1 $ tree
 2 .
 3 ├── mplayer.go
 4 └── src
 5     ├── mlib
 6     │   ├── manager.go
 7     │   └── manager_test.go
 8     └── mp
 9         ├── mp3.go
10         └── play.go

 1 package library
 2 
 3 import "errors"
 4 
 5 type MusicEntry struct {
 6     Id        string
 7     Name    string
 8     Artist    string
 9     Genre    string
10     Source    string
11     Type    string
12 }
13 
14 type MusicManager struct {
15     musics []MusicEntry
16 }
17 
18 func NewMusicManager() * MusicManager {
19     return &MusicManager {make( []MusicEntry, 0)}
20 }
21 
22 func (m * MusicManager) Len() int {
23     return len(m.musics);
24 }
25 
26 func (m* MusicManager ) Get(index int) (music * MusicEntry, err error) {
27     if index < 0 || index >= len(m.musics) {
28         return nil, errors.New("Index out of range.")
29     }
30 
31     return &m.musics[index], nil
32 }
33 
34 func (m * MusicManager) Find (name string) * MusicEntry {
35     if len(m.musics) == 0 {
36         return nil
37     }
38 
39     for _,m := range m.musics {
40         if m.Name == name {
41             return &m
42         }
43     }
44     return nil
45 }
46 
47 func (m * MusicManager) Add (music * MusicEntry) {
48     m.musics = append(m.musics, * music)
49 }
50 
51 func (m * MusicManager) Remove (index int) * MusicEntry {
52     if index < 0 || index >= len(m.musics) {
53         return nil
54     }
55     removedMusic := &m.musics[index]
56 
57     if index < len(m.musics) - 1 {
58         m.musics = append(m.musics[:index - 1], m.musics[index + 1:]...)
59     }else if index == 0 {
60         m.musics = make([]MusicEntry, 0)
61     } else {
62         m.musics = m.musics[:index - 1]
63     }
64 
65     return removedMusic
66 }
67 
68 func (m * MusicManager) RemoveByName (name string) * MusicEntry {
69     var removedMusic * MusicEntry = nil
70     var iPos int = -1
71     for i := 0; i < m.Len(); i++ {
72         if m.musics[i].Name == name {
73             iPos = i
74             break
75         }
76     }
77 
78     if iPos < 0 {
79         return nil
80     }
81 
82     removedMusic = m.Remove(iPos)
83 
84     return removedMusic
85 }

 1 package library
 2 
 3 import (
 4     "testing"
 5 )
 6 
 7 func TestOps(t * testing.T) {
 8     mm := NewMusicManager()
 9     if mm == nil {
10         t.Error("NewMusicManager faild.");
11     }
12     if mm.Len() != 0 {
13         t.Error("NewMusicManager faild, not empty")
14     }
15     m0 := &MusicEntry { "1", "My Heart Will Go On", "Celion Dion", "Pop", "http://qbox.me/24501234", "MP3" }
16     mm.Add(m0)
17 
18     if mm.Len() != 1 {
19         t.Error("MusicManager.Add faild.")
20     }
21 
22     m := mm.Find(m0.Name)
23     if m == nil {
24         t.Error("MusicManager.Find faild")
25     }
26 
27     if    m.Id != m0.Id ||
28         m.Name != m0.Name ||
29         m.Artist != m0.Artist ||
30         m.Genre != m0.Genre ||
31         m.Source != m0.Source ||
32         m.Type != m0.Type {
33             t.Error("MusicManager.Find() faild. Found item mismatch.")
34     }
35 
36     m, err := mm.Get(0)
37     if m == nil {
38         t.Error("MusicManager.Get() faild.", err)
39     }
40 
41     m = mm.Remove(0)
42     if m == nil || mm.Len() != 0 {
43         t.Error("MusicManager.Remove() faild.", err)
44     }
45 }

 1 package mp
 2 
 3 import (
 4     "fmt"
 5     "time"
 6 )
 7 
 8 type MP3Player struct {
 9     stat int
10     progress int
11 }
12 
13 type WAVPlayer struct {
14     stat int
15     progress int
16 }
17 
18 func (p * MP3Player) Play (source string) {
19     fmt.Println("Playing MP3 music", source)
20 
21     p.progress = 0
22 
23     for p.progress < 100 {
24         time.Sleep(100 * time.Millisecond)
25         fmt.Print(".")
26         p.progress += 10
27     }
28     fmt.Println("\nFinished playing", source)
29 }
30 
31 func (p * WAVPlayer) Play (source string) {
32     fmt.Println("Playing WAV music", source)
33 
34     p.progress = 0
35 
36     for p.progress < 100 {
37         time.Sleep(100 * time.Millisecond)
38         fmt.Print(".")
39         p.progress += 10
40     }
41     fmt.Println("\nFinished playing", source)
42 }

 1 package mp
 2 
 3 import "fmt"
 4 
 5 type Player interface {
 6     Play(source string)
 7 }
 8 
 9 func Play(source, mtype string) {
10     var p Player
11 
12     switch mtype {
13     case "MP3" :
14         p = &MP3Player{}
15     case "WAV" :
16         p = &WAVPlayer{}
17         default :
18         fmt.Println("Unsupported music type", mtype)
19         return
20     }
21     p.Play(source)
22 }

 1 package main
 2 
 3 import (
 4     "bufio"
 5     "fmt"
 6     "os"
 7     "strconv"
 8     "strings"
 9 
10     "mlib"
11     "mp"
12 )
13 
14 var lib * library.MusicManager
15 var id int = 1
16 var ctrl, signal chan int
17 
18 func handleLibCommands(tokens []string) {
19     switch tokens[1] {
20     case "list" :
21         for i := 0; i < lib.Len(); i++ {
22             e, _ := lib.Get(i)
23             fmt.Println(i + 1, ":", e.Name, e.Artist, e.Source, e.Type)
24         }
25     case "add" :
26         if len(tokens) == 7 {
27             id++
28             lib.Add(&library.MusicEntry { strconv.Itoa(id), tokens[2], tokens[3], tokens[4], tokens[5], tokens[6] })
29         } else {
30             fmt.Println("USAGE : lib add <name><artist><genre><source><type> (7 argv)")
31         }
32     case "remove" :
33         if len(tokens) == 3 {
34             lib.RemoveByName(tokens[2])
35         } else {
36             fmt.Println("USAGE: lib remove <name>")
37         }
38         default :
39         fmt.Println("Unrecogized lib command: ", tokens[1])
40     }
41 }
42 
43 func handlePlayCommands(tokens []string) {
44     if len(tokens) != 2 {
45         fmt.Println("USAGE : play <name>")
46         return
47     }
48 
49     e := lib.Find(tokens[1])
50     if e == nil {
51         fmt.Println("The music", tokens[1], "does not exist.")
52         return
53     }
54 
55     mp.Play(e.Source, e.Type)
56 }
57 
58 func main() {
59     fmt.Println(`
60     Enter following commands to control the player:
61     lib list --View the existing music lib
62     lib add <name><artist><genre><source><type> -- Add a music to the music lib
63     lib remove <name> --Remove the specified music from the lib
64     play <name> -- Play the specified music
65     `)
66     lib = library.NewMusicManager()
67 
68     r := bufio.NewReader(os.Stdin)
69 
70     for i := 0; i <= 100; i++ {
71         fmt.Print("Enter command-> ")
72         rawLine, _, _ := r.ReadLine()
73 
74         line := string(rawLine)
75         if line == "q" || line == "e" {
76             break
77         }
78         tokens := strings.Split(line, " ")
79 
80         if tokens[0] == "lib" {
81             handleLibCommands(tokens)
82         } else if tokens[0] == "play" {
83             handlePlayCommands(tokens)
84         } else {
85             fmt.Println("Unrecognized command :", tokens[0])
86         }
87     }
88 }

$ export GOPATH="/home/normal/musicplayer"

1 $ go build

 1 .
 2 ├── mplayer.go
 3 ├── musicplayer
 4 └── src
 5     ├── mlib
 6     │   ├── manager.go
 7     │   └── manager_test.go
 8     └── mp
 9         ├── mp3.go
10         └── play.go

$ ./musicplayer 

    Enter following commands to control the player:
    lib list --View the existing music lib
    lib add <name><artist><genre><source><type> -- Add a music to the music lib
    lib remove <name> --Remove the specified music from the lib
    play <name> -- Play the specified music
    
Enter command-> lib add a b c d e
Enter command-> lib list
1 : a b d e
Enter command-> play a
Unsupported music type e
Enter command-> lib remove a
Enter command-> lib add a b c d e MP3
USAGE : lib add <name><artist><genre><source><type> (7 argv)
Enter command-> lib add a b c d MP3
Enter command-> lib list
1 : a b d MP3
Enter command-> play a
Playing MP3 music d
..........
Finished playing d
Enter command-> q