added kernel component

src/Kernel/Kernel.php

@@ -0,0 +1,82 @@
+<?php
+/**
+ * @author Alexey Samoylov <[email protected]>
+ */
+
+namespace YarCode\Yii2\Kernel;
+
+use yii\base\BootstrapInterface;
+use yii\base\Component;
+use yii\base\InvalidConfigException;
+use yii\helpers\ArrayHelper;
+
+class Kernel extends Component implements BootstrapInterface
+{
+    /** @var KernelPlugin[] */
+    protected $plugins = [];
+
+    public function bootstrap($app)
+    {
+        static::getInstance();
+    }
+
+    /**
+     * @return static
+     * @throws \yii\base\InvalidConfigException
+     */
+    public static function getInstance()
+    {
+        return \Yii::$app->get('kernel');
+    }
+
+    /**
+     * @param array $config
+     */
+    public function setPlugins($config)
+    {
+        if (!is_array($config)) {
+            throw new \LogicException("Plugins configuration must be an array");
+        }
+
+        foreach ($config as $pluginClassName) {
+            $this->registerPlugin($pluginClassName);
+        }
+    }
+
+    /**
+     * @param string $className
+     * @throws InvalidConfigException
+     */
+    public function registerPlugin($className)
+    {
+        if (!class_exists($className)) {
+            throw new \LogicException("Unknown plugin className {$className}");
+        }
+
+        if (isset($this->plugins[$className])) {
+            return;
+        }
+
+        /** @var KernelPlugin $plugin */
+        $plugin = \Yii::createObject($className);
+        $plugin->kernel = $this;
+        $this->plugins[$className] = $plugin;
+        $this->plugins[$className]->bootstrap();
+    }
+
+    /**
+     * @param $class
+     * @return KernelPlugin
+     */
+    public function getPlugin($class)
+    {
+        $plugin = ArrayHelper::getValue($this->plugins, $class);
+
+        if (null === $plugin) {
+            throw new \LogicException("Unknown plugin: {$class}");
+        }
+
+        return $plugin;
+    }
+
+}

src/Kernel/KernelPlugin.php

@@ -0,0 +1,34 @@
+<?php
+namespace YarCode\Yii2\Kernel;
+
+use yii\base\Component;
+
+abstract class KernelPlugin extends Component
+{
+    /** @var Kernel */
+    public $kernel;
+
+    /**
+     * Bootstrap method for this plugin
+     */
+    abstract public function bootstrap();
+
+    /**
+     * Plugin instance getter
+     * @return static
+     */
+    public static function getInstance()
+    {
+        return Kernel::getInstance()->getPlugin(static::class);
+    }
+
+    /**
+     * Performs active transaction check and fails if the transaction is missing
+     */
+    protected function ensureDbTransaction()
+    {
+        if (null === \Yii::$app->db->transaction) {
+            throw new \LogicException('You must use DB transaction to call ' . __METHOD__);
+        }
+    }
+}