Working on a refactor that allows multiple-to-multiple relations between songs, albums and artists.

client/src/api.ts

@@ -13,8 +13,14 @@ export interface ListSongsRequest {}
 export interface ListSongsResponseItem {
     title: String;
     id: Number;
-    artistName: String;
-    artistId: Number;
+    artists: {
+        name: String;
+        id: Number;
+    }[];
+    albums: {
+        name: String;
+        id: Number;
+    }[];
 }
 export interface ListSongsResponse extends Array<ListSongsResponseItem>{};
 export function checkListSongsRequest(req:any): boolean {
@@ -37,21 +43,23 @@ export function checkListArtistsRequest(req:any): boolean {
 export const CreateSongEndpoint = '/song/create';
 export interface CreateSongRequest {
     title: String;
-    artistId: Number;
+    artistIds?: Number[];
+    albumIds?: Number[];
 }
 export interface CreateSongResponse {
     id: Number;
 }
 export function checkCreateSongRequest(req:any): boolean {
     return "body" in req &&
-    "title" in req.body &&
-    "artistId" in req.body;
+    "title" in req.body;
 }
 
 // Create a new artist.
 export const CreateArtistEndpoint = '/artist/create';
 export interface CreateArtistRequest {
     name: String;
+    songIds?: Number[];
+    albumIds?: Number[];
 }
 export interface CreateArtistResponse {
     id: Number;

server/endpoints/CreateSongEndpointHandler.ts

@@ -8,27 +8,61 @@ export const CreateSongEndpointHandler = (req: any, res: any) => {
     return;
   }
   const reqObject: api.CreateSongRequest = req.body;
-  console.log("Request create song: ", reqObject); // TODO: remove
-  // First check that the artist exists.
+
+  // Start retrieving the artist instances to link the song to.
+  var artistInstancePromises: Promise<any>[] = [];
+  reqObject.artistIds?.forEach((artistId: Number) => {
+    artistInstancePromises.push(
       models.Artist.findAll({
-    where: { id: reqObject.artistId }
+        where: { id: artistId }
       })
         .then((artist: any[]) => {
           if (artist.length != 1) {
-        console.log('Invalid CreateSong request: ' + JSON.stringify(req.body)
-          + ". There is no artist with id " + reqObject.artistId + ".");
-        res.sendStatus(400);
-        return;
+            throw 'There is no artist with id ' + artistId + '.';
           }
+          return artist[0];
+        })
+    );
+  });
+  var artistInstancesPromise = Promise.all(artistInstancePromises);
+
+  // Start retrieving the album instances to link the song to.
+  var albumInstancePromises: Promise<any>[] = [];
+  reqObject.albumIds?.forEach((albumId: Number) => {
+    albumInstancePromises.push(
+      models.Album.findAll({
+        where: { id: albumId }
+      })
+        .then((album: any[]) => {
+          if (album.length != 1) {
+            throw 'There is no album with id ' + albumId + '.';
+          }
+          return album[0];
+        })
+    );
+  });
+  var albumInstancesPromise = Promise.all(albumInstancePromises);
+
+  // Upon finish retrieving artists and albums, create the song and associate it.
+  Promise.all([artistInstancesPromise, albumInstancesPromise])
+    .then((values: any) => {
+      var [artists, albums] = values;
       models.Song.create({
         title: reqObject.title,
-        ArtistId: reqObject.artistId
       })
+        .then(Promise.all([
+          (song: any) => {
+            song.addArtists(artists);
+          },
+          (song: any) => {
+            song.addAlbums(albums);
+          }
+        ]))
         .then((song: any) => {
           const responseObject: api.CreateSongResponse = {
             id: song.id
           };
           res.status(200).send(responseObject);
         })
-    })
+  });
 }

server/endpoints/ListSongsEndpointHandler.ts

@@ -8,7 +8,7 @@ export const ListSongsEndpointHandler = (req: any, res: any) => {
         return;
     }
     models.Song.findAll({
-        include: [models.Artist]
+        include: [models.Artist, models.Album]
     })
         .then((songs: any[]) => {
             console.log(songs);
@@ -16,8 +16,14 @@ export const ListSongsEndpointHandler = (req: any, res: any) => {
                 return {
                     title: song.title,
                     id: song.id,
-                    artistName: song.Artist.name,
-                    artistId: song.ArtistId,
+                    artists: song.Artists.map((artist: any) => { return {
+                        name: artist.name,
+                        id: artist.id,
+                    }; }),
+                    albums: song.Albums.map((album: any) => { return {
+                        name: album.name,
+                        id: album.id,
+                    }; }),
                 };
             });
             res.send(response);

server/models/album.js

@@ -0,0 +1,12 @@
+module.exports = (sequelize, DataTypes) => {
+    var Album = sequelize.define('Album', {
+        name: DataTypes.STRING,
+    });
+
+    Album.associate = function (models) {
+        models.Album.belongsToMany(models.Song, { through: "SongAlbums" })
+        models.Album.belongsToMany(models.Artist, { through: "AlbumArtists" })
+    };
+
+    return Album;
+};

server/models/artist.js

@@ -3,9 +3,10 @@ module.exports = (sequelize, DataTypes) => {
     name: DataTypes.STRING,
   });
 
-    Artist.associate = function(models) {
-      models.Artist.hasMany(models.Song);
+  Artist.associate = function (models) {
+    models.Artist.belongsToMany(models.Song, { through: "SongArtists" });
+    models.Artist.belongsToMany(models.Album, { through: "AlbumArtists" })
   };
 
   return Artist;
-  };
+};

server/models/song.js

@@ -3,11 +3,10 @@ module.exports = (sequelize, DataTypes) => {
     title: DataTypes.STRING,
   });
 
-    Song.associate = function(models) {
-      models.Song.belongsTo(models.Artist, {
-          onDelete: "CASCADE"
-      });
+  Song.associate = function (models) {
+    models.Song.belongsToMany(models.Artist, { through: "SongArtists" });
+    models.Song.belongsToMany(models.Album, { through: "SongAlbums" });
   };
 
   return Song;
-  };
+};