From a464a14deb7c3c70bf465c713bf4bc9951ae27f7 Mon Sep 17 00:00:00 2001
From: Pierre-Emmanuel Jacquier
 <15922119+pierre-emmanuelJ@users.noreply.github.com>
Date: Fri, 13 Dec 2019 09:59:12 +0100
Subject: [PATCH] Add marshall Function

---
 m3u.go      | 40 +++++++++++++++++++++++++++++++---
 m3u_test.go | 63 ++++++++++++++++++++++++++++++++++++++++++++++-------
 2 files changed, 92 insertions(+), 11 deletions(-)

diff --git a/m3u.go b/m3u.go
index 14ee9d1..e0eb5f0 100644
--- a/m3u.go
+++ b/m3u.go
@@ -2,7 +2,9 @@ package m3u
 
 import (
 	"bufio"
+	"bytes"
 	"errors"
+	"fmt"
 	"io"
 	"net/http"
 	"os"
@@ -18,7 +20,7 @@ type Playlist struct {
 
 // A Tag is a simple key/value pair
 type Tag struct {
-	Name string
+	Name  string
 	Value string
 }
 
@@ -40,7 +42,7 @@ func Parse(fileName string) (playlist Playlist, err error) {
 	} else {
 		f, err = os.Open(fileName)
 	}
-	
+
 	if err != nil {
 		err = errors.New("Unable to open playlist file")
 		return
@@ -50,7 +52,7 @@ func Parse(fileName string) (playlist Playlist, err error) {
 	onFirstLine := true
 	scanner := bufio.NewScanner(f)
 	tagsRegExp, _ := regexp.Compile("([a-zA-Z0-9-]+?)=\"([^\"]+)\"")
-	
+
 	for scanner.Scan() {
 		line := scanner.Text()
 		if onFirstLine && !strings.HasPrefix(line, "#EXTM3U") {
@@ -92,3 +94,35 @@ func Parse(fileName string) (playlist Playlist, err error) {
 
 	return playlist, nil
 }
+
+// Marshall Playlist to an m3u file.
+func Marshall(p Playlist) (io.Reader, error) {
+	buf := new(bytes.Buffer)
+	w := bufio.NewWriter(buf)
+	if err := MarshallInto(p, w); err != nil {
+		return nil, err
+	}
+
+	return buf, nil
+}
+
+// MarshallInto a *bufio.Writer a Playlist.
+func MarshallInto(p Playlist, into *bufio.Writer) error {
+	into.WriteString("#EXTM3U\n")
+	for _, track := range p.Tracks {
+		into.WriteString("#EXTINF:")
+		into.WriteString(fmt.Sprintf("%d ", track.Length))
+		for i := range track.Tags {
+			if i == len(track.Tags)-1 {
+				into.WriteString(fmt.Sprintf("%s=%q", track.Tags[i].Name, track.Tags[i].Value))
+				continue
+			}
+			into.WriteString(fmt.Sprintf("%s=%q ", track.Tags[i].Name, track.Tags[i].Value))
+		}
+		into.WriteString(", ")
+
+		into.WriteString(fmt.Sprintf("%s\n%s\n", track.Name, track.URI))
+	}
+
+	return into.Flush()
+}
diff --git a/m3u_test.go b/m3u_test.go
index c581240..0487bfc 100644
--- a/m3u_test.go
+++ b/m3u_test.go
@@ -1,7 +1,10 @@
 package m3u
 
 import (
+	"bytes"
 	"fmt"
+	"io/ioutil"
+	"os"
 	"testing"
 )
 
@@ -25,13 +28,13 @@ func TestPlaylist(t *testing.T) {
 			t.Fatalf("Expected track URI to be Track%d.mp4 but was '%s'", i+1, playlist.Tracks[i].URI)
 		}
 
-                if playlist.Tracks[i].Tags[0].Name != "group-title" {
+		if playlist.Tracks[i].Tags[0].Name != "group-title" {
 			t.Fatalf("Expected tag to be group-title but was '%s'", playlist.Tracks[i].Tags[0].Name)
-                }
+		}
 
-                if playlist.Tracks[i].Tags[0].Value != "Album1" {
+		if playlist.Tracks[i].Tags[0].Value != "Album1" {
 			t.Fatalf("Expected group-title tag value to be Album1 but was '%s'", playlist.Tracks[i].Tags[0].Value)
-                }
+		}
 	}
 }
 
@@ -55,13 +58,13 @@ func TestRemotePlaylist(t *testing.T) {
 			t.Fatalf("Expected track URI to be Track%d.mp4 but was '%s'", i+1, playlist.Tracks[i].URI)
 		}
 
-                if playlist.Tracks[i].Tags[0].Name != "group-title" {
+		if playlist.Tracks[i].Tags[0].Name != "group-title" {
 			t.Fatalf("Expected tag to be group-title but was '%s'", playlist.Tracks[i].Tags[0].Name)
-                }
+		}
 
-                if playlist.Tracks[i].Tags[0].Value != "Album1" {
+		if playlist.Tracks[i].Tags[0].Value != "Album1" {
 			t.Fatalf("Expected group-title tag value to be Album1 but was '%s'", playlist.Tracks[i].Tags[0].Value)
-                }
+		}
 	}
 }
 
@@ -92,3 +95,47 @@ func TestPlaylistMissingInf(t *testing.T) {
 		t.Fatalf("Expected parse error")
 	}
 }
+
+func TestMarshallPlaylist(t *testing.T) {
+	playlist, err := Parse("testdata/playlist.m3u")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	reader, err := Marshall(playlist)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	b := reader.(*bytes.Buffer)
+
+	ioutil.WriteFile("/tmp/test_m3u_marshalling.m3u", b.Bytes(), os.ModePerm)
+
+	playlist, _ = Parse("/tmp/test_m3u_marshalling.m3u")
+
+	if len(playlist.Tracks) != 5 {
+		t.Fatalf("Expected track count to be 5")
+	}
+
+	for i := 0; i < 5; i++ {
+		if playlist.Tracks[i].Length != i+1 {
+			t.Fatalf("Expected track Length to be %d but was %d", i+1, playlist.Tracks[i].Length)
+		}
+
+		if playlist.Tracks[i].Name != fmt.Sprintf("Track %d", i+1) {
+			t.Fatalf("Expected track name to be Track %d but was '%s'", i+1, playlist.Tracks[i].Name)
+		}
+
+		if playlist.Tracks[i].URI != fmt.Sprintf("Track%d.mp4", i+1) {
+			t.Fatalf("Expected track URI to be Track%d.mp4 but was '%s'", i+1, playlist.Tracks[i].URI)
+		}
+
+		if playlist.Tracks[i].Tags[0].Name != "group-title" {
+			t.Fatalf("Expected tag to be group-title but was '%s'", playlist.Tracks[i].Tags[0].Name)
+		}
+
+		if playlist.Tracks[i].Tags[0].Value != "Album1" {
+			t.Fatalf("Expected group-title tag value to be Album1 but was '%s'", playlist.Tracks[i].Tags[0].Value)
+		}
+	}
+}