Feat: Dependent features (#187)

src/DTO/DefaultFeature.php

@@ -5,15 +5,17 @@
 final readonly class DefaultFeature implements Feature
 {
     /**
-     * @param iterable<Strategy> $strategies
-     * @param array<Variant>     $variants
+     * @param iterable<Strategy>       $strategies
+     * @param array<Variant>           $variants
+     * @param array<FeatureDependency> $dependencies
      */
     public function __construct(
         private string $name,
         private bool $enabled,
         private iterable $strategies,
         private array $variants = [],
         private bool $impressionData = false,
+        private array $dependencies = [],
     ) {
     }
 
@@ -47,4 +49,12 @@ public function hasImpressionData(): bool
     {
         return $this->impressionData;
     }
+
+    /**
+     * @return array<FeatureDependency>
+     */
+    public function getDependencies(): array
+    {
+        return $this->dependencies;
+    }
 }

src/DTO/DefaultFeatureDependency.php

@@ -0,0 +1,36 @@
+<?php
+
+namespace Unleash\Client\DTO;
+
+final readonly class DefaultFeatureDependency implements FeatureDependency
+{
+    /**
+     * @param array<Variant>|null $requiredVariants
+     */
+    public function __construct(
+        private ?Feature $feature,
+        private bool $expectedState,
+        private ?array $requiredVariants,
+    ) {
+    }
+
+    public function getFeature(): ?Feature
+    {
+        return $this->feature;
+    }
+
+    public function getExpectedState(): bool
+    {
+        return $this->expectedState;
+    }
+
+    public function getRequiredVariants(): ?array
+    {
+        return $this->requiredVariants;
+    }
+
+    public function isResolved(): bool
+    {
+        return true;
+    }
+}

src/DTO/Feature.php

@@ -2,6 +2,9 @@
 
 namespace Unleash\Client\DTO;
 
+/**
+ * @method array<FeatureDependency> getDependencies()
+ */
 interface Feature
 {
     public function getName(): string;

src/DTO/FeatureDependency.php

@@ -0,0 +1,17 @@
+<?php
+
+namespace Unleash\Client\DTO;
+
+interface FeatureDependency
+{
+    public function getFeature(): ?Feature;
+
+    public function getExpectedState(): bool;
+
+    /**
+     * @return array<Variant>|null
+     */
+    public function getRequiredVariants(): ?array;
+
+    public function isResolved(): bool;
+}

src/DTO/Internal/UnresolvedFeature.php

@@ -0,0 +1,50 @@
+<?php
+
+namespace Unleash\Client\DTO\Internal;
+
+use Unleash\Client\DTO\Feature;
+use Unleash\Client\DTO\FeatureDependency;
+
+/**
+ * @internal
+ */
+final readonly class UnresolvedFeature implements Feature
+{
+    public function __construct(
+        private string $name,
+    ) {
+    }
+
+    public function getName(): string
+    {
+        return $this->name;
+    }
+
+    public function isEnabled(): bool
+    {
+        return false;
+    }
+
+    public function getStrategies(): iterable
+    {
+        return [];
+    }
+
+    public function getVariants(): array
+    {
+        return [];
+    }
+
+    public function hasImpressionData(): bool
+    {
+        return false;
+    }
+
+    /**
+     * @return array<FeatureDependency>
+     */
+    public function getDependencies(): array
+    {
+        return [];
+    }
+}

src/DTO/Internal/UnresolvedFeatureDependency.php

@@ -0,0 +1,43 @@
+<?php
+
+namespace Unleash\Client\DTO\Internal;
+
+use Unleash\Client\DTO\Feature;
+use Unleash\Client\DTO\FeatureDependency;
+use Unleash\Client\DTO\Variant;
+
+/**
+ * @internal
+ */
+final readonly class UnresolvedFeatureDependency implements FeatureDependency
+{
+    /**
+     * @param array<Variant>|null $requiredVariants
+     */
+    public function __construct(
+        private Feature $feature,
+        private bool $expectedState,
+        private ?array $requiredVariants,
+    ) {
+    }
+
+    public function getFeature(): Feature
+    {
+        return $this->feature;
+    }
+
+    public function getExpectedState(): bool
+    {
+        return $this->expectedState;
+    }
+
+    public function getRequiredVariants(): ?array
+    {
+        return $this->requiredVariants;
+    }
+
+    public function isResolved(): bool
+    {
+        return false;
+    }
+}

src/DTO/Internal/UnresolvedVariant.php

@@ -0,0 +1,62 @@
+<?php
+
+namespace Unleash\Client\DTO\Internal;
+
+use JetBrains\PhpStorm\ExpectedValues;
+use Unleash\Client\DTO\Variant;
+use Unleash\Client\DTO\VariantPayload;
+use Unleash\Client\Enum\Stickiness;
+
+/**
+ * @internal
+ */
+final readonly class UnresolvedVariant implements Variant
+{
+    public function __construct(
+        private string $name,
+    ) {
+    }
+
+    public function getName(): string
+    {
+        return $this->name;
+    }
+
+    public function isEnabled(): bool
+    {
+        return false;
+    }
+
+    public function getPayload(): ?VariantPayload
+    {
+        return null;
+    }
+
+    public function getWeight(): int
+    {
+        return 0;
+    }
+
+    public function getOverrides(): array
+    {
+        return [];
+    }
+
+    #[ExpectedValues(valuesFromClass: Stickiness::class)]
+    public function getStickiness(): string
+    {
+        return Stickiness::DEFAULT;
+    }
+
+    /**
+     * todo Change to null once rector supports it
+     *
+     * @return null
+     *
+     * @noinspection PhpMixedReturnTypeCanBeReducedInspection
+     */
+    public function jsonSerialize(): mixed
+    {
+        return null;
+    }
+}

src/DefaultUnleash.php

@@ -7,6 +7,7 @@
 use Unleash\Client\Configuration\UnleashConfiguration;
 use Unleash\Client\DTO\DefaultFeatureEnabledResult;
 use Unleash\Client\DTO\Feature;
+use Unleash\Client\DTO\FeatureDependency;
 use Unleash\Client\DTO\FeatureEnabledResult;
 use Unleash\Client\DTO\Strategy;
 use Unleash\Client\DTO\Variant;
@@ -155,6 +156,24 @@ private function isFeatureEnabled(?Feature $feature, Context $context, bool $def
             return new DefaultFeatureEnabledResult();
         }
 
+        $dependencies = method_exists($feature, 'getDependencies')
+            ? $feature->getDependencies()
+            : [];
+
+        foreach ($dependencies as $dependency) {
+            if ($this->isParentDependencySatisfied($dependency, $context, $default) !== $dependency->getExpectedState()) {
+                $event = new FeatureToggleDisabledEvent($feature, $context);
+                $this->configuration->getEventDispatcher()->dispatch(
+                    $event,
+                    UnleashEvents::FEATURE_TOGGLE_DISABLED,
+                );
+
+                $this->metricsHandler->handleMetrics($feature, false);
+
+                return new DefaultFeatureEnabledResult();
+            }
+        }
+
         $strategies = $feature->getStrategies();
         if (!is_countable($strategies)) {
             $strategies = iterator_to_array($strategies);
@@ -208,4 +227,35 @@ private function findStrategyHandlers(Strategy $strategy): array
 
         return $handlers;
     }
+
+    private function isParentDependencySatisfied(FeatureDependency $dependency, Context $context, bool $default): bool
+    {
+        if (!$dependency->isResolved()) {
+            return false;
+        }
+
+        $enabled = $this->isFeatureEnabled($dependency->getFeature(), $context, $default);
+        if (!$enabled->isEnabled()) {
+            return false;
+        }
+
+        assert($dependency->getFeature() !== null);
+
+        if (
+            method_exists($dependency->getFeature(), 'getDependencies')
+            && count($dependency->getFeature()->getDependencies())
+        ) {
+            return false;
+        }
+
+        if ($dependency->getRequiredVariants() === null || !count($dependency->getRequiredVariants())) {
+            return true;
+        }
+
+        $variant = $this->getVariant($dependency->getFeature()->getName(), $context);
+
+        $requiredVariants = array_map(fn (Variant $variant) => $variant->getName(), $dependency->getRequiredVariants());
+
+        return in_array($variant->getName(), $requiredVariants, true);
+    }
 }