Add cache_id option for Clash cache file

experimental/clashapi/cachefile/cache.go

@@ -14,10 +14,11 @@ var bucketSelected = []byte("selected")
 var _ adapter.ClashCacheFile = (*CacheFile)(nil)
 
 type CacheFile struct {
-	DB *bbolt.DB
+	DB      *bbolt.DB
+	cacheID []byte
 }
 
-func Open(path string) (*CacheFile, error) {
+func Open(path string, cacheID string) (*CacheFile, error) {
 	const fileMode = 0o666
 	options := bbolt.Options{Timeout: time.Second}
 	db, err := bbolt.Open(path, fileMode, &options)
@@ -31,13 +32,39 @@ func Open(path string) (*CacheFile, error) {
 	if err != nil {
 		return nil, err
 	}
-	return &CacheFile{db}, nil
+	var cacheIDBytes []byte
+	if cacheID != "" {
+		cacheIDBytes = append([]byte{0}, []byte(cacheID)...)
+	}
+	return &CacheFile{db, cacheIDBytes}, nil
+}
+
+func (c *CacheFile) bucket(t *bbolt.Tx, key []byte) *bbolt.Bucket {
+	if c.cacheID == nil {
+		return t.Bucket(key)
+	}
+	bucket := t.Bucket(c.cacheID)
+	if bucket == nil {
+		return nil
+	}
+	return bucket.Bucket(key)
+}
+
+func (c *CacheFile) createBucket(t *bbolt.Tx, key []byte) (*bbolt.Bucket, error) {
+	if c.cacheID == nil {
+		return t.CreateBucketIfNotExists(key)
+	}
+	bucket, err := t.CreateBucketIfNotExists(c.cacheID)
+	if bucket == nil {
+		return nil, err
+	}
+	return bucket.CreateBucketIfNotExists(key)
 }
 
 func (c *CacheFile) LoadSelected(group string) string {
 	var selected string
 	c.DB.View(func(t *bbolt.Tx) error {
-		bucket := t.Bucket(bucketSelected)
+		bucket := c.bucket(t, bucketSelected)
 		if bucket == nil {
 			return nil
 		}
@@ -52,7 +79,7 @@ func (c *CacheFile) LoadSelected(group string) string {
 
 func (c *CacheFile) StoreSelected(group, selected string) error {
 	return c.DB.Batch(func(t *bbolt.Tx) error {
-		bucket, err := t.CreateBucketIfNotExists(bucketSelected)
+		bucket, err := c.createBucket(t, bucketSelected)
 		if err != nil {
 			return err
 		}