Updated mediamodule

1 files changed, 63 insertions, 0 deletions

diff --git a/media.erl b/media.erl
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+-module(media).
+-export([init/0,insert/3, ask/2, all/0]).
+
+% 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),
+    {_, artist, title, _, _, fp} = Head,
+    Cmd = "mplayer -quiet " ++ fp,
+    Port = erlang:open_port({spawn, Cmd}, [exit_status]).
+    
+% We want to execute commands locally
+