implement file sources

If the file is not cached we have to get it from somewhere. For that I
implemented a webdav file source which gets the file from reva.

pkg/thumbnails/imgsource/imgsource.go

@@ -0,0 +1,33 @@
+package imgsource
+
+import "image"
+
+// Source defines the interface for image sources
+type Source interface {
+	Get(path string, ctx SourceContext) (image.Image, error)
+}
+
+// NewContext creates a new SourceContext instance
+func NewContext() SourceContext {
+	return SourceContext{
+		m: make(map[string]interface{}),
+	}
+}
+
+// SourceContext is used to pass source specific parameters
+type SourceContext struct {
+	m map[string]interface{}
+}
+
+// GetString tries to cast the value to a string
+func (s SourceContext) GetString(key string) string {
+	if s, ok := s.m[key].(string); ok {
+		return s
+	}
+	return ""
+}
+
+// Set sets a value
+func (s SourceContext) Set(key string, val interface{}) {
+	s.m[key] = val
+}

pkg/thumbnails/imgsource/webdav.go

@@ -0,0 +1,41 @@
+package imgsource
+
+import (
+	"fmt"
+	"image"
+	"net/http"
+	"net/url"
+	"path"
+)
+
+// WebDav implements the Source interface for webdav services
+type WebDav struct {
+	Basepath string
+}
+
+const (
+	// WebDavAuth is the parameter name for the autorization token
+	WebDavAuth = "Authorization"
+)
+
+// Get downloads the file from a webdav service
+func (s WebDav) Get(file string, ctx SourceContext) (image.Image, error) {
+	u, _ := url.Parse(s.Basepath)
+	u.Path = path.Join(u.Path, file)
+	req, err := http.NewRequest(http.MethodGet, u.String(), nil)
+	if err != nil {
+		return nil, fmt.Errorf("could not get the file %s error: %s", file, err.Error())
+	}
+
+	auth := ctx.GetString(WebDavAuth)
+	req.Header.Add("Authorization", auth)
+
+	client := &http.Client{}
+	resp, err := client.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("could not get the file %s error: %s", file, err.Error())
+	}
+
+	img, _, _ := image.Decode(resp.Body)
+	return img, nil
+}

pkg/thumbnails/thumbnails.go

@@ -3,7 +3,6 @@ package thumbnails
 import (
 	"bytes"
 	"image"
-	"os"
 	"strings"
 	"time"
 
@@ -16,14 +15,13 @@ type ThumbnailContext struct {
 	Width     int
 	Height    int
 	ImagePath string
-
-	Encoder Encoder
+	Encoder   Encoder
 }
 
 // Manager is responsible for generating thumbnails
 type Manager interface {
 	// Get will return a thumbnail for a file
-	Get(ThumbnailContext) ([]byte, error)
+	Get(ThumbnailContext, image.Image) ([]byte, error)
 	GetCached(ThumbnailContext) []byte
 }
 
@@ -33,18 +31,14 @@ type SimpleManager struct {
 }
 
 // Get implements the Get Method of Manager
-func (s SimpleManager) Get(ctx ThumbnailContext) ([]byte, error) {
-	key := buildCacheKey(ctx)
+func (s SimpleManager) Get(ctx ThumbnailContext, img image.Image) ([]byte, error) {
+	thumbnail := s.generate(ctx, img)
 
-	cached := s.Cache.Get(key)
-	if cached == nil {
-		thumbnail := s.generate(ctx)
-		s.Cache.Set(key, thumbnail)
-		cached = thumbnail
-	}
+	key := buildCacheKey(ctx)
+	s.Cache.Set(key, thumbnail)
 
 	buf := new(bytes.Buffer)
-	err := ctx.Encoder.Encode(buf, cached)
+	err := ctx.Encoder.Encode(buf, thumbnail)
 	if err != nil {
 		return nil, err
 	}
@@ -64,15 +58,11 @@ func (s SimpleManager) GetCached(ctx ThumbnailContext) []byte {
 	return buf.Bytes()
 }
 
-func (s SimpleManager) generate(ctx ThumbnailContext) image.Image {
+func (s SimpleManager) generate(ctx ThumbnailContext, img image.Image) image.Image {
 	// TODO: remove, just for demo purposes
 	time.Sleep(time.Second * 2)
 
-	// TODO: get file from reva
-	reader, _ := os.Open(ctx.ImagePath)
-	defer reader.Close()
-	m, _, _ := image.Decode(reader)
-	thumbnail := resize.Thumbnail(uint(ctx.Width), uint(ctx.Height), m, resize.Lanczos2)
+	thumbnail := resize.Thumbnail(uint(ctx.Width), uint(ctx.Height), img, resize.Lanczos2)
 	return thumbnail
 }