2 files changed, 88 insertions, 2 deletions
diff --git a/src/Compiler/Compiler.php b/src/Compiler/Compiler.php
new file mode 100644
index 0000000..6a587d2
--- /dev/null
+++ b/src/Compiler/Compiler.php
@@ -0,0 +1,80 @@
+<?php
+declare(strict_types=1);
+
+/**
+ * @author: Alexander Kiryukhin <alexander@kiryukhin.su>
+ * @license: MIT
+ */
+
+namespace NeonXP\Dotenv\Compiler;
+
+use NeonXP\Dotenv\Exception\RuntimeException;
+use NeonXP\Dotenv\Types\KeyValue;
+
+/**
+ * Class Compiler
+ * @package NeonXP\Dotenv\Compiler
+ */
+class Compiler implements CompilerInterface
+{
+    const REGEX_VARIABLE = '/\$\{(.+?)\}/';
+
+    /**
+     * @var KeyValue[]
+     */
+    protected $collection = [];
+
+    /**
+     * @var KeyValue[]
+     */
+    protected $cache = [];
+
+    /**
+     * @inheritdoc
+     * @param KeyValue[] $collection
+     */
+    public function setRawCollection(array $collection): void
+    {
+        $this->collection = [];
+        $this->cache = [];
+        foreach ($collection as $keyValue) {
+            $this->collection[$keyValue->getKey()] = $keyValue;
+        }
+    }
+
+    /**
+     * @inheritdoc
+     * @param KeyValue $keyValue
+     * @return KeyValue
+     */
+    public function compileKeyValue(KeyValue $keyValue): KeyValue
+    {
+        $newValue = preg_replace_callback(self::REGEX_VARIABLE, function ($variable) use ($keyValue) {
+            $variable = $variable[1];
+            if ($variable === $keyValue->getKey()) {
+                throw new RuntimeException('Self referencing');
+            }
+            if (isset($this->cache[$variable])) {
+                return $this->cache[$variable]->getValue();
+            } elseif (isset($this->collection[$variable]) && !$this->needToCompile($this->collection[$variable])) {
+                return $this->collection[$variable]->getValue();
+            } elseif (isset($this->collection[$variable]) && $this->needToCompile($this->collection[$variable])) {
+                return $this->compileKeyValue($this->collection[$variable])->getValue();
+            }
+            return "UNKNOWN VARIABLE {$variable}";
+        }, $keyValue->getValue());
+        $result = new KeyValue($keyValue->getKey(), $newValue);
+        $this->cache[$result->getKey()] = $result;
+
+        return $result;
+    }
+
+    /**
+     * @param KeyValue $keyValue
+     * @return bool
+     */
+    protected function needToCompile(KeyValue $keyValue): bool
+    {
+        return !!preg_match(self::REGEX_VARIABLE, $keyValue->getValue());
+    }
+}
+\ No newline at end of file
diff --git a/src/Compiler/CompilerInterface.php b/src/Compiler/CompilerInterface.php
index 042a7d0..15b6823 100644
--- a/src/Compiler/CompilerInterface.php
+++ b/src/Compiler/CompilerInterface.php
@@ -1,4 +1,6 @@
 <?php
+declare(strict_types=1);
+
 /**
  * @author: Alexander Kiryukhin <alexander@kiryukhin.su>
  * @license: MIT
@@ -8,16 +10,20 @@ namespace NeonXP\Dotenv\Compiler;
 
 use NeonXP\Dotenv\Types\KeyValue;
 
+/**
+ * Interface CompilerInterface
+ * @package NeonXP\Dotenv\Compiler
+ */
 interface CompilerInterface
 {
     /**
      * @param KeyValue[] $collection
      */
-    function setRawCollection(array $collection): void;
+    public function setRawCollection(array $collection): void;
 
     /**
      * @param KeyValue $keyValue
      * @return KeyValue
      */
-    function compileKeyValue(KeyValue $keyValue): KeyValue;
+    public function compileKeyValue(KeyValue $keyValue): KeyValue;
 }
 \ No newline at end of file