design: Work on playlist design

Signed-off-by: Bryan Schumaker <bjschuma@gmail.com>

design.txt

@@ -9,6 +9,10 @@ that have already been solved.  For example, this means using SQL to store
 a library rather than developing my own file format.  This should help with
 future maintenance because I'll have less code to navigate.
 
+I will also create unit tests as I add features so bugs can be found faster.
+
+
+
 SQLite:
 	I plan on using SQLite for data storage as much as possible.  I had
 	been using my own custom file formats for storing preferences or
@@ -20,14 +24,29 @@ SQLite:
 
 		$ pkg-config --cflags --libs sqlite3
 
+
+
 Files:
+	ocarina/
+		design.txt
+	ocarina/gui/
+	ocarina/include/
+		library.h
+		playlist.h
+	ocarina/lib/
+		library.cpp
+		playlist.cpp
+	ocarina/tests/
+
 	$HOME/.ocarina{-debug}/ocarina.db
 
+
+
 Database: (ocarina.db)
 	Paths -
 		create table if not exists paths(
 			id INTEGER PRIMARY KEY AUTOINCREMENT,
-			filepath TEXT UNIQUE, /* root path of library */
+			dirpath TEXT UNIQUE, /* root path of library */
 			enabled INTEGER, /* 0 = false, 1 = true */
 		);
 
@@ -67,16 +86,11 @@ Database: (ocarina.db)
 			banned INT, /* 0 = false, 1 = true */
 		);
 
-	Playlist -
-		create table if not exists playlists(
-			id INTEGER PRIMARY KEY AUTOINCREMENT,
-			flags UNSIGNED INTEGER
-		)
+	<Research FTS tables and inverted indexes for filtering>
 
-	Playlist #N -
-		create table if not exists playlist{0-9}(
-			FOREIGN KEY(track) REFERENCES tracks(id),
-		);
+	Tags index -
+		<another FTS table>
+		Tag Name -> song ids
 
 	User settings - 
 		create table if not exists config(
@@ -84,5 +98,73 @@ Database: (ocarina.db)
 			value INT,
 		);
 
+
+
+Library: (lib/library.cpp)
+
+	The purpose of library.cpp is to control access to the library tables
+	in the SQLite database.  This file will set up prepared statements and
+	wrapper functions to make it really easy for the Ocarina gui to affect
+	the library.
+
+- API
+	/* Path management */
+	add_path_to_library(dir);
+		Add new row to paths table, update
+	rm_path_from_library(dir);
+		Remove row from paths table
+	update_path(dir);
+		Scan tracks table, remove paths that don't exist
+		Scan dir, add new files to database
+		Consider having SQLite create an index on tracks.filepath
+	update_all();
+		Call update_path() for each paths.dirpath
+	list_paths(list<>);
+		Tell the caller basic information about library paths
+		(dir, enabled, size,...)
+
+
+
+Playlist: (lib/playlist.cpp)
+	A playlist is a simple list of songs that can be played either randomly
+	or in a user-defined order.  It would probably be best to use a linked
+	list or vector to represent playlists, rather than creating a SQLite
+	table.  I will be able to easily rearrange tracks in the playlist this
+	way.  This will also make it easier to deal with playlist renames and
+	reordering by the user.
+
+- API
+	/* Playlist management */
+	new_playlist();
+	del_playlist(playlist);
+	add_to_playlist(playlist, songid);
+	rm_from_playlist(playlist, songid);
+	playlist_size(playlist)
+	set_flag(playlist, flag)
+
+- Flags
+	PL_ENABLED (1 << 0)
+	PL_RANDOM  (1 << 1)
+	PL_DRAIN   (1 << 2)
+
+
+
+Tags:
+	Tags will be a new feature in Ocarina 6 and will be a more generic way
+	of implementing a banned-songs playlist.  Users will be able to create
+	new tags on the fly and add songs to and from them.  I can also use
+	an SQLite trigger to manage automatic tags.
+
+	The following tags will be created by default and will not be
+	deletable by the user: Artist, Album, Unplayed Songs, Genre
+
+- API
+	new_tag(name);
+	del_tag(name);
+	tag_song(name, songid);
+	untag_song(name, songid);
+	set_tag_visible(name, visible);
+
+
 Archlinux packages:
 	extra/sqlite