fix(rewriter): prevent mixing of cached rule engines (#44)

internal/proxy/director/layer/util/rule_engine_cache.go

@@ -0,0 +1,28 @@
+package util
+
+import (
+	"forge.cadoles.com/cadoles/bouncer/internal/cache"
+	"forge.cadoles.com/cadoles/bouncer/internal/cache/memory"
+)
+
+type RuleEngineCache[V any, O any] struct {
+	cache   cache.Cache[string, *RevisionedRuleEngine[V, O]]
+	factory RuleEngineFactoryFunc[V, O]
+}
+
+func (c *RuleEngineCache[V, O]) Get(key string) *RevisionedRuleEngine[V, O] {
+	revisionedRuleEngine, exists := c.cache.Get(key)
+	if !exists {
+		revisionedRuleEngine = NewRevisionedRuleEngine(c.factory)
+		c.cache.Set(key, revisionedRuleEngine)
+	}
+
+	return revisionedRuleEngine
+}
+
+func NewInMemoryRuleEngineCache[V any, O any](factory RuleEngineFactoryFunc[V, O]) *RuleEngineCache[V, O] {
+	return &RuleEngineCache[V, O]{
+		factory: factory,
+		cache:   memory.NewCache[string, *RevisionedRuleEngine[V, O]](),
+	}
+}