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1 /* Part of DML (Digital Music Laboratory)
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2 Copyright 2014-2015 Samer Abdallah, University of London
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3
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4 This program is free software; you can redistribute it and/or
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5 modify it under the terms of the GNU General Public License
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6 as published by the Free Software Foundation; either version 2
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7 of the License, or (at your option) any later version.
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8
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9 This program is distributed in the hope that it will be useful,
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10 but WITHOUT ANY WARRANTY; without even the implied warranty of
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11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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12 GNU General Public License for more details.
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13
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14 You should have received a copy of the GNU General Public
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15 License along with this library; if not, write to the Free Software
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16 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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17 */
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18
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19 :- module(echonest,
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20 [ echocall/4
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21 ]).
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22
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23 /** <module> Interface to echonest Web API
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24 */
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25
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26 :- use_module(library(fileutils)).
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27 :- use_module(library(http/json)).
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28 :- use_module(library(jpath)).
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29 :- use_module(library(webby)).
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30 :- use_module(library(state)).
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31
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32 :- set_prolog_flag(double_quotes,string).
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33
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34 :- setting(min_wait,number,3,"Minimum time between echonest requests").
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35 :- initialization set_state(next_request_time,0).
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36
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37 wait_respectfully :-
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38 get_time(Now),
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39 setting(min_wait,TMin),
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40 get_state(next_request_time,T0), T1 is max(Now,T0) + TMin,
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41 set_state(next_request_time,T1),
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42 ( Now>=T0 -> true
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43 ; DT is T0-Now,
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44 debug(echonest,"Sleeping for ~f seconds to respect rate limit",[DT]),
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45 sleep(DT)
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46 ).
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47
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48 echocall(Key,PathParts,Params,Response) :-
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49 debug(echonest,"Echonest call: ~q, ~q...",[PathParts,Params]),
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50 parts_path([api,v4|PathParts],Path),
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51 wait_respectfully,
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52 catch( restcall(get([api_key=Key, format=json | Params]), json(Response),
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53 [protocol(http), host('developer.echonest.com'), path(Path)], []),
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54 Ex, handle(Ex)).
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55
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56 handle(http_bad_status(SC,codes(Doc))) :- !,
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57 with_input_from(codes(Doc),json_read_dict(current_input,Dict)),
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58 jpath(response:status:(code:Code,message:Msg),Dict),
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59 throw(echonest_error(SC,Code,Msg)).
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60 handle(Ex) :- throw(Ex).
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61
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62
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63 prolog:message(echonest_error(SC,Code,Msg)) -->
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64 {http_status(SC,Meaning)},
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65 ["(HTTP ~w: ~w) Echonest error ~w: '~s'."-[SC,Meaning,Code,Msg]].
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