support deleting items from queue (#76)

pkg/bot/bot.go

@@ -114,6 +114,7 @@ func (bot *MusicBot) registerCommands() {
 	bot.registerCommand(playCommand)
 	bot.registerCommand(currentCommand)
 	bot.registerCommand(queueCommand)
+	bot.registerCommand(queueDeleteCommand)
 	bot.registerCommand(flushCommand)
 	bot.registerCommand(shuffleCommand)
 	bot.registerCommand(whiteListCommand)

pkg/bot/commands.go

@@ -222,6 +222,32 @@ var queueCommand = Command{
 	},
 }
 
+var queueDeleteCommand = Command{
+	Name: "queue-delete",
+	Function: func(bot *MusicBot, message Message) {
+		words := strings.Fields(message.Message)
+		// !music queue-delete #
+		if len(words) <= 2 {
+			bot.ReplyToMessage(message, "No queue item provided")
+			return
+		}
+
+		queueItem, err := strconv.Atoi(words[2])
+		if err != nil {
+			bot.ReplyToMessage(message, "Invalid queue-item provided")
+			return
+		}
+
+		queue := bot.GetMusicPlayer().GetQueue()
+		if err = queue.Delete(queueItem); err != nil {
+			bot.ReplyToMessage(message, fmt.Sprintf("Could not delete queue-item: %s", err))
+			return
+		}
+
+		bot.ReplyToMessage(message, fmt.Sprintf("queue-item %d deleted", queueItem))
+	},
+}
+
 var flushCommand = Command{
 	Name: "flush",
 	Function: func(bot *MusicBot, message Message) {

pkg/music/queue.go

@@ -1,6 +1,7 @@
 package music
 
 import (
+	"fmt"
 	"log"
 	"math/rand"
 	"sync"
@@ -11,7 +12,8 @@ import (
 )
 
 const (
-	songAdded eventemitter.EventType = "song-added"
+	songAdded   eventemitter.EventType = "song-added"
+	songDeleted eventemitter.EventType = "song-deleted"
 )
 
 var (
@@ -35,6 +37,25 @@ func (queue *Queue) Append(songs ...Song) {
 	queue.EmitEvent(songAdded)
 }
 
+func (queue *Queue) Delete(item int) error {
+	queue.lock.Lock()
+	defer queue.lock.Unlock()
+
+	if item < 1 {
+		return fmt.Errorf("can not remove negative queue item %d", item)
+	}
+
+	if len(queue.songs)+1 < item {
+		return fmt.Errorf("queue-item %d is not in queue", item)
+	}
+
+	queue.songs = append(queue.songs[:item-1], queue.songs[item:]...)
+	log.Println("Song deleted from the queue")
+	queue.EmitEvent(songDeleted)
+
+	return nil
+}
+
 // GetNext returns the next item in the queue if it exists
 func (queue *Queue) GetNext() (Song, error) {
 	queue.lock.Lock()

pkg/music/queue_test.go

@@ -35,6 +35,60 @@ func TestQueue_Append(t *testing.T) {
 	assert.Equal(t, queue.songs[0], song)
 }
 
+func TestQueue_Delete(t *testing.T) {
+	t.Run("delete valid item", func(t *testing.T) {
+		t.Parallel()
+
+		// fill new queue
+		queue := NewQueue()
+
+		song1 := Song{Name: "banaan1"}
+		song2 := Song{Name: "banaan2"}
+		song3 := Song{Name: "banaan3"}
+
+		queue.Append(song1)
+		queue.Append(song2)
+		queue.Append(song3)
+
+		// remove middle queue song
+		err := queue.Delete(2)
+		if !assert.NoError(t, err) {
+			return
+		}
+
+		assert.Equal(t, 2, len(queue.songs))
+		assert.Equal(t, song1.Name, queue.songs[0].Name)
+		assert.Equal(t, song3.Name, queue.songs[1].Name)
+	})
+
+	t.Run("delete negative item", func(t *testing.T) {
+		t.Parallel()
+
+		queue := NewQueue()
+		err := queue.Delete(-1)
+
+		if assert.Error(t, err) {
+			assert.Equal(t, "can not remove negative queue item -1", err.Error())
+		}
+	})
+
+	t.Run("delete nonexisting item", func(t *testing.T) {
+		t.Parallel()
+
+		// fill new queue
+		queue := NewQueue()
+		queue.Append(Song{Name: "banaan1"})
+		queue.Append(Song{Name: "banaan2"})
+		queue.Append(Song{Name: "banaan3"})
+
+		err := queue.Delete(6)
+
+		if assert.Error(t, err) {
+			assert.Equal(t, "queue-item 6 is not in queue", err.Error())
+		}
+	})
+}
+
 func TestQueue_Flush(t *testing.T) {
 	t.Parallel()
 	queue := NewQueue()