Accept collaborative parameter for CreatePlaylistForUser (#158)

* Accept collaborative parameter for CreatePlaylistForUser

The collaborative parameter is optional in the Spotify Web API, and was
not supported in this library. I add the parameter to directly to the
CreatePlaylistForUser function, though a case could be made for writing
a separate function in order to avoid breaking existing calls.

Note that I do not check for the relationship between public and
collaborative in the body of the function, instead I let the Web API
return an error.

I added two tests for the private/public-collaborative permutations in
order to demonstrate the intended usage of the fields.

* Break out CreateCollaborativePlaylistForUser

In order to avoid breaking users of V1 CreatePlaylistForUser, we create
a separate function specific to creating collaborative playlists and
undo the changes to CreatePlaylistForUser.

* Remove unnecessary comment

Author: samuelrey

playlist.go

@@ -309,6 +309,8 @@ func (c *Client) GetPlaylistTracksOpt(playlistID ID,
 // creating a private playlist requires ScopePlaylistModifyPrivate.
 //
 // On success, the newly created playlist is returned.
+// TODO Accept a collaborative parameter and delete
+// CreateCollaborativePlaylistForUser.
 func (c *Client) CreatePlaylistForUser(userID, playlistName, description string, public bool) (*FullPlaylist, error) {
 	spotifyURL := fmt.Sprintf("%susers/%s/playlists", c.baseURL, userID)
 	body := struct {
@@ -339,6 +341,42 @@ func (c *Client) CreatePlaylistForUser(userID, playlistName, description string,
 	return &p, err
 }
 
+// CreateCollaborativePlaylistForUser creates a playlist for a Spotify user.
+// A collaborative playlist is one that could have tracks added to and removed
+// from by other Spotify users.
+// Collaborative playlists must be private as per the Spotify API.
+func (c *Client) CreateCollaborativePlaylistForUser(userID, playlistName, description string) (*FullPlaylist, error) {
+	spotifyURL := fmt.Sprintf("%susers/%s/playlists", c.baseURL, userID)
+	body := struct {
+		Name          string `json:"name"`
+		Public        bool   `json:"public"`
+		Description   string `json:"description"`
+		Collaborative bool   `json:"collaborative"`
+	}{
+		playlistName,
+		false,
+		description,
+		true,
+	}
+	bodyJSON, err := json.Marshal(body)
+	if err != nil {
+		return nil, err
+	}
+	req, err := http.NewRequest("POST", spotifyURL, bytes.NewReader(bodyJSON))
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Set("Content-Type", "application/json")
+
+	var p FullPlaylist
+	err = c.execute(req, &p, http.StatusCreated)
+	if err != nil {
+		return nil, err
+	}
+
+	return &p, err
+}
+
 // ChangePlaylistName changes the name of a playlist.  This call requires that the
 // user has authorized the ScopePlaylistModifyPublic or ScopePlaylistModifyPrivate
 // scopes (depending on whether the playlist is public or private).

playlist_test.go

@@ -154,9 +154,10 @@ func TestUserFollowsPlaylist(t *testing.T) {
 	}
 }
 
+// NOTE collaborative is a fmt boolean.
 var newPlaylist = `
 {
-"collaborative": false,
+"collaborative": %t,
 "description": "Test Description",
 "external_urls": {
 	"spotify": "http://open.spotify.com/user/thelinmichael/playlist/7d2D2S200NyUE5KYs80PwO"
@@ -194,7 +195,7 @@ var newPlaylist = `
 }`
 
 func TestCreatePlaylist(t *testing.T) {
-	client, server := testClientString(http.StatusCreated, newPlaylist)
+	client, server := testClientString(http.StatusCreated, fmt.Sprintf(newPlaylist, false))
 	defer server.Close()
 
 	p, err := client.CreatePlaylistForUser("thelinmichael", "A New Playlist", "Test Description", false)
@@ -213,6 +214,34 @@ func TestCreatePlaylist(t *testing.T) {
 	if p.Tracks.Total != 0 {
 		t.Error("Expected new playlist to be empty")
 	}
+	if p.Collaborative {
+		t.Error("Expected non-collaborative playlist, got collaborative")
+	}
+}
+
+func TestCreateCollaborativePlaylist(t *testing.T) {
+	client, server := testClientString(http.StatusCreated, fmt.Sprintf(newPlaylist, true))
+	defer server.Close()
+
+	p, err := client.CreateCollaborativePlaylistForUser("thelinmichael", "A New Playlist", "Test Description")
+	if err != nil {
+		t.Error(err)
+	}
+	if p.IsPublic {
+		t.Error("Expected private playlist, got public")
+	}
+	if p.Name != "A New Playlist" {
+		t.Errorf("Expected 'A New Playlist', got '%s'\n", p.Name)
+	}
+	if p.Description != "Test Description" {
+		t.Errorf("Expected 'Test Description', got '%s'\n", p.Description)
+	}
+	if p.Tracks.Total != 0 {
+		t.Error("Expected new playlist to be empty")
+	}
+	if !p.Collaborative {
+		t.Error("Expected collaborative playlist, got non-collaborative")
+	}
 }
 
 func TestRenamePlaylist(t *testing.T) {