feat(thumbnails): make ggp thumbnails work

Signed-off-by: jkoberg <jkoberg@owncloud.com>

services/thumbnails/pkg/errors/error.go

@@ -9,6 +9,8 @@ var (
 	ErrInvalidType = errors.New("thumbnails: can't encode this type")
 	// ErrNoEncoderForType represents the error when an encoder couldn't be found for a type.
 	ErrNoEncoderForType = errors.New("thumbnails: no encoder for this type found")
+	// ErrNoGeneratorForType represents the error when a generator couldn't be found for a type.
+	ErrNoGeneratorForType = errors.New("thumbnails: no generator for this type found")
 	// ErrNoImageFromAudioFile defines an error when an image cannot be extracted from an audio file
 	ErrNoImageFromAudioFile = errors.New("thumbnails: could not extract image from audio file")
 	// ErrNoConverterForExtractedImageFromGgsFile defines an error when the extracted image from an ggs file could not be converted

services/thumbnails/pkg/preprocessor/preprocessor.go

@@ -4,6 +4,8 @@ import (
 	"archive/zip"
 	"bufio"
 	"bytes"
+	"encoding/base64"
+	"encoding/json"
 	"image"
 	"image/draw"
 	"image/gif"
@@ -176,6 +178,57 @@ Scan: // Label for the scanner loop, so we can break it easily
 	return img, scanner.Err()
 }
 
+// GGPStruct is the layout of a ggp file (which is basically json)
+type GGPStruct struct {
+	Sections []struct {
+		Cards []struct {
+			Element struct {
+				Image struct {
+					Base64Image string
+				}
+			}
+		}
+	}
+}
+
+// GgpDecoder is a converter for the geogebra pinboard file
+type GgpDecoder struct{}
+
+// Convert reads the ggp file and returns the first thumbnail image
+func (j GgpDecoder) Convert(r io.Reader) (interface{}, error) {
+	ggp := &GGPStruct{}
+	err := json.NewDecoder(r).Decode(ggp)
+	if err != nil {
+		return nil, err
+	}
+
+	elem, err := extractBase64ImageFromGGP(ggp)
+	if err != nil {
+		return nil, err
+	}
+
+	b, err := base64.StdEncoding.DecodeString(elem)
+	if err != nil {
+		return nil, err
+	}
+
+	img, _, err := image.Decode(bytes.NewReader(b))
+	return img, err
+}
+
+func extractBase64ImageFromGGP(ggp *GGPStruct) (string, error) {
+	if len(ggp.Sections) < 1 || len(ggp.Sections[0].Cards) < 1 {
+		return "", errors.New("cant find thumbnail in ggp file")
+	}
+
+	raw := strings.Split(ggp.Sections[0].Cards[0].Element.Image.Base64Image, "base64,")
+	if len(raw) < 2 {
+		return "", errors.New("cant decode ggp thumbnail")
+	}
+
+	return raw[1], nil
+}
+
 // Draw the word in the canvas. The mixX and maxX defines the drawable range
 // (X axis) where the word can be drawn (in case the word is too big and doesn't
 // fit in the canvas), and the incY defines the increment in the Y axis if we
@@ -259,7 +312,7 @@ func ForType(mimeType string, opts map[string]interface{}) FileConverter {
 	case "application/vnd.geogebra.slides":
 		return GgsDecoder{"_slide0/geogebra_thumbnail.png"}
 	case "application/vnd.geogebra.pinboard":
-		return GgsDecoder{"geogebra_thumbnail.png"}
+		return GgpDecoder{}
 	case "image/gif":
 		return GifDecoder{}
 	case "audio/flac":

services/thumbnails/pkg/thumbnail/generator.go

@@ -89,11 +89,11 @@ func (g GifGenerator) imageToPaletted(img image.Image, p color.Palette) *image.P
 // or nil if the type is not supported.
 func GeneratorFor(fileType, processorID string) (Generator, error) {
 	switch strings.ToLower(fileType) {
-	case typePng, typeJpg, typeJpeg, typeGgs:
+	case typePng, typeJpg, typeJpeg, typeGgs, typeGgp:
 		return NewSimpleGenerator(fileType, processorID)
 	case typeGif:
 		return NewGifGenerator(fileType, processorID)
 	default:
-		return nil, errors.ErrNoEncoderForType
+		return nil, errors.ErrNoGeneratorForType
 	}
 }

services/thumbnails/pkg/thumbnail/thumbnail.go

@@ -13,18 +13,19 @@ import (
 var (
 	// SupportedMimeTypes contains an all mimetypes which are supported by the thumbnailer.
 	SupportedMimeTypes = map[string]struct{}{
-		"image/png":                       {},
-		"image/jpg":                       {},
-		"image/jpeg":                      {},
-		"image/gif":                       {},
-		"image/bmp":                       {},
-		"image/x-ms-bmp":                  {},
-		"image/tiff":                      {},
-		"text/plain":                      {},
-		"audio/flac":                      {},
-		"audio/mpeg":                      {},
-		"audio/ogg":                       {},
-		"application/vnd.geogebra.slides": {},
+		"image/png":                         {},
+		"image/jpg":                         {},
+		"image/jpeg":                        {},
+		"image/gif":                         {},
+		"image/bmp":                         {},
+		"image/x-ms-bmp":                    {},
+		"image/tiff":                        {},
+		"text/plain":                        {},
+		"audio/flac":                        {},
+		"audio/mpeg":                        {},
+		"audio/ogg":                         {},
+		"application/vnd.geogebra.slides":   {},
+		"application/vnd.geogebra.pinboard": {},
 	}
 )