diff --git a/src/main/nim/wdiwtlt/db.nim b/src/main/nim/wdiwtlt/db.nim
index d7bcefc..e23e22c 100644
--- a/src/main/nim/wdiwtlt/db.nim
+++ b/src/main/nim/wdiwtlt/db.nim
@@ -1,4 +1,4 @@
-import std/json, std/jsonutils, std/os, std/strtabs, std/tables, std/times
+import std/[logging, json, jsonutils, options, os, tables, times]
 import timeutils, uuids, zero_functional
 
 import ./models
@@ -10,7 +10,7 @@ type
     bookmarks: TableRef[UUID, Bookmark]
     mediaFiles: TableRef[UUID, MediaFile]
     playlists: TableRef[UUID, Playlist]
-    tags: StringTableRef
+    tags: TableRef[string, Option[string]]
 
     albumsToMediaFiles: TableRef[UUID, seq[UUID]]
     artistsToMediaFiles: TableRef[UUID, seq[UUID]]
@@ -18,128 +18,390 @@ type
     playlistsToMediaFiles: TableRef[UUID, seq[UUID]]
     tagsAndMediaFiles: seq[tuple[tagName: string, mediaFileId: UUID]]
 
+    mediaFileHashToId: TableRef[string, UUID]
+
   WdiwtltDb* = ref object
     jsonFilePath: string
     root: DbRoot
 
-## API Contract
+proc debug*(db: WdiwtltDb): string =
+  "\p\talbums: " & $db.root.albums &
+  "\p\tartists: " & $db.root.artists &
+  "\p\tbookmarks: " & $db.root.bookmarks &
+  "\p\tmediaFiles: " & $db.root.mediaFiles &
+  "\p\tplaylists: " & $db.root.playlists &
+  "\p\ttags: " & $db.root.tags &
+  "\p\talbumsToMediaFiles: " & $db.root.albumsToMediaFiles &
+  "\p\tartistsToMediaFiles: " & $db.root.artistsToMediaFiles &
+  "\p\tartistsAndAlbums: " & $db.root.artistsAndAlbums &
+  "\p\tplaylistsToMediaFiles: " & $db.root.playlistsToMediaFiles &
+  "\p\ttagsAndMediaFiles: " & $db.root.tagsAndMediaFiles &
+  "\p\tmediaFileHashToId: " & $db.root.mediaFileHashToId & "\p"
+
+## ========================================================================= ##
+##                            API Contract                                   ##
+## ========================================================================= ##
 proc initDb*(path: string): WdiwtltDb;
 proc loadDb*(path: string): WdiwtltDb;
 proc persist*(db: WdiwtltDb): void;
 
-proc delete*(db: WdiwtltDb, a: Album);
-proc delete*(db: WdiwtltDb, a: Artist);
-proc delete*(db: WdiwtltDb, b: Bookmark);
-proc delete*(db: WdiwtltDb, mf: MediaFile);
-proc delete*(db: WdiwtltDb, p: Playlist);
-proc delete*(db: WdiwtltDb, t: Tag);
+## Albums
+## --------------------
+proc add*(db: WdiwtltDb, a: Album);
+proc remove*(db: WdiwtltDb, a: Album);
+proc update*(db: WdiwtltDb, a: Album);
 
+proc findAlbumsByArtist*(db: WdiwtltDb, a: Artist): seq[Album];
+proc findAlbumsByName*(db: WdiwtltDb, name: string): seq[Album];
+
+proc add*(db: WdiwtltDb, a: Album, mf: MediaFile);
 proc remove*(db: WdiwtltDb, a: Album, mf: MediaFile);
-proc remove*(db: WdiwtltDb, a: Artist, mf: MediaFile);
-proc remove*(db: WdiwtltDb, artist: Artist, album: Album);
 
+## Artists
+## --------------------
+proc add*(db: WdiwtltDb, a: Artist);
+proc remove*(db: WdiwtltDb, a: Artist);
+proc update*(db: WdiwtltDb, a: Artist);
+
+proc findArtistsByAlbum*(db: WdiwtltDb, a: Album): seq[Artist];
+proc findArtistsByName*(db: WdiwtltDb, name: string): seq[Artist];
+
+proc add*(db: WdiwtltDb, a: Artist, mf: MediaFile);
+proc remove*(db: WdiwtltDb, a: Artist, mf: MediaFile);
+
+proc isAssociated*(db: WdiwtltDb, artist: Artist, album: Album): bool;
+proc associate*(db: WdiwtltDb, artist: Artist, album: Album);
+proc disassociate*(db: WdiwtltDb, artist: Artist, album: Album);
+
+## Bookmarks
+## --------------------
+proc add*(db: WdiwtltDb, b: Bookmark);
+proc update*(db: WdiwtltDb, b: Bookmark);
+proc remove*(db: WdiwtltDb, b: Bookmark);
+
+## Media Files
+## --------------------
+proc add*(db: WdiwtltDb, mf: MediaFile);
+proc remove*(db: WdiwtltDb, mf: MediaFile);
+proc update*(db: WdiwtltDb, mf: MediaFile);
+proc findMediaFilesByAlbum*(db: WdiwtltDb, a: Album): seq[MediaFile];
+proc findMediaFilesByArtist*(db: WdiwtltDb, a: Artist): seq[MediaFile];
+proc findMediaFileByHash*(db: WdiwtltDb, hash: string): Option[MediaFile];
+
+## Playlists
+## --------------------
+proc add*(db: WdiwtltDb, p: Playlist);
+proc remove*(db: WdiwtltDb, p: Playlist);
+proc update*(db: WdiwtltDb, p: Playlist);
+
+## Tags
+## --------------------
+proc add*(db: WdiwtltDb, t: Tag);
+proc remove*(db: WdiwtltDb, t: Tag);
+proc update*(db: WdiwtltDb, t: Tag);
+
+## Housekeeping
+## --------------------
 proc pruneStalePlaylists*(db: WdiwtltDb, ts: DateTime);
 proc pruneStaleBookmarks*(db: WdiwtltDb, ts: DateTime);
 proc removeEmptyAlbums*(db: WdiwtltDb): void;
 proc removeEmptyArtists*(db: WdiwtltDb): void;
 proc removeEmptyPlaylists*(db: WdiwtltDb): void;
 
+proc toJsonHook(t: TableRef[UUID, Album]): JsonNode;
+proc fromJsonHook(t: var TableRef[UUID, Album], n: JsonNode);
+proc toJsonHook(t: TableRef[UUID, Artist]): JsonNode;
+proc fromJsonHook(t: var TableRef[UUID, Artist], n: JsonNode);
+proc toJsonHook(t: TableRef[UUID, Bookmark]): JsonNode;
+proc fromJsonHook(t: var TableRef[UUID, Bookmark], n: JsonNode);
+proc toJsonHook(t: TableRef[UUID, MediaFile]): JsonNode;
+proc fromJsonHook(t: var TableRef[UUID, MediaFile], n: JsonNode);
+proc toJsonHook(t: TableRef[UUID, Playlist]): JsonNode;
+proc fromJsonHook(t: var TableRef[UUID, Playlist], n: JsonNode);
+proc toJsonHook(t: TableRef[UUID, seq[UUID]]): JsonNode;
+proc fromJsonHook(t: var TableRef[UUID, seq[UUID]], n: JsonNode);
+proc toJsonHook(uuid: UUID): JsonNode;
+proc fromJsonHook(u: var UUID, node: JsonNode);
+proc toJsonHook(dt: DateTime): JsonNode;
+proc fromJsonHook(dt: var DateTime, node: JsonNode);
+
+
+## ========================================================================= ##
+##                            API Implementation                             ##
+## ========================================================================= ##
 ## Internals
+## --------------------
+proc toJsonHook(t: TableRef[UUID, Album]): JsonNode =
+  result = newJObject()
+  for k, v in t.pairs: result[$k] = toJson(v)
+
+proc fromJsonHook(t: var TableRef[UUID, Album], n: JsonNode) =
+  for k in n.keys:
+    var a: Album
+    fromJson(a, n[k])
+    t[parseUUID(k)] = a
+
+proc toJsonHook(t: TableRef[UUID, Artist]): JsonNode =
+  result = newJObject()
+  for k, v in t.pairs: result[$k] = toJson(v)
+
+proc fromJsonHook(t: var TableRef[UUID, Artist], n: JsonNode) =
+  for k in n.keys:
+    var a: Artist
+    fromJson(a, n[k])
+    t[parseUUID(k)] = a
+
+proc toJsonHook(t: TableRef[UUID, Bookmark]): JsonNode =
+  result = newJObject()
+  for k, v in t.pairs: result[$k] = toJson(v)
+
+proc fromJsonHook(t: var TableRef[UUID, Bookmark], n: JsonNode) =
+  for k in n.keys:
+    var b: Bookmark
+    fromJson(b, n[k])
+    t[parseUUID(k)] = b
+
+proc toJsonHook(t: TableRef[UUID, MediaFile]): JsonNode =
+  result = newJObject()
+  for k, v in t.pairs: result[$k] = toJson(v)
+
+proc fromJsonHook(t: var TableRef[UUID, MediaFile], n: JsonNode) =
+  for k in n.keys:
+    var mf: MediaFile
+    fromJson(mf, n[k])
+    t[parseUUID(k)] = mf
+
+proc toJsonHook(t: TableRef[UUID, Playlist]): JsonNode =
+  result = newJObject()
+  for k, v in t.pairs: result[$k] = toJson(v)
+
+proc fromJsonHook(t: var TableRef[UUID, Playlist], n: JsonNode) =
+  for k in n.keys:
+    var p: Playlist
+    fromJson(p, n[k])
+    t[parseUUID(k)] = p
+
+proc toJsonHook(t: TableRef[UUID, seq[UUID]]): JsonNode =
+  result = newJObject()
+  for k, v in t.pairs: result[$k] = toJson(v)
+
+proc fromJsonHook(t: var TableRef[UUID, seq[UUID]], n: JsonNode) =
+  for k in n.keys:
+    var s: seq[UUID]
+    fromJson(s, n[k])
+    t[parseUUID(k)] = s
+
 proc toJsonHook(uuid: UUID): JsonNode = %($uuid)
-proc fromJsonHook(u: var UUID,node: JsonNode) =
+proc fromJsonHook(u: var UUID, node: JsonNode) =
   u = parseUUID(node.getStr)
 
 proc toJsonHook(dt: DateTime): JsonNode = %(dt.formatIso8601)
 proc fromJsonHook(dt: var DateTime, node: JsonNode) =
   dt = parseIso8601(node.getStr)
 
-## API Implementation
+
+proc initDbRoot(): DbRoot =
+  DbRoot(
+    albums: newTable[UUID, Album](),
+    artists: newTable[UUID, Artist](),
+    bookmarks: newTable[UUID, Bookmark](),
+    mediaFiles: newTable[UUID, MediaFile](),
+    playlists: newTable[UUID, Playlist](),
+    tags: newTable[string, Option[string]](),
+    albumsToMediaFiles: newTable[UUID, seq[UUID]](),
+    artistsToMediaFiles: newTable[UUID, seq[UUID]](),
+    artistsAndAlbums: @[],
+    playlistsToMediaFiles: newTable[UUID, seq[UUID]](),
+    tagsAndMediaFiles: @[],
+    mediaFileHashToId: newTable[string, UUID]())
+
 proc initDb*(path: string): WdiwtltDb =
   WdiwtltDb(
     jsonFilePath: path,
-    root: DbRoot(
-      albums: newTable[UUID, Album](),
-      artists: newTable[UUID, Artist](),
-      bookmarks: newTable[UUID, Bookmark](),
-      mediaFiles: newTable[UUID, MediaFile](),
-      playlists: newTable[UUID, Playlist](),
-      tags: newStringTable(),
-      albumsToMediaFiles: newTable[UUID, seq[UUID]](),
-      artistsToMediaFiles: newTable[UUID, seq[UUID]](),
-      artistsAndAlbums: @[],
-      playlistsToMediaFiles: newTable[UUID, seq[UUID]](),
-      tagsAndMediaFiles: @[]
-  ))
+    root: initDbRoot())
 
 proc loadDb*(path: string): WdiwtltDb =
   if not fileExists(path):
     raise newException(Exception, "Unable to open database file '" & path & "'")
 
-  let jsonRoot = parseJson(path)
-  var root: DbRoot
+  let jsonRoot = parseJson(path.readFile)
+  var root: DbRoot = initDbRoot()
   root.fromJson(jsonRoot)
 
+  debug "loaded DB"
   result = WdiwtltDb(
     jsonFilePath: path,
     root: root)
+  debug result.debug
 
 proc persist*(db: WdiwtltDb): void =
   let jsonRoot = db.root.toJson
   db.jsonFilePath.writeFile($jsonRoot)
 
-proc delete*(db: WdiwtltDb, a: Album) =
+## Albums
+## --------------------
+proc add*(db: WdiwtltDb, a: Album) = db.root.albums[a.id] = a
+
+proc remove*(db: WdiwtltDb, a: Album) =
   db.root.albums.del(a.id)
   db.root.albumsToMediaFiles.del(a.id)
   db.root.artistsAndAlbums =
     db.root.artistsAndAlbums --> filter(it.albumId != a.id)
 
-proc delete*(db: WdiwtltDb, a: Artist) =
+proc update*(db: WdiwtltDb, a: Album) = db.add(a)
+
+proc findAlbumsByArtist*(db: WdiwtltDb, a: Artist): seq[Album] =
+  db.root.artistsAndAlbums -->
+    filter(it.artistId == a.id and db.root.artists.contains(a.id)).
+    map(db.root.albums[it.albumId])
+
+proc findAlbumsByName*(db: WdiwtltDb, name: string): seq[Album] =
+  result = @[]
+  for a in db.root.albums.values:
+    if a.name == name: result.add(a)
+
+proc add*(db: WdiwtltDb, a: Album, mf: MediaFile) =
+  if not db.root.albumsToMediaFiles.contains(a.id):
+    db.root.albumsToMediaFiles[a.id] = @[mf.id]
+  else:
+    let idsInAlbum = db.root.albumsToMediaFiles[a.id]
+    if not idsInAlbum.contains(mf.id):
+      db.root.albumsToMediaFiles[a.id].add(mf.id)
+
+proc remove*(db: WdiwtltDb, a: Album, mf: MediaFile) =
+  if db.root.albumsToMediaFiles.contains(a.id):
+    db.root.albumsToMediaFiles[a.id] =
+      db.root.albumsToMediaFiles[a.id] --> filter(it != mf.id)
+
+## Artists
+## --------------------
+proc add*(db: WdiwtltDb, a: Artist) = db.root.artists[a.id] = a
+
+proc remove*(db: WdiwtltDb, a: Artist) =
   db.root.artists.del(a.id)
   db.root.artistsToMediaFiles.del(a.id)
   db.root.artistsAndAlbums =
     db.root.artistsAndAlbums --> filter(it.artistId != a.id)
 
-proc delete*(db: WdiwtltDb, b: Bookmark) = db.root.bookmarks.del(b.id)
+proc update*(db: WdiwtltDb, a: Artist) = db.add(a)
 
-proc delete*(db: WdiwtltDb, mf: MediaFile) =
+proc findArtistsByAlbum*(db: WdiwtltDb, a: Album): seq[Artist] =
+  db.root.artistsAndAlbums -->
+    filter(it.albumId == a.id and db.root.albums.contains(a.id)).
+    map(db.root.artists[it.artistId])
+
+proc findArtistsByName*(db: WdiwtltDb, name: string): seq[Artist] =
+  result = @[]
+  for a in db.root.artists.values:
+    if a.name == name: result.add(a)
+
+proc add*(db: WdiwtltDb, a: Artist, mf: MediaFile) =
+  if not db.root.artistsToMediaFiles.contains(a.id):
+    db.root.artistsToMediaFiles[a.id] = @[mf.id]
+  else:
+    let idsInArtist = db.root.artistsToMediaFiles[a.id]
+    if not idsInArtist.contains(mf.id):
+      db.root.artistsToMediaFiles[a.id].add(mf.id)
+
+proc remove*(db: WdiwtltDb, a: Artist, mf: MediaFile) =
+  if db.root.artistsToMediaFiles.contains(a.id):
+    db.root.artistsToMediaFiles[a.id] =
+      db.root.artistsToMediaFiles[a.id] --> filter(it != mf.id)
+
+proc isAssociated*(
+    db: WdiwtltDb,
+    artist: Artist,
+    album: Album
+  ): bool =
+  let matching = db.root.artistsAndAlbums -->
+    filter(it.artistId == artist.id and it.albumId == album.id)
+  return matching.len > 0
+
+proc associate*(db: WdiwtltDb, artist: Artist, album: Album) =
+  if not db.isAssociated(artist, album):
+    db.root.artistsAndAlbums.add((artist.id, album.id))
+
+proc disassociate*(db: WdiwtltDb, artist: Artist, album: Album) =
+  db.root.artistsAndAlbums = db.root.artistsAndAlbums -->
+    filter(it.albumId != album.id or it.artistId != artist.id)
+
+## Bookmarks
+## --------------------
+proc add*(db: WdiwtltDb, b: Bookmark) = db.root.bookmarks[b.id] = b
+proc remove*(db: WdiwtltDb, b: Bookmark) = db.root.bookmarks.del(b.id)
+proc update*(db: WdiwtltDb, b: Bookmark) = db.add(b)
+
+## Media Files
+## --------------------
+proc add*(db: WdiwtltDb, mf: MediaFile) =
+  db.root.mediaFiles[mf.id] = mf
+  db.root.mediaFileHashToId[mf.fileHash] = mf.id
+
+proc remove*(db: WdiwtltDb, mf: MediaFile) =
   db.root.mediaFiles.del(mf.id)
 
   for albumId, mfIds in db.root.albumsToMediaFiles.pairs:
     if mfIds.contains(mf.id):
       db.remove(db.root.albums[albumId], mf)
 
-proc delete*(db: WdiwtltDb, p: Playlist) =
+  db.root.mediaFileHashToId.del(mf.fileHash)
+
+proc update*(db: WdiwtltDb, mf: MediaFile) = db.add(mf)
+
+proc findMediaFilesByAlbum*(db: WdiwtltDb, a: Album): seq[MediaFile] =
+  result = @[]
+  if db.root.albumsToMediaFiles.contains(a.id):
+    return db.root.albumsToMediaFiles[a.id] -->
+      filter(db.root.mediaFiles.contains(it)).
+      map(db.root.mediaFiles[it])
+
+proc findMediaFilesByArtist*(db: WdiwtltDb, a: Artist): seq[MediaFile] =
+  result = @[]
+  if db.root.artistsToMediaFiles.contains(a.id):
+    return db.root.artistsToMediaFiles[a.id] -->
+      filter(db.root.mediaFiles.contains(it)).
+      map(db.root.mediaFiles[it])
+
+proc findMediaFileByHash*(db: WdiwtltDb, hash: string): Option[MediaFile] =
+  if db.root.mediaFileHashToId.contains(hash):
+    let mfId = db.root.mediaFileHashToId[hash]
+    if db.root.mediaFiles.contains(mfId):
+      return some(db.root.mediaFiles[mfId])
+
+  return none[MediaFile]()
+
+## Playlists
+## --------------------
+proc add*(db: WdiwtltDb, p: Playlist) = db.root.playlists[p.id] = p
+
+proc remove*(db: WdiwtltDb, p: Playlist) =
   db.root.playlists.del(p.id)
   db.root.playlistsToMediaFiles.del(p.id)
   for b in db.root.bookmarks.values:
-    if b.playlistId == p.id: db.delete(b)
+    if b.playlistId == p.id: db.remove(b)
 
-proc delete*(db: WdiwtltDb, t: Tag) =
+proc update*(db: WdiwtltDb, p: Playlist) = db.add(p)
+
+## Tags
+## --------------------
+proc add*(db: WdiwtltDb, t: Tag) = db.root.tags[t.name] = t.description
+
+proc remove*(db: WdiwtltDb, t: Tag) =
   db.root.tags.del(t.name)
   db.root.tagsAndMediaFiles = db.root.tagsAndMediaFiles -->
     filter(it.tagName != t.name)
 
-proc remove*(db: WdiwtltDb, a: Album, mf: MediaFile) =
-  db.root.albumsToMediaFiles[a.id] =
-    db.root.albumsToMediaFiles[a.id] -->
-      filter(it != mf.id)
-
-proc remove*(db: WdiwtltDb, a: Artist, mf: MediaFile) =
-  db.root.artistsToMediaFiles[a.id] =
-    db.root.artistsToMediaFiles[a.id] -->
-      filter(it != mf.id)
-
-proc remove*(db: WdiwtltDb, artist: Artist, album: Album) =
-  db.root.artistsAndAlbums = db.root.artistsAndAlbums -->
-    filter(it.albumId != album.id or it.artistId != artist.id)
+proc update*(db: WdiwtltDb, t: Tag) = db.add(t)
 
+## Housekeeping
+## --------------------
 proc pruneStalePlaylists*(db: WdiwtltDb, ts: DateTime) =
   db.root.playlists.values -->
-    filter(it.lastUsed > ts).foreach(db.delete(it))
+    filter(it.lastUsed > ts).foreach(db.remove(it))
 
 proc pruneStaleBookmarks*(db: WdiwtltDb, ts: DateTime) =
   db.root.bookmarks.values -->
-    filter(it.lastUsed > ts).foreach(db.delete(it))
+    filter(it.lastUsed > ts).foreach(db.remove(it))
 
 proc removeEmptyAlbums*(db: WdiwtltDb): void =
   let emptyAlbumIds = db.root.albumsToMediaFiles.pairs -->