Finish graph logic

.gitignore

@@ -1,2 +1,7 @@
-/vendor/
+.vscode
+build
 composer.lock
+phpunit.xml
+vendor
+.php_cs.cache
+coverage

.php_cs.dist

@@ -0,0 +1,13 @@
+<?php
+
+$config = new Amp\CodeStyle\Config();
+$config->getFinder()
+    ->in(__DIR__ . '/examples')
+    ->in(__DIR__ . '/src')
+    ->in(__DIR__ . '/test');
+
+$cacheDir = getenv('TRAVIS') ? getenv('HOME') . '/.php-cs-fixer' : __DIR__;
+
+$config->setCacheFile($cacheDir . '/.php_cs.cache');
+
+return $config;

composer.json

@@ -5,11 +5,22 @@
     "require": {
         "nikic/php-parser": "^4.7"
     },
+    "require-dev": {
+        "phpunit/phpunit": "^7 | ^8 | ^9",
+        "amphp/php-cs-fixer-config": "dev-master"
+    },
     "license": "MIT",
-    "authors": [
+    "authors": [{
-        {
+        "name": "Daniil Gentili",
-            "name": "Daniil Gentili",
+        "email": "daniil@daniil.it"
-            "email": "daniil@daniil.it"
+    }],
-        }
+    "scripts": {
-    ]
+        "check": [
+            "@cs",
+            "@test"
+        ],
+        "cs": "php-cs-fixer fix -v --diff --dry-run",
+        "cs-fix": "php-cs-fixer fix -v --diff",
+        "test": "@php -dzend.assertions=1 -dassert.exception=1 ./vendor/bin/phpunit --coverage-text"
+    }
 }

src/Context.php

@@ -4,5 +4,4 @@ namespace Phabel;
 
 class Context
 {
-    
 }

src/Context/UniqueId.php

@@ -6,5 +6,4 @@ use Phabel\Plugin;
 
 class UniqueId extends Plugin
 {
-    
 }

src/Plugin.php

@@ -18,6 +18,16 @@ abstract class Plugin implements PluginInterface
      * Configuration array.
      */
     private array $config = [];
+    /**
+     * Set configuration array.
+     *
+     * @param array $config
+     * @return void
+     */
+    public function setConfigArray(array $config)
+    {
+        $this->config = $config;
+    }
     /**
      * Replace node of one type with another.
      *
@@ -141,14 +151,28 @@ abstract class Plugin implements PluginInterface
     /**
      * {@inheritDoc}
      */
-    public static function needs(): array
+    public static function runAfter(): array
     {
         return [];
     }
     /**
      * {@inheritDoc}
      */
-    public static function extends(): array
+    public static function runBefore(): array
+    {
+        return [];
+    }
+    /**
+     * {@inheritDoc}
+     */
+    public static function runWithBefore(): array
+    {
+        return [];
+    }
+    /**
+     * {@inheritDoc}
+     */
+    public static function runWithAfter(): array
     {
         return [];
     }

src/Plugin/Amp/YieldFromReplacer.php

@@ -4,7 +4,6 @@ namespace Spatie\Php7to5\NodeVisitors;
 
 use PhpParser\Node;
 use PhpParser\NodeVisitorAbstract;
-use PhpParser\ParserFactory;
 
 class YieldFromReplacer extends NodeVisitorAbstract
 {

src/Plugin/Amp/YieldReturnDetector.php

@@ -3,13 +3,7 @@
 namespace Spatie\Php7to5\NodeVisitors;
 
 use PhpParser\Node;
-use PhpParser\NodeTraverser;
-use PhpParser\Node\Stmt\Declare_;
-use PhpParser\Node\Stmt\Namespace_;
-use PhpParser\Node\Stmt\Use_;
 use PhpParser\NodeVisitorAbstract;
-use Spatie\Php7to5\Converter;
-use Spatie\Php7to5\Exceptions\InvalidPhpCode;
 
 class YieldReturnDetector extends NodeVisitorAbstract
 {
@@ -26,13 +20,13 @@ class YieldReturnDetector extends NodeVisitorAbstract
         if ($node instanceof Node\Expr\Yield_ ||
             $node instanceof Node\Expr\YieldFrom
         ) {
-            end($this->hasYield)->hasYield = true;
+            \end($this->hasYield)->hasYield = true;
         }
     }
     public function leaveNode(Node $node)
     {
         if ($node instanceof Node\FunctionLike) {
-            array_pop($this->hasYield);
+            \array_pop($this->hasYield);
         }
     }
 }

src/Plugin/Amp/YieldReturnReplacer.php

@@ -24,7 +24,7 @@ class YieldReturnReplacer extends NodeVisitorAbstract
     public function leaveNode(Node $node)
     {
         if ($node instanceof Node\FunctionLike) {
-            array_pop($this->functions);
+            \array_pop($this->functions);
             return;
         }
         if (!$node instanceof Node\Stmt\Return_) {
@@ -34,7 +34,7 @@ class YieldReturnReplacer extends NodeVisitorAbstract
             return new Node\Stmt\Return_();
         }
 
-        if (!(end($this->functions)->hasYield ?? false)) {
+        if (!(\end($this->functions)->hasYield ?? false)) {
             return;
         }
 

src/PluginCache.php

@@ -0,0 +1,157 @@
+<?php
+
+namespace Phabel;
+
+/**
+ * Caches plugin information.
+ */
+class PluginCache
+{
+    /**
+     * Enter method names for each plugin.
+     *
+     * @var array<class-string<PluginInterface>, string[]>
+     */
+    private static array $enterMethods = [];
+    /**
+     * Leave method names.
+     *
+     * @var array<class-string<PluginInterface>, string[]>
+     */
+    private static array $leaveMethods = [];
+
+    /**
+     * Cache method information.
+     *
+     * @param class-string<PluginInterface> $plugin Plugin
+     *
+     * @return void
+     */
+    private static function cacheMethods(string $plugin): void
+    {
+        if (!isset(self::$enterMethods[$plugin])) {
+            self::$enterMethods[$plugin] = [];
+            self::$leaveMethods[$plugin] = [];
+            foreach (\get_class_methods($plugin) as $method) {
+                if (\str_starts_with($method, 'enter')) {
+                    self::$enterMethods[$plugin] []= $method;
+                } elseif (\str_starts_with($method, 'leave')) {
+                    self::$leaveMethods[$plugin] []= $method;
+                }
+            }
+        }
+    }
+    /**
+     * Return whether this plugin can be required by another plugin.
+     *
+     * If false, this plugin should only be extended by other plugins, to reduce complexity.
+     *
+     * @param class-string<PluginInterface> $plugin Plugin
+     *
+     * @return boolean
+     */
+    public static function canBeRequired(string $plugin): bool
+    {
+        self::cacheMethods($plugin);
+        return empty(self::$leaveMethods[$plugin]);
+    }
+    /**
+     * Get enter methods array.
+     *
+     * @param class-string<PluginInterface> $plugin Plugin name
+     *
+     * @return string[]
+     */
+    public static function enterMethods(string $plugin): array
+    {
+        self::cacheMethods($plugin);
+        return self::$enterMethods[$plugin];
+    }
+    /**
+     * Get leave methods array.
+     *
+     * @param class-string<PluginInterface> $plugin Plugin name
+     *
+     * @return string[]
+     */
+    public static function leaveMethods(string $plugin): array
+    {
+        self::cacheMethods($plugin);
+        return self::$leaveMethods[$plugin];
+    }
+    /**
+     * Get runBefore requirements.
+     *
+     * @param class-string<PluginInterface> $plugin Plugin
+     *
+     * @return array<class-string<PluginInterface>, array>
+     */
+    public static function runBefore(string $plugin): array
+    {
+        /** @var array<class-string<PluginInterface>, array<class-string<PluginInterface>, array>> */
+        static $cache = [];
+        if (isset($cache[$plugin])) {
+            return $cache[$plugin];
+        }
+        return $cache[$plugin] = self::simplify($plugin::runBefore());
+    }
+    /**
+     * Get runAfter requirements.
+     *
+     * @param class-string<PluginInterface> $plugin Plugin
+     *
+     * @return array<class-string<PluginInterface>, array>
+     */
+    public static function runAfter(string $plugin): array
+    {
+        /** @var array<class-string<PluginInterface>, array<class-string<PluginInterface>, array>> */
+        static $cache = [];
+        if (isset($cache[$plugin])) {
+            return $cache[$plugin];
+        }
+        return $cache[$plugin] = self::simplify($plugin::runAfter());
+    }
+    /**
+     * Get runWithBefore requirements.
+     *
+     * @param class-string<PluginInterface> $plugin Plugin
+     *
+     * @return array<class-string<PluginInterface>, array>
+     */
+    public static function runWithBefore(string $plugin): array
+    {
+        /** @var array<class-string<PluginInterface>, array<class-string<PluginInterface>, array>> */
+        static $cache = [];
+        if (isset($cache[$plugin])) {
+            return $cache[$plugin];
+        }
+        return $cache[$plugin] = self::simplify($plugin::runWithBefore());
+    }
+    /**
+     * Get runWithAfter requirements.
+     *
+     * @param class-string<PluginInterface> $plugin Plugin
+     *
+     * @return array<class-string<PluginInterface>, array>
+     */
+    public static function runWithAfter(string $plugin): array
+    {
+        /** @var array<class-string<PluginInterface>, array<class-string<PluginInterface>, array>> */
+        static $cache = [];
+        if (isset($cache[$plugin])) {
+            return $cache[$plugin];
+        }
+        return $cache[$plugin] = self::simplify($plugin::runWithAfter());
+    }
+    /**
+     * Simplify requirements.
+     *
+     * @param (array<class-string<PluginInterface>, array>|class-string<PluginInterface>[]) $requirements Requirements
+     *
+     * @return array<class-string<PluginInterface>, array>
+     */
+    private static function simplify(array $requirements): array
+    {
+        return isset($requirements[0]) ? \array_fill_keys($requirements, []) : $requirements;
+    }
+}

src/PluginGraph/CircularException.php

@@ -0,0 +1,35 @@
+<?php
+
+namespace Phabel\PluginGraph;
+
+use Phabel\PluginInterface;
+
+class CircularException extends \Exception
+{
+    /**
+     * Plugin array.
+     *
+     * @var class-string<PluginInterface>[]
+     */
+    private array $plugins = [];
+    /**
+     * Constructor.
+     *
+     * @param class-string<PluginInterface>[] $plugins  Plugin array
+     * @param \Throwable                      $previous Previous exception
+     */
+    public function __construct(array $plugins, \Throwable $previous = null)
+    {
+        $this->plugins = $plugins;
+        parent::__construct("Detected circular reference: ".\implode(" => ", $plugins), 0, $previous);
+    }
+    /**
+     * Get plugins.
+     *
+     * @return class-string<PluginInterface>[]
+     */
+    public function getPlugins(): array
+    {
+        return $this->plugins;
+    }
+}

src/PluginGraph/Graph.php

@@ -2,24 +2,22 @@
 
 namespace Phabel\PluginGraph;
 
-use Phabel\PluginInterface;
+/**
-
+ * Graph API wrapper.
+ */
 class Graph
 {
     /**
-     * Plugin nodes, indexed by plugin name+config.
+     * Graph instance.
-     *
-     * @var array<class-string<PluginInterface>, array<string, Node>>
      */
-    private array $plugins = [];
+    private GraphInternal $graph;
-
     /**
-     * Package contexts.
+     * Constructr.
-     *
-     * @var PackageContext[]
      */
-    private array $packageContexts = [];
+    public function __construct()
-
+    {
+        $this->graph = new GraphInternal;
+    }
     /**
      * Get new package context.
      *
@@ -27,9 +25,7 @@ class Graph
      */
     public function getPackageContext(): PackageContext
     {
-        $packageContext = new PackageContext;
+        return $this->graph->getPackageContext();
-        $this->packageContexts []= $packageContext;
-        return $packageContext;
     }
 
     /**
@@ -45,31 +41,15 @@ class Graph
      */
     public function addPlugin(string $plugin, array $config, PackageContext $ctx): array
     {
-        $configs = $plugin::splitConfig($config);
+        return $this->graph->addPlugin($plugin, $config, $ctx);
-        $nodes = [];
-        foreach ($configs as $config) {
-            $nodes []= $this->addPluginInternal($plugin, $config, $ctx);
-        }
-        return $nodes;
     }
     /**
-     * Add plugin.
+     * Flatten graph.
      *
-     * @param string         $plugin Plugin to add
+     * @return SplQueue<SplQueue<Plugin>>
-     * @param array          $config Plugin configuration
-     * @param PackageContext $ctx    Package context
-     *
-     * @psalm-param class-string<PluginInterface> $plugin Plugin name
-     *
-     * @return Node
      */
-    private function addPluginInternal(string $plugin, array $config, PackageContext $ctx): Node
+    public function flatten(): \SplQueue
     {
-        $configStr = \var_export($config, true);
+        return $this->graph->flatten();
-        if (isset($this->plugins[$plugin][$configStr])) {
-            return $this->plugins[$plugin][$configStr]->addPackageContext($ctx);
-        }
-        $this->plugins[$plugin][$configStr] = $node = new Node;
-        return $node->init($this, $plugin, $config, $ctx);
     }
 }

src/PluginGraph/GraphInternal.php

@@ -0,0 +1,132 @@
+<?php
+
+namespace Phabel\PluginGraph;
+
+use Phabel\PluginInterface;
+use SplObjectStorage;
+use SplQueue;
+
+class GraphInternal
+{
+    /**
+     * Plugin nodes, indexed by plugin name+config.
+     *
+     * @var array<class-string<PluginInterface>, array<string, Node>>
+     */
+    private array $plugins = [];
+
+    /**
+     * Package contexts.
+     *
+     * @var PackageContext[]
+     */
+    private array $packageContexts = [];
+
+    /**
+     * Stores list of Nodes that are not required by any other node.
+     *
+     * @var SplObjectStorage<Node, void>
+     */
+    private SplObjectStorage $unlinkedNodes;
+
+    /**
+     * Constructor.
+     */
+    public function __construct()
+    {
+        $this->unlinkedNodes = new SplObjectStorage;
+    }
+    /**
+     * Get new package context.
+     *
+     * @return PackageContext
+     */
+    public function getPackageContext(): PackageContext
+    {
+        $packageContext = new PackageContext;
+        $this->packageContexts []= $packageContext;
+        return $packageContext;
+    }
+
+    /**
+     * Add plugin.
+     *
+     * @param class-string<PluginInterface> $plugin Plugin to add
+     * @param array                         $config Plugin configuration
+     * @param PackageContext                $ctx    Package context
+     *
+     * @return Node[]
+     */
+    public function addPlugin(string $plugin, array $config, PackageContext $ctx): array
+    {
+        if ($config === ['*']) {
+            if (isset($this->plugins[$plugin])) {
+                return \array_map(fn (Node $node) => $node->addPackageContext($ctx), $this->plugins[$plugin]);
+            }
+            $config = [];
+        }
+        $configs = $plugin::splitConfig($config);
+        $nodes = [];
+        foreach ($configs as $config) {
+            $nodes []= $this->addPluginInternal($plugin, $config, $ctx);
+        }
+        return $nodes;
+    }
+    /**
+     * Add plugin.
+     *
+     * @param string         $plugin Plugin to add
+     * @param array          $config Plugin configuration
+     * @param PackageContext $ctx    Package context
+     *
+     * @psalm-param class-string<PluginInterface> $plugin Plugin name
+     *
+     * @return Node
+     */
+    private function addPluginInternal(string $plugin, array $config, PackageContext $ctx): Node
+    {
+        $configStr = \var_export($config, true);
+        if (isset($this->plugins[$plugin][$configStr])) {
+            return $this->plugins[$plugin][$configStr]->addPackageContext($ctx);
+        }
+        $this->plugins[$plugin][$configStr] = $node = new Node($this);
+        $this->unlinkedNodes->attach($node);
+        return $node->init($plugin, $config, $ctx);
+    }
+
+    /**
+     * Set unlinked node as linked.
+     *
+     * @param Node $node
+     *
+     * @return void
+     */
+    public function linkNode(Node $node): void
+    {
+        $this->unlinkedNodes->detach($node);
+    }
+
+
+    /**
+     * Flatten graph.
+     *
+     * @return SplQueue<SplQueue<Plugin>>
+     */
+    public function flatten(): \SplQueue
+    {
+        if (!$this->plugins) {
+            return new \SplQueue;
+        }
+        if ($this->unlinkedNodes->count()) {
+            foreach ($this->unlinkedNodes as $node) {
+                if (isset($initNode)) {
+                    $node = $initNode->merge($node);
+                }
+                /** @var Node */
+                $initNode = $node;
+            }
+            return $initNode->circular()->flatten();
+        }
+        return \array_values(\array_values($this->plugins)[0])[0]->circular()->flatten();
+    }
+}

src/PluginGraph/Node.php

@@ -2,8 +2,10 @@
 
 namespace Phabel\PluginGraph;
 
+use Phabel\PluginCache;
 use Phabel\PluginInterface;
 use SplObjectStorage;
+use SplQueue;
 
 /**
  * Represents a plugin with a certain configuration.
@@ -11,66 +13,85 @@ use SplObjectStorage;
 class Node
 {
     /**
-     * Plugin name.
+     * Plugins and configs.
+     *
+     * @var Plugin
      */
-    private string $plugin = '';
+    private Plugin $plugin;
+
     /**
-     * Plugin configuration.
+     * Original plugin name.
+     *
+     * @var class-string<PluginInterface>
      */
-    private array $config = [];
+    private string $name;
 
     /**
      * Associated package contexts.
+     *
+     * @var SplObjectStorage<PackageContext, void>
      */
     private SplObjectStorage $packageContexts;
     /**
      * Nodes that this node requires.
      *
-     * @var Node[]
+     * @var SplObjectStorage<Node, void>
      */
-    private array $requires = [];
+    private SplObjectStorage $requires;
 
     /**
      * Nodes that this node extends.
      *
-     * @var Node[]
+     * @var SplObjectStorage<Node, void>
      */
-    private array $extends = [];
+    private SplObjectStorage $extends;
 
     /**
      * Nodes that require this node.
      *
-     * @var Node[]
+     * @var SplObjectStorage<Node, void>
      */
-    private array $requiredBy = [];
+    private SplObjectStorage $requiredBy;
 
     /**
      * Nodes that extend this node.
      *
-     * @var Node[]
+     * @var SplObjectStorage<Node, void>
      */
-    private array $extendedBy = [];
+    private SplObjectStorage $extendedBy;
 
     /**
-     * Whether this node was visited when looking for circular requirement references.
+     * Graph instance.
      */
-    private bool $visitedRequires = false;
+    private GraphInternal $graph;
+
     /**
-     * Whether this node was visited when looking for circular requirement references.
+     * Whether this node was visited when looking for circular requirements.
      */
-    private bool $visitedExtends = false;
+    private bool $visitedCircular = false;
+
+    /**
+     * Whether this node can be required, or only extended.
+     */
+    private bool $canBeRequired = true;
 
     /**
      * Constructor.
+     *
+     * @param GraphInternal  $graph  Graph instance
      */
-    public function __construct()
+    public function __construct(GraphInternal $graph)
     {
+        $this->graph = $graph;
         $this->packageContexts = new SplObjectStorage;
+        $this->requiredBy = new SplObjectStorage;
+        $this->extendedBy = new SplObjectStorage;
+        $this->requires = new SplObjectStorage;
+        $this->extends = new SplObjectStorage;
     }
     /**
      * Initialization function.
      *
-     * @param Graph          $graph  Graph instance
      * @param string         $plugin Plugin name
      * @param array          $config Plugin configuration
      * @param PackageContext $ctx    Context
@@ -79,25 +100,31 @@ class Node
      *
      * @return self
      */
-    public function init(Graph $graph, string $plugin, array $config, PackageContext $ctx): self
+    public function init(string $plugin, array $config, PackageContext $ctx): self
     {
-        $this->plugin = $plugin;
+        $this->name = $plugin;
-        $this->config = $config;
+        $this->plugin = new Plugin($plugin, $config);
         $this->packageContexts->attach($ctx);
 
-        $requirements = self::simplify($plugin::needs());
+        $this->canBeRequired = PluginCache::canBeRequired($plugin);
-        $extends = self::simplify($plugin::extends());
+        foreach (PluginCache::runAfter($plugin) as $class => $config) {
-
+            foreach ($this->graph->addPlugin($class, $config, $ctx) as $node) {
-        foreach ($requirements as $class => $config) {
+                $this->require($node);
-            foreach ($graph->addPlugin($class, $config, $ctx) as $node) {
-                $this->requires []= $node;
-                $node->requiredBy []= $this;
             }
         }
-        foreach ($extends as $class => $config) {
+        foreach (PluginCache::runBefore($plugin) as $class => $config) {
-            foreach ($graph->addPlugin($class, $config, $ctx) as $node) {
+            foreach ($this->graph->addPlugin($class, $config, $ctx) as $node) {
-                $this->extends []= $node;
+                $node->require($this);
-                $node->extendedBy []= $this;
+            }
+        }
+        foreach (PluginCache::runWithAfter($plugin) as $class => $config) {
+            foreach ($this->graph->addPlugin($class, $config, $ctx) as $node) {
+                $this->extend($node);
+            }
+        }
+        foreach (PluginCache::runWithBefore($plugin) as $class => $config) {
+            foreach ($this->graph->addPlugin($class, $config, $ctx) as $node) {
+                $node->extend($this);
             }
         }
 
@@ -105,15 +132,43 @@ class Node
     }
 
     /**
-     * Simplify requirements.
+     * Make node require another node.
      *
-     * @param (array<class-string<PluginInterface>, array>|class-string<PluginInterface>[]) $requirements Requirements
+     * @param self $node Node
      *
-     * @return array<class-string<PluginInterface>, array>
+     * @return void
      */
-    private static function simplify(array $requirements): array
+    private function require(self $node): void
     {
-        return isset($requirements[0]) ? \array_fill_keys($requirements, []) : $requirements;
+        if (!$node->canBeRequired) {
+            $this->extend($node);
+            return;
+        }
+        if ($this->extends->contains($node) || $node->extendedBy->contains($this)) {
+            $this->extends->detach($node);
+            $node->extendedBy->detach($this);
+        }
+        $this->requires->attach($node);
+        $node->requiredBy->attach($this);
+
+        $this->graph->linkNode($this);
+    }
+    /**
+     * Make node extend another node.
+     *
+     * @param self $node Node
+     *
+     * @return void
+     */
+    private function extend(self $node): void
+    {
+        if ($this->requires->contains($node) || $node->requiredBy->contains($this)) {
+            return;
+        }
+        $this->extends->attach($node);
+        $node->extendedBy->attach($this);
+
+        $this->graph->linkNode($this);
     }
 
     /**
@@ -139,21 +194,133 @@ class Node
     }
 
     /**
-     * Check if this node requires only one other node.
+     * Merge node with another node.
      *
-     * @return boolean
+     * @param self $other Other node
+     *
+     * @return Node
      */
-    private function oneRequire(): bool
+    public function merge(self $other): Node
     {
-        return \count($this->requires) === 1 && empty($this->extends);
+        $this->plugin->merge($other->plugin);
+        foreach ($other->requiredBy as $node) {
+            $node->require($this);
+            $node->requires->detach($other);
+        }
+        foreach ($other->extendedBy as $node) {
+            $node->extend($this);
+            $node->extends->detach($other);
+        }
+
+        return $this;
+    }
+
+    /**
+     * Flatten tree.
+     *
+     * @return SplQueue<SplQueue<PluginInterface>>
+     */
+    public function flatten(): SplQueue
+    {
+        /** @var SplQueue<PluginInterface> */
+        $initQueue = new SplQueue;
+
+        /** @var SplQueue<SplQueue<PluginInterface>> */
+        $queue = new SplQueue;
+        $queue->enqueue($initQueue);
+
+        $this->flattenInternal($queue);
+
+        return $queue;
     }
     /**
-     * Check if this node extends only one other node.
+     * Look for circular references.
      *
-     * @return boolean
+     * @return self
      */
-    private function oneExtend(): bool
+    public function circular(): self
     {
-        return \count($this->extends) === 1;
+        if ($this->visitedCircular) {
+            $plugins = [$this->name];
+            foreach (\debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS, DEBUG_BACKTRACE_PROVIDE_OBJECT) as $frame) {
+                $plugins []= $frame['object']->name;
+                if ($frame['object'] === $this) {
+                    break;
+                }
+            }
+            throw new CircularException($plugins);
+        }
+        $this->visitedCircular = true;
+
+        foreach ($this->requiredBy as $node) {
+            $node->circular();
+        }
+        foreach ($this->extendedBy as $node) {
+            $node->circular();
+        }
+
+        $this->visitedCircular = false;
+
+        return $this;
+    }
+    /**
+     * Internal flattening.
+     *
+     * @param SplQueue<SplQueue<PluginInterface>> $splQueue Queue
+     *
+     * @return void
+     */
+    private function flattenInternal(SplQueue $splQueue): void
+    {
+        $queue = $splQueue->top();
+        $this->plugin->enqueue($queue);
+
+        /** @var SplQueue<Node> */
+        $extendedBy = new SplQueue;
+        $prevNode = null;
+        foreach ($this->extendedBy as $node) {
+            if (\count($node->requires) + \count($node->extends) === 1) {
+                if ($prevNode instanceof self) {
+                    $node->merge($prevNode);
+                }
+                $prevNode = $node;
+            } else {
+                $extendedBy->enqueue($node);
+            }
+        }
+        if ($prevNode) {
+            $extendedBy->enqueue($prevNode);
+        }
+
+        /** @var SplQueue<Node> */
+        $requiredBy = new SplQueue;
+        $prevNode = null;
+        foreach ($this->requiredBy as $node) {
+            if (\count($node->requires) + \count($node->extends) === 1) {
+                if ($prevNode instanceof self) {
+                    $node->merge($prevNode);
+                }
+                $prevNode = $node;
+            } else {
+                $requiredBy->enqueue($node);
+            }
+        }
+        if ($prevNode) {
+            $requiredBy->enqueue($prevNode);
+        }
+
+        foreach ($extendedBy as $node) {
+            $node->extends->detach($this);
+            if (\count($node->extends) + \count($node->requires) === 0) {
+                $node->flattenInternal($splQueue);
+            }
+        }
+        foreach ($requiredBy as $node) {
+            $node->requires->detach($this);
+            if (\count($node->extends) + \count($node->requires) === 0) {
+                $splQueue->enqueue(new SplQueue);
+                $node->flattenInternal($splQueue);
+            }
+        }
     }
 }

src/PluginGraph/PackageContext.php

@@ -25,7 +25,7 @@ class PackageContext
         $this->packages[$package] = null;
     }
     /**
-     * Merge two contexts
+     * Merge two contexts.
      *
      * @param self $other Other context
      *
@@ -38,12 +38,12 @@ class PackageContext
     }
 
     /**
-     * Get package list
+     * Get package list.
      *
      * @return array
      */
     public function getPackages(): array
     {
-        return array_values($this->packages);
+        return \array_values($this->packages);
     }
 }

src/PluginGraph/Plugin.php

@@ -0,0 +1,66 @@
+<?php
+
+namespace Phabel\PluginGraph;
+
+use Phabel\PluginInterface;
+use SplQueue;
+
+/**
+ * Representation of multiple plugins+configs.
+ */
+class Plugin
+{
+    /**
+     * Plugin configs, indexed by plugin name.
+     *
+     * @var array<class-string<PluginInterface>, array[]>
+     */
+    private array $plugins = [];
+
+    /**
+     * Constructor.
+     *
+     * @param class-string<PluginInterface> $plugin Plugin
+     * @param array                         $config Config
+     */
+    public function __construct(string $plugin, array $config)
+    {
+        $this->plugins[$plugin] = [$config];
+    }
+
+    /**
+     * Merge with other plugins.
+     *
+     * @param self $other Plugins
+     *
+     * @return void
+     */
+    public function merge(self $other): void
+    {
+        foreach ($other->plugins as $plugin => $configs) {
+            if (isset($this->plugins[$plugin])) {
+                $this->plugins[$plugin] = \array_merge($this->plugins[$plugin], $configs);
+            } else {
+                $this->plugins[$plugin] = $configs;
+            }
+        }
+    }
+
+    /**
+     * Enqueue plugins.
+     *
+     * @param SplQueue<PluginInterface> $queue
+     *
+     * @return void
+     */
+    public function enqueue(SplQueue $queue): void
+    {
+        foreach ($this->plugins as $plugin => $configs) {
+            foreach ($plugin::mergeConfigs(...$configs) as $config) {
+                $pluginObj = new $plugin;
+                $pluginObj->setConfigArray($config);
+                $queue->enqueue($pluginObj);
+            }
+        }
+    }
+}

src/PluginInterface.php

@@ -16,7 +16,15 @@ interface PluginInterface
      *
      * @psalm-return class-string<PluginInterface>[]|array<class-string<PluginInterface>, array>
      */
-    public static function needs(): array;
+    public static function runAfter(): array;
+    /**
+     * Specify which plugins should run before this plugin.
+     *
+     * @return array Plugin name(s)
+     *
+     * @psalm-return class-string<PluginInterface>[]|array<class-string<PluginInterface>, array>
+     */
+    public static function runBefore(): array;
     /**
      * Specify which plugins does this plugin extend.
      *
@@ -28,7 +36,14 @@ interface PluginInterface
      *
      * @psalm-return class-string<PluginInterface>[]|array<class-string<PluginInterface>, array>
      */
-    public static function extends(): array;
+    public static function runWithBefore(): array;
+    /**
+     *
+     * @return array Plugin name(s)
+     *
+     * @psalm-return class-string<PluginInterface>[]|array<class-string<PluginInterface>, array>
+     */
+    public static function runWithAfter(): array;
 
     /**
      * Specify a list of composer dependencies.
@@ -36,6 +51,14 @@ interface PluginInterface
      * @return array
      */
     public static function composerRequires(): array;
+    /**
+     * Set configuration array.
+     *
+     * @param array $config
+     *
+     * @return void
+     */
+    public function setConfigArray(array $config): void;
     /**
      * Get configuration key.
      *

src/Target/Php70/AnonymousClassReplacer.php

@@ -53,7 +53,7 @@ class AnonymousClassReplacer extends NodeVisitorAbstract
      */
     public function afterTraverse(array $nodes)
     {
-        if (count($this->anonymousClassNodes) === 0) {
+        if (\count($this->anonymousClassNodes) === 0) {
             return $nodes;
         }
 
@@ -106,10 +106,10 @@ class AnonymousClassReplacer extends NodeVisitorAbstract
      */
     protected function moveAnonymousClassesToHook(array $nodes, $hookIndex, $anonymousClassStatements)
     {
-        $preStatements = array_slice($nodes, 0, $hookIndex);
+        $preStatements = \array_slice($nodes, 0, $hookIndex);
-        $postStatements = array_slice($nodes, $hookIndex);
+        $postStatements = \array_slice($nodes, $hookIndex);
 
-        return array_merge($preStatements, $anonymousClassStatements, $postStatements);
+        return \array_merge($preStatements, $anonymousClassStatements, $postStatements);
     }
 
     /**

src/Target/Php70/ClosureCallReplacer.php

@@ -12,7 +12,7 @@ use PhpParser\Node\Name;
 class ClosureCallReplacer extends Plugin
 {
     /**
-     * Replace composite function calls
+     * Replace composite function calls.
      *
      * @param FuncCall $node Function call
      *

src/Target/Php70/DefineArrayReplacer.php

@@ -14,7 +14,7 @@ use PhpParser\Node\Stmt\Const_;
 class DefineArrayReplacer extends Plugin
 {
     /**
-     * Convert define() arrays into const arrays
+     * Convert define() arrays into const arrays.
      *
      * @param FuncCall $node Node
      *

src/Target/Php70/GroupUseReplacer.php

@@ -11,7 +11,7 @@ use PhpParser\Node\Stmt\UseUse;
 class GroupUseReplacer extends Plugin
 {
     /**
-     * Replace group use with multiple use statements
+     * Replace group use with multiple use statements.
      *
      * @param GroupUse $node Group use statement
      *

src/Target/Php70/ScalarTypeHintsRemover.php

@@ -12,7 +12,7 @@ class ScalarTypeHintsRemover extends Plugin
      *
      * @return array
      */
-    public static function needs(): array
+    public static function runAfter(): array
     {
         return [
             TypeHintStripper::class => [

src/Target/Php70/ThrowableReplacer.php

@@ -56,18 +56,18 @@ class ThrowableReplacer extends Plugin
     {
         foreach ($node->catches as $catch) {
             $alreadyHasError = false;
-            $needs = false;
+            $runAfter = false;
             foreach ($catch->types as &$type) {
                 if ($type instanceof FullyQualified &&
                     $type->getLast() === "Error") {
                     $alreadyHasError = true;
                 }
                 if ($this->isThrowable($type)) {
-                    $needs = true;
+                    $runAfter = true;
                     $type = new FullyQualified('Exception');
                 }
             }
-            if ($needs && !$alreadyHasError) {
+            if ($runAfter && !$alreadyHasError) {
                 $catch->types[] = new FullyQualified('Error');
             }
         }
@@ -78,7 +78,7 @@ class ThrowableReplacer extends Plugin
      *
      * @return array
      */
-    public static function extends(): array
+    public static function runWithBefore(): array
     {
         return [
             TypeHintStripper::class => [

src/Target/Php71/ListKey.php

@@ -4,7 +4,6 @@ namespace Phabel\Target\Php71;
 
 use Phabel\Plugin;
 use PhpParser\Node\Expr\Array_;
-use PhpParser\Node\Expr\ArrayItem;
 use PhpParser\Node\Expr\Assign;
 use PhpParser\Node\Expr\List_;
 use PhpParser\Node\Stmt\Foreach_;
@@ -110,7 +109,7 @@ class ListKey extends Plugin
     /**
      * {@inheritDoc}
      */
-    public static function needs(): array
+    public static function runAfter(): array
     {
         return [ArrayList::class];
     }

src/Target/Php71/MultipleCatchReplacer.php

@@ -36,13 +36,13 @@ class MultipleCatchReplacer extends Plugin
         $node->catches = $catches;
     }
     /**
-     * Extends throwable replacer
+     * Extends throwable replacer.
      *
      * @return string
      *
      * @psalm-return class-string
      */
-    public static function extends(): string
+    public static function runWithBefore(): string
     {
         return [ThrowableReplacer::class];
     }

src/Target/Php71/NullableTypeRemover.php

@@ -8,11 +8,11 @@ use Phabel\Plugin\TypeHintStripper;
 class NullableTypeRemover extends Plugin
 {
     /**
-     * Remove nullable typehint
+     * Remove nullable typehint.
      *
      * @return array
      */
-    public static function needs(): array
+    public static function runAfter(): array
     {
         return [
             TypeHintStripper::class => [

src/Traverser.php

@@ -4,126 +4,4 @@ namespace Phabel;
 
 class Traverser
 {
-    /**
-     * Plugins by level.
-     *
-     * @var array<int, array<class-string<PluginInterface>, array>>
-     */
-    private array $plugins = [];
-    /**
-     * Excluded plugins by level.
-     *
-     * @var array<int, array<class-string<PluginInterface>, bool>>
-     */
-    private array $excludedPlugins = [];
-    /**
-     * Files indexed by level.
-     *
-     * @var array<int, string[]>
-     */
-    private array $files = [];
-    /**
-     * Add plugin at a certain dependency level.
-     *
-     * @param class-string<PluginInterface> $plugin Plugin to add
-     * @param array                         $config Plugin configuration
-     * @param integer                       $level  Dependency level
-     *
-     * @return void
-     */
-    public function addPlugin(string $plugin, array $config, int $level): void
-    {
-        $this->plugins[$level][$plugin] = $config;
-    }
-    /**
-     * Exclude plugin at a certain dependency level.
-     *
-     * @param class-string<PluginInterface> $plugin            Plugin to exclude
-     * @param bool                          $excludeNextLevels Whether to exclude plugin from next levels, too
-     * @param integer                       $level             Dependency level
-     *
-     * @return void
-     */
-    public function excludePlugin(string $plugin, bool $excludeNextLevels, int $level): void
-    {
-        $this->excludedPlugins[$level][$plugin] = $excludeNextLevels;
-    }
-
-    /**
-     * Add file.
-     *
-     * @param string $path
-     * @param integer $level
-     * @return void
-     */
-    public function addFile(string $path, int $level): void
-    {
-        if (\in_array($path, $this->files[$level])) {
-            return;
-        }
-        $this->files[$level][] = $path;
-    }
-
-    /**
-     * Start traversing files.
-     *
-     * @return void
-     */
-    public function traverse(): void
-    {
-    }
-
-    private function resolveCycle(string $class, bool $need, array &$stack): void
-    {
-        
-        $allPlugins = [];
-        foreach ($this->plugins as $level => $plugins) {
-            foreach ($plugins as $plugin => $config) {
-                $needs = self::simpleNeeds($plugin);
-                foreach ($needs as $class => $config) {
-                    if ()
-                }
-            }
-        }
-    }
-
-    /**
-     * Simplify need requirements
-     *
-     * @param class-string<PluginInterface> $class Class to resolve
-     * 
-     * @return array<class-string<PluginInterface>, array>
-     */
-    private static function simpleNeeds(string $class): array
-    {
-        /**
-         * @var array<class-string<PluginInterface>, array>[]
-         */
-        static $cache = [];
-        if (isset($cache[$class])) {
-            return $cache[$class];
-        }
-        $needs = $class::needs();
-        return $cache[$class] = isset($needs[0]) ? array_fill_keys($needs, []) : $needs
-    }
-
-    /**
-     * Simplify extend requirements
-     *
-     * @param class-string<PluginInterface> $class Class to resolve
-     * 
-     * @return array<class-string<PluginInterface>, array>
-     */
-    private static function simpleExtends(string $class): array
-    {
-        /**
-         * @var array<class-string<PluginInterface>, array>[]
-         */
-        static $cache = [];
-        if (isset($cache[$class])) {
-            return $cache[$class];
-        }
-        $needs = $class::extends();
-        return $cache[$class] = isset($needs[0]) ? array_fill_keys($needs, []) : $needs
-    }
 }

src/TraverserConfig.php

@@ -1,99 +0,0 @@
-<?php
-
-namespace Phabel;
-
-class TraverserConfig
-{
-    /**
-     * Plugin configurations, indexed by level.
-     *
-     * @var array<int, array<class-string<PluginInterface>, array<0: bool, 1: array>[]>>
-     */
-    private array $plugins = [];
-    /**
-     * Excluded plugins by level.
-     *
-     * @var array<int, array<class-string<PluginInterface>, array[]>>
-     */
-    private array $excludedPlugins = [];
-    /**
-     * Files indexed by level.
-     *
-     * @var array<int, string[]>
-     */
-    private array $files = [];
-    /**
-     * Add plugin at a certain dependency level.
-     *
-     * @param class-string<PluginInterface> $plugin Plugin to add
-     * @param array                         $config Plugin configuration
-     * @param integer                       $level  Dependency level
-     *
-     * @return void
-     */
-    public function addPlugin(string $plugin, array $config, int $level): void
-    {
-        $this->plugins[$level][$plugin] []= $config;
-    }
-    /**
-     * Get all plugins at a certain level.
-     *
-     * @param integer $level Level
-     *
-     * @return array
-     */
-    public function getPlugins(int $level): array
-    {
-        return $this->plugins[$level];
-    }
-    /**
-     * Exclude plugin at a certain dependency level.
-     *
-     * @param class-string<PluginInterface> $plugin            Plugin to exclude
-     * @param bool                          $excludeNextLevels Whether to exclude plugin from next levels, too
-     * @param integer                       $level             Dependency level
-     *
-     * @return void
-     */
-    public function excludePlugin(string $plugin, bool $excludeNextLevels, int $level): void
-    {
-        $this->excludedPlugins[$level][$plugin][] = $excludeNextLevels;
-    }
-
-    /**
-     * Get final plugin array.
-     *
-     * @return array<int, array<class-string<PluginInterface, array>>>
-     */
-    public function final(): array
-    {
-        \ksort($this->plugins);
-        \ksort($this->excludedPlugins);
-        return [];
-    }
-
-    /**
-     * Trickle plugins down the dependency tree.
-     *
-     * @return void Insert 1% joke
-     */
-    private function trickleDown(): void
-    {
-        $met = [];
-        $maxLevel = \array_key_last($this->plugins);
-        foreach ($this->plugins as $level => $plugins) {
-            foreach ($plugins as $plugin => $config) {
-                $found = false;
-                for ($checkLevel = $level + 1; $checkLevel <= $maxLevel; $checkLevel++) {
-                    if (isset($this->plugins[$checkLevel][$plugin])
-                        && $this->plugins[$checkLevel][$plugin] !== $config) {
-                        $found = true;
-                        break;
-                    }
-                    $this->plugins[$checkLevel][$plugin] = $config;
-                }
-                $checkLevel--;
-            }
-        }
-    }
-}