%%%------------------------------------------------------------------------
%% Copyright 2022, 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
%% @end
%%%-------------------------------------------------------------------------
-module(otel_view).

-export([new/2,
         new/3,
         match_instrument_to_views/2]).

-include_lib("opentelemetry_api_experimental/include/otel_metrics.hrl").
-include_lib("opentelemetry_api/include/opentelemetry.hrl").
-include_lib("opentelemetry_experimental/include/otel_metrics.hrl").
-include("otel_view.hrl").

-type name() :: atom().

-type criteria() :: #{instrument_name => otel_instrument:name(),
                      instrument_kind => otel_instrument:kind(),
                      meter_name => unicode:unicode_binary() | undefined,
                      meter_version => unicode:unicode_binary() | undefined,
                      meter_schema_url => unicode:unicode_binary() | undefined}.
-type config() :: #{description => unicode:unicode_binary(),
                    attribute_keys => [atom()],
                    aggregation_module => module() | default,
                    aggregation_options => map()
                    %% exemplar_reservoir
                   }.

-type t() :: #view{}.

-export_type([t/0,
              name/0,
              criteria/0,
              config/0]).

-include_lib("opentelemetry_api/include/gradualizer.hrl").

%% no name means Instrument name is used
%% must reject wildcard Criteria  in this case
-dialyzer({nowarn_function,new/2}).
-spec new(criteria() | undefined, config()) -> t().
new(Criteria, Config) ->
    CriteriaInstrumentName = view_name_from_criteria(Criteria),
    Matchspec = criteria_to_instrument_matchspec(Criteria),
    %% no name given so use the name of the instrument in the selection
    %% if no instrument name is given then it'll stay `undefined'
    #view{name=CriteriaInstrumentName,
          instrument_matchspec=Matchspec,
          description=maps:get(description, Config, undefined),
          attribute_keys=maps:get(attribute_keys, Config, []),
          aggregation_module=maps:get(aggregation_module, Config, undefined),
          aggregation_options=maps:get(aggregation_options, Config, #{})}.

-dialyzer({nowarn_function,new/3}).
-spec new(name(), criteria() | undefined, config()) -> t().
new(undefined, Criteria, Config) ->
    new(Criteria, Config);
new(Name, Criteria, Config) ->
    View = new(Criteria, Config),
    View#view{name=Name}.

-dialyzer({nowarn_function,match_instrument_to_views/2}).
-spec match_instrument_to_views(otel_instrument:t(), [otel_view:t()]) ->
          [{otel_view:t() | undefined, #view_aggregation{}}].
match_instrument_to_views(Instrument=#instrument{name=InstrumentName,
                                                 meter=Meter,
                                                 description=Description}, Views) ->
    IsMonotonic = otel_instrument:is_monotonic(Instrument),
    Temporality = otel_aggregation:instrument_temporality(Instrument),
    Scope = otel_meter:scope(Meter),
    case lists:filtermap(fun(View=#view{name=ViewName,
                                        description=ViewDescription,
                                        aggregation_options=AggregationOptions,
                                        instrument_matchspec=Matchspec}) ->
                                 case ets:match_spec_run([Instrument], Matchspec) of
                                     [] ->
                                         false;
                                     _ ->
                                         {true, {View, #view_aggregation{name=value_or(ViewName,
                                                                                       InstrumentName),
                                                                         scope=Scope,
                                                                         instrument=Instrument,
                                                                         temporality=Temporality,
                                                                         is_monotonic=IsMonotonic,
                                                                         aggregation_options=AggregationOptions,
                                                                         description=value_or(ViewDescription,
                                                                                              Description)
                                                                        }}}
                                 end
                         end, Views) of
        [] ->
            [{undefined, #view_aggregation{name=InstrumentName,
                                           scope=Scope,
                                           instrument=Instrument,
                                           temporality=Temporality,
                                           is_monotonic=IsMonotonic,
                                           aggregation_options=#{},
                                           description=Description}}];
        Aggs ->
            Aggs
    end.

%%

value_or(undefined, Other) ->
    Other;
value_or(Value, _Other) ->
    Value.

-dialyzer({nowarn_function,criteria_to_instrument_matchspec/1}).
-spec criteria_to_instrument_matchspec(map() | undefined) -> ets:compiled_match_spec().
criteria_to_instrument_matchspec(Criteria) when is_map(Criteria) ->
    Instrument =
      maps:fold(fun(instrument_name, InstrumentName, InstrumentAcc) ->
                        InstrumentAcc#instrument{name=InstrumentName};
                   (instrument_kind, Kind, InstrumentAcc) ->
                        InstrumentAcc#instrument{kind=Kind};
                   (meter_name, MeterName, InstrumentAcc) ->
                        Meter = maybe_init_meter(InstrumentAcc),
                        Meter1 = update_meter_name(MeterName, Meter),
                        InstrumentAcc#instrument{meter=Meter1};
                   (meter_version, MeterVersion, InstrumentAcc) ->
                        Meter = maybe_init_meter(InstrumentAcc),
                        Meter1 = update_meter_version(MeterVersion, Meter),
                        InstrumentAcc#instrument{meter=Meter1};
                   (meter_schema_url, SchemaUrl, InstrumentAcc) ->
                        Meter = maybe_init_meter(InstrumentAcc),
                        Meter1 = update_meter_schema_url(SchemaUrl, Meter),
                        InstrumentAcc#instrument{meter=Meter1}
                        %% eqwalizer:ignore building a matchspec and don't want '_' polluting the type
                end, #instrument{_='_'}, Criteria),
    ets:match_spec_compile([{Instrument, [], [true]}]);
criteria_to_instrument_matchspec(_) ->
    %% eqwalizer:ignore building a matchspec and don't want '_' polluting the type
    ets:match_spec_compile([{#instrument{_='_'}, [], [true]}]).

-dialyzer({nowarn_function,maybe_init_meter/1}).
maybe_init_meter(#instrument{meter='_'}) ->
    {'_', #meter{instrumentation_scope=#instrumentation_scope{_='_'},
                 _='_'}}.

-dialyzer({nowarn_function,update_meter_name/2}).
update_meter_name(MeterName, {_, Meter=#meter{instrumentation_scope=Scope}}) ->
    {'_', Meter#meter{instrumentation_scope=Scope#instrumentation_scope{name=MeterName}}}.

-dialyzer({nowarn_function,update_meter_version/2}).
update_meter_version(MeterVersion, {_, Meter=#meter{instrumentation_scope=Scope}}) ->
    {'_', Meter#meter{instrumentation_scope=Scope#instrumentation_scope{version=MeterVersion}}}.

-dialyzer({nowarn_function,update_meter_schema_url/2}).
update_meter_schema_url(SchemaUrl, {_, Meter=#meter{instrumentation_scope=Scope}}) ->
    {'_', Meter#meter{instrumentation_scope=Scope#instrumentation_scope{schema_url=SchemaUrl}}}.

view_name_from_criteria(Criteria) when is_map(Criteria) ->
    maps:get(instrument_name, Criteria, undefined);
view_name_from_criteria(_) ->
    undefined.