%% -------------------------------------------------------------------
%%
%% Copyright (c) 2014 Basho Technologies, Inc.  All Rights Reserved.
%%
%%   This Source Code Form is subject to the terms of the Mozilla Public
%%   License, v. 2.0. If a copy of the MPL was not distributed with this
%%   file, You can obtain one at http://mozilla.org/MPL/2.0/.
%%
%% -------------------------------------------------------------------

%% @doc Exometer reporter for lager backend
%%
%% This reporter emits messages to the lager logging backend,
%% at a reporting level chosen by the user (default: `notice').
%%
%% To change the reporting level, pass on the option `{level, Level}'.
%%
%% Example:
%% <pre lang="erlang">
%% Eshell V5.9.2  (abort with ^G)
%% 1&gt; exometer:start().
%% 17:41:14.078 [info] Application lager started on node nonode@nohost
%% ok
%% 17:41:14.125 [info] Starting reporters with []
%% 17:41:14.125 [info] Application exometer started on node nonode@nohost
%%
%% 2&gt; lager:set_loglevel(lager_console_backend,notice).
%% ok
%% 3&gt; exometer:new([c], counter).
%% ok
%% 4&gt; exometer:update([c], 2).
%% ok
%% 5&gt; exometer_report:add_reporter(
%%        exometer_report_lager,[{type_map,[{'_',integer}]}]).
%% ok
%% 6&gt; exometer_report:subscribe(exometer_report_lager,[c],[value],10000).
%% ok
%% 17:42:47.496 [notice] exometer_report_lager: c_value 1398008567:2 (integer)
%% 17:42:57.498 [notice] exometer_report_lager: c_value 1398008577:2 (integer)
%% 17:43:07.499 [notice] exometer_report_lager: c_value 1398008587:2 (integer)
%% 7&gt; exometer:update([c], 2).
%% ok
%% 17:43:17.501 [notice] exometer_report_lager: c_value 1398008597:4 (integer)
%% </pre>
%% @end

-module(exometer_report_lager).

-behaviour(exometer_report).

-export(
   [
    exometer_init/1,
    exometer_info/2,
    exometer_cast/2,
    exometer_call/3,
    exometer_report/5,
    exometer_subscribe/5,
    exometer_unsubscribe/4,
    exometer_newentry/2,
    exometer_setopts/4,
    exometer_terminate/2
   ]).

-include_lib("exometer_core/include/exometer.hrl").
-include("log.hrl").

-define(SERVER, ?MODULE).
%% calendar:datetime_to_gregorian_seconds({{1970,1,1},{0,0,0}}).
-define(UNIX_EPOCH, 62167219200).

-record(st, {type_map = [], level = notice}).

%%%===================================================================
%%% exometer_report callback API
%%%===================================================================

exometer_init(Opts) ->
    ?info("~p(~p): Starting~n", [?MODULE, Opts]),
    St0 = #st{},
    TypeMap = proplists:get_value(type_map, Opts, St0#st.type_map),
    Level = proplists:get_value(level, Opts, St0#st.level),
    {ok, St0#st{type_map = TypeMap, level = Level}}.

exometer_subscribe(_Metric, _DataPoint, _Extra, _Interval, St) ->
    {ok, St}.

exometer_unsubscribe(_Metric, _DataPoint, _Extra, St) ->
    {ok, St}.

%% Invoked through the remote_exometer() function to
%% send out an update.
exometer_report(Metric, DataPoint, _Extra, Value, #st{level = Level} = St)  ->
    ?debug("Report metric ~p_~p = ~p~n", [Metric, DataPoint, Value]),
    %% Report the value and setup a new refresh timer.
    Str = [?MODULE_STRING, ": ", name(Metric, DataPoint),
           ":", value(Value), $\n],
    log(Level, lists:flatten(Str)),
    {ok, St}.

exometer_call(Unknown, From, St) ->
    ?info("Unknown call ~p from ~p", [Unknown, From]),
    {ok, St}.

exometer_cast(Unknown, St) ->
    ?info("Unknown cast: ~p", [Unknown]),
    {ok, St}.

exometer_info(Unknown, St) ->
    ?info("Unknown info: ~p", [Unknown]),
    {ok, St}.

exometer_newentry(_Entry, St) ->
    {ok, St}.

exometer_setopts(_Metric, _Options, _Status, St) ->
    {ok, St}.

exometer_terminate(_, _) ->
    ignore.

%%%===================================================================
%%% Internal functions
%%%===================================================================

%% Add metric and datapoint within metric
name(Metric, DataPoint) ->
    metric_to_string(Metric) ++ "_" ++ thing_to_list(DataPoint).

metric_to_string([Final]) ->
    thing_to_list(Final);
metric_to_string([H | T]) ->
    thing_to_list(H) ++ "_" ++ metric_to_string(T).

thing_to_list(E) when is_atom(E) -> atom_to_list(E);
thing_to_list(E) when is_list(E) -> E;
thing_to_list(E) when is_integer(E) -> integer_to_list(E);
thing_to_list(E) when is_binary(E)  -> binary_to_list(E).


%% Add value, int or float, converted to list
value(V) when is_integer(V) -> integer_to_list(V);
value(V) when is_float(V)   -> io_lib:format("~f", [V]);
value(_) -> "0".

log(Level, String) ->
    lager:log(Level, self(), String).