%%%------------------------------------------------------------------------
%% Copyright 2019, OpenTelemetry Authors
%% Licensed under the Apache License, Version 2.0 (the "License");
%% you may not use this file except in compliance with the License.
%% You may obtain a copy of the License at
%%
%% http://www.apache.org/licenses/LICENSE-2.0
%%
%% Unless required by applicable law or agreed to in writing, software
%% distributed under the License is distributed on an "AS IS" BASIS,
%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
%% See the License for the specific language governing permissions and
%% limitations under the License.
%%
%% @doc An aggregator that keeps each recorded measurement in a list of
%% values. The list is reset to the empty list after each checkpoint.
%% @end
%%%-------------------------------------------------------------------------
-module(ot_metric_aggregator_array).

-behaviour(ot_metric_aggregator).

-export([update/4,
         checkpoint/2,
         merge/2,
         initial_value/1]).

%% ignore the warningi about use of `current=[Number | Current]' in `select_replace'
-dialyzer(no_improper_lists).

-include("ot_meter.hrl").
-include_lib("stdlib/include/ms_transform.hrl").

-spec update(ets:tab(), ot_meter:key(), ot_meter:input_type(), number()) -> boolean().
update(Tab, Key, _, Number) ->
    select_replace(Tab, Key, Number).

-spec checkpoint(ets:tab(), {ot_meter:name(), ot_meter:label_set()}) -> boolean().
checkpoint(Tab, NameLabelSet) ->
    MS = ets:fun2ms(fun(A=#active_instrument{key=Key,
                                             aggregator=Aggregator,
                                             instrument=#instrument{input_type=integer},
                                             current=Current}) when Key =:= NameLabelSet ->
                            A#active_instrument{checkpoint=Current,
                                                current=[]};
                       (A=#active_instrument{key=Key,
                                             aggregator=Aggregator,
                                             instrument=#instrument{input_type=float},
                                             current=Current}) when Key =:= NameLabelSet ->
                            A#active_instrument{checkpoint=Current,
                                                current=[]}
                    end),
    case ets:select_replace(Tab, MS) of
      0 ->
          false;
      _ ->
          true
    end.

-spec merge([number()], [number()]) -> [number()].
merge(List1, List2) ->
    List1 ++ List2.

-spec initial_value(ot_meter:input_type()) -> [].
initial_value(_) ->
    [].

%%

select_replace(Tab, NameLabelSet, Number) ->
    MS = ets:fun2ms(fun(A=#active_instrument{key=Key,
                                             current=Current}) when Key =:= NameLabelSet ->
                            A#active_instrument{current=[Number | Current]}
                    end),
    case ets:select_replace(Tab, MS) of
        1 ->
            true;
        _ ->
            false
    end.