%%%-------------------------------------------------------------------
%%% @doc Административный обработчик для получения статистики.
%%% GET – возвращает агрегированную статистику для дашборда.
%%% Поддерживает фильтрацию по диапазону дат (from, to).
%%% @end
%%%-------------------------------------------------------------------
-module(admin_handler_stats).
-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) ->
  case cowboy_req:method(Req) of
    <<"GET">> -> get_stats(Req);
    _ -> handler_utils:send_error(Req, 405, <<"Method not allowed">>)
  end.

%%% Swagger metadata
-spec trails() -> [map()].
trails() ->
  [
    #{
      path => <<"/v1/admin/stats">>,
      method => <<"GET">>,
      description => <<"Get admin dashboard statistics">>,
      tags => [<<"Statistics">>],
      parameters => [
        #{name => <<"from">>, in => <<"query">>, schema => #{type => string, format => <<"date-time">>}, description => <<"Start date (ISO8601)">>},
        #{name => <<"to">>, in => <<"query">>, schema => #{type => string, format => <<"date-time">>}, description => <<"End date (ISO8601)">>}
      ],
      responses => #{
        200 => #{
          description => <<"Statistics object">>,
          content => #{<<"application/json">> => #{schema => stats_schema()}}
        },
        403 => #{description => <<"Admin access required">>}
      }
    }
  ].

stats_schema() ->
  #{
    type => object,
    properties => #{
      <<"users_total">> => #{type => integer, description => <<"Total number of users">>},
      <<"pending_users_total">> => #{type => integer, description => <<"Number of users awaiting email verification">>},
      <<"events_total">> => #{type => integer, description => <<"Total number of events">>},
      <<"calendars_total">> => #{type => integer, description => <<"Total number of calendars">>},
      <<"reviews_total">> => #{type => integer, description => <<"Total number of reviews">>},
      <<"reports_total">> => #{type => integer, description => <<"Total number of reports (all statuses)">>},
      <<"reports_pending">> => #{type => integer, description => <<"Number of pending reports">>},
      <<"reports_reviewed">> => #{type => integer, description => <<"Number of reviewed reports">>},
      <<"reports_dismissed">> => #{type => integer, description => <<"Number of dismissed reports">>},
      <<"tickets_total">> => #{type => integer, description => <<"Total number of tickets">>},
      <<"tickets_open">> => #{type => integer, description => <<"Number of open tickets">>},
      <<"subscriptions_total">> => #{type => integer, description => <<"Total number of subscriptions">>},
      <<"trial_subscriptions">> => #{type => integer, description => <<"Number of trial subscriptions">>},
      <<"avg_ticket_resolution_h">> => #{type => number, format => float, description => <<"Average ticket resolution time in hours">>},
      <<"registrations_by_day">> => #{
        type => array,
        items => #{type => object, properties => #{<<"date">> => #{type => string}, <<"count">> => #{type => integer}}},
        description => <<"Daily user registrations">>
      },
      <<"events_by_day">> => #{
        type => array,
        items => #{type => object, properties => #{<<"date">> => #{type => string}, <<"count">> => #{type => integer}}},
        description => <<"Daily event creations">>
      },
      <<"reviews_by_day">> => #{
        type => array,
        items => #{type => object, properties => #{<<"date">> => #{type => string}, <<"count">> => #{type => integer}}},
        description => <<"Daily review creations">>
      },
      <<"calendars_by_day">> => #{
        type => array,
        items => #{type => object, properties => #{<<"date">> => #{type => string}, <<"count">> => #{type => integer}}},
        description => <<"Daily calendar creations">>
      },
      <<"reports_by_day">> => #{
        type => array,
        items => #{type => object, properties => #{<<"date">> => #{type => string}, <<"count">> => #{type => integer}}},
        description => <<"Daily report creations">>
      },
      <<"tickets_by_day">> => #{
        type => array,
        items => #{type => object, properties => #{<<"date">> => #{type => string}, <<"count">> => #{type => integer}}},
        description => <<"Daily ticket creations">>
      },
      <<"subscriptions_by_day">> => #{
        type => array,
        items => #{type => object, properties => #{<<"date">> => #{type => string}, <<"count">> => #{type => integer}}},
        description => <<"Daily subscription creations">>
      },
      <<"pending_users_by_day">> => #{
        type => array,
        items => #{type => object, properties => #{<<"date">> => #{type => string}, <<"count">> => #{type => integer}}},
        description => <<"Daily pending user registrations">>
      },
      <<"admin_activity">> => #{
        type => array,
        items => #{type => object},
        description => <<"Recent admin actions (superadmin only)">>
      }
    }
  }.

%%% Internal functions

%% @doc Получить статистику с учетом параметров запроса.
-spec get_stats(cowboy_req:req()) -> {ok, binary(), cowboy_req:req()}.
get_stats(Req) ->
  case handler_utils:auth_admin(Req) of
    {ok, AdminId, Req1} ->
      {ok, Admin} = core_admin:get_by_id(AdminId),
      Role = Admin#admin.role,
      Stats = case parse_date_range(Req1) of
                {ok, From, To} ->
                  logic_stats:get_stats(Role, AdminId, From, To);
                _ ->
                  logic_stats:get_stats(Role, AdminId)
              end,
      handler_utils:send_json(Req1, 200, Stats);
    {error, Code, Message, Req1} ->
      handler_utils:send_error(Req1, Code, Message)
  end.

%% @private Разбирает параметры 'from' и 'to' из строки запроса.
%% В случае успеха возвращает {ok, FromDT, ToDT}.
-spec parse_date_range(cowboy_req:req()) -> {ok, calendar:datetime(), calendar:datetime()} | error.
parse_date_range(Req) ->
  Qs = cowboy_req:parse_qs(Req),
  From = handler_utils:parse_datetime_qs(proplists:get_value(<<"from">>, Qs)),
  To   = handler_utils:parse_datetime_qs(proplists:get_value(<<"to">>, Qs)),
  case {From, To} of
    {undefined, _} -> error;
    {_, undefined} -> error;
    {F, T} -> {ok, F, T}
  end.