From 32d2376c9d5c551314a412a230a5c7e556710bdb Mon Sep 17 00:00:00 2001
From: Richard Klees <richard.klees@concepts-and-training.de>
Date: Wed, 22 Nov 2023 12:38:37 +0100
Subject: [PATCH] Component/Dependencies: Find Cycles in Dependency Tree

---
 .../ILIAS/Component/src/Dependencies/Out.php  |  5 ++
 .../Component/src/Dependencies/Resolver.php   | 50 +++++++++++++++++++
 .../tests/Dependencies/ResolverTest.php       | 47 +++++++++++++++++
 3 files changed, 102 insertions(+)

diff --git a/components/ILIAS/Component/src/Dependencies/Out.php b/components/ILIAS/Component/src/Dependencies/Out.php
index 6c78296b258c..c70c2c4c1c6a 100644
--- a/components/ILIAS/Component/src/Dependencies/Out.php
+++ b/components/ILIAS/Component/src/Dependencies/Out.php
@@ -82,6 +82,11 @@ public function addDependency(In $in): void
         $this->dependencies[(string) $in] = $in;
     }
 
+    public function getDependencies(): array
+    {
+        return $this->dependencies;
+    }
+
     public function addResolves(In $in): void
     {
         $this->resolves[] = $in;
diff --git a/components/ILIAS/Component/src/Dependencies/Resolver.php b/components/ILIAS/Component/src/Dependencies/Resolver.php
index 66b95e5acab9..9a38a4f8c362 100644
--- a/components/ILIAS/Component/src/Dependencies/Resolver.php
+++ b/components/ILIAS/Component/src/Dependencies/Resolver.php
@@ -68,6 +68,23 @@ public function resolveDependencies(array $disambiguation, OfComponent ...$compo
             }
         }
 
+        $cycles = iterator_to_array($this->findCycles(...$components));
+        if (!empty($cycles)) {
+            throw new \LogicException(
+                "Detected Cycles in Dependency Tree: " .
+                join("\n", array_map(
+                    fn($cycle) => join(
+                        " <- ",
+                        array_map(
+                            fn($v) => "{$v[0]->getComponentName()} ({$v[1]})",
+                            $cycle
+                        )
+                    ),
+                    $cycles
+                ))
+            );
+        }
+
         return $components;
     }
 
@@ -157,4 +174,37 @@ protected function disambiguate(OfComponent $component, array &$disambiguation,
         }
         return null;
     }
+
+    /**
+     * @var Generator<array<OfComponent, Dependency>>
+     */
+    protected function findCycles(OfComponent ...$components): \Generator
+    {
+        foreach ($components as $component) {
+            foreach ($component->getInDependencies() as $in) {
+                foreach ($this->findCyclesWith([], $component, $in) as $cycle) {
+                    yield $cycle;
+                }
+            }
+        }
+    }
+
+    protected function findCyclesWith(array $visited, OfComponent $component, In $in): \Generator
+    {
+        if (!empty($visited) && $visited[0][0] === $component && $visited[0][1] == $in) {
+            yield $visited;
+            return;
+        }
+
+        array_push($visited, [$component, $in]);
+        foreach ($in->getResolvedBy() as $out) {
+            $other = $out->getComponent();
+            array_push($visited, [$component, $out]);
+            foreach ($out->getDependencies() as $next) {
+                yield from $this->findCyclesWith($visited, $out->getComponent(), $next);
+            }
+            array_pop($visited);
+        }
+        array_pop($visited);
+    }
 }
diff --git a/components/ILIAS/Component/tests/Dependencies/ResolverTest.php b/components/ILIAS/Component/tests/Dependencies/ResolverTest.php
index b3be9987afe9..be44a8a658ad 100644
--- a/components/ILIAS/Component/tests/Dependencies/ResolverTest.php
+++ b/components/ILIAS/Component/tests/Dependencies/ResolverTest.php
@@ -270,4 +270,51 @@ public function testUseDisambiguateDuplicateGeneric(): void
 
         $this->assertEquals([$c1, $c2, $c3], $result);
     }
+
+    public function testFindSimpleCycle(): void
+    {
+        $this->expectException(\LogicException::class);
+
+        $component = $this->createMock(Component::class);
+
+        $name = TestInterface::class;
+        $name2 = TestInterface2::class;
+
+        $pull = new D\In(D\InType::PULL, $name);
+        $provide = new D\Out(D\OutType::PROVIDE, $name2, "Some\\Class", [$pull], []);
+        $c1 = new D\OfComponent($component, $pull, $provide);
+
+        $pull = new D\In(D\InType::PULL, $name2);
+        $provide = new D\Out(D\OutType::PROVIDE, $name, "Some\\OtherClass", [$pull], []);
+        $c2 = new D\OfComponent($component, $pull, $provide);
+
+
+        $result = $this->resolver->resolveDependencies([], $c1, $c2);
+    }
+
+    public function testFindLongerCycle(): void
+    {
+        $this->expectException(\LogicException::class);
+
+        $component = $this->createMock(Component::class);
+
+        $name = TestInterface::class;
+        $name2 = TestInterface2::class;
+        $name3 = TestInterface3::class;
+
+        $pull = new D\In(D\InType::PULL, $name);
+        $provide = new D\Out(D\OutType::PROVIDE, $name2, "Some\\Class", [$pull], []);
+        $c1 = new D\OfComponent($component, $pull, $provide);
+
+        $pull = new D\In(D\InType::PULL, $name2);
+        $provide = new D\Out(D\OutType::PROVIDE, $name3, "Some\\OtherClass", [$pull], []);
+        $c2 = new D\OfComponent($component, $pull, $provide);
+
+        $pull = new D\In(D\InType::PULL, $name3);
+        $provide = new D\Out(D\OutType::PROVIDE, $name, "Some\\OtherOtherClass", [$pull], []);
+        $c3 = new D\OfComponent($component, $pull, $provide);
+
+
+        $result = $this->resolver->resolveDependencies([], $c1, $c2, $c3);
+    }
 }