Design: Create a preferences namespace

This will be used to store various values for the user.

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

design.txt

@@ -24,6 +24,7 @@ Files:
 		index.h
 		library.h
 		playlist.h
+		prefs.h
 	ocarina/lib/
 		database.cpp
 		file.cpp
@@ -31,6 +32,7 @@ Files:
 		index.cpp
 		library.cpp
 		playlist.cpp
+		prefs.cpp
 	ocarina/tests/
 
 	$HOME/.ocarina{-debug}/
@@ -57,19 +59,19 @@ On-disk files: (lib/file.cpp)
 	Items should be written to a file with either a space or new line
 	separating multiple values.
 
-Notation:
+- Notation:
 	File << aaaaa << bbbbb << endl is translated into "aaaaa bbbbb\n"
 
-File version:
+- File version:
 	#define FILE_VERSION 4
 
-Open mode:
+- Open mode:
 	enum OpenMode {
 		OPEN_READ,
 		OPEN_WRITE,
 	}
 
-File:
+- File:
 	class File {
 	private:
 		union {
@@ -87,10 +89,10 @@ File:
 		getline(string &);
 	}
 
-File format:
+- File format:
 	File << FILE_VERSION << <OTHER_DATA>
 
-API:
+- API:
 	File : File(filepath)
 		Resolve filepath to ~/.ocarina{-debug}/filepath
 	File : open(mode)
@@ -127,7 +129,7 @@ Database: (lib/database.cpp)
 	include/database.hpp, which will be included by database.h.  Any
 	function not relying on a template can be written in lib/database.cpp.
 
-DatabaseEntry:
+- DatabaseEntry:
 	class DatabaseEntry { /* let database modify valid flag */
 	private:
 		bool valid;
@@ -139,7 +141,7 @@ DatabaseEntry:
 
 	File << <CHILD_CLASS_DATA>
 
-Database:
+- Database:
 	template <class T>
 	class Database {
 	private:
@@ -161,7 +163,7 @@ Database:
 	File << Index_1 << db[INDEX_1].valid << db[INDEX_1] << endl;
 	...
 
-API:
+- API:
 	Database.Database(filename);
 		Initializes database to use ~/.ocarina{-debug}/filename
 	Database.load();
@@ -183,7 +185,7 @@ API:
 Index: (lib/index.cpp)
 	An inverted index allows me to map multiple values to a single key.
 
-Index:
+- Index:
 	class Index {
 	private:
 		map<string, set<int>>
@@ -194,14 +196,15 @@ Index:
 		void save();
 		void insert(key, int);
 		void delete(key, int);
+		void replace(key, int);
 		const set<string> &keys();
 		const set<int> &operator[](string);
 	};
 
-	File << key << map[key].size() << endl;
-	File << int_0 << int_1 << ... << int_n << endl;
+	File << key << endl;
+	File << map[key].size() << int_0 << int_1 << ... << int_n << endl;
 
-API:
+- API:
 	Index.Index(filename);
 		Initializes an index using ~/.ocarina{-debug}/filename
 	Index.load();
@@ -217,6 +220,9 @@ API:
 		1) Remove int from the set of values associated with key
 		2) Do not delete key if set is empty
 		3) Index.save()
+	Index.replace(key, int)
+		1) map[key].clear()
+		2) insert(key, int)
 	Index.keys();
 		Return a set of index keys
 	Index.operator[](string key);
@@ -233,7 +239,7 @@ Library: (lib/library.cpp)
 	When a library : Track is created, it should be added to the "Library"
 	group if it is NOT a member of the banned songs group.
 
-Album:
+- Album:
 	class library :: Album : public DatabaseEntry {
 		string name;
 		short  year;
@@ -241,21 +247,21 @@ Album:
 
 	File << year << name
 
-Artist:
+- Artist:
 	class library :: Artist : public DatabaseEntry {
 		string name;
 	};
 
 	File << name
 
-Genre:
+- Genre:
 	class library :: Genre : public DatabaseEntry {
 		string name;
 	};
 
 	File << name
 
-Path:
+- Path:
 	class library :: Path : public DatabaseEntry {
 		string root_path;
 		bool enabled;
@@ -263,7 +269,7 @@ Path:
 
 	File << enabled << root_path
 
-Track:
+- Track:
 	class library :: Track : public DatabaseEntry {
 		unsigned int artist_id;
 		unsigned int album_id;
@@ -286,7 +292,7 @@ Track:
 	File << title << endl;
 	File << filepath << endl;
 
-Track: /* This struct lies outside the library namespace */
+- Track: /* This struct lies outside the library namespace */
 	struct Track {
 		library :: Album   *album;
 		library :: Artist  *artist;
@@ -295,14 +301,14 @@ Track: /* This struct lies outside the library namespace */
 		library :: Track   *track;
 	};
 
-Databases:
+- Databases:
 	Database<library :: Album>   album_db(album.db);
 	Database<library :: Artist>  artist_db(artist.db);
 	Database<library :: Album>   genre_db(genre.db);
 	Database<library :: Library> library_db(library.db);
 	Database<library :: Track>   track_db(track.db);
 
-Updating algorithm:
+- Updating algorithm:
 	set<pair<lib_id, track_path>> known_tracks;
 
 	1) For each track currently in the library, check if the track exists
@@ -345,10 +351,10 @@ Groups: (lib/group.cpp)
 	that cannot be deleted by the user based on library status.  Similar
 	to the library, groups should exist in their own namespace.
 
-Index:
+- Index:
 	Index group_idx(groups.idx)
 
-Default groups:
+- Default groups:
 	All music
 		All tracks are added to this group
 	Library
@@ -372,6 +378,21 @@ Default groups:
 
 
 
+Preferences: (lib/prefs.cpp)
+	Preferences make use of a special index where the set<int> is always
+	size 1.  Preferences will be in the prefs namespace.
+
+- Index:
+	Index prefs(prefs.idx);
+
+- API:
+	prefs :: set(string, val);
+		prefs.replace(string, val);
+	prefs :: get(string)
+		return prefs[string].begin()
+
+
+
 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