feat: implement lfu based cache strategy

pkg/storage/driver/cache/lfu/fs/cache_test.go

@@ -0,0 +1,37 @@
+package fs
+
+import (
+	"bytes"
+	"io"
+	"path/filepath"
+	"testing"
+
+	"forge.cadoles.com/arcad/edge/pkg/storage/driver/cache/lfu"
+	"forge.cadoles.com/arcad/edge/pkg/storage/driver/cache/lfu/testsuite"
+	"github.com/pkg/errors"
+)
+
+func TestCacheWithFSStore(t *testing.T) {
+	testsuite.TestCacheWithStore(t, func(testName string) lfu.Store[string, string] {
+		dir := filepath.Join("testdata", "testsuite", testName)
+		store := NewStore[string, string](dir,
+			WithMarshalValue[string, string](func(value string) (io.Reader, error) {
+				return bytes.NewBuffer([]byte(value)), nil
+			}),
+			WithUnmarshalValue[string, string](func(r io.Reader) (string, error) {
+				data, err := io.ReadAll(r)
+				if err != nil {
+					return "", errors.WithStack(err)
+				}
+
+				return string(data), nil
+			}),
+		)
+
+		if err := store.Clear(); err != nil {
+			panic(errors.WithStack(err))
+		}
+
+		return store
+	})
+}

pkg/storage/driver/cache/lfu/fs/hash.go

@@ -0,0 +1,19 @@
+package fs
+
+import (
+	"strconv"
+
+	"github.com/mitchellh/hashstructure/v2"
+	"github.com/pkg/errors"
+)
+
+func DefaultGetPath[K comparable](key K) ([]string, error) {
+	uintHash, err := hashstructure.Hash(key, hashstructure.FormatV2, nil)
+	if err != nil {
+		return nil, errors.WithStack(err)
+	}
+
+	hash := strconv.FormatUint(uintHash, 16)
+
+	return []string{hash}, nil
+}

pkg/storage/driver/cache/lfu/fs/marshal.go

@@ -0,0 +1,31 @@
+package fs
+
+import (
+	"bytes"
+	"encoding/gob"
+	"io"
+
+	"github.com/pkg/errors"
+)
+
+func DefaultMarshalValue[V any](value V) (io.Reader, error) {
+	var buf bytes.Buffer
+	encoder := gob.NewEncoder(&buf)
+
+	if err := encoder.Encode(value); err != nil {
+		return nil, errors.WithStack(err)
+	}
+
+	return &buf, nil
+}
+
+func DefaultUnmarshalValue[V any](d io.Reader) (V, error) {
+	var value V
+	encoder := gob.NewDecoder(d)
+
+	if err := encoder.Decode(&value); err != nil {
+		return *new(V), errors.WithStack(err)
+	}
+
+	return value, nil
+}

pkg/storage/driver/cache/lfu/fs/options.go

@@ -0,0 +1,45 @@
+package fs
+
+import "io"
+
+type GetPathFunc[K comparable] func(key K) ([]string, error)
+type MarshalValueFunc[V any] func(value V) (io.Reader, error)
+type UnmarshalValueFunc[V any] func(r io.Reader) (V, error)
+
+type Options[K comparable, V any] struct {
+	GetPath        GetPathFunc[K]
+	MarshalValue   MarshalValueFunc[V]
+	UnmarshalValue UnmarshalValueFunc[V]
+}
+
+type OptionsFunc[K comparable, V any] func(opts *Options[K, V])
+
+func DefaultOptions[K comparable, V any](funcs ...OptionsFunc[K, V]) *Options[K, V] {
+	opts := &Options[K, V]{
+		GetPath:        DefaultGetPath[K],
+		MarshalValue:   DefaultMarshalValue[V],
+		UnmarshalValue: DefaultUnmarshalValue[V],
+	}
+	for _, fn := range funcs {
+		fn(opts)
+	}
+	return opts
+}
+
+func WithGetPath[K comparable, V any](getKeyHash GetPathFunc[K]) OptionsFunc[K, V] {
+	return func(opts *Options[K, V]) {
+		opts.GetPath = getKeyHash
+	}
+}
+
+func WithMarshalValue[K comparable, V any](marshalValue MarshalValueFunc[V]) OptionsFunc[K, V] {
+	return func(opts *Options[K, V]) {
+		opts.MarshalValue = marshalValue
+	}
+}
+
+func WithUnmarshalValue[K comparable, V any](unmarshalValue UnmarshalValueFunc[V]) OptionsFunc[K, V] {
+	return func(opts *Options[K, V]) {
+		opts.UnmarshalValue = unmarshalValue
+	}
+}

pkg/storage/driver/cache/lfu/fs/store.go

@@ -0,0 +1,165 @@
+package fs
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+
+	"forge.cadoles.com/arcad/edge/pkg/storage/driver/cache/lfu"
+	"github.com/pkg/errors"
+)
+
+type Store[K comparable, V any] struct {
+	baseDir        string
+	getPath        GetPathFunc[K]
+	marshalValue   MarshalValueFunc[V]
+	unmarshalValue UnmarshalValueFunc[V]
+}
+
+// Delete implements Store.
+func (s *Store[K, V]) Delete(key K) error {
+	path, err := s.getEntryPath(key)
+	if err != nil {
+		return errors.WithStack(err)
+	}
+
+	if err := os.Remove(path); err != nil && !errors.Is(err, os.ErrNotExist) {
+		return errors.WithStack(err)
+	}
+
+	return nil
+}
+
+// Get implements Store.
+func (s *Store[K, V]) Get(key K) (V, error) {
+	path, err := s.getEntryPath(key)
+	if err != nil {
+		return *new(V), errors.WithStack(err)
+	}
+
+	value, err := s.readValue(path)
+	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return *new(V), errors.WithStack(lfu.ErrNotFound)
+		}
+
+		return *new(V), errors.WithStack(err)
+	}
+
+	return value, nil
+}
+
+// Set implements Store.
+func (s *Store[K, V]) Set(key K, value V) error {
+	path, err := s.getEntryPath(key)
+	if err != nil {
+		return errors.WithStack(err)
+	}
+
+	if err := s.writeValue(path, value); err != nil {
+		return errors.WithStack(err)
+	}
+
+	return nil
+}
+
+func (s *Store[K, V]) Clear() error {
+	if err := os.RemoveAll(s.baseDir); err != nil {
+		return errors.WithStack(err)
+	}
+
+	return nil
+}
+
+func (s *Store[K, V]) getEntryPath(k K) (string, error) {
+	path, err := s.getPath(k)
+	if err != nil {
+		return "", errors.WithStack(err)
+	}
+
+	path = append([]string{s.baseDir}, path...)
+	return filepath.Join(path...), nil
+}
+
+func (s *Store[K, V]) writeValue(path string, value V) error {
+	fi, err := os.Stat(path)
+	if err == nil && !fi.Mode().IsRegular() {
+		return fmt.Errorf("%s already exists and is not a regular file", path)
+	}
+
+	dir := filepath.Dir(path)
+
+	if err := os.MkdirAll(dir, 0750); err != nil {
+		return errors.WithStack(err)
+	}
+
+	f, err := os.CreateTemp(dir, filepath.Base(path)+".tmp")
+	if err != nil {
+		return errors.WithStack(err)
+	}
+
+	tmpName := f.Name()
+	defer func() {
+		if err != nil {
+			f.Close()
+			os.Remove(tmpName)
+		}
+	}()
+
+	reader, err := s.marshalValue(value)
+	if err != nil {
+		return errors.WithStack(err)
+	}
+
+	if _, err := io.Copy(f, reader); err != nil {
+		return errors.WithStack(err)
+	}
+
+	if err := f.Sync(); err != nil {
+		return errors.WithStack(err)
+	}
+
+	if err := f.Close(); err != nil {
+		return errors.WithStack(err)
+	}
+
+	if err := os.Rename(tmpName, path); err != nil {
+		return errors.WithStack(err)
+	}
+
+	return nil
+}
+
+func (s *Store[K, V]) readValue(path string) (V, error) {
+	file, err := os.Open(path)
+	if err != nil {
+		return *new(V), errors.WithStack(err)
+	}
+
+	defer func() {
+		if err := file.Close(); err != nil && !errors.Is(err, os.ErrClosed) {
+			panic(errors.WithStack(err))
+		}
+	}()
+
+	value, err := s.unmarshalValue(file)
+
+	if err != nil {
+		return *new(V), errors.WithStack(err)
+	}
+
+	return value, nil
+}
+
+func NewStore[K comparable, V any](baseDir string, funcs ...OptionsFunc[K, V]) *Store[K, V] {
+	opts := DefaultOptions[K, V](funcs...)
+	return &Store[K, V]{
+		baseDir:        baseDir,
+		getPath:        opts.GetPath,
+		unmarshalValue: opts.UnmarshalValue,
+		marshalValue:   opts.MarshalValue,
+	}
+}
+
+var _ lfu.Store[string, int] = &Store[string, int]{}

pkg/storage/driver/cache/lfu/fs/testdata/.gitignore

@@ -0,0 +1,2 @@
+*
+!.gitignore