Add API for favorite playlist songs

app/controllers/api/v1/favorite_playlist/songs_controller.rb

@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+module Api
+  module V1
+    class FavoritePlaylist::SongsController < ApiController
+      before_action :find_playlist
+      before_action :find_song
+
+      def create
+        @playlist.playlists_songs.create(song_id: @song.id, position: 1)
+      rescue ActiveRecord::RecordNotUnique
+        render json: {error: "RecordNotUnique", message: t("error.already_in_playlist")}, status: :bad_request
+      end
+
+      def destroy
+        @playlist.songs.destroy(@song)
+      end
+
+      private
+
+      def find_song
+        @song = Song.find(params[:song_id])
+      end
+
+      def find_playlist
+        @playlist = Current.user.favorite_playlist
+      end
+    end
+  end
+end

config/routes.rb

@@ -56,9 +56,14 @@
       resources :stream, only: [:new]
       resources :transcoded_stream, only: [:new]
       resources :cached_transcoded_stream, only: [:new]
+
       namespace :current_playlist do
         resource :songs, only: [:show]
       end
+
+      namespace :favorite_playlist do
+        resource :songs, only: [:create, :destroy]
+      end
     end
   end
 end

test/controllers/api/v1/favorite_playlist/songs_controller_test.rb

@@ -0,0 +1,31 @@
+require "test_helper"
+
+class Api::V1::FavoritePlaylist::SongsControllerTest < ActionDispatch::IntegrationTest
+  setup do
+    @user = users(:visitor1)
+    @playlist = @user.favorite_playlist
+    @playlist.song_ids = [1, 2]
+  end
+
+  test "should add songs to playlist" do
+    post api_v1_favorite_playlist_songs_url, params: {song_id: 3}, headers: api_token_header(@user)
+    assert_equal [3, 1, 2], @playlist.reload.song_ids
+  end
+
+  test "should remove songs from playlist" do
+    delete api_v1_favorite_playlist_songs_url, params: {song_id: 1}, headers: api_token_header(@user)
+    assert_equal [2], @playlist.reload.song_ids
+
+    delete api_v1_favorite_playlist_songs_url, params: {song_id: 2}, headers: api_token_header(@user)
+    assert_equal [], @playlist.reload.song_ids
+  end
+
+  test "should not add song to playlist if already in playlist" do
+    post api_v1_favorite_playlist_songs_url, params: {song_id: 1}, headers: api_token_header(@user)
+    response = @response.parsed_body
+
+    assert_response :bad_request
+    assert_equal "RecordNotUnique", response["error"]
+    assert_equal I18n.t("error.already_in_playlist"), response["message"]
+  end
+end