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