%% -*- erlang-indent-level: 4;indent-tabs-mode: nil -*-
%% --------------------------------------------------
%% This file is provided to you 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    : parse_trans_pp.erl
%% @author  : Ulf Wiger <ulf@wiger.net>
%% @end
%% Description :
%%
%% Created : 3 Aug 2010 by Ulf Wiger <ulf@wiger.net>
%% --------------------------------------------------

%% @doc Generic parse transform library for Erlang.
%%
%% This module contains some useful utility functions for inspecting
%% the results of parse transforms or code generation.
%% The function `main/1' is called from escript, and can be used to
%% pretty-print debug info in a .beam file from a Linux shell.
%%
%% Using e.g. the following bash alias:
%% <pre>
%% alias pp='escript $PARSE_TRANS_ROOT/ebin/parse_trans_pp.beam'
%%% </pre>
%% a file could be pretty-printed using the following command:
%%
%% `$ pp ex_codegen.beam | less'
%% @end

-module(parse_trans_pp).

-export([
         pp_src/2,
         pp_beam/1, pp_beam/2
        ]).

-export([main/1]).


-spec main([string()]) -> any().
main([F]) ->
    pp_beam(F).


%% @spec (Forms, Out::filename()) -> ok
%%
%% @doc Pretty-prints the erlang source code corresponding to Forms into Out
%%
-spec pp_src(parse_trans:forms(), file:filename()) ->
    ok.
pp_src(Forms0, F) ->
    Forms = epp:restore_typed_record_fields(revert(Forms0)),
    Str = [io_lib:fwrite("~s~n",
                         [lists:flatten([erl_pp:form(Fm) ||
                                            Fm <- Forms])])],
    file:write_file(F, list_to_binary(Str)).

%% @spec (Beam::filename()) -> string() | {error, Reason}
%%
%% @doc
%% Reads debug_info from the beam file Beam and returns a string containing
%% the pretty-printed corresponding erlang source code.
%% @end
-spec pp_beam(file:filename()) -> ok | {error, any()}.
pp_beam(Beam) ->
    case pp_beam_to_str(Beam) of
        {ok, Str} ->
            io:put_chars(Str);
        Other ->
            Other
    end.

%% @spec (Beam::filename(), Out::filename()) -> ok | {error, Reason}
%%
%% @doc
%% Reads debug_info from the beam file Beam and pretty-prints it as
%% Erlang source code, storing it in the file Out.
%% @end
%%
-spec pp_beam(file:filename(), file:filename()) -> ok | {error,any()}.
pp_beam(F, Out) ->
    case pp_beam_to_str(F) of
        {ok, Str} ->
            file:write_file(Out, list_to_binary(Str));
        Other ->
            Other
    end.

pp_beam_to_str(F) ->
    case beam_lib:chunks(F, [abstract_code]) of
        {ok, {_, [{abstract_code,{_,AC0}}]}} ->
            AC = epp:restore_typed_record_fields(AC0),
            {ok, lists:flatten(
                   %% io_lib:fwrite("~s~n", [erl_prettypr:format(
                   %%                          erl_syntax:form_list(AC))])
                   io_lib:fwrite("~s~n", [lists:flatten(
                                            [erl_pp:form(Form) ||
                                                Form <- AC])])
                  )};
        Other ->
            {error, Other}
    end.

-spec revert(parse_trans:forms()) ->
    parse_trans:forms().
revert(Tree) ->
    [erl_syntax:revert(T) || T <- lists:flatten(Tree)].