From eb79cecc44628d3e24b2196e1d680f2b1ba15f97 Mon Sep 17 00:00:00 2001
From: sentriz <senan@senan.xyz>
Date: Tue, 2 Jan 2024 23:06:32 +0000
Subject: [PATCH] fix(scanner): gracefully handle multi value tag delim splits
 with adjacent delimiters

closes #448

Co-authored-by: Chris Hayes <chayes@interrobang.sh>
---
 scanner/scanner.go                     | 18 +++++++++++-------
 scanner/scanner_test.go                | 16 ++++++++++++++++
 server/ctrlsubsonic/handlers_common.go |  6 +++++-
 3 files changed, 32 insertions(+), 8 deletions(-)

diff --git a/scanner/scanner.go b/scanner/scanner.go
index 7296a5ed..aefa4c11 100644
--- a/scanner/scanner.go
+++ b/scanner/scanner.go
@@ -9,6 +9,7 @@ import (
 	"os"
 	"path/filepath"
 	"regexp"
+	"slices"
 	"sort"
 	"strconv"
 	"strings"
@@ -319,7 +320,7 @@ func (s *Scanner) populateTrackAndArtists(tx *db.DB, st *State, i int, album *db
 		return fmt.Errorf("%w: %w", err, ErrReadingTags)
 	}
 
-	genreNames := parseMulti(trags, s.multiValueSettings[Genre], tagcommon.MustGenres, tagcommon.MustGenre)
+	genreNames := ParseMulti(s.multiValueSettings[Genre], tagcommon.MustGenres(trags), tagcommon.MustGenre(trags))
 	genreIDs, err := populateGenres(tx, genreNames)
 	if err != nil {
 		return fmt.Errorf("populate genres: %w", err)
@@ -331,7 +332,7 @@ func (s *Scanner) populateTrackAndArtists(tx *db.DB, st *State, i int, album *db
 			return fmt.Errorf("delete artist appearances: %w", err)
 		}
 
-		albumArtistNames := parseMulti(trags, s.multiValueSettings[AlbumArtist], tagcommon.MustAlbumArtists, tagcommon.MustAlbumArtist)
+		albumArtistNames := ParseMulti(s.multiValueSettings[AlbumArtist], tagcommon.MustAlbumArtists(trags), tagcommon.MustAlbumArtist(trags))
 		var albumArtistIDs []int
 		for _, albumArtistName := range albumArtistNames {
 			albumArtist, err := populateArtist(tx, albumArtistName)
@@ -364,7 +365,7 @@ func (s *Scanner) populateTrackAndArtists(tx *db.DB, st *State, i int, album *db
 		return fmt.Errorf("populate track genres: %w", err)
 	}
 
-	trackArtistNames := parseMulti(trags, s.multiValueSettings[Artist], tagcommon.MustArtists, tagcommon.MustArtist)
+	trackArtistNames := ParseMulti(s.multiValueSettings[Artist], tagcommon.MustArtists(trags), tagcommon.MustArtist(trags))
 	var trackArtistIDs []int
 	for _, trackArtistName := range trackArtistNames {
 		trackArtist, err := populateArtist(tx, trackArtistName)
@@ -704,19 +705,22 @@ type MultiValueSetting struct {
 	Delim string
 }
 
-func parseMulti(parser tagcommon.Info, setting MultiValueSetting, getMulti func(tagcommon.Info) []string, get func(tagcommon.Info) string) []string {
+func ParseMulti(setting MultiValueSetting, values []string, value string) []string {
 	var parts []string
 	switch setting.Mode {
 	case Multi:
-		parts = getMulti(parser)
+		parts = values
 	case Delim:
-		parts = strings.Split(get(parser), setting.Delim)
+		parts = strings.Split(value, setting.Delim)
 	default:
-		parts = []string{get(parser)}
+		parts = []string{value}
 	}
 	for i := range parts {
 		parts[i] = strings.TrimSpace(parts[i])
 	}
+	parts = slices.DeleteFunc(parts, func(s string) bool {
+		return s == ""
+	})
 	return parts
 }
 
diff --git a/scanner/scanner_test.go b/scanner/scanner_test.go
index c2b281bc..77f4b1c6 100644
--- a/scanner/scanner_test.go
+++ b/scanner/scanner_test.go
@@ -810,3 +810,19 @@ func TestPrefixOverlap(t *testing.T) {
 	require.NoError(t, m.DB().Model(db.Album{}).Where("root_dir LIKE ?", `%/tagged`).Count(&tagged).Error)
 	require.Greater(t, tagged, 1)
 }
+
+// https://github.com/sentriz/gonic/pull/448
+func TestParseMultiDoubleDelim(t *testing.T) {
+	t.Parallel()
+
+	setting := scanner.MultiValueSetting{
+		Mode:  scanner.Delim,
+		Delim: `/`,
+	}
+
+	values := scanner.ParseMulti(setting, nil, `DON'T//BE//⚜⚜⚜`)
+	require.Len(t, values, 3)
+	require.Equal(t, `DON'T`, values[0])
+	require.Equal(t, `BE`, values[1])
+	require.Equal(t, `⚜⚜⚜`, values[2])
+}
diff --git a/server/ctrlsubsonic/handlers_common.go b/server/ctrlsubsonic/handlers_common.go
index ca9adb65..ac1ef70b 100644
--- a/server/ctrlsubsonic/handlers_common.go
+++ b/server/ctrlsubsonic/handlers_common.go
@@ -518,7 +518,11 @@ func getMusicFolder(musicPaths []MusicPath, p params.Params) string {
 }
 
 func lowerUDecOrHash(in string) string {
-	lower := unicode.ToLower(rune(in[0]))
+	inRunes := []rune(in)
+	if len(inRunes) == 0 {
+		return ""
+	}
+	lower := unicode.ToLower(inRunes[0])
 	if !unicode.IsLetter(lower) {
 		return "#"
 	}