Refactor into packages

internal/playlist/playlist.go

@@ -0,0 +1,72 @@
+package playlist
+
+import (
+	"segmento/internal/segment"
+	"time"
+)
+
+const DefaultPlaylistDuration = 20 * time.Second
+
+type Playlist interface {
+	// These could be moved to an interface?
+	Duration() time.Duration
+	TargetDuration() time.Duration
+	AddSegment(s *segment.Segment) error
+}
+
+type MediaPlaylist struct {
+	Segments []*segment.Segment
+}
+
+func NewMediaPlaylist() *MediaPlaylist {
+	return &MediaPlaylist{
+		Segments: make([]*segment.Segment, 0, 10),
+	}
+}
+
+func (p *MediaPlaylist) Duration() time.Duration {
+	return p.durationOf(p.Segments)
+}
+
+func (p *MediaPlaylist) TargetDuration() time.Duration {
+	return DefaultPlaylistDuration
+}
+
+func (p *MediaPlaylist) AddSegment(s *segment.Segment) error {
+	p.Segments = append(p.Segments, s)
+
+	if len(p.Segments) == 1 {
+		return nil
+	}
+
+	for {
+		if p.durationOf(p.Segments[1:]) > p.TargetDuration() {
+			p.Segments = p.Segments[1:]
+		}
+		break
+	}
+
+	return nil
+}
+
+func (p *MediaPlaylist) durationOf(ss []*segment.Segment) time.Duration {
+	var t time.Duration
+	for _, s := range ss {
+		t += s.Duration()
+	}
+	return t
+}
+
+func (p *MediaPlaylist) Run() error {
+	for {
+		// TODO block here and listen to the channel of incoming segments.
+		// As the reader is Read and segments are produced, update the Playlist
+		// struct and possibly notify consumers.
+		// What would actually be a useful API and/or Go best practices?
+	}
+}
+
+type PlaylistListener interface {
+	SegmentAdded(s *segment.Segment) error
+	SegmentRemoved(s *segment.Segment) error
+}

internal/playlist/playlist_test.go

@@ -0,0 +1,25 @@
+package playlist_test
+
+import (
+	"segmento/internal/playlist"
+	"segmento/internal/segment"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestMediaPlaylistImplements(t *testing.T) {
+	require.Implements(t, (*playlist.Playlist)(nil), playlist.NewMediaPlaylist())
+}
+
+func TestMediaPlaylist(t *testing.T) {
+	playlist := playlist.NewMediaPlaylist()
+
+	for i := 0; i < 8; i++ {
+		s := segment.NewSegment(10*time.Second, 0)
+		s.IncrementDuration(3 * time.Second)
+		playlist.AddSegment(s)
+	}
+	require.Equal(t, 21*time.Second, playlist.Duration())
+}

internal/segment/segment.go

@@ -0,0 +1,109 @@
+package segment
+
+import (
+	"bytes"
+	"io"
+	"log"
+	"time"
+
+	"github.com/tcolgate/mp3"
+)
+
+const DefaultTargetDuration = 3 * time.Second
+
+type Segment struct {
+	targetDuration time.Duration
+	duration       time.Duration
+	data           *bytes.Buffer
+}
+
+// Initialize a new Segment struct. The capacity is the initial maximum capacity of the internal
+// buffer, in bytes. It should be initialized with a value greater than the expected maximum buffer size,
+// depending on the implementation.
+func NewSegment(targetDuration time.Duration, capacity int) *Segment {
+	return &Segment{
+		data:           bytes.NewBuffer(make([]byte, 0, capacity)),
+		duration:       0,
+		targetDuration: targetDuration,
+	}
+}
+
+func (s *Segment) ReadFrom(r io.Reader) (n int64, err error) {
+	return s.data.ReadFrom(r)
+}
+
+func (s *Segment) IncrementDuration(d time.Duration) time.Duration {
+	s.duration += d
+	return s.duration
+}
+
+func (s *Segment) CanWrite(d time.Duration) bool {
+	return s.targetDuration-s.duration >= d
+}
+
+func (s *Segment) Duration() time.Duration {
+	return s.duration
+}
+
+func (s *Segment) Len() int {
+	return s.data.Len()
+}
+
+type MP3HTTPSegmenter struct {
+	decoder *mp3.Decoder
+}
+
+func (s *MP3HTTPSegmenter) Segment(r io.Reader) (chan *Segment, error) {
+	c := make(chan *Segment)
+
+	go func() {
+		d := mp3.NewDecoder(r)
+
+		var (
+			v       mp3.Frame
+			skipped int
+		)
+
+		var (
+			s *Segment
+		)
+
+		for {
+			if err := d.Decode(&v, &skipped); err != nil {
+				if err == io.EOF {
+					break
+				}
+				log.Fatal(err)
+			}
+
+			if s != nil && !s.CanWrite(v.Duration()) {
+				// publish the current segment, and initialize a new one.
+				c <- s
+				s = nil
+			}
+
+			if s == nil {
+				// TODO what is a good initial capacity?
+				s = NewSegment(DefaultTargetDuration, 1024)
+			}
+
+			n, err := s.ReadFrom(v.Reader())
+			if err != nil {
+				log.Fatal(err) // TODO: some proper error handling
+			}
+
+			if n != int64(v.Size()) {
+				// TODO would this ever happen? What should IncrementDuration be called with?
+				log.Fatal("unexpeced frame size, want = ", v.Size(), "got = ", n)
+			}
+
+			s.IncrementDuration(v.Duration())
+		}
+	}()
+
+	return c, nil
+}
+
+func NewMP3HTTPSegmenter() *MP3HTTPSegmenter {
+	return &MP3HTTPSegmenter{}
+}

internal/segment/segment_test.go

@@ -1,14 +1,16 @@
-package main
+package segment_test
 
 import (
 	"testing"
 	"time"
 
+	"segmento/internal/segment"
+
 	"github.com/stretchr/testify/require"
 )
 
 func TestSegment(t *testing.T) {
-	segment := newSegment(10*time.Second, 0)
+	segment := segment.NewSegment(10*time.Second, 0)
 
 	require.Equal(t, time.Duration(0), segment.Duration())
 	require.True(t, segment.CanWrite(9*time.Second))
@@ -20,18 +22,3 @@ func TestSegment(t *testing.T) {
 	require.Equal(t, 10*time.Second, segment.Duration())
 	require.False(t, segment.CanWrite(1*time.Millisecond))
 }
-
-func TestMediaPlaylistImplements(t *testing.T) {
-	require.Implements(t, (*Playlist)(nil), newMediaPlaylist())
-}
-
-func TestMediaPlaylist(t *testing.T) {
-	playlist := newMediaPlaylist()
-
-	for i := 0; i < 8; i++ {
-		s := newSegment(10*time.Second, 0)
-		s.IncrementDuration(3 * time.Second)
-		playlist.AddSegment(s)
-	}
-	require.Equal(t, 21*time.Second, playlist.Duration())
-}

main.go

@@ -1,181 +1,15 @@
 package main
 
 import (
-	"bytes"
 	"flag"
-	"io"
 	"log"
 	"net/http"
 	"os"
 	"time"
 
-	"github.com/tcolgate/mp3"
+	"segmento/internal/segment"
 )
 
-const DefaultTargetDuration = 3 * time.Second
-const DefaultPlaylistDuration = 20 * time.Second
-
-type Segment struct {
-	targetDuration time.Duration
-	duration       time.Duration
-	data           *bytes.Buffer
-}
-
-// Initialize a new Segment struct. The capacity is the initial maximum capacity of the internal
-// buffer, in bytes. It should be initialized with a value greater than the expected maximum buffer size,
-// depending on the implementation.
-func newSegment(targetDuration time.Duration, capacity int) *Segment {
-	return &Segment{
-		data:           bytes.NewBuffer(make([]byte, 0, capacity)),
-		duration:       0,
-		targetDuration: targetDuration,
-	}
-}
-
-func (s *Segment) ReadFrom(r io.Reader) (n int64, err error) {
-	return s.data.ReadFrom(r)
-}
-
-func (s *Segment) IncrementDuration(d time.Duration) time.Duration {
-	s.duration += d
-	return s.duration
-}
-
-func (s *Segment) CanWrite(d time.Duration) bool {
-	return s.targetDuration-s.duration >= d
-}
-
-func (s *Segment) Duration() time.Duration {
-	return s.duration
-}
-
-func (s *Segment) Len() int {
-	return s.data.Len()
-}
-
-type MP3HTTPSegmenter struct {
-	decoder *mp3.Decoder
-}
-
-func (s *MP3HTTPSegmenter) Segment(r io.Reader) (chan *Segment, error) {
-	c := make(chan *Segment)
-
-	go func() {
-		d := mp3.NewDecoder(r)
-
-		var (
-			v       mp3.Frame
-			skipped int
-		)
-
-		var (
-			s *Segment
-		)
-
-		for {
-			if err := d.Decode(&v, &skipped); err != nil {
-				if err == io.EOF {
-					break
-				}
-				log.Fatal(err)
-			}
-
-			if s != nil && !s.CanWrite(v.Duration()) {
-				// publish the current segment, and initialize a new one.
-				c <- s
-				s = nil
-			}
-
-			if s == nil {
-				// TODO what is a good initial capacity?
-				s = newSegment(DefaultTargetDuration, 1024)
-			}
-
-			n, err := s.ReadFrom(v.Reader())
-			if err != nil {
-				log.Fatal(err) // TODO: some proper error handling
-			}
-
-			if n != int64(v.Size()) {
-				// TODO would this ever happen? What should IncrementDuration be called with?
-				log.Fatal("unexpeced frame size, want = ", v.Size(), "got = ", n)
-			}
-
-			s.IncrementDuration(v.Duration())
-		}
-	}()
-
-	return c, nil
-}
-
-func newMP3HTTPSegmenter() *MP3HTTPSegmenter {
-	return &MP3HTTPSegmenter{}
-}
-
-type Playlist interface {
-	// These could be moved to an interface?
-	Duration() time.Duration
-	TargetDuration() time.Duration
-	AddSegment(s *Segment) error
-}
-
-type MediaPlaylist struct {
-	Segments []*Segment
-}
-
-func newMediaPlaylist() *MediaPlaylist {
-	return &MediaPlaylist{
-		Segments: make([]*Segment, 0, 10),
-	}
-}
-
-func (p *MediaPlaylist) Duration() time.Duration {
-	return p.durationOf(p.Segments)
-}
-
-func (p *MediaPlaylist) TargetDuration() time.Duration {
-	return DefaultPlaylistDuration
-}
-
-func (p *MediaPlaylist) AddSegment(s *Segment) error {
-	p.Segments = append(p.Segments, s)
-
-	if len(p.Segments) == 1 {
-		return nil
-	}
-
-	for {
-		if p.durationOf(p.Segments[1:]) > p.TargetDuration() {
-			p.Segments = p.Segments[1:]
-		}
-		break
-	}
-
-	return nil
-}
-
-func (p *MediaPlaylist) durationOf(ss []*Segment) time.Duration {
-	var t time.Duration
-	for _, s := range ss {
-		t += s.Duration()
-	}
-	return t
-}
-
-func (p *MediaPlaylist) Run() error {
-	for {
-		// TODO block here and listen to the channel of incoming segments.
-		// As the reader is Read and segments are produced, update the Playlist
-		// struct and possibly notify consumers.
-		// What would actually be a useful API and/or Go best practices?
-	}
-}
-
-type PlaylistListener interface {
-	SegmentAdded(s *Segment) error
-	SegmentRemoved(s *Segment) error
-}
-
 func main() {
 	// TODO accept some flags with:
 	// URL - source of stream
@@ -204,7 +38,7 @@ func main() {
 
 	defer resp.Body.Close()
 
-	segmenter := newMP3HTTPSegmenter()
+	segmenter := segment.NewMP3HTTPSegmenter()
 	segments, err := segmenter.Segment(resp.Body)
 	if err != nil {
 		log.Fatal(err)