ORM: implemented methods to remove empty albums, artists, and playlists.

core/src/main/groovy/com/jdbernard/wdiwtlt/db/ORM.groovy

@@ -4,6 +4,7 @@ import java.lang.reflect.Modifier
 import java.sql.Connection
 import java.sql.PreparedStatement
 import java.sql.ResultSet
+import java.sql.Timestamp
 import java.text.SimpleDateFormat
 import java.util.regex.Pattern
 import javax.persistence.Entity
@@ -191,12 +192,12 @@ public class ORM {
     public def associate(def m1, def m2) {
         return associate(m1.class, m2.class, m1.id, m2.id) }
 
-
     /// ### Album-specific methods
     //  =======================================================================
     public Album getAlbumById(int id) { return getById(Album, id) }
 
     public List<Album> getAlbums() { return getAll(Album) }
+
     public List<Album> getAlbumsOrderedByName() {
         return getAll(Album, 'name ASC') }
 
@@ -207,7 +208,7 @@ public class ORM {
         def query = new StringBuilder()
         def sqlParams = []
 
-        query.append('SELECT al.* FROM albums al ')
+        query.append('SELECT DISTINCT al.* FROM albums al ')
 
         if (params.artistId) {
             query.append(' JOIN artists_albums aa ON al.id = aa.album_id ')
@@ -244,17 +245,26 @@ public class ORM {
             query, sqlParams)
         return sql.rows(query, sqlParams).collect { recordToModel(Album, it) } }
 
-    public List<Album> removeEmptyAlbums() {
-        throw new UnsupportedOperationException('Not yet implemented.');
-    }
+    public void removeEmptyAlbums() {
+
+        String query = """\
+            DELETE FROM albums WHERE id IN (
+                SELECT DISTINCT al.id
+                FROM albums al LEFT OUTER JOIN albums_media_files almf ON
+                    al.id = almf.album_id
+                WHERE almf.album_id IS NULL)"""
+
+        logger.debug('Deleting empty albums.\n\tSQL: {}', query)
+        sql.execute(query) }
 
     /// ### Artist-specific methods
+    public List<Artist> getArtists() { return getAll(Artist) }
     public Artist getArtistById(int id) { return getById(Artist, id) }
+
     public Artist getArtistByName(String name) {
         def artists = getByName(Artist, name)
         if (artists) return artists[0] }
 
-    public List<Artist> getArtists() { return getAll(Artist) }
     public List<Artist> getArtistsOrderedByName() {
         return getAll(Artist, 'name ASC') }
 
@@ -262,7 +272,7 @@ public class ORM {
         def query = new StringBuilder()
         def sqlParams = []
 
-        query.append('SELECT ar.* FROM artists ar ')
+        query.append('SELECT DISTINCT ar.* FROM artists ar ')
 
         if (params.albumId) {
             query.append(' JOIN artists_albums aa ON ar.id = aa.artist_id ')
@@ -295,13 +305,21 @@ public class ORM {
     public List<Artist> getArtistsLikeName(String name) {
         return getLike(Artist, ['name'], [name]) }
 
-    public List<Artist> removeEmptyArtists() {
-        throw new UnsupportedOperationException('Not yet implemented.');
-    }
-
     public def addAlbumArtist(int albumId, int artistId) {
         return associate(Artist, Album, artistId, albumId) }
 
+    public void removeEmptyArtists() {
+
+        String query = """\
+            DELETE FROM artists WHERE id IN (
+                SELECT DISTINCT ar.id
+                FROM artists ar LEFT OUTER JOIN artists_media_files armf ON
+                    ar.id = armf.artist_id
+                WHERE armf.artist_id IS NULL)"""
+
+        logger.debug('Deleting empty artists.\n\tSQL: {}', query)
+        sql.execute(query) }
+
     /// ### Bookmark-specific methods
     public Bookmark getBookmarkById(int id) { return getById(Bookmark, id) }
 
@@ -436,7 +454,6 @@ public class ORM {
         return sql.rows(query, sqlParams).collect {
             recordToModel(MediaFile, it) } }
 
-
     public def associateMediaFileWithAlbum(int mediaFileId, int albumId) {
         return associate(Album, MediaFile, albumId, mediaFileId) }
 
@@ -459,13 +476,12 @@ public class ORM {
         return mf }
 
     /// ### Playlist-specific methods
+    public List<Playlist> getPlaylists() { return getAll(Playlist) }
     public Playlist getPlaylistById(int id) { return getById(Playlist, id) }
 
     public List<Playlist> getPlaylistByName(String name) {
         return getByName(Playlist, name) }
 
-    public List<Playlist> getPlaylists() { return getAll(Playlist) }
-
     public List<Playlist> getPlaylistsWhere(Map params) {
         def query = new StringBuilder()
         def sqlParams = []
@@ -600,9 +616,17 @@ public class ORM {
             p.mediaFileCount = 0
             return update(p) } }
 
-    public List<Playlist> removeEmptyPlaylists() {
-        throw new UnsupportedOperationException('Not yet implemented.');
-    }
+    public void removeEmptyPlaylists() {
+
+        String query = """\
+            DELETE FROM playlists WHERE id IN (
+                SELECT DISTINCT p.id
+                FROM playlists p LEFT OUTER JOIN playlists_media_files pmf ON
+                    p.id = pmf.playlist_id
+                WHERE pmf.playlist_id IS NULL)"""
+
+        logger.debug('Deleting empty playlists.\n\tSQL: {}', query)
+        sql.execute(query) }
 
     /// ### Tag-specific methods
     public Tag getTagById(int id) { return getById(Tag, id) }
@@ -613,7 +637,7 @@ public class ORM {
         def query = new StringBuilder()
         def sqlParams = []
 
-        query.append('SELECT t.* FROM tags ')
+        query.append('SELECT DISTINCT t.* FROM tags ')
 
         if (params.mediaFileId || params.artistId || params.albumId ||
             params.playlistId)