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-module(media).
-export([init/0,insert/3, ask/2, all/0, play/3]).
% Since we are not willing to calculate and deliver all the id3 tags everytime they are requested,
% we try to get something persistent with mnesia.
% Concerning the parsing of id3tags we use the library id3v2 by Brendon Hogger. For detailed information take a
% look at the header of the library.
% What is an entry in our database made of? By the way the filepath includes the filename.
-record(track, {artist, title, votes, locked, filepath }).
% With which application do we play mp3s?
player(path) ->
{ok, ["/usr/bin/env", "mplayer", "-quiet", path]}.
% Before this module becomes usable, we must initialize it with the following steps:
% 1. Initialize the mnesiadatabase and create the table within it.
% 2. Parse the mp3s in the working directory and add them to the database
% 3. Get into a loop so the database can be actually queried and files can be played.
init() ->
mnesia:create_schema([node()]),
mnesia:start(),
mnesia:create_table(track, [{attributes, record_info(fields, track)}]),
io:format("Initialisation of mnesia successful.\n").
% Basic insertion of entrys into the database. Some entries are left out because they are 0 or false.
insert(Artist, Title, Filepath) ->
F = fun() ->
mnesia:write(#track{artist = Artist, title = Title, votes = 0, locked = false, filepath = Filepath})
end,
mnesia:transaction(F).
% We want to query in order to simplify the next calls.
ask(Artist, Title) ->
F = fun() ->
mnesia:match_object({track, Artist, Title, '_', '_', '_'})
end,
{atomic, Results} = mnesia:transaction(F),
Results.
% Just in case the client is interested in everything we got.
all() ->
F = fun() ->
mnesia:match({track, '_','_','_','_','_'})
end,
{atomic, Results} = mnesia:transaction(F),
Results.
% We want to play mp3s from our database.
play(Artist, Title, Callback) ->
[Head|_] = ask(Artist, Title),
{_, _, _, _, _, Fp} = Head,
% Port = erlang:open_port({spawn, Cmd}, [exit_status]).
Port = erlang:open_port({spawn_executable, "/usr/bin/mplayer"}, [{args, [Fp]}]).
% We want to execute commands locally
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