%%%-------------------------------------------------------------------
%%% @doc Follow / unfollow чужого календаря.
%%%
%%% POST   /v1/calendars/:id/follow — подписаться
%%% DELETE /v1/calendars/:id/follow — отписаться
%%% @end
%%%-------------------------------------------------------------------
-module(handler_calendar_follow).
-behaviour(cowboy_handler).

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

-include("records.hrl").

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

-spec trails() -> [map()].
trails() ->
  BaseParams = [
    #{
      name        => <<"id">>,
      in          => <<"path">>,
      description => <<"Calendar ID">>,
      required    => true,
      schema      => #{type => string}
    }
  ],
  FollowResponse = #{
    type       => object,
    properties => #{
      calendar_id => #{type => string},
      following   => #{type => boolean}
    }
  },
  [
    #{
      path        => <<"/v1/calendars/:id/follow">>,
      method      => <<"POST">>,
      description => <<"Follow a calendar (not paid subscription)">>,
      tags        => [<<"Calendars">>],
      parameters  => BaseParams,
      responses => #{
        200 => #{
          description => <<"Following">>,
          content     => #{<<"application/json">> => #{schema => FollowResponse}}
        },
        401 => #{description => <<"Unauthorized">>},
        403 => #{description => <<"Own calendar or access denied">>},
        404 => #{description => <<"Calendar not found">>}
      }
    },
    #{
      path        => <<"/v1/calendars/:id/follow">>,
      method      => <<"DELETE">>,
      description => <<"Unfollow a calendar">>,
      tags        => [<<"Calendars">>],
      parameters  => BaseParams,
      responses => #{
        200 => #{
          description => <<"Unfollowed">>,
          content     => #{<<"application/json">> => #{schema => FollowResponse}}
        },
        401 => #{description => <<"Unauthorized">>},
        403 => #{description => <<"Own calendar">>},
        404 => #{description => <<"Calendar not found">>}
      }
    }
  ].

-spec handle(cowboy_req:req(), any()) -> {ok, cowboy_req:req(), any()}.
handle(Req, _Opts) ->
  case cowboy_req:method(Req) of
    <<"POST">>   -> follow(Req);
    <<"DELETE">> -> unfollow(Req);
    _            -> handler_utils:send_error(Req, 405, <<"Method not allowed">>)
  end.

-spec follow(cowboy_req:req()) -> {ok, cowboy_req:req(), any()}.
follow(Req) ->
  case handler_utils:auth_user(Req) of
    {ok, UserId, Req1} ->
      CalendarId = cowboy_req:binding(id, Req1),
      case logic_calendar_follow:follow(UserId, CalendarId) of
        {ok, _} ->
          handler_utils:send_json(Req1, 200, #{
            calendar_id => CalendarId,
            following   => true
          });
        {error, not_found} ->
          handler_utils:send_error(Req1, 404, <<"Calendar not found">>);
        {error, own_calendar} ->
          handler_utils:send_error(Req1, 403, <<"Cannot follow own calendar">>);
        {error, access_denied} ->
          handler_utils:send_error(Req1, 403, <<"Access denied">>);
        {error, _} ->
          handler_utils:send_error(Req1, 500, <<"Internal server error">>)
      end;
    {error, Code, Message, Req1} ->
      handler_utils:send_error(Req1, Code, Message)
  end.

-spec unfollow(cowboy_req:req()) -> {ok, cowboy_req:req(), any()}.
unfollow(Req) ->
  case handler_utils:auth_user(Req) of
    {ok, UserId, Req1} ->
      CalendarId = cowboy_req:binding(id, Req1),
      case logic_calendar_follow:unfollow(UserId, CalendarId) of
        ok ->
          handler_utils:send_json(Req1, 200, #{
            calendar_id => CalendarId,
            following   => false
          });
        {error, own_calendar} ->
          handler_utils:send_error(Req1, 403, <<"Cannot unfollow own calendar">>);
        {error, _} ->
          handler_utils:send_error(Req1, 500, <<"Internal server error">>)
      end;
    {error, Code, Message, Req1} ->
      handler_utils:send_error(Req1, Code, Message)
  end.