feat: collect and display usage stats

stat/store.go

@@ -0,0 +1,154 @@
+package stat
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"sync"
+
+	"log/slog"
+
+	"github.com/pkg/errors"
+)
+
+type Store struct {
+	data         sync.Map
+	loadSaveLock sync.Mutex
+}
+
+func (s *Store) Load(path string) error {
+	s.loadSaveLock.Lock()
+	defer s.loadSaveLock.Unlock()
+
+	file, err := os.OpenFile(path, os.O_RDONLY, os.ModePerm)
+	if err != nil {
+		return errors.WithStack(err)
+	}
+
+	decoder := json.NewDecoder(file)
+	data := map[string]any{}
+
+	if err := decoder.Decode(&data); err != nil {
+		return errors.WithStack(err)
+	}
+
+	s.data.Range(func(key, value any) bool {
+		s.data.Delete(key)
+		return true
+	})
+
+	for k, v := range data {
+		s.data.Store(k, v)
+	}
+
+	return nil
+}
+
+func (s *Store) Save(path string) error {
+	s.loadSaveLock.Lock()
+	defer s.loadSaveLock.Unlock()
+
+	data, err := s.Snapshot()
+	if err != nil {
+		return errors.WithStack(err)
+	}
+
+	dir := filepath.Dir(path)
+	filename := filepath.Base(path)
+
+	temp, err := os.CreateTemp(dir, filename+".new*")
+	if err != nil {
+		return errors.WithStack(err)
+	}
+
+	defer func() {
+		if err := os.Remove(temp.Name()); err != nil && !errors.Is(err, os.ErrNotExist) {
+			slog.Error("could not remove temporary file",
+				slog.String("file", temp.Name()),
+				slog.Any("error", errors.WithStack(err)),
+			)
+		}
+	}()
+
+	encoder := json.NewEncoder(temp)
+	if err := encoder.Encode(data); err != nil {
+		return errors.WithStack(err)
+	}
+
+	if err := os.Rename(temp.Name(), path); err != nil {
+		return errors.WithStack(err)
+	}
+
+	return nil
+}
+
+func (s *Store) Snapshot() (map[string]float64, error) {
+	data := map[string]float64{}
+
+	var err error
+	s.data.Range(func(rawKey, rawValue any) bool {
+		key, ok := rawKey.(string)
+		if !ok {
+			err = errors.Errorf("unexpected stat key of '%v'", rawKey)
+
+			return false
+		}
+
+		value, ok := rawValue.(float64)
+		if !ok {
+			err = errors.Errorf("unexpected stat value of '%v'", rawValue)
+
+			return false
+		}
+
+		data[key] = value
+
+		return true
+	})
+	if err != nil {
+		return nil, errors.WithStack(err)
+	}
+
+	return data, nil
+}
+
+func (s *Store) Add(name string, added float64, defaultValue float64) float64 {
+	for {
+		value := s.Get(name, defaultValue)
+		if value == defaultValue {
+			s.data.Store(name, defaultValue)
+		}
+
+		sum := value + added
+		if s.data.CompareAndSwap(name, value, value+added) {
+			return sum
+		}
+	}
+}
+
+func (s *Store) Set(name string, value float64) float64 {
+	s.data.Store(name, value)
+
+	return value
+}
+
+func (s *Store) Get(name string, defaultValue float64) float64 {
+	rawValue, ok := s.data.Load(name)
+	if !ok {
+		return defaultValue
+	}
+
+	value, ok := rawValue.(float64)
+	if !ok {
+		return defaultValue
+	}
+
+	return value
+}
+
+func NewStore() *Store {
+	return &Store{
+		data:         sync.Map{},
+		loadSaveLock: sync.Mutex{},
+	}
+}