#89 Generalise the three Storage interfaces and structs into one generic storage manager.

pkg/storage/storage.go

@@ -0,0 +1,107 @@
+package storage
+
+import (
+	"sync"
+)
+
+// Storage is an interface for storing objects.
+type Storage[T any] interface {
+	// List returns all objects from the storage.
+	List() []T
+
+	// Add adds an object to the storage.
+	// It overwrites the old object if one with the same id was already stored.
+	Add(id string, o T)
+
+	// Get returns an object from the storage.
+	// Iff the object does not exist in the storage, ok will be false.
+	Get(id string) (o T, ok bool)
+
+	// Delete deletes the object with the passed id from the storage.
+	// It does nothing if no object with the id is present in the store.
+	Delete(id string)
+
+	// Pop deletes the object with the given id from the storage and returns it.
+	// Iff no such execution exists, ok is false and true otherwise.
+	Pop(id string) (o T, ok bool)
+
+	// Purge removes all objects from the storage.
+	Purge()
+
+	// Length returns the number of currently stored objects in the storage.
+	Length() uint
+
+	// Sample returns and removes an arbitrary object from the storage.
+	// ok is true iff an object was returned.
+	Sample() (o T, ok bool)
+}
+
+// localStorage stores objects in the local application memory.
+type localStorage[T any] struct {
+	sync.RWMutex
+	objects map[string]T
+}
+
+// NewLocalStorage responds with a Storage implementation.
+// This implementation stores the data thread-safe in the local application memory.
+func NewLocalStorage[T any]() *localStorage[T] {
+	return &localStorage[T]{
+		objects: make(map[string]T),
+	}
+}
+
+func (s *localStorage[T]) List() (o []T) {
+	s.RLock()
+	defer s.RUnlock()
+	for _, value := range s.objects {
+		o = append(o, value)
+	}
+	return o
+}
+
+func (s *localStorage[T]) Add(id string, o T) {
+	s.Lock()
+	defer s.Unlock()
+	s.objects[id] = o
+}
+
+func (s *localStorage[T]) Get(id string) (o T, ok bool) {
+	s.RLock()
+	defer s.RUnlock()
+	o, ok = s.objects[id]
+	return
+}
+
+func (s *localStorage[T]) Delete(id string) {
+	s.Lock()
+	defer s.Unlock()
+	delete(s.objects, id)
+}
+
+func (s *localStorage[T]) Pop(id string) (T, bool) {
+	o, ok := s.Get(id)
+	s.Delete(id)
+	return o, ok
+}
+
+func (s *localStorage[T]) Purge() {
+	s.Lock()
+	defer s.Unlock()
+	s.objects = make(map[string]T)
+}
+
+func (s *localStorage[T]) Sample() (o T, ok bool) {
+	s.Lock()
+	defer s.Unlock()
+	for key, object := range s.objects {
+		delete(s.objects, key)
+		return object, true
+	}
+	return
+}
+
+func (s *localStorage[T]) Length() uint {
+	s.RLock()
+	defer s.RUnlock()
+	return uint(len(s.objects))
+}

pkg/storage/storage_test.go

@@ -0,0 +1,100 @@
+package storage
+
+import (
+	"github.com/stretchr/testify/suite"
+	"testing"
+)
+
+func TestRunnerPoolTestSuite(t *testing.T) {
+	suite.Run(t, new(ObjectPoolTestSuite))
+}
+
+type ObjectPoolTestSuite struct {
+	suite.Suite
+	objectStorage *localStorage[any]
+	object        int
+}
+
+func (s *ObjectPoolTestSuite) SetupTest() {
+	s.objectStorage = NewLocalStorage[any]()
+	s.object = 42
+}
+
+func (s *ObjectPoolTestSuite) TestAddedObjectCanBeRetrieved() {
+	s.objectStorage.Add("my_id", s.object)
+	retrievedRunner, ok := s.objectStorage.Get("my_id")
+	s.True(ok, "A saved object should be retrievable")
+	s.Equal(s.object, retrievedRunner)
+}
+
+func (s *ObjectPoolTestSuite) TestObjectWithSameIdOverwritesOldOne() {
+	otherObject := 21
+	// assure object is actually different
+	s.NotEqual(s.object, otherObject)
+
+	s.objectStorage.Add("my_id", s.object)
+	s.objectStorage.Add("my_id", otherObject)
+	retrievedObject, _ := s.objectStorage.Get("my_id")
+	s.NotEqual(s.object, retrievedObject)
+	s.Equal(otherObject, retrievedObject)
+}
+
+func (s *ObjectPoolTestSuite) TestDeletedObjectsAreNotAccessible() {
+	s.objectStorage.Add("my_id", s.object)
+	s.objectStorage.Delete("my_id")
+	retrievedObject, ok := s.objectStorage.Get("my_id")
+	s.Nil(retrievedObject)
+	s.False(ok, "A deleted object should not be accessible")
+}
+
+func (s *ObjectPoolTestSuite) TestSampleReturnsObjectWhenOneIsAvailable() {
+	s.objectStorage.Add("my_id", s.object)
+	sampledObject, ok := s.objectStorage.Sample()
+	s.NotNil(sampledObject)
+	s.True(ok)
+}
+
+func (s *ObjectPoolTestSuite) TestSampleReturnsFalseWhenNoneIsAvailable() {
+	sampledObject, ok := s.objectStorage.Sample()
+	s.Nil(sampledObject)
+	s.False(ok)
+}
+
+func (s *ObjectPoolTestSuite) TestSampleRemovesObjectFromPool() {
+	s.objectStorage.Add("my_id", s.object)
+	_, _ = s.objectStorage.Sample()
+	_, ok := s.objectStorage.Get("my_id")
+	s.False(ok)
+}
+
+func (s *ObjectPoolTestSuite) TestLenOfEmptyPoolIsZero() {
+	s.Equal(uint(0), s.objectStorage.Length())
+}
+
+func (s *ObjectPoolTestSuite) TestLenChangesOnStoreContentChange() {
+	s.Run("len increases when object is added", func() {
+		s.objectStorage.Add("my_id_1", s.object)
+		s.Equal(uint(1), s.objectStorage.Length())
+	})
+
+	s.Run("len does not increase when object with same id is added", func() {
+		s.objectStorage.Add("my_id_1", s.object)
+		s.Equal(uint(1), s.objectStorage.Length())
+	})
+
+	s.Run("len increases again when different object is added", func() {
+		anotherObject := 21
+		s.objectStorage.Add("my_id_2", anotherObject)
+		s.Equal(uint(2), s.objectStorage.Length())
+	})
+
+	s.Run("len decreases when object is deleted", func() {
+		s.objectStorage.Delete("my_id_1")
+		s.Equal(uint(1), s.objectStorage.Length())
+	})
+
+	s.Run("len decreases when object is sampled", func() {
+		_, _ = s.objectStorage.Sample()
+		s.Equal(uint(0), s.objectStorage.Length())
+	})
+}