#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))
+}