First steps in IdentityMap implementation

Author: Ivan Sushkov

grade/internal/infrastructure/seedwork/identity/manageable.go

@@ -1,35 +1,36 @@
 package identity
 
-import "errors"
+import (
+	"errors"
+
+	"github.com/emacsway/grade/grade/pkg/collections"
+)
 
 var (
 	ErrObjectAlreadyWatched = errors.New("")
 	ErrObjectNotFound       = errors.New("")
 )
 
 type IdentityMap[K comparable, V any] struct {
-	manageable cacheMap[K, V]
+	manageable collections.ReplacingMap[K, V]
 	isolation  IsolationStrategy[K, V]
 }
 
-func NewIdentityMap[K comparable, V any]() *IdentityMap[K, V] {
-	manageable := newCacheMap[K, V]()
+func NewIdentityMap[K comparable, V any](size uint) *IdentityMap[K, V] {
+	manageable := collections.NewReplacingMap[K, V](size)
 	isolation := serializableStrategy[K, V]{manageable: manageable}
 
 	return &IdentityMap[K, V]{
 		manageable: manageable,
-		isolation:  isolation,
+		isolation:  &isolation,
 	}
 }
 
 func (im *IdentityMap[K, V]) Add(key K, object V) (bool, error) {
-	im.isolation.add(key, object)
-
-	//if _, found := im.objects[key]; found {
-	//	return false, ErrObjectAlreadyWatched
-	//}
+	if err := im.isolation.add(key, object); err != nil {
+		return false, err
+	}
 
-	//im.objects[key] = object
 	return true, nil
 }
 

grade/internal/infrastructure/seedwork/identity/map.go

@@ -1,6 +1,10 @@
 package identity
 
-import "errors"
+import (
+	"errors"
+
+	"github.com/emacsway/grade/grade/pkg/collections"
+)
 
 type IsolationLevel uint
 
@@ -11,21 +15,24 @@ const (
 	Serializable                   = iota
 )
 
-var ErrDeniedOperationForStrategy = errors.New("")
+var (
+	ErrNonexistentObject          = errors.New("")
+	ErrDeniedOperationForStrategy = errors.New("")
+)
 
 type IsolationStrategy[K comparable, V any] interface {
-	add(key K, object V)
+	add(key K, object V) error
 	get(key K) (V, error)
 	has(key K) bool
 }
 
-///////
-
 type readUncommittedStrategy[K comparable, V any] struct {
-	manageable cacheMap[K, V]
+	manageable collections.ReplacingMap[K, V]
 }
 
-func (r *readUncommittedStrategy[K, V]) add(key K, object V) {}
+func (r *readUncommittedStrategy[K, V]) add(key K, object V) error {
+	return nil
+}
 
 func (r *readUncommittedStrategy[K, V]) get(key K) (object V, err error) {
 	return object, ErrDeniedOperationForStrategy
@@ -41,45 +48,43 @@ type readCommittedStrategy[K comparable, V any] struct {
 	readUncommittedStrategy[K, V]
 }
 
-// //
 type repeatableReadsStrategy[K comparable, V any] struct {
-	manageable cacheMap[K, V]
+	manageable collections.ReplacingMap[K, V]
 }
 
-func (r *repeatableReadsStrategy[K, V]) add(key K, object V) {
+func (r *repeatableReadsStrategy[K, V]) add(key K, object V) error {
 	if object != nil {
-		r.manageable.add(key, object)
+		r.manageable.Add(key, object)
 	}
+
+	return nil
 }
 
 func (r *repeatableReadsStrategy[K, V]) get(key K) (V, error) {
-	object, found := r.manageable.get(key)
-
+	return r.manageable.Get(key)
 }
 
 func (r *repeatableReadsStrategy[K, V]) has(key K) bool {
-	return r.manageable.has(key)
+	return r.manageable.Has(key)
 }
 
-// ///
 type serializableStrategy[K comparable, V any] struct {
-	manageable cacheMap[K, V]
+	manageable collections.ReplacingMap[K, V]
 }
 
-func (s serializableStrategy[K, V]) add(key K, object V) {
-	//TODO implement me
-	panic("implement me")
-}
+func (s *serializableStrategy[K, V]) add(key K, object V) error {
+	if object == nil {
+		return ErrNonexistentObject
+	}
 
-func (s serializableStrategy[K, V]) get(key K) (V, error) {
-	//obj = self._identity_map().do_get(key)
-	//if isinstance(obj, NonexistentObject):
-	//raise ObjectDoesNotExist()
-	//return obj
+	s.manageable.Add(key, object)
+	return nil
+}
 
-	s.manageable.get(ke)
+func (s *serializableStrategy[K, V]) get(key K) (V, error) {
+	return s.manageable.Get(key)
 }
 
-func (s serializableStrategy[K, V]) has(key K) bool {
-	return s.manageable.has(key)
+func (s *serializableStrategy[K, V]) has(key K) bool {
+	return s.manageable.Has(key)
 }

grade/internal/infrastructure/seedwork/identity/strategy.go

@@ -0,0 +1,52 @@
+package cache
+
+import (
+	"container/list"
+)
+
+type Lru[T comparable] struct {
+	items map[T]*list.Element
+	order *list.List
+	size  uint
+}
+
+func NewLru[T comparable](size uint) Lru[T] {
+	return Lru[T]{
+		items: make(map[T]*list.Element, size),
+		order: list.New(),
+		size:  size,
+	}
+}
+
+func (l *Lru[T]) Add(value T) {
+	order := l.order.PushBack(&value)
+	l.items[value] = order
+
+	if (uint)(len(l.items)) > l.size {
+		order = l.order.Front()
+		l.order.Remove(order)
+
+		delete(l.items, order.Value.(T))
+	}
+}
+
+func (l *Lru[T]) Touch(value T) {
+	order := l.items[value]
+	l.order.MoveToBack(order)
+}
+
+func (l *Lru[T]) Remove(value T) {
+	order := l.items[value]
+
+	delete(l.items, value)
+	l.order.Remove(order)
+}
+
+func (l *Lru[T]) Clear() {
+	l.order = list.New()
+	l.items = make(map[T]*list.Element, l.size)
+}
+
+func (l *Lru[T]) SetSize(size uint) {
+	l.size = size
+}

grade/pkg/cache/lru.go

@@ -0,0 +1,17 @@
+package cache
+
+import "testing"
+
+func TestLru(t *testing.T) {
+
+	lru := NewLru[string](2)
+
+	//lru.Add("1")
+	//lru.Add("2")
+	lru.Add("3")
+	lru.Add("2")
+	lru.Add("1")
+
+	//lru.Touch("3")
+	//lru.Add("3")
+}

grade/pkg/cache/lru_test.go

@@ -0,0 +1,103 @@
+package collections
+
+import (
+	"container/list"
+	"errors"
+)
+
+var (
+	ErrKeyDoesNotContains = errors.New("")
+)
+
+type CachedMap[K comparable, V any] struct {
+	m map[K]V
+}
+
+func NewCachedMap[K comparable, V any]() CachedMap[K, V] {
+	return CachedMap[K, V]{
+		m: map[K]V{},
+	}
+}
+
+func (m CachedMap[K, V]) Add(key K, value V) {
+	m.m[key] = value
+}
+
+func (m CachedMap[K, V]) Get(key K) (value V, err error) {
+	if value, found := m.m[key]; found {
+		return value, nil
+	}
+
+	return value, ErrKeyDoesNotContains
+}
+
+func (m CachedMap[K, V]) Remove(key K) {
+	delete(m.m, key)
+}
+
+func (m CachedMap[K, V]) Has(key K) bool {
+	_, found := m.m[key]
+	return found
+}
+
+type item[K comparable, V any] struct {
+	key   K
+	value V
+}
+
+type ReplacingMap[K comparable, V any] struct {
+	items map[K]*list.Element
+	order *list.List
+	size  uint
+}
+
+func NewReplacingMap[K comparable, V any](size uint) ReplacingMap[K, V] {
+	return ReplacingMap[K, V]{
+		items: make(map[K]*list.Element, size),
+		order: list.New(),
+		size:  size,
+	}
+}
+
+func (m *ReplacingMap[K, V]) Add(key K, value V) {
+	element := m.order.PushBack(item[K, V]{key, value})
+	m.items[key] = element
+
+	if (uint)(len(m.items)) > m.size {
+		element = m.order.Front()
+		m.order.Remove(element)
+		delete(m.items, element.Value.(item[K, V]).key)
+	}
+}
+
+func (m *ReplacingMap[K, V]) Get(key K) (value V, err error) {
+	if element, found := m.items[key]; found {
+		return element.Value.(item[K, V]).value, nil
+	}
+
+	return value, ErrKeyDoesNotContains
+}
+
+func (m *ReplacingMap[K, V]) Touch(key K) {
+	element := m.items[key]
+	m.order.MoveToBack(element)
+}
+
+func (m *ReplacingMap[K, V]) Remove(key K) {
+	element, found := m.items[key]
+	if !found {
+		return
+	}
+
+	delete(m.items, key)
+	m.order.Remove(element)
+}
+
+func (m *ReplacingMap[K, V]) Has(key K) bool {
+	_, found := m.items[key]
+	return found
+}
+
+func (m *ReplacingMap[K, V]) SetSize(size uint) {
+	m.size = size
+}