Add caching for upload avatars

pkg/modules/avatar/upload/upload.go

@@ -17,15 +17,45 @@
 package upload
 
 import (
+	"bytes"
 	"code.vikunja.io/api/pkg/files"
 	"code.vikunja.io/api/pkg/user"
+	"github.com/disintegration/imaging"
+	"image"
+	"image/png"
 	"io/ioutil"
+	"sync"
 )
 
+var (
+	// This is a map with a map so we're able to clear all cached avatar (in all sizes) for one user at once
+	// The first map has as key the user id, the second one has the size as key
+	resizedCache     = map[int64]map[int64][]byte{}
+	resizedCacheLock = sync.Mutex{}
+)
+
+func init() {
+	resizedCache = make(map[int64]map[int64][]byte)
+}
+
 type Provider struct {
 }
 
 func (p *Provider) GetAvatar(u *user.User, size int64) (avatar []byte, mimeType string, err error) {
+
+	a, cached := resizedCache[u.ID]
+	if cached {
+		if a != nil && a[size] != nil {
+			return a[size], "", nil
+		}
+		if a == nil {
+			resizedCache[u.ID] = make(map[int64][]byte)
+		}
+	} else {
+		resizedCache[u.ID] = make(map[int64][]byte)
+	}
+
+	// If we get this far, the avatar is either not cached at all or not in this size
 	f := &files.File{ID: u.AvatarFileID}
 	if err := f.LoadFileByID(); err != nil {
 		return nil, "", err
@@ -35,6 +65,25 @@ func (p *Provider) GetAvatar(u *user.User, size int64) (avatar []byte, mimeType
 		return nil, "", err
 	}
 
-	avatar, err = ioutil.ReadAll(f.File)
+	img, _, err := image.Decode(f.File)
+	if err != nil {
+		return nil, "", err
+	}
+	resizedImg := imaging.Resize(img, 0, int(size), imaging.Lanczos)
+	buf := &bytes.Buffer{}
+	if err := png.Encode(buf, resizedImg); err != nil {
+		return nil, "", err
+	}
+
+	avatar, err = ioutil.ReadAll(buf)
+	resizedCacheLock.Lock()
+	resizedCache[u.ID][size] = avatar
+	resizedCacheLock.Unlock()
 	return avatar, f.Mime, err
 }
+
+func InvalidateCache(u *user.User) {
+	resizedCacheLock.Lock()
+	delete(resizedCache, u.ID)
+	resizedCacheLock.Unlock()
+}