First steps in IdentityMap implementation (#23)

Co-authored-by: Ivan Sushkov

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

@@ -0,0 +1,63 @@
+package identity
+
+import (
+	"errors"
+
+	"github.com/emacsway/grade/grade/pkg/collections"
+)
+
+var (
+	ErrObjectAlreadyWatched = errors.New("")
+	ErrObjectNotFound       = errors.New("")
+)
+
+type IdentityMap[K comparable, V any] struct {
+	manageable collections.ReplacingMap[K, V]
+	isolation  IsolationStrategy[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,
+	}
+}
+
+func (im *IdentityMap[K, V]) Add(key K, object V) (bool, error) {
+	if err := im.isolation.add(key, object); err != nil {
+		return false, err
+	}
+
+	return true, nil
+}
+
+func (im *IdentityMap[K, V]) Get(key K) (object V, err error) {
+	return im.isolation.get(key)
+}
+
+func (im *IdentityMap[K, V]) Has(key K) bool {
+	return im.isolation.has(key)
+}
+
+func (im *IdentityMap[K, V]) SetSize(size uint) {
+	im.manageable.SetSize(size)
+}
+
+func (im *IdentityMap[K, V]) SetIsolationLevel(level IsolationLevel) {
+
+	switch level {
+	case ReadUncommitted:
+		im.isolation = &readUncommittedStrategy[K, V]{manageable: im.manageable}
+	case RepeatableReads:
+		im.isolation = &repeatableReadsStrategy[K, V]{manageable: im.manageable}
+	case Serializable:
+		im.isolation = &serializableStrategy[K, V]{manageable: im.manageable}
+	case ReadCommitted:
+		im.isolation = &readCommittedStrategy[K, V]{manageable: im.manageable}
+	default:
+		im.isolation = &serializableStrategy[K, V]{manageable: im.manageable}
+	}
+}

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

@@ -0,0 +1,91 @@
+package identity
+
+import (
+	"errors"
+
+	"github.com/emacsway/grade/grade/pkg/collections"
+)
+
+type IsolationLevel uint
+
+const (
+	ReadUncommitted IsolationLevel = iota
+	ReadCommitted                  = iota
+	RepeatableReads                = iota
+	Serializable                   = iota
+)
+
+var (
+	ErrNonexistentObject          = errors.New("")
+	ErrDeniedOperationForStrategy = errors.New("")
+)
+
+type IsolationStrategy[K comparable, V any] interface {
+	add(key K, object V) error
+	get(key K) (V, error)
+	has(key K) bool
+}
+
+type readUncommittedStrategy[K comparable, V any] struct {
+	manageable collections.ReplacingMap[K, 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
+}
+
+func (r *readUncommittedStrategy[K, V]) has(key K) bool {
+	return false
+}
+
+type readCommittedStrategy[K comparable, V any] struct {
+	manageable collections.ReplacingMap[K, V]
+}
+
+func (r *readCommittedStrategy[K, V]) add(key K, object V) error {
+	return nil
+}
+
+func (r *readCommittedStrategy[K, V]) get(key K) (object V, err error) {
+	return object, nil
+}
+
+func (r *readCommittedStrategy[K, V]) has(key K) bool {
+	return false
+}
+
+type repeatableReadsStrategy[K comparable, V any] struct {
+	manageable collections.ReplacingMap[K, V]
+}
+
+func (r *repeatableReadsStrategy[K, V]) add(key K, object V) error {
+	return nil
+}
+
+func (r *repeatableReadsStrategy[K, V]) get(key K) (V, error) {
+	return r.manageable.Get(key)
+}
+
+func (r *repeatableReadsStrategy[K, V]) has(key K) bool {
+	return r.manageable.Has(key)
+}
+
+type serializableStrategy[K comparable, V any] struct {
+	manageable collections.ReplacingMap[K, V]
+}
+
+func (s *serializableStrategy[K, V]) add(key K, object V) error {
+	return nil
+}
+
+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)
+}

grade/pkg/collections/map.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
+}