add migrator between avatar stores

backend/app/store/avatar/gridfs.go

@@ -97,6 +97,8 @@ func (gf *GridFS) Remove(avatar string) error {
 	})
 }
 
+// List all avatars (ids) on gfs
+// note: id includes .image suffix
 func (gf *GridFS) List() (ids []string, err error) {
 
 	type gfsFile struct {

backend/app/store/avatar/localfs.go

@@ -97,6 +97,8 @@ func (fs *LocalFS) Remove(avatar string) error {
 	return os.Remove(avFile)
 }
 
+// List all avatars (ids) on local file system
+// note: id includes .image suffix
 func (fs *LocalFS) List() (ids []string, err error) {
 	err = filepath.Walk(fs.storePath,
 		func(path string, info os.FileInfo, err error) error {

backend/app/store/avatar/store.go

@@ -35,6 +35,28 @@ type Store interface {
 
 }
 
+// Migrate avatars between stores
+func Migrate(dst Store, src Store) (int, error) {
+	ids, err := src.List()
+	if err != nil {
+		return 0, err
+	}
+	for _, id := range ids {
+		srcReader, _, err := src.Get(id)
+		if err != nil {
+			log.Printf("[WARN] can't get reader for avatar %s", id)
+			continue
+		}
+		if _, err = dst.Put(id, srcReader); err != nil {
+			log.Printf("[WARN] can't put avatar %s", id)
+		}
+		if err = srcReader.Close(); err != nil {
+			log.Printf("[WARN] failed to close avatar %s", id)
+		}
+	}
+	return len(ids), nil
+}
+
 // resize an image of supported format (PNG, JPG, GIF) to the size of "limit" px of the biggest side
 // (width or height) preserving aspect ratio.
 // Returns original reader if resizing is not needed or failed.

backend/app/store/avatar/store_test.go

@@ -5,6 +5,8 @@ import (
 	"image"
 	"io"
 	"io/ioutil"
+	"os"
+	"sort"
 	"strings"
 	"testing"
 
@@ -63,3 +65,45 @@ func TestAvatarStore_resize(t *testing.T) {
 		assert.Equalf(t, c.hr, bounds.Dy(), "file %s", c.file)
 	}
 }
+
+func TestAvatarStore_Migrate(t *testing.T) {
+	// prep localfs
+	plocal := NewLocalFS("/tmp/avatars.test", 300)
+	err := os.MkdirAll("/tmp/avatars.test", 0700)
+	require.NoError(t, err)
+	defer os.RemoveAll("/tmp/avatars.test")
+
+	// prep gridfs
+	pgfs, skip := prepGFStore(t)
+	if skip {
+		return
+	}
+
+	// write to localfs
+	_, err = plocal.Put("user1", strings.NewReader("some picture bin data 1"))
+	require.Nil(t, err)
+	_, err = plocal.Put("user2", strings.NewReader("some picture bin data 2"))
+	require.Nil(t, err)
+	_, err = plocal.Put("user3", strings.NewReader("some picture bin data 3"))
+	require.Nil(t, err)
+
+	// migrate and check reported count
+	count, err := Migrate(pgfs, plocal)
+	require.NoError(t, err)
+	assert.Equal(t, 3, count, "all 3 recs migrated")
+
+	// list avatars
+	l, err := pgfs.List()
+	assert.NoError(t, err)
+	assert.Equal(t, 3, len(l), "3 avatars listed in destination store")
+	sort.Strings(l)
+	assert.Equal(t, []string{"0b7f849446d3383546d15a480966084442cd2193.image", "a1881c06eec96db9901c7bbfe41c42a3f08e9cb4.image", "b3daa77b4c04a9551b8781d03191fe098f325e67.image"}, l)
+
+	// try to read one of migrated avatars
+	r, size, err := pgfs.Get("0b7f849446d3383546d15a480966084442cd2193.image")
+	assert.Nil(t, err)
+	assert.Equal(t, 23, size)
+	data, err := ioutil.ReadAll(r)
+	assert.Nil(t, err)
+	assert.Equal(t, "some picture bin data 3", string(data))
+}