%% Copyright (c) 2008-2024 Robert Virding
%%
%% 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.

%%% File    : lfe_init.erl
%%% Author  : Robert Virding
%%% Purpose : Lisp Flavoured Erlang init module.

%%% This little beauty allows you to start Erlang with the LFE shell
%%% running and still has ^G and user_drv enabled. Use it as follows:
%%%
%%% erl -user lfe_init
%%%
%%% Add -pa to find modules if necessary.
%%%
%%% Thanks to Attila Babo for showing me how to do this.

%%% The calls needed to start user/user_drv have changed from OTP
%%% 26. In the release after 26 the module user no longer exists and
%%% user_drv has a different interface. Note that this is sort of
%%% documented but these modules are not included in the standard
%%% Erlang documentation.

-module(lfe_init_new_1).

-export([start/0]).
-export([do_eval/1,do_script/1]).

-include("lfe.hrl").

%% Exit status.
-define(OK_STATUS, 0).
-define(ERROR_STATUS, 127).

%% Default repl to use when none is given.
-define(DEFAULT_REPL, lfe_repl).

%% Start LFE running a script or the shell depending on arguments.

start() ->

    erlang:display(init:get_arguments()),
    erlang:display(init:get_plain_arguments()),

    OTPRelease = erlang:system_info(otp_release),
    %% Find out which repl/shell we want to use.
    Repl = case init:get_argument(repl) of
	       {ok, [[R|_]]} -> list_to_atom(R);
	       _Other -> ?DEFAULT_REPL
	   end,
    %% Get the LFE evals to be done.
    Evals = case init:get_argument('lfe-eval') of
		{ok, Es} -> lists:append(Es);
		error -> []
	    end,
    %% Check whether we are to start the repl or run a terminating
    %% script file.
    case init:get_argument('run-script') of
	error ->				%No script file to run
	    if OTPRelease >= "26" ->
		    %% The new way 26 and later.
		    user_drv:start(#{initial_shell => {Repl,start,[]}});
	       true ->
		    %% The old way before 26.
		    user_drv:start(['tty_sl -c -e',{Repl,start,[]}])
	    end,
	    do_eval(Evals);
        {ok, [Script | _]} ->			%There is a script file
	    if OTPRelease >= "26" ->
		    %% The new way 26 and later)
		    user_drv:start(#{initial_shell => noshell});
	       true ->
		    %% The old way before 26.
		    user:start()
	    end,
            do_eval_script(Evals, Script, Repl)
    end.

%% Tools to run at initialisation.

%% do_eval(EvalStrings) -> ok.
%%  Parse and evaluate the strings.

do_eval(Evals) ->
    foreach(fun run_eval/1, Evals).

do_script(Script) ->
    lfescript_new:start(Script).

%% do_eval_script(Evals, Script, Repl) -> Pid.
%%  Run the script after which LFE is terminated.

do_eval_script(Evals, Script, Repl) ->
    Run = fun () ->
		  %% io:format(user, "es ~p\n", [{Evals,Script}]),
		  %% St = Repl:run_strings(Evals),
		  do_eval(Evals),
		  do_script(Script)
	  end,
    spawn_link(fun () -> run_script(Repl, Run) end).

%% run_eval(EvalString) -> Value.

run_eval(Eval) ->
    case lfe_io:read_string(Eval) of
	{ok,Exprs} ->
	    lfe_eval:exprs(Exprs);
	{error, E} ->
	    error(E)
    end.

%% run_script(Repl, Run)
%%  Run a script and terminate the erlang process afterwards.

run_script(Repl, Run) ->
    try
        Run(),				        %Evaluate the evals and script
        %% For some reason we need to wait a bit before stopping.
        timer:sleep(1),
        init:stop(?OK_STATUS)
    catch
        ?CATCH(Class, Error, Stack)
            Skip = fun (M, _F, _A) ->
                           (M =:= lfe_eval) or (M =:= Repl) or (M =:= ?MODULE)
                   end,
            Format = fun (T, I) -> lfe_io:prettyprint1(T, 15, I, 80) end,
            Cs = lfe_error:format_exception(Class, Error, Stack, 
                                            Skip, Format, 1),
            io:put_chars(Cs),
            halt(?ERROR_STATUS)
    end.

%% Implement our own lists functions to get around stacktrace printing
%% problems.

%% foldl(F, Accu, [Hd|Tail]) ->
%%     foldl(F, F(Hd, Accu), Tail);
%% foldl(F, Accu, []) when is_function(F, 2) -> Accu.

foreach(F, [Hd | Tail]) ->
    F(Hd),
    foreach(F, Tail);
foreach(F, []) when is_function(F, 1) -> ok.