Add compiler pass 1 -- resolve dependencies between variables and evaluate values

app/Engine/Cfnpp/Compiler.php

@@ -7,7 +7,9 @@ namespace App\Engine\Cfnpp;
 use App\Dom\Document;
 use App\Dom\Node;
 use App\Dom\NodeFunction;
+use App\Dom\NodeFunctionValue;
 use App\Engine\IOptions;
+use App\Util\DependencyGraph;
 
 /**
  * Compiler that implements the cfnpp "language" and allows you to
@@ -87,7 +89,10 @@ class Compiler implements \App\Engine\ICompile
 		$cfnpp_functions = new Functions($this, $options);
 		$cfnpp_functions->register($this);
 
-		return $this->pass_0($documents, $options);
+		$document = $this->pass_0($documents, $options);
+		$this->pass_1($document, $options);
+
+		return $document;
 
 		// Process each passed document
 		/*
@@ -112,7 +117,7 @@ class Compiler implements \App\Engine\ICompile
 	{
 
 		// Build dependency graph
-		$graph = new \App\Util\DependencyGraph();
+		$graph = new DependencyGraph();
 		foreach ($documents as $doc)
 		{
 			$stack = [];
@@ -146,7 +151,7 @@ class Compiler implements \App\Engine\ICompile
 
 		// Run our merge + merge functions
 		$document = new Document();
-		foreach ($documents as $next_document)
+		foreach ($ordered_documents as $next_document)
 		{
 			$this->runMergeFunctions($document, $next_document);
 			$this->merge($document, $next_document);
@@ -164,6 +169,76 @@ class Compiler implements \App\Engine\ICompile
 		return $document;
 	}
 
+	/**
+	 * Compiler Pass 1 - Grab all variables, build dependency graph of
+	 * dependencies between variable values, resolve variables values. Then
+	 * set them on $options to include them in program state.
+	 *
+	 * @param  Document $document
+	 * @param  IOptions $options
+	 * @return void
+	 */
+	protected function pass_1(Document $document, IOptions $options): void
+	{
+		$variables_node = $document->getChildByPath('cfnpp.variables');
+		// If there are no variables, we're done here.
+		if (!isset($variables_node))
+		{
+			return;
+		}
+
+		$variables_raw = [];
+		$graph = new DependencyGraph();
+
+		foreach ($variables_node as $variable_node)
+		{
+			$variables_raw[$variable_node->getName()] = $variable_node;
+			$graph->add($variable_node->getName(), $this->pass_1_getVariableDependencies($variable_node));
+		}
+
+		$variables_ordered = $graph->solve();
+
+		foreach ($variables_ordered as $variable)
+		{
+			$this->runFunctions($variables_raw[$variable]);
+			$options->setVariable($variable, Node::toPhp($variables_node->getChildByName($variable)));
+		}
+	}
+
+	/**
+	 * Given a node tree, get a list of variables that are referenced in that
+	 * tree.
+	 *
+	 * @todo whenever we add expressions this will have to be extended/rewritten
+	 * @param  Node     $node
+	 * @return string[]
+	 */
+	protected function pass_1_getVariableDependencies(Node $node): array
+	{
+		$stack = [$node];
+
+		$variables = [];
+
+		while (sizeof($stack))
+		{
+			$node = array_shift($stack);
+
+			if ($node->hasChildren())
+			{
+				$stack = array_merge($stack, $node->getChildren());
+			}
+
+			// We're really only handling one case here right now
+			if ($node instanceof NodeFunctionValue &&
+				$node->getName() == 'var')
+			{
+				$variables[] = $node->getValue();
+			}
+		}
+
+		return $variables;
+	}
+
 	/**
 	 * Performs a basic recursive merge of two dom trees with target overwriting
 	 * original.