Work on BagReader interface

constants/constants.go

@@ -7,8 +7,10 @@ const (
 	AlgSha512                 = "sha512"
 	BagItProfileBTR           = "btr-v1.0.json"
 	BagItProfileDefault       = "aptrust-v2.2.json"
-	BagWriterTypeTar          = "tar"
+	BagReaderTypeFileSystem   = "filesystem"
+	BagReaderTypeTar          = "tar"
 	BagWriterTypeFileSystem   = "filesystem"
+	BagWriterTypeTar          = "tar"
 	BTRProfileIdentifier      = "https://github.com/dpscollaborative/btr_bagit_profile/releases/download/1.0/btr-bagit-profile.json"
 	DefaultProfileIdentifier  = "https://raw.githubusercontent.com/APTrust/preservation-services/master/profiles/aptrust-v2.2.json"
 	EmptyProfileIdentifier    = "https://raw.githubusercontent.com/APTrust/dart/tree/master/profiles/empty_profile.json"
@@ -112,6 +114,15 @@ var BagWriterTypeFor = map[string]string{
 	SerialFormatTar:  BagWriterTypeTar,
 }
 
+// BagReaderTypeFor maps a BagIt serialization format to the
+// type of reader that can write that format.
+var BagReaderTypeFor = map[string]string{
+	"":               BagReaderTypeFileSystem,
+	".tar":           BagReaderTypeTar,
+	SerialFormatNone: BagReaderTypeFileSystem,
+	SerialFormatTar:  BagReaderTypeTar,
+}
+
 var SerializationOptions = []string{
 	SerializationForbidden,
 	SerializationOptional,

core/bag_reader.go

@@ -1,5 +1,7 @@
 package core
 
+import "github.com/APTrust/dart-runner/constants"
+
 // BagReader describes the interface that bag readers must implement,
 // whether reading from a file system, tar file, zip file, etc.
 type BagReader interface {
@@ -21,3 +23,17 @@ type BagReader interface {
 	// Close closes the underlying reader.
 	Close()
 }
+
+// GetBagReader returns a bag writer of the specified type.
+// Valid types include constants.BagWriterTypeFileSystem and
+// constants.BagWriterTypeTar.
+func GetBagReader(readerType string, validator *Validator) (BagReader, error) {
+	switch readerType {
+	case constants.BagReaderTypeFileSystem:
+		return NewFileSystemBagReader(validator)
+	case constants.BagWriterTypeTar:
+		return NewTarredBagReader(validator)
+	default:
+		return nil, constants.ErrUnknownType
+	}
+}

core/bag_reader_test.go

@@ -0,0 +1,42 @@
+package core_test
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/APTrust/dart-runner/constants"
+	"github.com/APTrust/dart-runner/core"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestGetBagReader(t *testing.T) {
+	pathToBag := filepath.Join(os.TempDir(), "testbag.tar")
+	_, err := os.Create(pathToBag)
+	defer os.Remove(pathToBag)
+	require.NoError(t, err)
+
+	profile := loadProfile(t, "aptrust-v2.2.json")
+	validator, err := core.NewValidator(pathToBag, profile)
+	require.Nil(t, err)
+
+	// This should get us a file system bag reader
+	fsReader, err := core.GetBagReader(constants.BagWriterTypeFileSystem, validator)
+	require.NoError(t, err)
+	require.NotNil(t, fsReader)
+	_, ok := fsReader.(*core.FileSystemBagReader)
+	assert.True(t, ok)
+
+	// And this should get us a tarred bag writer
+	tarReader, err := core.GetBagReader(constants.BagReaderTypeTar, validator)
+	require.NoError(t, err)
+	require.NotNil(t, fsReader)
+	_, ok = tarReader.(*core.TarredBagReader)
+	assert.True(t, ok)
+
+	// And this should get us an error
+	noWriter, err := core.GetBagWriter("bad type", filepath.Join(os.TempDir(), "test.tar"), []string{})
+	require.Error(t, err)
+	require.Nil(t, noWriter)
+}

core/file_system_bag_reader.go

@@ -4,3 +4,25 @@ package core
 
 // TODO: Define bag reader interface, similar to bag writer interface.
 //       Then implement this so it's interchangeable with TarredBagReader.
+
+type FileSystemBagReader struct {
+	validator *Validator
+}
+
+func NewFileSystemBagReader(validator *Validator) (*FileSystemBagReader, error) {
+	return &FileSystemBagReader{
+		validator: validator,
+	}, nil
+}
+
+func (reader *FileSystemBagReader) ScanMetadata() error {
+	return nil
+}
+
+func (reader *FileSystemBagReader) ScanPayload() error {
+	return nil
+}
+
+func (reader *FileSystemBagReader) Close() {
+	// No op?
+}