gen_smtp_server.erl

%%% vim:ts=2:sw=2:et
%%% Copyright 2009 Andrew Thompson <andrew@hijacked.us>. All rights reserved.
%%%
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%% @doc Setup ranch socket acceptor for gen_smtp_server_session

-module(gen_smtp_server).

-define(PORT, 2525).

-include_lib("hut/include/hut.hrl").

%% External API
-export([
	start/3, start/2, start/1,
	stop/1, child_spec/3, sessions/1]).
-export_type([options/0]).

-type server_name() :: any().
-type options() ::
		[{domain, string()}
		 | {address, inet:ip4_address()}
		 | {family, inet | inet6}
		 | {port, inet:port_number()}
		 | {protocol, 'tcp' | 'ssl'}
		 | {ranch_opts, ranch:opts()}
		 | {sessionoptions, gen_smtp_server_session:options()}].

%% @doc Start the listener as a registered process with callback module `Module' with options `Options' linked to no process.
-spec start(ServerName :: server_name(),
			CallbackModule :: module(),
			Options :: options()) -> {'ok', pid()} | {'error', any()}.
start(ServerName, CallbackModule, Options) when is_list(Options) ->
	case convert_options(CallbackModule, Options) of
		{ok, Transport, TransportOpts, ProtocolOpts} ->
			ranch:start_listener(
			  ServerName, Transport, TransportOpts, gen_smtp_server_session, ProtocolOpts);
		{error, Reason} -> {error, Reason}
	end.

child_spec(ServerName, CallbackModule, Options) ->
	case convert_options(CallbackModule, Options) of
		{ok, Transport, TransportOpts, ProtocolOpts} ->
			ranch:child_spec(
			  ServerName, Transport, TransportOpts, gen_smtp_server_session, ProtocolOpts);
		{error, Reason} ->
			% `supervisor:child_spec' is not compatible with ok/error tuples.
			% This error is likely to occur when starting the application,
			% so the user can sort out the configuration parameters and try again.
			erlang:error(Reason)
	end.

convert_options(CallbackModule, Options) ->
	Transport = case proplists:get_value(protocol, Options, tcp) of
					tcp -> ranch_tcp;
					ssl -> ranch_ssl
				end,
	Family = proplists:get_value(family, Options, inet),
	Address = proplists:get_value(address, Options, {0, 0, 0, 0}),
	Port = proplists:get_value(port, Options, ?PORT),
	Hostname = proplists:get_value(domain, Options, smtp_util:guess_FQDN()),
	ProtocolOpts = proplists:get_value(sessionoptions, Options, []),
	EmailTransferProtocol = proplists:get_value(protocol, ProtocolOpts, smtp),
	case {EmailTransferProtocol, Port} of
		{lmtp, 25} ->
			?log(error, "LMTP is different from SMTP, it MUST NOT be used on the TCP port 25"),
			% Error defined in section 5 of https://tools.ietf.org/html/rfc2033
			{error, invalid_lmtp_port};
		_ ->
			ProtocolOpts1 = {CallbackModule, [{hostname, Hostname} | ProtocolOpts]},
			RanchOpts = proplists:get_value(ranch_opts, Options, #{}),
			SocketOpts = maps:get(socket_opts, RanchOpts, []),
			TransportOpts = RanchOpts#{
									   socket_opts =>
										   [{port, Port},
											{ip, Address},
											{keepalive, true},
											%% binary, {active, false}, {reuseaddr, true} - ranch defaults
											Family
										   | SocketOpts]},
			{ok, Transport, TransportOpts, ProtocolOpts1}
	end.


%% @doc Start the listener with callback module `Module' with options `Options' linked to no process.
-spec start(CallbackModule :: module(), Options :: options()) -> {'ok', pid()} | 'ignore' | {'error', any()}.
start(CallbackModule, Options) when is_list(Options) ->
	start(?MODULE, CallbackModule, Options).

%% @doc Start the listener with callback module `Module' with default options linked to no process.
-spec start(CallbackModule :: atom()) -> {'ok', pid()} | 'ignore' | {'error', any()}.
start(CallbackModule) ->
	start(CallbackModule, []).

%% @doc Stop the listener pid() `Pid' with reason `normal'.
-spec stop(Name :: server_name()) -> 'ok'.
stop(Name) ->
	ranch:stop_listener(Name).

%% @doc Return the list of active SMTP session pids.
-spec sessions(Name :: server_name()) -> [pid()].
sessions(Name) ->
	ranch:procs(Name, connections).