Add geogebra previews

Co-authored-by: Florian Schade <fschade@owncloud.com>

Signed-off-by: Christian Richter <crichter@owncloud.com>

services/thumbnails/pkg/preprocessor/preprocessor.go

@@ -1,8 +1,10 @@
 package preprocessor
 
 import (
+	"archive/zip"
 	"bufio"
 	"bytes"
+	"fmt"
 	"image"
 	"image/draw"
 	"image/gif"
@@ -44,6 +46,36 @@ func (i GifDecoder) Convert(r io.Reader) (interface{}, error) {
 	return img, nil
 }
 
+type GgsDecoder struct{}
+
+func (g GgsDecoder) Convert(r io.Reader) (interface{}, error) {
+	geogebraThumbnail := "_slide0/geogebra_thumbnail.png"
+	var buf bytes.Buffer
+	_, err := io.Copy(&buf, r)
+	if err != nil {
+		return nil, err
+	}
+	zipReader, err := zip.NewReader(bytes.NewReader(buf.Bytes()), int64(buf.Len()))
+	if err != nil {
+		return nil, err
+	}
+	for _, file := range zipReader.File {
+		if file.Name == geogebraThumbnail {
+			thumbnail, err := file.Open()
+			if err != nil {
+				return nil, err
+			}
+
+			img, err := imaging.Decode(thumbnail, imaging.AutoOrientation(true))
+			if err != nil {
+				return nil, errors.Wrap(err, `could not decode the image`)
+			}
+			return img, nil
+		}
+	}
+	return nil, errors.New(fmt.Sprintf("%s not found", geogebraThumbnail))
+}
+
 type AudioDecoder struct{}
 
 func (i AudioDecoder) Convert(r io.Reader) (interface{}, error) {
@@ -223,6 +255,8 @@ func ForType(mimeType string, opts map[string]interface{}) FileConverter {
 		return TxtToImageConverter{
 			fontLoader: fontLoader,
 		}
+	case "application/vnd.geogebra.slides":
+		return GgsDecoder{}
 	case "image/gif":
 		return GifDecoder{}
 	case "audio/flac":

services/thumbnails/pkg/preprocessor/preprocessor_test.go

@@ -0,0 +1,57 @@
+package preprocessor
+
+import (
+	"bytes"
+	"image"
+	"io"
+	"reflect"
+
+	"testing"
+)
+
+// implement tests for the following structs and functions:
+// ImageDecoder
+// GifDecoder
+// GgsDecoder
+
+// TestImageDecoderConvert tests the function Convert of the struct ImageDecoder
+func TestImageDecoderConvert(t *testing.T) {
+	type args struct {
+		r io.Reader
+	}
+	tests := []struct {
+		name    string
+		i       ImageDecoder
+		args    args
+		want    interface{}
+		wantErr bool
+	}{
+		{
+			name: "Test successful convert image",
+			args: args{
+				r: bytes.NewReader([]byte("")),
+			},
+			want:    image.Image{},
+			wantErr: false,
+		},
+		{
+			name: "Test unsuccessful convert image",
+			args: args{
+				r: bytes.NewReader([]byte("")),
+			},
+			want:    nil,
+			wantErr: true,
+		},
+	}
+	for _, tt := range tests {
+		i := ImageDecoder{}
+		got, err := i.Convert(tt.args.r)
+		if (err != nil) != tt.wantErr {
+			t.Errorf("%q. ImageDecoder.Convert() error = %v, wantErr %v", tt.name, err, tt.wantErr)
+			return
+		}
+		if !reflect.DeepEqual(reflect.TypeOf(got), reflect.TypeOf(tt.want)) {
+			t.Errorf("%q. ImageDecoder.Convert() = %v, want %v", tt.name, got, tt.want)
+		}
+	}
+}

services/thumbnails/pkg/thumbnail/encoding.go

@@ -103,7 +103,7 @@ func (e GifEncoder) MimeType() string {
 // or nil if the type is not supported.
 func EncoderForType(fileType string) (Encoder, error) {
 	switch strings.ToLower(fileType) {
-	case typePng:
+	case typePng, typeGgs:
 		return PngEncoder{}, nil
 	case typeJpg, typeJpeg:
 		return JpegEncoder{}, nil

services/thumbnails/pkg/thumbnail/generator.go

@@ -71,24 +71,14 @@ func (g GifGenerator) imageToPaletted(img image.Image, p color.Palette) *image.P
 	return pm
 }
 
-// GgsGenerator is used to create a web friendly version of the provided ggs image.
-type GgsGenerator struct{}
-
-func (g GgsGenerator) Generate(size image.Rectangle, img interface{}, processor Processor) (interface{}, error) {
-	// TODO: write zip extractor, get image from zip, process image, return image
-	return nil, nil
-}
-
 // GeneratorForType returns the generator for a given file type
 // or nil if the type is not supported.
 func GeneratorForType(fileType string) (Generator, error) {
 	switch strings.ToLower(fileType) {
-	case typePng, typeJpg, typeJpeg:
+	case typePng, typeJpg, typeJpeg, typeGgs:
 		return SimpleGenerator{}, nil
 	case typeGif:
 		return GifGenerator{}, nil
-	case typeGgs:
-		return GgsGenerator{}, nil
 	default:
 		return nil, ErrNoEncoderForType
 	}