%%%-------------------------------------------------------------------
%%% @doc Обработчик подписки текущего пользователя (клиентский API).
%%%
%%% GET  – получить информацию о подписке.
%%% POST – активировать подписку или начать пробный период.
%%% @end
%%%-------------------------------------------------------------------
-module(handler_subscription).
-behaviour(cowboy_handler).

-export([init/2]).
-export([trails/0]).

-include("records.hrl").

%%% cowboy_handler callback
-spec init(cowboy_req:req(), any()) -> {ok, cowboy_req:req(), any()}.
init(Req, Opts) ->
  handle(Req, Opts).

%%% Swagger metadata
-spec trails() -> [map()].
trails() ->
  [
    #{  % GET
      path        => <<"/v1/subscription">>,
      method      => <<"GET">>,
      description => <<"Get current user subscription">>,
      tags        => [<<"Subscription">>],
      responses   => #{
        200 => #{
          description => <<"Subscription details">>,
          content     => #{<<"application/json">> => #{schema => subscription_schema()}}
        },
        401 => #{description => <<"Unauthorized">>}
      }
    },
    #{  % POST
      path        => <<"/v1/subscription">>,
      method      => <<"POST">>,
      description => <<"Activate subscription or start trial">>,
      tags        => [<<"Subscription">>],
      requestBody => #{
        required => true,
        content  => #{<<"application/json">> => #{schema => #{
          type       => object,
          required   => [<<"action">>],
          properties => #{
            action       => #{type => string, enum => [<<"start_trial">>, <<"activate">>]},
            plan         => #{type => string, enum => [<<"monthly">>, <<"quarterly">>, <<"biannual">>, <<"annual">>]},
            payment_info => #{type => object, description => <<"Payment information">>}
          }
        }}}
      },
      responses => #{
        201 => #{description => <<"Subscription activated or trial started">>},
        400 => #{description => <<"Invalid action or JSON">>},
        402 => #{description => <<"Payment failed">>},
        409 => #{description => <<"Already has active subscription">>}
      }
    }
  ].

subscription_schema() ->
  #{
    type       => object,
    properties => #{
      id          => #{type => string},
      user_id     => #{type => string},
      plan        => #{type => string, enum => [<<"monthly">>, <<"quarterly">>, <<"biannual">>, <<"annual">>]},
      status      => #{type => string, enum => [<<"active">>, <<"expired">>, <<"cancelled">>]},
      trial_used  => #{type => boolean},
      started_at  => #{type => string, format => <<"date-time">>},
      expires_at  => #{type => string, format => <<"date-time">>},
      created_at  => #{type => string, format => <<"date-time">>},
      updated_at  => #{type => string, format => <<"date-time">>}
    }
  }.

%%%===================================================================
%%% HTTP-методы
%%%===================================================================

%% @private
-spec handle(cowboy_req:req(), any()) -> {ok, cowboy_req:req(), any()}.
handle(Req, _Opts) ->
  case cowboy_req:method(Req) of
    <<"GET">>  -> get_subscription(Req);
    <<"POST">> -> create_subscription(Req);
    _          -> handler_utils:send_error(Req, 405, <<"Method not allowed">>)
  end.

%% @doc GET /v1/subscription — получить подписку текущего пользователя.
-spec get_subscription(cowboy_req:req()) -> {ok, binary(), cowboy_req:req()}.
get_subscription(Req) ->
  case handler_utils:auth_user(Req) of
    {ok, UserId, Req1} ->
      case logic_subscription:get_user_subscription(UserId) of
        {ok, Subscription} ->
          handler_utils:send_json(Req1, 200, subscription_to_json(Subscription));
        {error, _} ->
          handler_utils:send_error(Req1, 500, <<"Internal server error">>)
      end;
    {error, Code, Message, Req1} ->
      handler_utils:send_error(Req1, Code, Message)
  end.

%% @doc POST /v1/subscription — активировать подписку.
-spec create_subscription(cowboy_req:req()) -> {ok, binary(), cowboy_req:req()}.
create_subscription(Req) ->
  case handler_utils:auth_user(Req) of
    {ok, UserId, Req1} ->
      {ok, Body, Req2} = cowboy_req:read_body(Req1),
      try jsx:decode(Body, [return_maps]) of
        Decoded when is_map(Decoded) ->
          case Decoded of
            #{<<"action">> := <<"start_trial">>} ->
              case logic_subscription:start_trial(UserId) of
                {ok, Subscription} ->
                  Response = subscription_to_json(Subscription),
                  handler_utils:send_json(Req2, 201, Response);
                {error, already_has_subscription} ->
                  handler_utils:send_error(Req2, 409, <<"Already has active subscription">>);
                {error, _} ->
                  handler_utils:send_error(Req2, 500, <<"Internal server error">>)
              end;
            #{<<"action">> := <<"activate">>, <<"plan">> := PlanBin} ->
              Plan = parse_plan(PlanBin),
              PaymentInfo = maps:get(<<"payment_info">>, Decoded, #{}),
              case logic_subscription:activate_subscription(UserId, Plan, PaymentInfo) of
                {ok, Subscription} ->
                  Response = subscription_to_json(Subscription),
                  handler_utils:send_json(Req2, 201, Response);
                {error, payment_failed} ->
                  handler_utils:send_error(Req2, 402, <<"Payment failed">>);
                {error, _} ->
                  handler_utils:send_error(Req2, 500, <<"Internal server error">>)
              end;
            _ ->
              handler_utils:send_error(Req2, 400, <<"Invalid action. Use 'start_trial' or 'activate'">>)
          end;
        _ ->
          handler_utils:send_error(Req2, 400, <<"Invalid JSON">>)
      catch
        _:_ -> handler_utils:send_error(Req2, 400, <<"Invalid JSON format">>)
      end;
    {error, Code, Message, Req1} ->
      handler_utils:send_error(Req1, Code, Message)
  end.

%%%===================================================================
%%% Внутренние функции
%%%===================================================================

%% @private Преобразует бинарное имя плана в атом.
-spec parse_plan(binary()) -> monthly | quarterly | biannual | annual.
parse_plan(<<"monthly">>)   -> monthly;
parse_plan(<<"quarterly">>) -> quarterly;
parse_plan(<<"biannual">>)  -> biannual;
parse_plan(<<"annual">>)    -> annual;
parse_plan(_)               -> monthly.

%% @private Формирует JSON-представление подписки (поддерживает как запись, так и карту).
-spec subscription_to_json(#subscription{} | map()) -> map().
subscription_to_json(Subscription) when is_tuple(Subscription) ->
  handler_utils:subscription_to_json(Subscription);
subscription_to_json(Subscription) when is_map(Subscription) ->
  Subscription.