diff --git a/Retos/sesion3-reto1-carlosrodriguez/reto-1.js b/Retos/sesion3-reto1-carlosrodriguez/reto-1.js
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+// Reto HackSpace Estructura de Datos de Spotify
+
+class Genre {
+  constructor(type) {
+    this.type = type;
+  }
+}
+
+class Author {
+  constructor(name, nationality){
+    this.name = name;
+    this.nationality = nationality;
+  }
+}
+
+class Song {
+  constructor(title, length, genre, author){
+    this.title = title;
+    this.length = length;
+    this.genre = new Genre(genre.type);
+    this.author = new Author(author.name, author.nationality);
+    this.status = false;
+  }
+
+  playSong() {
+    this.status = true;
+  }
+
+  stopSong() {
+    this.status = false;
+  }
+
+}
+
+// Structures that common user handles
+class Playlist {
+  constructor(name, description, userId) {
+    this.name = name;
+    this.description = description;
+    this.userId = userId;
+    this.lastUsedPosition = 0;
+    this.head = null;
+    this.tail = null;
+  }
+
+  appendSong(song) {
+    let node = new Node(song);
+
+    if(!this.head) {
+      this.head = node;
+      this.tail = node;
+    } else {
+      node.prev = this.tail;
+      this.tail.next = node;
+      this.tail = node;
+    }
+  }
+
+  removeSong(song) {
+    let current = this.head;
+    while( current ) {
+      if( current.data === song ) {
+        if( current == this.head && current == this.tail ) {
+          this.head = null;
+          this.tail = null;
+        } else if ( current == this.head ) {
+          this.head = this.head.next;
+          this.head.prev = null;
+        } else if ( current == this.tail ) {
+          this.tail = this.tail.prev;
+          this.tail.next = null;
+        } else {
+          current.prev.next = current.next;
+          current.next.prev = current.prev;
+        }
+     }
+     current = current.next;
+    }
+  }
+
+  removeSongAt(position) {
+    let current = this.head;
+    let counter = 1;
+    if( position == 0 ) {
+      this.head = this.head.next;
+      this.head.prev = null;
+    } else {
+      while( current ) {
+        current = current.next;
+        if ( current == this.tail ) {
+          this.tail = this.tail.prev;
+          this.tail.next = null;
+        } else if( counter == position ) {
+          current.prev.next = current.next;
+          current.next.prev = current.prev;
+          break;
+        }
+        counter++;
+      }
+    }
+  }
+
+  playSongInPlaylist(song) {
+    let current = this.head;
+    let counter = 0;
+    while( current ) {
+      if( current.data == song ) {
+        song.playSong();
+        return song;
+      }
+      current = current.next;
+      counter++;
+    }
+  }
+
+  playNextSong(song){
+    let current = this.head;
+    let counter = 0;
+    while( current ) {
+      if( current.data == song ) {
+        song.stopSong();
+        let nextSong = current.next.data;
+        nextSong.playSong();
+        return nextSong;
+      }
+      current = current.next;
+      counter++;
+    }
+  }
+
+  playPreviousSong(song){
+    let current = this.head;
+    let counter = 0;
+    while( current ) {
+      if( current.data == song ) {
+        song.stopSong();
+        let nextSong = current.prev.data;
+        nextSong.playSong();
+        return nextSong;
+      }
+      current = current.next;
+      counter++;
+    }
+  }
+
+}
+
+class MyPlaylists {
+  constructor(lists, userId){
+    this.lists = lists;
+    this.userId = userId;
+  }
+
+  createNewList(name, description){
+    Spotifydb.lists.push(new Playlist(name, description));
+  }
+
+  getPlaylists(userId){
+    return SpotifyDB.lists.getListByUserId(userId);
+  }
+
+  getPlaylist(listId){
+    return SpotifyDB.lists.getListById();
+  }
+}
+
+
+class Node {
+  constructor(data){
+    this.data = data;
+    this.next = null;
+    this.prev = null;
+  }
+}
+
+
+class User {
+  constructor(name, email, pass, subscription, loggedIn){
+    this.name = name;
+    this.email = email;
+    this.subscription = new Subscription(subscription.name);
+    this.loggedIn = loggedIn;
+  }
+
+  createUser(name, email, subscription){
+    SpotifyDB.users.push([name, email, subscription, false]);
+  }
+
+  loginUser(email){
+    // after email validation and assuming a funciotn from the db
+    let user = SpotifyDB.users.getByEmail(email);
+    user.loggedIn = true;
+    return user;
+  }
+
+  findUser(id) {
+    let user = SpotifyDB.users.getByEmail(email);
+    user.loggedIn = true;
+    return user;
+  }
+
+  addSongToPlaylist(list, songData) {
+    let list = SpotifyDB.lists.getListById(list.id);
+    list.appendSong(songData);
+  }
+
+  removeSongFromPlaylist(listId, songId) {
+    let list = SpotifyDB.lists.getListById(listId);
+    list.removeSong(songData);
+  }
+
+  createPlaylist(name, description){
+    MyPlaylists.createNewList(name, description);
+  }
+}
+
+
+// ---------------------------------
+class db {
+    constructor(songs, lists, users, genres) {
+        this.songs = songs;
+        this.lists = lists;
+        this.users = users;
+        this.genres = genres;
+    }
+}
+
+let SpotifyDB;
+
+function Spotify () {
+    return {
+        init: function () {
+            SpotifyDB = new db([]);
+        },
+        createNewUser: function(name, email, subscription){
+          SpotifyDB.users.push(new User(name, email, subscription));
+          User.loginUser(email);
+        },
+        loginUser: function(email){
+          User.loginUser(email);
+        },
+        loadPlayLists: function(userId){
+          MyPlaylists.getPlaylists(user.id);
+        }
+    };
+}
+
+
+let spotifyInstance = Spotify();
+
+// initialize instance and db
+spotifyInstance.init();
+
+// login user
+let currentUser = spotifyInstance.loginUser("carlos@user.com");
+
+//load MyPlaylists
+let myPlaylists = spotifyInstance.loadPlayLists(currentUser.id);
+
+// perform some user actions
+myUser.createPlaylist("Dev Music", "lalala");
+
+// play song in Playlist
+let currentList = myPlaylists.getPlaylist(listId);
+let currentSong = currentList.playSongInPlaylist(song);
+
+currentList.playNextSong(currentSong);
+currentList.playPreviousSong(currentSong);
+
+// after searching some song
+myUser.addSongToPlaylist(selectedList, searchedSong);
+
+// delete song from Playlist
+myUser.removeSongFromPlaylist(selectedList, someSong);