%% This Source Code Form is subject to the terms of the Mozilla Public
%% License, v. 2.0. If a copy of the MPL was not distributed with this
%% file, You can obtain one at https://mozilla.org/MPL/2.0/.
%%
%% Copyright (c) 2007-2025 Broadcom. All Rights Reserved. The term “Broadcom” refers to Broadcom Inc. and/or its subsidiaries. All rights reserved.
%%

-module(rabbit_db_msup).

-include_lib("khepri/include/khepri.hrl").
-include("mirrored_supervisor.hrl").

-include("include/rabbit_khepri.hrl").
-include_lib("kernel/include/logger.hrl").

-export([
         create_tables/0,
         table_definitions/0,
         create_or_update/5,
         find_mirror/2,
         update_all/2,
         delete/2,
         delete_all/1,
         clear_in_khepri/0
        ]).

-export([clear/0]).

-export([khepri_mirrored_supervisor_path/2]).

-define(TABLE, mirrored_sup_childspec).
-define(TABLE_DEF,
        {?TABLE,
         [{record_name, mirrored_sup_childspec},
          {type, ordered_set},
          {attributes, record_info(fields, mirrored_sup_childspec)}]}).
-define(TABLE_MATCH, {match, #mirrored_sup_childspec{ _ = '_' }}).

%% -------------------------------------------------------------------
%% create_tables().
%% -------------------------------------------------------------------

-spec create_tables() -> Ret when
      Ret :: 'ok' | {error, Reason :: term()}.

create_tables() ->
    rabbit_khepri:handle_fallback(
      #{mnesia => fun() -> create_tables_in_mnesia([?TABLE_DEF]) end,
        khepri => fun() -> ok end
       }).

create_tables_in_mnesia([]) ->
    ok;
create_tables_in_mnesia([{Table, Attributes} | Ts]) ->
    case mnesia:create_table(Table, Attributes) of
        {atomic, ok}                        -> create_tables_in_mnesia(Ts);
        {aborted, {already_exists, ?TABLE}} -> create_tables_in_mnesia(Ts);
        Err                                 -> Err
    end.

%% -------------------------------------------------------------------
%% table_definitions().
%% -------------------------------------------------------------------

-spec table_definitions() -> [Def] when
      Def :: {Name :: atom(), term()}.

table_definitions() ->
    {Name, Attributes} = ?TABLE_DEF,
    [{Name, [?TABLE_MATCH | Attributes]}].

%% -------------------------------------------------------------------
%% create_or_update().
%% -------------------------------------------------------------------

-spec create_or_update(Group, Overall, Delegate, ChildSpec, Id) -> Ret when
      Group :: mirrored_supervisor:group_name(),
      Overall :: pid(),
      Delegate :: pid() | undefined,
      ChildSpec :: supervisor2:child_spec(),
      Id :: mirrored_supervisor:child_id(),
      Ret :: start | undefined | pid().

create_or_update(Group, Overall, Delegate, ChildSpec, Id) ->
    rabbit_khepri:handle_fallback(
      #{mnesia =>
            fun() ->
                    create_or_update_in_mnesia(Group, Overall, Delegate, ChildSpec, Id)
            end,
        khepri =>
            fun() ->
                    create_or_update_in_khepri(Group, Overall, Delegate, ChildSpec, Id)
            end
       }).

create_or_update_in_mnesia(Group, Overall, Delegate, ChildSpec, Id) ->
    rabbit_mnesia:execute_mnesia_transaction(
      fun() ->
              ReadResult = mnesia:wread({?TABLE, {Group, Id}}),
              ?LOG_DEBUG("Mirrored supervisor: check_start table ~ts read for key ~tp returned ~tp",
                               [?TABLE, {Group, Id}, ReadResult]),
              case ReadResult of
                  []  -> _ = write_in_mnesia(Group, Overall, ChildSpec, Id),
                         start;
                  [S] -> #mirrored_sup_childspec{key           = {Group, Id},
                                                 mirroring_pid = Pid} = S,
                         case Overall of
                             Pid ->
                                 ?LOG_DEBUG("Mirrored supervisor: overall matched mirrored pid ~tp", [Pid]),
                                 Delegate;
                             _   ->
                                 ?LOG_DEBUG("Mirrored supervisor: overall ~tp did not match mirrored pid ~tp", [Overall, Pid]),
                                 Sup = mirrored_supervisor:supervisor(Pid),
                                 ?LOG_DEBUG("Mirrored supervisor: supervisor(~tp) returned ~tp", [Pid, Sup]),
                                 case Sup of
                                     dead      ->
                                         _ = write_in_mnesia(Group, Overall, ChildSpec, Id),
                                         start;
                                     Delegate0 ->
                                         Delegate0
                                 end
                         end
              end
      end).

write_in_mnesia(Group, Overall, ChildSpec, Id) ->
    S = #mirrored_sup_childspec{key           = {Group, Id},
                                mirroring_pid = Overall,
                                childspec     = ChildSpec},
    ok = mnesia:write(?TABLE, S, write),
    ChildSpec.

create_or_update_in_khepri(Group, Overall, Delegate, ChildSpec, Id) ->
    Path = khepri_mirrored_supervisor_path(Group, Id),
    S = #mirrored_sup_childspec{key           = {Group, Id},
                                mirroring_pid = Overall,
                                childspec     = ChildSpec},
    case rabbit_khepri:adv_get(Path) of
        {ok, #{Path := #{data := #mirrored_sup_childspec{mirroring_pid = Pid},
                         payload_version := Vsn}}} ->
            case Overall of
                Pid ->
                    Delegate;
                _   ->
                    %% The supervisor(Pid) call can't happen inside of a transaction.
                    %% We have to read and update the record in two different khepri calls
                    case mirrored_supervisor:supervisor(Pid) of
                        dead ->
                            UpdatePath =
                                khepri_path:combine_with_conditions(
                                  Path, [#if_payload_version{version = Vsn}]),
                            Ret = rabbit_khepri:put(UpdatePath, S),
                            case Ret of
                                ok -> start;
                                {error, {khepri, mismatching_node, _}} ->
                                    create_or_update_in_khepri(Group, Overall, Delegate, ChildSpec, Id);
                                {error, _} = Error -> Error
                            end;
                        Delegate0 ->
                            Delegate0
                    end
            end;
        _  ->
            %% FIXME: Not atomic with the get above.
            ok = rabbit_khepri:put(Path, S),
            start
    end.

%% -------------------------------------------------------------------
%% delete().
%% -------------------------------------------------------------------

-spec delete(Group, Id) -> ok when
      Group :: mirrored_supervisor:group_name(),
      Id :: mirrored_supervisor:child_id().

delete(Group, Id) ->
    rabbit_khepri:handle_fallback(
      #{mnesia => fun() -> delete_in_mnesia(Group, Id) end,
        khepri => fun() -> delete_in_khepri(Group, Id) end
       }).

delete_in_mnesia(Group, Id) ->
    rabbit_mnesia:execute_mnesia_transaction(
      fun() ->
              ok = mnesia:delete({?TABLE, {Group, Id}})
      end).

delete_in_khepri(Group, Id) ->
    ok = rabbit_khepri:delete(khepri_mirrored_supervisor_path(Group, Id)).

%% -------------------------------------------------------------------
%% find_mirror().
%% -------------------------------------------------------------------

-spec find_mirror(Group, Id) -> Ret when
      Group :: mirrored_supervisor:group_name(),
      Id :: mirrored_supervisor:child_id(),
      Ret :: {ok, pid()} | {error, not_found}.

find_mirror(Group, Id) ->
    %% If we did this inside a tx we could still have failover
    %% immediately after the tx - we can't be 100% here. So we may as
    %% well dirty_select.
    rabbit_khepri:handle_fallback(
      #{mnesia => fun() -> find_mirror_in_mnesia(Group, Id) end,
        khepri => fun() -> find_mirror_in_khepri(Group, Id) end
       }).

find_mirror_in_mnesia(Group, Id) ->
    MatchHead = #mirrored_sup_childspec{mirroring_pid = '$1',
                                        key           = {Group, Id},
                                        _             = '_'},
    case mnesia:dirty_select(?TABLE, [{MatchHead, [], ['$1']}]) of
        [Mirror] -> {ok, Mirror};
        _ -> {error, not_found}
    end.

find_mirror_in_khepri(Group, Id) ->
    case rabbit_khepri:get(khepri_mirrored_supervisor_path(Group, Id)) of
        {ok, #mirrored_sup_childspec{mirroring_pid = Pid}} ->
            {ok, Pid};
        _ ->
            {error, not_found}
    end.

%% -------------------------------------------------------------------
%% update_all().
%% -------------------------------------------------------------------

-spec update_all(Overall, Overall) -> [ChildSpec] | Error when
      Overall :: pid(),
      ChildSpec :: supervisor2:child_spec(),
      Error :: {error, any()}.

update_all(Overall, OldOverall) ->
    rabbit_khepri:handle_fallback(
      #{mnesia => fun() -> update_all_in_mnesia(Overall, OldOverall) end,
        khepri => fun() -> update_all_in_khepri(Overall, OldOverall) end
       }).

update_all_in_mnesia(Overall, OldOverall) ->
    rabbit_mnesia:execute_mnesia_transaction(
      fun() ->
              MatchHead = #mirrored_sup_childspec{mirroring_pid = OldOverall,
                                                  key           = '$1',
                                                  childspec     = '$2',
                                                  _             = '_'},
              [write_in_mnesia(Group, Overall, C, Id) ||
                  [{Group, Id}, C] <- mnesia:select(?TABLE, [{MatchHead, [], ['$$']}])]
      end).

update_all_in_khepri(Overall, OldOverall) ->
    Pattern = #mirrored_sup_childspec{mirroring_pid = OldOverall,
                                      _             = '_'},
    Conditions = [?KHEPRI_WILDCARD_STAR_STAR, #if_data_matches{pattern = Pattern}],
    PathPattern = khepri_mirrored_supervisor_path(
                    ?KHEPRI_WILDCARD_STAR,
                    #if_all{conditions = Conditions}),
    rabbit_khepri:transaction(
      fun() ->
              case khepri_tx:get_many(PathPattern) of
                  {ok, Map} ->
                      [begin
                           S = S0#mirrored_sup_childspec{mirroring_pid = Overall},
                           ok = khepri_tx:put(Path, S),
                           S0#mirrored_sup_childspec.childspec
                       end || {Path, S0} <- maps:to_list(Map)]
              end
      end).

%% -------------------------------------------------------------------
%% delete_all().
%% -------------------------------------------------------------------

-spec delete_all(Group) -> ok when
      Group :: mirrored_supervisor:group_name().

delete_all(Group) ->
    rabbit_khepri:handle_fallback(
      #{mnesia => fun() -> delete_all_in_mnesia(Group) end,
        khepri => fun() -> delete_all_in_khepri(Group) end
       }).

delete_all_in_mnesia(Group) ->
    rabbit_mnesia:execute_mnesia_transaction(
      fun() ->
              MatchHead = #mirrored_sup_childspec{key       = {Group, '$1'},
                                                  _         = '_'},
              [ok = mnesia:delete({?TABLE, {Group, Id}}) ||
                  Id <- mnesia:select(?TABLE, [{MatchHead, [], ['$1']}])]
      end),
    ok.

delete_all_in_khepri(Group) ->
    Pattern = #mirrored_sup_childspec{key = {Group, '_'},
                                      _   = '_'},
    Conditions = [?KHEPRI_WILDCARD_STAR_STAR, #if_data_matches{pattern = Pattern}],
    rabbit_khepri:delete(khepri_mirrored_supervisor_path(
                           ?KHEPRI_WILDCARD_STAR,
                           #if_all{conditions = Conditions})).

%% -------------------------------------------------------------------
%% clear().
%% -------------------------------------------------------------------

-spec clear() -> ok.

clear() ->
    rabbit_khepri:handle_fallback(
      #{mnesia => fun() -> clear_in_mnesia() end,
        khepri => fun() -> clear_in_khepri() end
       }).

clear_in_mnesia() ->
    {atomic, ok} = mnesia:clear_table(?TABLE),
    ok.

clear_in_khepri() ->
    Path = khepri_mirrored_supervisor_path(
             ?KHEPRI_WILDCARD_STAR, ?KHEPRI_WILDCARD_STAR_STAR),
    case rabbit_khepri:delete(Path) of
        ok -> ok;
        Error -> throw(Error)
    end.

%% -------------------------------------------------------------------
%% Khepri paths
%% -------------------------------------------------------------------

khepri_mirrored_supervisor_path(Group, Id)
  when ?IS_KHEPRI_PATH_CONDITION(Group) andalso
       ?IS_KHEPRI_PATH_CONDITION(Id) ->
    ?RABBITMQ_KHEPRI_MIRRORED_SUPERVISOR_PATH(Group, Id);
khepri_mirrored_supervisor_path(Group, Id)
  when is_atom(Group) ->
    IdPath = Group:id_to_khepri_path(Id),
    ?RABBITMQ_KHEPRI_ROOT_PATH ++ [mirrored_supervisors, Group] ++ IdPath.
