-module(mapred).

%% API
-export([mapred/1, maptags/3, redtags/2,decoder/1,get_riak_hostport/1]).
-record(hostport, {host, port}).

get_riak_hostport(Name) ->
  {ok, Nodes} = application:get_env(twitterminer, riak_nodes),
  {Name, Keys} = lists:keyfind(Name, 1, Nodes),
  #hostport{host=keyfind(host, Keys),
            port=keyfind(port, Keys)}.

keyfind(Key, L) ->
  {Key, V} = lists:keyfind(Key, 1, L),
  V.

mapred(Keys) ->
RHP = get_riak_hostport(riak1),
  {ok, Pid} = riakc_pb_socket:start(RHP#hostport.host, RHP#hostport.port),
  {ok, [{1, [Result]}]} = riakc_pb_socket:mapred(
    Pid,
    Keys,
    [
      {map, {modfun, ?MODULE, maptags}, none, false},
      {reduce, {modfun, ?MODULE, redtags}, none, true}
    ]
  ),
  dict:to_list(Result).

maptags(RiakObject, _, _) ->  %We don't care about keydata or the static argument
  [dict:from_list([{I, 1} || I <- decoder(riak_object:get_value(RiakObject))])].

redtags(Input, _) ->  %Once again we don't care about the static argument
  [lists:foldl(
    fun(Tag, Acc) ->
      dict:merge(
        fun(_, Amount1, Amount2) ->
          Amount1 + Amount2
        end,
        Tag,
        Acc
      )
    end,
    dict:new(),
    Input
  )].

decoder(B) ->
  case jiffy:decode(B) of
    {L}->
      case lists:keyfind(<<"coordinates">>, 1, L) of
        {_, M} -> {found, M};
        false -> not_found
      end;
    _->{invalid_tweet, B}
  end.