%% -*- erlang-indent-level: 4;indent-tabs-mode: nil -*-
%% ex: ts=4 sw=4 et
%% -------------------------------------------------------------------
%%
%% rebar: Erlang Build Tools
%%
%% Copyright (c) 2011 Trifork
%%
%% Permission is hereby granted, free of charge, to any person obtaining a copy
%% of this software and associated documentation files (the "Software"), to deal
%% in the Software without restriction, including without limitation the rights
%% to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
%% copies of the Software, and to permit persons to whom the Software is
%% furnished to do so, subject to the following conditions:
%%
%% The above copyright notice and this permission notice shall be included in
%% all copies or substantial portions of the Software.
%%
%% THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
%% IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
%% FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
%% AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
%% LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
%% OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
%% THE SOFTWARE.
%% -------------------------------------------------------------------

-module(rebar_prv_shell).
-author("Kresten Krab Thorup <krab@trifork.com>").

-behaviour(provider).

-export([init/1,
         do/1,
         format_error/1]).

-include("rebar.hrl").

-define(PROVIDER, shell).
-define(DEPS, [compile]).

%% ===================================================================
%% Public API
%% ===================================================================

-spec init(rebar_state:t()) -> {ok, rebar_state:t()}.
init(State) ->
    State1 = rebar_state:add_provider(State, providers:create([{name, ?PROVIDER},
                                                               {module, ?MODULE},
                                                               {bare, false},
                                                               {deps, ?DEPS},
                                                               {example, "rebar3 shell"},
                                                               {short_desc, "Run shell with project apps and deps in path."},
                                                               {desc, info()},
                                                               {opts, [{config, undefined, "config", string, "Path to the config file to use. Defaults to the sys_config defined for relx, if present."}]}])),
    {ok, State1}.

-spec do(rebar_state:t()) -> {ok, rebar_state:t()} | {error, string()}.
do(Config) ->
    shell(Config),
    {ok, Config}.

-spec format_error(any()) -> iolist().
format_error(Reason) ->
    io_lib:format("~p", [Reason]).

%% NOTE:
%% this is an attempt to replicate `erl -pa ./ebin -pa deps/*/ebin`. it is
%% mostly successful but does stop and then restart the user io system to get
%% around issues with rebar being an escript and starting in `noshell` mode.
%% it also lacks the ctrl-c interrupt handler that `erl` features. ctrl-c will
%% immediately kill the script. ctrl-g, however, works fine

shell(State) ->
    %% scan all processes for any with references to the old user and save them to
    %% update later
    NeedsUpdate = [Pid || Pid <- erlang:processes(),
        proplists:get_value(group_leader, erlang:process_info(Pid)) == whereis(user)
    ],
    %% terminate the current user
    ok = supervisor:terminate_child(kernel_sup, user),
    %% start a new shell (this also starts a new user under the correct group)
    _ = user_drv:start(),
    %% wait until user_drv and user have been registered (max 3 seconds)
    ok = wait_until_user_started(3000),
    %% set any process that had a reference to the old user's group leader to the
    %% new user process
    _ = [erlang:group_leader(whereis(user), Pid) || Pid <- NeedsUpdate],
    %% enable error_logger's tty output
    ok = error_logger:swap_handler(tty),
    %% disable the simple error_logger (which may have been added multiple
    %% times). removes at most the error_logger added by init and the
    %% error_logger added by the tty handler
    ok = remove_error_handler(3),
    %% Add deps to path
    code:add_pathsa(rebar_state:code_paths(State, all_deps)),
    %% add project app test paths
    ok = add_test_paths(State),
    %% try to read in sys.config file
    ok = reread_config(State),
    %% this call never returns (until user quits shell)
    timer:sleep(infinity).

info() ->
    "Start a shell with project and deps preloaded similar to~n'erl -pa ebin -pa deps/*/ebin'.~n".

remove_error_handler(0) ->
    ?WARN("Unable to remove simple error_logger handler", []);
remove_error_handler(N) ->
    case gen_event:delete_handler(error_logger, error_logger, []) of
        {error, module_not_found} -> ok;
        {error_logger, _} -> remove_error_handler(N-1)
    end.

%% Timeout is a period to wait before giving up
wait_until_user_started(0) ->
    ?ABORT("Timeout exceeded waiting for `user` to register itself", []),
    erlang:error(timeout);
wait_until_user_started(Timeout) ->
    case whereis(user) of
        %% if user is not yet registered wait a tenth of a second and try again
        undefined -> timer:sleep(100), wait_until_user_started(Timeout - 100);
        _ -> ok
    end.

add_test_paths(State) ->
    lists:foreach(fun(App) ->
                          AppDir = rebar_app_info:out_dir(App),
                          %% ignore errors resulting from non-existent directories
                          _ = code:add_path(filename:join([AppDir, "test"]))
                  end, rebar_state:project_apps(State)),
    _ = code:add_path(filename:join([rebar_dir:base_dir(State), "test"])),
    ok.

reread_config(State) ->
    case find_config(State) of
        no_config ->
            ok;
        {ok, ConfigList} ->
            lists:foreach(fun ({Application, Items}) ->
                                  lists:foreach(fun ({Key, Val}) ->
                                                        application:set_env(Application, Key, Val)
                                                end,
                                                Items)
                          end,
                          ConfigList);
        {error, Error} ->
            ?ABORT("Error while attempting to read configuration file: ~p", [Error])
    end.

% First try the --config flag, then try the relx sys_config
-spec find_config(rebar_state:t()) -> {ok, [tuple()]}|no_config|{error, tuple()}.
find_config(State) ->
    case find_config_option(State) of
        no_config ->
            find_config_relx(State);
        Result ->
            Result
    end.

-spec find_config_option(rebar_state:t()) -> {ok, [tuple()]}|no_config|{error, tuple()}.
find_config_option(State) ->
    {Opts, _} = rebar_state:command_parsed_args(State),
    case proplists:get_value(config, Opts) of
        undefined ->
            no_config;
        Filename ->
            consult_config(State, Filename)
    end.

-spec find_config_relx(rebar_state:t()) -> {ok, [tuple()]}|no_config|{error, tuple()}.
find_config_relx(State) ->
    case proplists:get_value(sys_config, rebar_state:get(State, relx, [])) of
        undefined ->
            no_config;
        Filename ->
            consult_config(State, Filename)
    end.

-spec consult_config(rebar_state:t(), string()) -> {ok, [tuple()]}|{error, tuple()}.
consult_config(State, Filename) ->
    Fullpath = filename:join(rebar_dir:root_dir(State), Filename),
    ?DEBUG("Loading configuration from ~p", [Fullpath]),
    case file:consult(Fullpath) of
        {ok, [Config]} ->
            {ok, Config};
        {ok, []} ->
            {ok, []};
        {error, Error} ->
            {error, {Error, Fullpath}}
    end.