stuffs

disk-storage.go

@@ -0,0 +1,124 @@
+package main
+
+import (
+	"encoding/gob"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"log"
+	"os"
+	"time"
+)
+
+type DiskStorage struct {
+	stateFile string
+	lastSave  int64
+	LastSaves map[string]int64
+}
+
+func NewDiskStorage(stateFile string) (*DiskStorage, error) {
+	ret := &DiskStorage{
+		stateFile: stateFile,
+		LastSaves: make(map[string]int64),
+	}
+	err := ret.loadState()
+	return ret, err
+}
+
+func saveMessages(messages []Message, id string) error {
+	log.Printf("%d messages to save for %s", len(messages), id)
+	if len(messages) == 0 {
+		return nil
+	}
+	var file *os.File
+	var err error
+	path := getCartPath(id)
+	file, err = os.OpenFile(path, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+	// z := gzip.NewWriter(file)
+	// defer z.Close()
+	enc := gob.NewEncoder(file)
+	for _, m := range messages {
+		err = enc.Encode(m)
+	}
+	return err
+}
+
+func getCartPath(id string) string {
+	return fmt.Sprintf("data/%s.gob", id)
+}
+
+func loadMessages(grain Grain, id string) error {
+	var err error
+	path := getCartPath(id)
+	if _, err = os.Stat(path); errors.Is(err, os.ErrNotExist) {
+		return err
+	}
+	file, err := os.Open(path)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+	// z, err := gzip.NewReader(file)
+	// if err != nil {
+	// 	return err
+	// }
+	// defer z.Close()
+
+	var reply CartGrain
+	decoder := gob.NewDecoder(file)
+	for err == nil {
+		var message Message
+		err = decoder.Decode(&message)
+		if err != nil {
+			grain.HandleMessage(&message, true, &reply)
+		}
+	}
+	if err.Error() == "EOF" {
+		return nil
+	}
+	return err
+}
+
+func (s *DiskStorage) saveState() error {
+	tmpFile := s.stateFile + "_tmp"
+	file, err := os.Create(tmpFile)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+	err = json.NewEncoder(file).Encode(s.LastSaves)
+	if err != nil {
+		return err
+	}
+	os.Remove(s.stateFile + ".bak")
+	os.Rename(s.stateFile, s.stateFile+".bak")
+	return os.Rename(tmpFile, s.stateFile)
+}
+
+func (s *DiskStorage) loadState() error {
+	file, err := os.Open("data/state.json")
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+	return json.NewDecoder(file).Decode(&s.LastSaves)
+}
+
+func (s *DiskStorage) Store(id string, grain Grain) error {
+	lastSavedMessage, ok := s.LastSaves[id]
+	if ok && lastSavedMessage > grain.GetLastChange() {
+		return nil
+	}
+	err := saveMessages(grain.GetStorageMessage(lastSavedMessage), id)
+	if err != nil {
+		return err
+	}
+	ts := time.Now().Unix()
+	s.LastSaves[id] = ts
+	s.lastSave = ts
+	return nil
+}