%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 2008-2022. All Rights Reserved.
%%
%% Licensed under the Apache License, Version 2.0 (the "License");
%% you may not use this file except in compliance with the License.
%% You may obtain a copy of the License at
%%
%%     http://www.apache.org/licenses/LICENSE-2.0
%%
%% Unless required by applicable law or agreed to in writing, software
%% distributed under the License is distributed on an "AS IS" BASIS,
%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
%% See the License for the specific language governing permissions and
%% limitations under the License.
%%
%% %CopyrightEnd%
%%

%%
%%----------------------------------------------------------------------
%% Purpose: The ssh server instance supervisor, an instans of this supervisor
%%          exists for every ip-address and port combination, hangs under
%%          sshd_sup.
%%----------------------------------------------------------------------

-module(ssh_system_sup).

-behaviour(supervisor).

-include("ssh.hrl").

-export([start_link/3,
         stop_listener/1,
	 stop_system/2,
         start_system/3,
         start_subsystem/4,
	 get_daemon_listen_address/1,
         addresses/1,
         addresses/2,
         get_options/2,
         get_acceptor_options/1,
         replace_acceptor_options/2
        ]).

%% Supervisor callback
-export([init/1]).

%%%=========================================================================
%%% API
%%%=========================================================================

start_system(Role, Address0, Options) ->
    case find_system_sup(Role, Address0) of
        {ok,{SysPid,Address}} ->
            restart_acceptor(SysPid, Address, Options);
        {error,not_found} ->
            supervisor:start_child(sup(Role),
                                   #{id       => {?MODULE,Address0},
                                     start    => {?MODULE, start_link, [Role, Address0, Options]},
                                     restart  => temporary,
                                     type     => supervisor
                                    })
    end.

%%%----------------------------------------------------------------
stop_system(Role, SysSup) when is_pid(SysSup) ->
    case lists:keyfind(SysSup, 2, supervisor:which_children(sup(Role))) of
        {{?MODULE,Name}, SysSup, _, _} -> stop_system(Role, Name);
        false -> undefind
    end;
stop_system(Role, Name) ->
    supervisor:terminate_child(sup(Role), {?MODULE,Name}).


%%%----------------------------------------------------------------
stop_listener(SystemSup) when is_pid(SystemSup) ->
    {Name, _, _, _} = lookup(ssh_acceptor_sup, SystemSup),
    supervisor:terminate_child(SystemSup, Name),
    supervisor:delete_child(SystemSup, Name).

%%%----------------------------------------------------------------
get_daemon_listen_address(SystemSup) ->
    try lookup(ssh_acceptor_sup, SystemSup)
    of
        {{ssh_acceptor_sup,Address}, _, _, _} ->
            {ok, Address};
        _ ->
            {error, not_found}
    catch
        _:_ ->
            {error, not_found}
    end.

%%%----------------------------------------------------------------
%%% Start the subsystem child. It is a child of the system supervisor (callback = this module)
start_subsystem(Role, Address=#address{}, Socket, Options0) ->
    Options = ?PUT_INTERNAL_OPT([{user_pid, self()}], Options0),
    Id = make_ref(),
    case get_system_sup(Role, Address, Options) of
        {ok,SysPid} ->
            case supervisor:start_child(SysPid,
                                        #{id          => Id,
                                          start       => {ssh_subsystem_sup, start_link,
                                                          [Role,Address,Id,Socket,Options]
                                                         },
                                          restart     => temporary,
                                          significant => true,
                                          type        => supervisor
                                         })
            of
                {ok,_SubSysPid} ->
                    try
                        receive
                            {new_connection_ref, Id, ConnPid} ->
                                ssh_connection_handler:takeover(ConnPid, Role, Socket, Options)
                        after 10000 ->

                                error(timeout)
                        end
                    catch
                        error:{badmatch,{error,Error}} ->
                            {error,Error};
                        error:timeout ->
                            %% The connection was started, but the takover procedure timed out,
                            %% therefore it exists a subtree, but it is not quite ready and
                            %% must be removed (by the supervisor above):
                            supervisor:terminate_child(SysPid, Id),
                            {error, connection_start_timeout}
                    end;
                Others ->
                    Others
            end;
        Others ->
            Others
    end.


%%%----------------------------------------------------------------
start_link(Role, Address, Options) ->
    supervisor:start_link(?MODULE, [Role, Address, Options]).


%%%----------------------------------------------------------------
addresses(Role) ->
    addresses(Role,  #address{address=any, port=any, profile=any}).

addresses(Role,  #address{address=Address, port=Port, profile=Profile}) ->
    [{SysSup,A} || {{ssh_system_sup,A},SysSup,supervisor,_} <- 
                     supervisor:which_children(sup(Role)),
                 Address == any orelse A#address.address == Address,
                 Port == any    orelse A#address.port == Port,
                 Profile == any orelse A#address.profile == Profile].

%%%----------------------------------------------------------------
%% SysPid is the DaemonRef

get_acceptor_options(SysPid) ->
    case get_daemon_listen_address(SysPid) of
        {ok,Address} ->
            get_options(SysPid, Address);
        {error,Error} ->
            {error,Error}
    end.

replace_acceptor_options(SysPid, NewOpts) ->
    case get_daemon_listen_address(SysPid) of
        {ok,Address} ->
            try stop_listener(SysPid)
            of
                ok ->
                    restart_acceptor(SysPid, Address, NewOpts)
            catch
                error:_ ->
                    restart_acceptor(SysPid, Address, NewOpts)
            end;
        {error,Error} ->
            {error,Error}
    end.

%%%=========================================================================
%%%  Supervisor callback
%%%=========================================================================
init([Role, Address, Options]) ->
    SupFlags = #{strategy      => one_for_one,
                 auto_shutdown => all_significant,
                 intensity =>    0,
                 period    => 3600
                },
    ChildSpecs =
        case {Role, is_socket_server(Options)} of
            {server, false} ->
                [acceptor_sup_child_spec(_SysSup=self(), Address, Options)];
            _ ->
                []
        end,
    {ok, {SupFlags,ChildSpecs}}.

%%%=========================================================================
%%% Service API
%%%=========================================================================

%% A macro to keep get_options/2 and acceptor_sup_child_spec/3 synchronized
-define(accsup_start(SysSup,Addr,Opts),
        {ssh_acceptor_sup, start_link, [SysSup,Addr,Opts]}
       ).

get_options(Sup, Address = #address{}) ->
    %% Lookup the Option parameter in the running ssh_acceptor_sup:
    try
        {ok, #{start:=?accsup_start(_, _, Options)}} =
            supervisor:get_childspec(Sup, {ssh_acceptor_sup,Address}),
        {ok, Options}
    catch
        _:_ -> {error,not_found}
    end.

%%%=========================================================================
%%%  Internal functions
%%%=========================================================================

%% A separate function because this spec is need in >1 places
acceptor_sup_child_spec(SysSup, Address, Options) ->
    #{id       => {ssh_acceptor_sup,Address},
      start    => ?accsup_start(SysSup, Address, Options),
      restart  => transient,
      significant => true,
      type     => supervisor
     }.

lookup(SupModule, SystemSup) ->
    lists:keyfind([SupModule], 4,
                  supervisor:which_children(SystemSup)).

get_system_sup(Role, Address0, Options) ->
    case find_system_sup(Role, Address0) of
        {ok,{SysPid,_Address}} ->
            {ok,SysPid};
        {error,not_found} ->
            start_system(Role, Address0, Options);
        {error,Error} ->
            {error,Error}
    end.

find_system_sup(Role, Address0) ->
    case addresses(Role, Address0) of
        [{SysSupPid,Address}] -> {ok,{SysSupPid,Address}};
        [] -> {error,not_found};
        [_,_|_] -> {error,ambiguous}
    end.

sup(client) -> sshc_sup;
sup(server) -> sshd_sup.


is_socket_server(Options) ->
    undefined =/= ?GET_INTERNAL_OPT(connected_socket,Options,undefined).

restart_acceptor(SysPid, Address, Options) ->
    case lookup(ssh_acceptor_sup, SysPid) of
        {_,_,supervisor,_} ->
            {error, eaddrinuse};
        false ->
            ChildSpec = acceptor_sup_child_spec(SysPid, Address, Options),
            case supervisor:start_child(SysPid, ChildSpec) of
                {ok,_ChildPid} ->
                    {ok,SysPid}; % sic!
                {ok,_ChildPid,_Info} ->
                    {ok,SysPid}; % sic!
                {error,Error} ->
                    {error,Error}
            end
    end.