Write only db

pkg/persistence/interface.go

@@ -42,6 +42,35 @@ type Database interface {
 	GetStatistics(from string, n uint) (*Statistics, error)
 }
 
+//implements only a subset (the read functions) of Database
+type WriteOnlyDatabase struct{kind databaseEngine}
+func (wod *WriteOnlyDatabase) WriteOnlyError() error{
+	return errors.New(`This dummy storage engine ("`+wod.kind.String()+`") is write-only`)
+}
+func (wod *WriteOnlyDatabase) GetTorrent(infoHash []byte) (*TorrentMetadata, error) {
+	return nil, wod.WriteOnlyError()
+}
+func (wod *WriteOnlyDatabase) GetFiles(infoHash []byte) ([]File, error) {
+	return nil, wod.WriteOnlyError()
+}
+func (wod *WriteOnlyDatabase) GetStatistics(from string, n uint) (*Statistics, error) {
+	return nil, wod.WriteOnlyError()
+}
+func (wod *WriteOnlyDatabase) GetNumberOfTorrents() (uint, error) {
+	return 0, wod.WriteOnlyError()
+}
+func (wod *WriteOnlyDatabase) QueryTorrents(
+	query string,
+	epoch int64,
+	orderBy OrderingCriteria,
+	ascending bool,
+	limit uint,
+	lastOrderedValue *float64,
+	lastID *uint64,
+) ([]TorrentMetadata, error) {
+	return nil, wod.WriteOnlyError()
+}
+
 type OrderingCriteria uint8
 
 const (
@@ -57,10 +86,18 @@ const (
 // TODO: search `swtich (orderBy)` and see if all cases are covered all the time
 
 type databaseEngine uint8
+func( dbe databaseEngine) String() string{
+	switch dbe{
+	case Sqlite3:{return "Sqlite3"}
+	case Stdout:{return "Stdout"}
+	default:
+		return "unnamed"
+	}
+}
 
 const (
-	Sqlite3 databaseEngine = 1
-	Stdout
+	Sqlite3    databaseEngine = 1
+	Stdout     databaseEngine = 3
 )
 
 type Statistics struct {
@@ -88,6 +125,12 @@ type TorrentMetadata struct {
 	Relevance    float64 `json:"relevance"`
 }
 
+type SimpleTorrentSummary struct {
+	InfoHash string `json:"infoHash"`
+	Name     string `json:"name"`
+	Files    []File `json:"files"`
+}
+
 func (tm *TorrentMetadata) MarshalJSON() ([]byte, error) {
 	type Alias TorrentMetadata
 	return json.Marshal(&struct {

pkg/persistence/stdout.go

@@ -9,26 +9,20 @@ import (
 	"github.com/pkg/errors"
 )
 
-type out struct {
-	InfoHash string `json:"infoHash"`
-	Name     string `json:"name"`
-	Files    []File `json:"files"`
-}
-
-var notSupportedError = errors.New("This dummy database engine (\"stdout\") does not support any sort of queries")
-
 func makeStdoutDatabase(_ *url.URL) (Database, error) {
 	s := new(stdout)
 	s.encoder = json.NewEncoder(os.Stdout)
 	return s, nil
 }
 
 type stdout struct {
+	WriteOnlyDatabase
 	encoder *json.Encoder
 }
 
 func (s *stdout) Engine() databaseEngine {
-	return Stdout
+	s.kind = Stdout
+	return s.kind
 }
 
 func (s *stdout) DoesTorrentExist(infoHash []byte) (bool, error) {
@@ -41,7 +35,7 @@ func (s *stdout) DoesTorrentExist(infoHash []byte) (bool, error) {
 }
 
 func (s *stdout) AddNewTorrent(infoHash []byte, name string, files []File) error {
-	err := s.encoder.Encode(out{
+	err := s.encoder.Encode(SimpleTorrentSummary{
 		InfoHash: hex.EncodeToString(infoHash),
 		Name:     name,
 		Files:    files,
@@ -55,32 +49,4 @@ func (s *stdout) AddNewTorrent(infoHash []byte, name string, files []File) error
 
 func (s *stdout) Close() error {
 	return os.Stdout.Sync()
-}
-
-func (s *stdout) GetNumberOfTorrents() (uint, error) {
-	return 0, notSupportedError
-}
-
-func (s *stdout) QueryTorrents(
-	query string,
-	epoch int64,
-	orderBy OrderingCriteria,
-	ascending bool,
-	limit uint,
-	lastOrderedValue *float64,
-	lastID *uint64,
-) ([]TorrentMetadata, error) {
-	return nil, notSupportedError
-}
-
-func (s *stdout) GetTorrent(infoHash []byte) (*TorrentMetadata, error) {
-	return nil, notSupportedError
-}
-
-func (s *stdout) GetFiles(infoHash []byte) ([]File, error) {
-	return nil, notSupportedError
-}
-
-func (s *stdout) GetStatistics(from string, n uint) (*Statistics, error) {
-	return nil, notSupportedError
-}
+}