Introduced engine.Scrobbler

Also refactored mocks into their original packages, to avoid cyclic references. Is there a better way to have mocks in GoLang tests?

persistence/mock_mediafile_repo.go

@@ -0,0 +1,67 @@
+package persistence
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+
+	"github.com/deluan/gosonic/domain"
+)
+
+func CreateMockMediaFileRepo() *MockMediaFile {
+	return &MockMediaFile{}
+}
+
+type MockMediaFile struct {
+	domain.MediaFileRepository
+	data map[string]*domain.MediaFile
+	err  bool
+}
+
+func (m *MockMediaFile) SetError(err bool) {
+	m.err = err
+}
+
+func (m *MockMediaFile) SetData(j string, size int) {
+	m.data = make(map[string]*domain.MediaFile)
+	var l = make(domain.MediaFiles, size)
+	err := json.Unmarshal([]byte(j), &l)
+	if err != nil {
+		fmt.Println("ERROR: ", err)
+	}
+	for _, a := range l {
+		m.data[a.Id] = &a
+	}
+}
+
+func (m *MockMediaFile) Exists(id string) (bool, error) {
+	if m.err {
+		return false, errors.New("Error!")
+	}
+	_, found := m.data[id]
+	return found, nil
+}
+
+func (m *MockMediaFile) Get(id string) (*domain.MediaFile, error) {
+	if m.err {
+		return nil, errors.New("Error!")
+	}
+	mf := m.data[id]
+	return mf, nil
+}
+
+func (m *MockMediaFile) FindByAlbum(artistId string) (*domain.MediaFiles, error) {
+	if m.err {
+		return nil, errors.New("Error!")
+	}
+	var res = make(domain.MediaFiles, len(m.data))
+	i := 0
+	for _, a := range m.data {
+		if a.AlbumId == artistId {
+			res[i] = *a
+			i++
+		}
+	}
+
+	return &res, nil
+}