diff cpack/dml/lib/spotify/echonest.pl @ 0:718306e29690 tip

commiting public release

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/cpack/dml/lib/spotify/echonest.pl	Tue Feb 09 21:05:06 2016 +0100
@@ -0,0 +1,65 @@
+/* Part of DML (Digital Music Laboratory)
+	Copyright 2014-2015 Samer Abdallah, University of London
+	 
+	This program is free software; you can redistribute it and/or
+	modify it under the terms of the GNU General Public License
+	as published by the Free Software Foundation; either version 2
+	of the License, or (at your option) any later version.
+
+	This program is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public
+	License along with this library; if not, write to the Free Software
+	Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+*/
+
+:- module(echonest, 
+   [	echocall/4
+   ]).
+
+/** <module> Interface to echonest Web API
+ */
+
+:- use_module(library(fileutils)).
+:- use_module(library(http/json)).
+:- use_module(library(jpath)).
+:- use_module(library(webby)).
+:- use_module(library(state)).
+
+:- set_prolog_flag(double_quotes,string).
+
+:- setting(min_wait,number,3,"Minimum time between echonest requests").
+:- initialization set_state(next_request_time,0). 
+
+wait_respectfully :-
+   get_time(Now),
+   setting(min_wait,TMin),
+   get_state(next_request_time,T0), T1 is max(Now,T0) + TMin,
+   set_state(next_request_time,T1),
+   (  Now>=T0 -> true
+   ;  DT is T0-Now, 
+      debug(echonest,"Sleeping for ~f seconds to respect rate limit",[DT]),
+      sleep(DT)
+   ).
+
+echocall(Key,PathParts,Params,Response) :-
+   debug(echonest,"Echonest call: ~q, ~q...",[PathParts,Params]),
+   parts_path([api,v4|PathParts],Path),
+   wait_respectfully,
+   catch( restcall(get([api_key=Key, format=json | Params]), json(Response), 
+                   [protocol(http), host('developer.echonest.com'), path(Path)], []),
+      Ex, handle(Ex)).
+
+handle(http_bad_status(SC,codes(Doc))) :- !,
+   with_input_from(codes(Doc),json_read_dict(current_input,Dict)),
+   jpath(response:status:(code:Code,message:Msg),Dict),
+   throw(echonest_error(SC,Code,Msg)).
+handle(Ex) :- throw(Ex).   
+
+
+prolog:message(echonest_error(SC,Code,Msg)) --> 
+   {http_status(SC,Meaning)},
+   ["(HTTP ~w: ~w) Echonest error ~w: '~s'."-[SC,Meaning,Code,Msg]].