-module(mongo@aggregation).
-compile(no_auto_import).

-export([aggregate/1, match/2, lookup/5, project/2, add_fields/2, sort/2, group/2, skip/2, limit/2, exec/1]).
-export_type([pipeline/0]).

-opaque pipeline() :: {pipeline,
                       mongo@client:collection(),
                       list(bson@types:value())}.

-spec aggregate(mongo@client:collection()) -> pipeline().
aggregate(Collection) ->
    {pipeline, Collection, []}.

-spec match(pipeline(), bson@types:value()) -> pipeline().
match(Pipeline, Doc) ->
    {pipeline,
     erlang:element(2, Pipeline),
     gleam@list:append(
         erlang:element(3, Pipeline),
         [{document, [{<<"$match"/utf8>>, Doc}]}]
     )}.

-spec lookup(pipeline(), binary(), binary(), binary(), binary()) -> pipeline().
lookup(Pipeline, From, Local_field, Foreign_field, Alias) ->
    {pipeline,
     erlang:element(2, Pipeline),
     gleam@list:append(
         erlang:element(3, Pipeline),
         [{document,
           [{<<"$lookup"/utf8>>,
             {document,
              [{<<"from"/utf8>>, {str, From}},
               {<<"localField"/utf8>>, {str, Local_field}},
               {<<"foreignField"/utf8>>, {str, Foreign_field}},
               {<<"as"/utf8>>, {str, Alias}}]}}]}]
     )}.

-spec project(pipeline(), bson@types:value()) -> pipeline().
project(Pipeline, Doc) ->
    {pipeline,
     erlang:element(2, Pipeline),
     gleam@list:append(
         erlang:element(3, Pipeline),
         [{document, [{<<"$project"/utf8>>, Doc}]}]
     )}.

-spec add_fields(pipeline(), bson@types:value()) -> pipeline().
add_fields(Pipeline, Doc) ->
    {pipeline,
     erlang:element(2, Pipeline),
     gleam@list:append(
         erlang:element(3, Pipeline),
         [{document, [{<<"$addFields"/utf8>>, Doc}]}]
     )}.

-spec sort(pipeline(), bson@types:value()) -> pipeline().
sort(Pipeline, Doc) ->
    {pipeline,
     erlang:element(2, Pipeline),
     gleam@list:append(
         erlang:element(3, Pipeline),
         [{document, [{<<"$sort"/utf8>>, Doc}]}]
     )}.

-spec group(pipeline(), bson@types:value()) -> pipeline().
group(Pipeline, Doc) ->
    {pipeline,
     erlang:element(2, Pipeline),
     gleam@list:append(
         erlang:element(3, Pipeline),
         [{document, [{<<"$group"/utf8>>, Doc}]}]
     )}.

-spec skip(pipeline(), integer()) -> pipeline().
skip(Pipeline, Count) ->
    {pipeline,
     erlang:element(2, Pipeline),
     gleam@list:append(
         erlang:element(3, Pipeline),
         [{document, [{<<"$skip"/utf8>>, {integer, Count}}]}]
     )}.

-spec limit(pipeline(), integer()) -> pipeline().
limit(Pipeline, Count) ->
    {pipeline,
     erlang:element(2, Pipeline),
     gleam@list:append(
         erlang:element(3, Pipeline),
         [{document, [{<<"$limit"/utf8>>, {integer, Count}}]}]
     )}.

-spec exec(pipeline()) -> {ok, list(bson@types:value())} | {error, nil}.
exec(Pipeline) ->
    case mongo@client:execute(
        erlang:element(2, Pipeline),
        {document,
         [{<<"cursor"/utf8>>, {document, []}},
          {<<"pipeline"/utf8>>, {array, erlang:element(3, Pipeline)}},
          {<<"aggregate"/utf8>>,
           {str, erlang:element(3, erlang:element(2, Pipeline))}}]}
    ) of
        {ok, Result} ->
            [{<<"ok"/utf8>>, Ok}, {<<"cursor"/utf8>>, {document, Result@1}}] = Result,
            [{<<"ns"/utf8>>, _@1},
             {<<"id"/utf8>>, _@2},
             {<<"firstBatch"/utf8>>, {array, Docs}}] = Result@1,
            case Ok of
                {double, 1.0} ->
                    {ok, Docs};

                _@3 ->
                    {error, nil}
            end;

        {error, nil} ->
            {error, nil}
    end.