package Drupal\Console\Utils
+ */
+class RequirementChecker
+{
+    /**
+   * @var array
+   */
+    protected $requirements = [];
+
+    /**
+   * @var array
+   */
+    protected $checkResult = [];
+
+    public function __construct($config)
+    {
+        $this->requirements = $config->getFileContents(__DIR__.'/../../requirements.yml');
+    }
+
+    private function checkPHPVersion()
+    {
+        $requiredPHP = $this->requirements['requirements']['php-version']['required'];
+        $currentPHP = phpversion();
+        $this->checkResult['php-version']['required'] = $requiredPHP;
+        $this->checkResult['php-version']['current'] = $currentPHP;
+        if (version_compare($currentPHP, $requiredPHP, '<')) {
+            $this->checkResult['php-version']['invalid'] = true;
+        }
+    }
+
+    private function checkRequiredExtensions()
+    {
+        foreach ($this->requirements['requirements']['extensions']['required'] as $extension) {
+            if (!extension_loaded($extension)) {
+                $this->checkResult['extensions']['required']['missing'] = $extension;
+            }
+        }
+    }
+
+    private function checkRecommendedExtensions()
+    {
+        foreach ($this->requirements['requirements']['extensions']['recommended'] as $extension) {
+            if (!extension_loaded($extension)) {
+                $this->checkResult['extensions']['recommended']['missing'] = $extension;
+            }
+        }
+    }
+
+    private function checkRequiredConfigurations()
+    {
+        foreach ($this->requirements['requirements']['configurations']['required'] as $configuration) {
+            $defaultValue = null;
+            if (is_array($configuration)) {
+                $defaultValue = current($configuration);
+                $configuration = key($configuration);
+            }
+
+            if (!ini_get($configuration)) {
+                if ($defaultValue) {
+                    ini_set($configuration, $defaultValue);
+                    $this->checkResult['configurations']['required']['override'] = [
+                    $configuration => $defaultValue
+                    ];
+                    continue;
+                }
+
+                $this->checkResult['configurations']['required']['missing'] = $configuration;
+            }
+        }
+    }
+
+    /**
+   * @return array
+   */
+    public function validate()
+    {
+        $this->checkPHPVersion();
+        $this->checkRequiredExtensions();
+        $this->checkRecommendedExtensions();
+        $this->checkRequiredConfigurations();
+        return $this->checkResult;
+    }
+}