Compiler pass 0 using new dependency graph/etc

This gets us back mostly to where we were, sans running non-merge !functions and variable/parameter support

app/Engine/Cfnpp/Compiler.php

@@ -7,6 +7,7 @@ namespace App\Engine\Cfnpp;
 use App\Dom\Document;
 use App\Dom\Node;
 use App\Dom\NodeFunction;
+use App\Engine\IOptions;
 
 /**
  * Compiler that implements the cfnpp "language" and allows you to
@@ -67,18 +68,18 @@ class Compiler implements \App\Engine\ICompile
 	 * Compile a set of documents and return the result.
 	 *
 	 * @param  Document[] $documents
-	 * @param  \App\Engine\IOptions   $options
+	 * @param  IOptions   $options
 	 * @return void
 	 */
-	public function compile(array $documents, \App\Engine\IOptions $options): Document
+	public function compile(array $documents, IOptions $options): Document
 	{
 		if (!($options instanceof Options))
 		{
-			throw new \Exception('Cfnpp\Compiler requires Cfnpp\Options');
+			throw new \Exception('Cfnpp\\Compiler requires Cfnpp\\Options');
 		}
 
 		// Initialize state
-		$document = new Document();
+		$document = null;
 		$this->functions = [];
 		$this->merge_functions = [];
 
@@ -86,13 +87,80 @@ class Compiler implements \App\Engine\ICompile
 		$cfnpp_functions = new Functions($this, $options);
 		$cfnpp_functions->register($this);
 
+		return $this->pass_0($documents, $options);
+
 		// Process each passed document
+		/*
 		foreach ($documents as $next_document)
 		{
 			$this->runMergeFunctions($document, $next_document);
 			$this->merge($document, $next_document);
 			$this->runFunctions($document);
 		}
+		 */
+	}
+
+	/**
+	 * Compiler Pass 0 - Build a dependency graph, run mergeFunctions + merge
+	 * for each as appropriate. Return the resulting document.
+	 *
+	 * @param  Document[] $documents
+	 * @param  IOptions   $options
+	 * @return Document
+	 */
+	protected function pass_0(array $documents, IOptions $options): Document
+	{
+
+		// Build dependency graph
+		$graph = new \App\Util\DependencyGraph();
+		foreach ($documents as $doc)
+		{
+			$stack = [];
+			try
+			{
+				$stack = $doc->getMeta('stack');
+			}
+			catch (\Exception $ex)
+			{
+			}
+			$graph->add($doc->getDocumentName(), $stack);
+		}
+
+		$graph->link();
+		$docs = $graph->flatten();
+
+		// Reorder all our documents in whatever order the dependency solver
+		// says we should process them in.
+		// O(N^2), fix this if it ever actually becomes a problem.
+		$ordered_documents = [];
+		foreach ($docs as $doc_name)
+		{
+			foreach ($documents as $document)
+			{
+				if ($document->getDocumentName() == $doc_name)
+				{
+					$ordered_documents[] = $document;
+					continue 2;
+				}
+			}
+		}
+
+		// Run our merge + merge functions
+		$document = new Document();
+		foreach ($documents as $next_document)
+		{
+			$this->runMergeFunctions($document, $next_document);
+			$this->merge($document, $next_document);
+		}
+
+		// Throw some of our state into the document for posterity's sake
+		$prefix = $this->getShortestCommonPrefix($docs);
+		foreach ($docs as &$doc)
+		{
+			$doc = substr($doc, strlen($prefix));
+		}
+		unset($doc);
+		$document->setChildByPath('Metadata.Stack', Node::fromPhp($docs));
 
 		return $document;
 	}
@@ -274,4 +342,34 @@ class Compiler implements \App\Engine\ICompile
 	{
 		return $this->merge_functions[$function->getName()]($original, $target, $function);
 	}
+
+	/**
+	 * Given a list of strings, find and return the shortest common prefix of all
+	 * strings. Can return an empty string if there's no prefix in common.
+	 *
+	 * @param  string[] $strings
+	 * @return string
+	 */
+	protected function getShortestCommonPrefix(array $strings): string
+	{
+		// Find longest common prefix
+		$shortest_string_length = array_reduce($strings, static function(int $carry, string $item) {
+			return min($carry, strlen($item));
+		}, PHP_INT_MAX);
+
+		for ($i = 0; $i < $shortest_string_length; $i++)
+		{
+			$c = $strings[0][$i];
+			for ($x = 1; $x < sizeof($strings); $x++)
+			{
+				if ($strings[$x][$i] != $c)
+				{
+					--$i;
+					break 2;
+				}
+			}
+		}
+
+		return $i == 0 ? '' : substr($strings[0], 0, $i);
+	}
 }