-module(admin_handler_calendars).
-behaviour(cowboy_handler).
-export([init/2]).
-export([trails/0]).
-export([calendar_schema/0]).

-include("records.hrl").

init(Req, _Opts) ->
    case cowboy_req:method(Req) of
        <<"GET">> -> list_calendars(Req);
        _ -> handler_utils:send_error(Req, 405, <<"Method not allowed">>)
    end.

trails() ->
    [
        #{
            path => <<"/v1/admin/calendars">>,
            method => <<"GET">>,
            description => <<"List all calendars (admin)">>,
            tags => [<<"Admin Calendars">>],
            parameters => [
                #{name => <<"status">>,   in => <<"query">>, schema => #{type => string}, description => <<"Filter by status">>},
                #{name => <<"type">>,     in => <<"query">>, schema => #{type => string}, description => <<"Filter by type">>},
                #{name => <<"q">>,        in => <<"query">>, schema => #{type => string}, description => <<"Search in title/description">>},
                #{name => <<"sort_by">>,  in => <<"query">>, schema => #{type => string}, description => <<"Sort field (title, created_at, updated_at)">>},
                #{name => <<"sort_order">>, in => <<"query">>, schema => #{type => string, enum => [<<"asc">>, <<"desc">>]}, description => <<"Sort direction">>},
                #{name => <<"limit">>,    in => <<"query">>, schema => #{type => integer}, description => <<"Page size">>},
                #{name => <<"offset">>,   in => <<"query">>, schema => #{type => integer}, description => <<"Offset">>}
            ],
            responses => #{
                200 => #{
                    description => <<"Array of calendars">>,
                    content => #{<<"application/json">> => #{
                        schema => #{
                            type => array,
                            items => calendar_schema()
                        }
                    }}
                },
                403 => #{description => <<"Forbidden">>}
            }
        }
    ].

calendar_schema() ->
    #{
        type => object,
        properties => #{
            id => #{type => string},
            owner_id => #{type => string},
            title => #{type => string},
            description => #{type => string},
            short_name => #{type => string},
            category => #{type => string},
            color => #{type => string},
            image_url => #{type => string},
            settings => #{type => object},
            tags => #{type => array, items => #{type => string}},
            type => #{type => string, enum => [<<"personal">>, <<"commercial">>]},
            confirmation => #{type => string},
            rating_avg => #{type => number},
            rating_count => #{type => integer},
            status => #{type => string, enum => [<<"active">>, <<"frozen">>, <<"deleted">>]},
            reason => #{type => string},
            created_at => #{type => string, format => date_time},
            updated_at => #{type => string, format => date_time}
        }
    }.

%%% HTTP-метод

list_calendars(Req) ->
    case handler_utils:auth_admin(Req) of
        {ok, _AdminId, Req1} ->
            Pagination = handler_utils:parse_pagination_params(Req1),
            Filters = parse_calendar_filters(Req1),
            {ok, AllCalendars} = logic_calendar:admin_list_all(),
            Filtered = apply_calendar_filters(AllCalendars, Filters),
            % Формируем параметры сортировки из query-параметров
            Qs = cowboy_req:parse_qs(Req1),
            SortBy = proplists:get_value(<<"sort_by">>, Qs, <<"created_at">>),
            SortOrder = proplists:get_value(<<"sort_order">>, Qs, <<"desc">>),
            Sorted = sort_calendars(Filtered, SortBy, SortOrder),
            Total = length(Sorted),
            Page = lists:sublist(Sorted, maps:get(offset, Pagination) + 1, maps:get(limit, Pagination)),
            Json = [handler_utils:calendar_to_json(C) || C <- Page],
            ExtraHeaders = handler_utils:pagination_headers(Pagination, Total),
            handler_utils:send_json(Req1, 200, Json, ExtraHeaders);
        {error, Code, Msg, Req1} ->
            handler_utils:send_error(Req1, Code, Msg)
    end.

%%% Фильтрация

parse_calendar_filters(Req) ->
    Qs = cowboy_req:parse_qs(Req),
    #{
        status => proplists:get_value(<<"status">>, Qs),
        type   => proplists:get_value(<<"type">>, Qs),
        q      => proplists:get_value(<<"q">>, Qs)
    }.

apply_calendar_filters(Calendars, Filters) ->
    StatusBin = maps:get(status, Filters),
    TypeBin = maps:get(type, Filters),
    Q = maps:get(q, Filters),

    F1 = case StatusBin of
             undefined -> Calendars;
             _ -> Status = binary_to_existing_atom(StatusBin, utf8),
                 [C || C <- Calendars, C#calendar.status =:= Status]
         end,
    F2 = case TypeBin of
             undefined -> F1;
             _ -> Type = binary_to_existing_atom(TypeBin, utf8),
                 [C || C <- F1, C#calendar.type =:= Type]
         end,
    case Q of
        undefined -> F2;
        _ ->
            QLower = string:lowercase(binary_to_list(Q)),
            [C || C <- F2,
                string:str(string:lowercase(binary_to_list(C#calendar.title)), QLower) > 0 orelse
                    string:str(string:lowercase(binary_to_list(C#calendar.description)), QLower) > 0]
    end.

%%% Сортировка

sort_calendars(Calendars, SortBy, SortOrder) ->
    Index = case SortBy of
                <<"title">>      -> #calendar.title;      % элемент 3
                <<"created_at">> -> #calendar.created_at;  % элемент 17
                <<"updated_at">> -> #calendar.updated_at;  % элемент 18
                _                -> #calendar.created_at
            end,
    Sorted = lists:sort(fun(A, B) ->
        VA = element(Index, A),
        VB = element(Index, B),
        case SortOrder of
            <<"desc">> -> VA > VB;
            _ -> VA < VB
        end
                        end, Calendars),
    Sorted.