Add clash persistence support

experimental/clashapi/cachefile/cache.go

@@ -0,0 +1,61 @@
+package cachefile
+
+import (
+	"os"
+	"time"
+
+	"github.com/sagernet/sing-box/adapter"
+
+	"go.etcd.io/bbolt"
+)
+
+var bucketSelected = []byte("selected")
+
+var _ adapter.ClashCacheFile = (*CacheFile)(nil)
+
+type CacheFile struct {
+	DB *bbolt.DB
+}
+
+func Open(path string) (*CacheFile, error) {
+	const fileMode = 0o666
+	options := bbolt.Options{Timeout: time.Second}
+	db, err := bbolt.Open(path, fileMode, &options)
+	switch err {
+	case bbolt.ErrInvalid, bbolt.ErrChecksum, bbolt.ErrVersionMismatch:
+		if err = os.Remove(path); err != nil {
+			break
+		}
+		db, err = bbolt.Open(path, 0o666, &options)
+	}
+	if err != nil {
+		return nil, err
+	}
+	return &CacheFile{db}, nil
+}
+
+func (c *CacheFile) LoadSelected(group string) string {
+	var selected string
+	c.DB.View(func(t *bbolt.Tx) error {
+		bucket := t.Bucket(bucketSelected)
+		if bucket == nil {
+			return nil
+		}
+		selectedBytes := bucket.Get([]byte(group))
+		if len(selectedBytes) > 0 {
+			selected = string(selectedBytes)
+		}
+		return nil
+	})
+	return selected
+}
+
+func (c *CacheFile) StoreSelected(group, selected string) error {
+	return c.DB.Batch(func(t *bbolt.Tx) error {
+		bucket, err := t.CreateBucketIfNotExists(bucketSelected)
+		if err != nil {
+			return err
+		}
+		return bucket.Put([]byte(group), []byte(selected))
+	})
+}