%% erlfmt:ignore-begin
%% =====================================================================
%% %CopyrightBegin%
%%
%% SPDX-License-Identifier: Apache-2.0 OR LGPL-2.1-or-later
%%
%% Copyright 2001-2006 Richard Carlsson
%% Copyright Ericsson AB 2009-2025. 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.
%%
%% Alternatively, you may use this file under the terms of the GNU Lesser
%% General Public License (the "LGPL") as published by the Free Software
%% Foundation; either version 2.1, or (at your option) any later version.
%% If you wish to allow use of your version of this file only under the
%% terms of the LGPL, you should delete the provisions above and replace
%% them with the notice and other provisions required by the LGPL; see
%% <http://www.gnu.org/licenses/>. If you do not delete the provisions
%% above, a recipient may use your version of this file under the terms of
%% either the Apache License or the LGPL.
%%
%% %CopyrightEnd%
%%
%% @author Richard Carlsson <carlsson.richard@gmail.com>
%% @end
%% =====================================================================

%% NOTES:
%%
%% * It's OK if the result does not parse - then at least nothing
%% strange happens, and the user can resort to full preprocessing.
%% However, we must avoid generating a token stream that is accepted by
%% the parser, but has a different meaning than the intended. A typical
%% example is when someone uses token-level string concatenation with
%% macros, as in `"foo" ?bar' (where `?bar' expands to a string). If we
%% replace the tokens `? bar' with `( ... )', to preserve precedence,
%% the result will be parsed as an application `"foo" ( ... )' and cause
%% trouble later on. We must detect such cases and report an error.
%%
%% * It is pointless to add a mechanism for tracking which macros are
%% known to take arguments, and which are known to take no arguments,
%% since a lot of the time we will not have seen the macro definition
%% anyway (it's usually in a header file). Hence, we try to use
%% heuristics instead. In most cases, the token sequence `? foo ('
%% indicates that it is a call of a macro that is supposed to take
%% arguments, but e.g., in the context `: ? foo (', the argument list
%% typically belongs to a remote function call, as in `m:?f(...)' and
%% should be parsed as `m:(?f)(...)' unless it is actually a try-clause
%% pattern such as `throw:?f(...) ->'.
%%
%% * We do our best to make macros without arguments pass the parsing
%% stage transparently. Atoms are accepted in most contexts, but
%% variables are not, so we use only atoms to encode these macros.
%% Sadly, the parsing sometimes discards even the location info from
%% atom tokens, so we can only use the actual characters for this.
%%
%% * We recognize `?m(...' at the start of a form and prevent this from
%% being interpreted as a macro with arguments, since it is probably a
%% function definition. Likewise with attributes `-?m(...'.

-module(ktn_dodger).
%-moduledoc """
%Bypassing the Erlang preprocessor.
%
%This module tokenises and parses most Erlang source code without expanding
%preprocessor directives and macro applications, as long as these are
%syntactically "well-behaved". Because the normal parse trees of the `erl_parse`
%module cannot represent these things (normally, they are expanded by the Erlang
%preprocessor [`//stdlib/epp`](`m:epp`) before the parser sees them), an extended
%syntax tree is created, using the `m:erl_syntax` module.
%""".

-compile(nowarn_deprecated_catch).

%% We have snake_case macros here
-elvis([{elvis_style, macro_names, disable}]).
-elvis([{elvis_style, no_catch_expressions, disable}]).
-elvis([{elvis_style, no_throw, disable}]).
-elvis([{elvis_style, consistent_variable_casing, disable}]).
-elvis([{elvis_style, nesting_level, disable}]).

-export([parse_file/1, quick_parse_file/1, parse_file/2, quick_parse_file/2, parse/1,
         quick_parse/1, parse/2, quick_parse/2, parse/3, quick_parse/3, parse_form/2, parse_form/3,
         quick_parse_form/2, quick_parse_form/3, format_error/1, tokens_to_string/1]).

%% The following should be: 1) pseudo-uniquely identifiable, and 2)
%% cause nice looking error messages when the parser has to give up.

-define(macro_call, '? <macro> (').
-define(atom_prefix, "? ").
-define(var_prefix, "?,").
-define(pp_form, '?preprocessor declaration?').

-type errorinfo() :: erl_scan:error_info().

-type option() :: atom() | {atom(), term()}.

-export_type([errorinfo/0, option/0]).

-hank([{unnecessary_function_arguments, [{no_fix, 1}, {quick_parser, 2}]}]).

%-doc #{equiv => parse_file(File, [])}.
-spec parse_file(file:filename()) -> {ok, erl_syntax:forms()} | {error, errorinfo()}.
parse_file(File) ->
    parse_file(File, []).

%-doc """
%Reads and parses a file.
%
%If successful, `{ok, Forms}` is returned, where `Forms` is a list of
%abstract syntax trees representing the "program forms" of the file
%(see `erl_syntax:is_form/1`). Otherwise, `{error, errorinfo()}` is
%returned, typically if the file could not be opened. Note that parse
%errors show up as error markers in the returned list of forms; they do
%not cause this function to fail or return `{error, errorinfo()}`.
%
%Options:
%
%- **`{no_fail, boolean()}`** - If `true`, this makes `epp_dodger` replace any
%  program forms that could not be parsed with nodes of type `text` (see
%  `erl_syntax:text/1`), representing the raw token sequence of the form, instead
%  of reporting a parse error. The default value is `false`.
%
%- **`{clever, boolean()}`** - If set to `true`, this makes `epp_dodger` try to
%  repair the source code as it seems fit, in certain cases where parsing would
%  otherwise fail. Currently, it inserts `++` operators between string literals
%  and macros where it looks like concatenation was intended. The default value
%  is `false`.
%
%_See also: _`parse/2`, `quick_parse_file/1`, `erl_syntax:is_form/1`.
%""".
-spec parse_file(file:filename(), [option()]) ->
                    {ok, erl_syntax:forms()} | {error, errorinfo()}.
parse_file(File, Options) ->
    parse_file(File, fun parse/3, Options).

%-doc #{equiv => quick_parse_file(File, [])}.
-spec quick_parse_file(file:filename()) ->
                          {ok, erl_syntax:forms()} | {error, errorinfo()}.
quick_parse_file(File) ->
    quick_parse_file(File, []).

%-doc """
%Similar to `parse_file/2`, but does a more quick-and-dirty processing of the
%code.
%
%Macro definitions and other preprocessor directives are discarded, and all
%macro calls are replaced with atoms. This is useful when only the main structure
%of the code is of interest, and not the details. Furthermore, the quick-parse
%method can usually handle more strange cases than the normal, more exact
%parsing.
%
%Options: see `parse_file/2`. However, note that for
%[`quick_parse_file/2`](`quick_parse_file/2`), the option `no_fail` is `true` by
%default.
%
%_See also: _`parse_file/2`, `quick_parse/2`.
%""".
-spec quick_parse_file(file:filename(), [option()]) ->
                          {ok, erl_syntax:forms()} | {error, errorinfo()}.
quick_parse_file(File, Options) ->
    parse_file(File, fun quick_parse/3, Options ++ [no_fail]).

parse_file(File, Parser, Options) ->
    case do_parse_file(utf8, File, Parser, Options) of
        {ok, Forms} = Ret ->
            case find_invalid_unicode(Forms) of
                none ->
                    Ret;
                invalid_unicode ->
                    case epp:read_encoding(File) of
                        utf8 ->
                            Ret;
                        _ ->
                            do_parse_file(latin1, File, Parser, Options)
                    end
            end;
        Else ->
            Else
    end.

do_parse_file(DefEncoding, File, Parser, Options) ->
    case file:open(File, [read]) of
        {ok, Dev} ->
            _ = epp:set_encoding(Dev, DefEncoding),
            try
                Parser(Dev, 1, Options)
            after
                ok = file:close(Dev)
            end;
        {error, Error} ->
            {error, {0, file, Error}}  % defer to file:format_error/1
    end.

find_invalid_unicode([H | T]) ->
    case H of
        {error, {_Location, file_io_server, invalid_unicode}} ->
            invalid_unicode;
        _Other ->
            find_invalid_unicode(T)
    end;
find_invalid_unicode([]) ->
    none.

%% =====================================================================

%-doc #{equiv => parse(IODevice, 1)}.
-spec parse(file:io_device()) -> {ok, erl_syntax:forms()}.
parse(Dev) ->
    parse(Dev, 1).

%-doc #{equiv => parse(IODevice, StartLocation, [])}.
-spec parse(file:io_device(), erl_anno:location()) -> {ok, erl_syntax:forms()}.
parse(Dev, L) ->
    parse(Dev, L, []).

%-doc """
%Reads and parses program text from an I/O stream.
%
%Characters are read from `IODevice` until end-of-file; apart from
%this, the behavior is the same as for `parse_file/2`. `StartLocation`
%is the initial location.
%
%_See also: _`parse/2`, `parse_file/2`, `parse_form/2`, `quick_parse/3`.
%""".
-spec parse(file:io_device(), erl_anno:location(), [option()]) ->
               {ok, erl_syntax:forms()}.
parse(Dev, L0, Options) ->
    parse(Dev, L0, fun parse_form/3, Options).

%-doc #{equiv => quick_parse(IODevice, 1)}.
-spec quick_parse(file:io_device()) -> {ok, erl_syntax:forms()}.
quick_parse(Dev) ->
    quick_parse(Dev, 1).

%-doc #{equiv => quick_parse(IODevice, StartLocation, [])}.
-spec quick_parse(file:io_device(), erl_anno:location()) -> {ok, erl_syntax:forms()}.
quick_parse(Dev, L) ->
    quick_parse(Dev, L, []).

%-doc """
%Similar to `parse/3`, but does a more quick-and-dirty processing of the code.
%
%See `quick_parse_file/2` for details.
%
%_See also: _`parse/3`, `quick_parse/2`, `quick_parse_file/2`,
%`quick_parse_form/2`.
%""".
-spec quick_parse(file:io_device(), erl_anno:location(), [option()]) -> {ok, erl_syntax:forms()}.
quick_parse(Dev, L0, Options) ->
    parse(Dev, L0, fun quick_parse_form/3, Options).

parse(Dev, L0, Parser, Options) ->
    parse(Dev, L0, [], Parser, Options).

parse(Dev, L0, Fs, Parser, Options) ->
    case Parser(Dev, L0, Options) of
        {ok, none, L1} ->
            parse(Dev, L1, Fs, Parser, Options);
        {ok, F, L1} ->
            parse(Dev, L1, [F | Fs], Parser, Options);
        {error, IoErr, L1} ->
            parse(Dev, L1, [{error, IoErr} | Fs], Parser, Options);
        {eof, _L1} ->
            {ok, lists:reverse(Fs)}
    end.

%-doc #{equiv => parse_form(IODevice, StartLocation, [])}.
-spec parse_form(file:io_device(), erl_anno:location()) ->
                    {ok, erl_syntax:forms(), erl_anno:location()} |
                    {eof, erl_anno:location()} |
                    {error, errorinfo(), erl_anno:location()}.
parse_form(Dev, L0) ->
    parse_form(Dev, L0, []).

%-doc """
%Reads and parses a single program form from an I/O stream.
%
%Characters are read from `IODevice` until an end-of-form marker is
%found (a period character followed by whitespace), or until
%end-of-file; apart from this, the behavior is similar to that of
%[`parse/3`](`parse/3`), except that the return values also contain the
%final location given that `StartLocation` is the initial location, and
%that `{eof, Location}` may be returned.
%
%_See also: _`parse/3`, `parse_form/2`, `quick_parse_form/3`.
%""".
-spec parse_form(file:io_device(), erl_anno:location(), [option()]) ->
                    {ok, erl_syntax:forms(), erl_anno:location()} |
                    {eof, erl_anno:location()} |
                    {error, errorinfo(), erl_anno:location()}.
parse_form(Dev, L0, Options) ->
    parse_form(Dev, L0, fun normal_parser/2, Options).

%-doc #{equiv => quick_parse_form(IODevice, StartLocation, [])}.
-spec quick_parse_form(file:io_device(), erl_anno:location()) ->
                          {ok, erl_syntax:forms(), erl_anno:location()} |
                          {eof, erl_anno:location()} |
                          {error, errorinfo(), erl_anno:location()}.
quick_parse_form(Dev, L0) ->
    quick_parse_form(Dev, L0, []).

%-doc """
%Similar to `parse_form/3`, but does a more quick-and-dirty processing of the
%code. See `quick_parse_file/2` for details.
%
%_See also: _`parse/3`, `parse_form/3`, `quick_parse_form/2`.
%""".
-spec quick_parse_form(file:io_device(), erl_anno:location(), [option()]) ->
                          {ok, erl_syntax:forms(), erl_anno:location()} |
                          {eof, erl_anno:location()} |
                          {error, errorinfo(), erl_anno:location()}.
quick_parse_form(Dev, L0, Options) ->
    parse_form(Dev, L0, fun quick_parser/2, Options).

-type pre_fixer() :: fun((erl_scan:tokens()) -> no_fix | {retry, erl_scan:tokens()}).
-type post_fixer() ::
    fun((erl_parse:abstract_form()) -> no_fix | {form, erl_parse:abstract_form()}).

-record(opt,
        {clever = false :: boolean(),
         parse_macro_definitions = false :: boolean(),
         compact_strings = false :: boolean(),
         pre_fixer = fun no_fix/1 :: pre_fixer(),
         post_fixer = fun no_fix/1 :: post_fixer()}).

parse_form(Dev, L0, Parser, Options) ->
    NoFail = proplists:get_bool(no_fail, Options),
    Opt = #opt{clever = proplists:get_bool(clever, Options),
               parse_macro_definitions = proplists:get_bool(parse_macro_definitions, Options),
               compact_strings = proplists:get_bool(compact_strings, Options),
               pre_fixer = proplists:get_value(pre_fixer, Options, fun no_fix/1),
               post_fixer = proplists:get_value(post_fixer, Options, fun no_fix/1)},

    %% This has the *potential* to read options for enabling/disabling
    %% (i.e. `{feature, TheFeature, enable}') when parsing the file.
    {ok, {_Ftrs, ResWordFun}} = erl_features:keyword_fun(Options, fun reserved_word/1),

    ScanOpts = [{reserved_word_fun, ResWordFun} | proplists:get_value(scan_opts, Options, [])],
    case io:scan_erl_form(Dev, "", L0, ScanOpts) of
        {ok, Ts, L1} ->
            case extract_escript_header(Ts) of
                no_header ->
                    parse_form(Parser, Ts, L1, NoFail, Opt);
                {LineNo, {Header, Rest}} ->
                    case parse_form(Parser, Rest, L1, NoFail, Opt) of
                        {ok, Form, L2} ->
                            {ok,
                             erl_syntax:form_list([erl_syntax:set_pos(
                                                       erl_syntax:text(tokens_to_string(Header)),
                                                       LineNo),
                                                   Form]),
                             L2};
                        Error ->
                            Error
                    end
            end;
        {error, _IoErr, _L1} = Err ->
            Err;
        {error, _Reason} ->
            {eof, L0}; % This is probably encoding problem
        {eof, _L1} = Eof ->
            Eof
    end.

extract_escript_header([{'#', Anno}, {'!', _} | _] = Ts) ->
    LineNo = erl_anno:line(Anno),
    {LineNo, lists:splitwith(fun(Token) -> erl_scan:line(Token) == LineNo end, Ts)};
extract_escript_header(_) ->
    no_header.

parse_form(Parser, Ts, L1, NoFail, Opt) ->
    case catch {ok, Parser(Ts, Opt)} of
        {'EXIT', Term} ->
            {error, io_error(L1, {unknown, Term}), L1};
        {error, Term} ->
            IoErr = io_error(L1, Term),
            {error, IoErr, L1};
        {parse_error, _IoErr} when NoFail ->
            {ok,
             erl_syntax:set_pos(
                 erl_syntax:text(tokens_to_string(Ts)),
                 erl_anno:new(start_pos(Ts, L1))),
             L1};
        {parse_error, IoErr} ->
            {error, IoErr, L1};
        {ok, F} ->
            {ok, F, L1}
    end.

io_error(L, Desc) ->
    {L, ?MODULE, Desc}.

start_pos([T | _Ts], _L) ->
    erl_anno:location(element(2, T));
start_pos([], L) ->
    L.

%% Exception-throwing wrapper for the standard Erlang parser stage

parse_tokens(Ts) ->
    parse_tokens(Ts, fun no_fix/1, fun fix_form/1, fun no_fix/1).

%-doc """
%PreFix adjusts the tokens before parsing them.
%FormFix adjusts the tokens after parsing them, if erl_parse failed.
%PostFix adjusts the forms after parsing them, if erl_parse worked.
%""".
parse_tokens(Ts, PreFix, FormFix, PostFix) ->
    case PreFix(Ts) of
        {form, Form} ->
            Form;
        {retry, Ts1} ->
            parse_tokens(Ts1, PreFix, FormFix, PostFix);
        no_fix ->
            case erl_parse:parse_form(Ts) of
                {ok, Form} ->
                    case PostFix(Form) of
                        no_fix ->
                            Form;
                        {form, NewForm} ->
                            NewForm
                    end;
                {error, _IoErr} ->
                    case FormFix(Ts) of
                        {form, Form} ->
                            Form;
                        {retry, Ts1, FormFix1} ->
                            parse_tokens(Ts1, PreFix, FormFix1, PostFix);
                        no_fix ->
                            parse_tokens_as_terms(Ts, PreFix, FormFix)
                    end
            end
    end.

%-doc """
%This handles config files, app.src, etc.
%PreFix adjusts the tokens before parsing them.
%FormFix adjusts the tokens after parsing them, only if erl_parse failed.
%""".
parse_tokens_as_terms(Ts, PreFix, FormFix) ->
    case PreFix(Ts) of
        {form, Form} ->
            Form;
        {retry, Ts1} ->
            parse_tokens_as_terms(Ts1, PreFix, FormFix);
        no_fix ->
            case erl_parse:parse_exprs(Ts) of
                {ok, Forms} ->
                    erl_syntax:form_list(Forms ++ [expression_dot()]);
                {error, IoErr} ->
                    case FormFix(Ts) of
                        {form, Form} ->
                            Form;
                        {retry, Ts1, FormFix1} ->
                            parse_tokens_as_terms(Ts1, PreFix, FormFix1);
                        no_fix ->
                            throw({parse_error, IoErr})
                    end
            end
    end.

expression_dot() ->
    erl_syntax:set_ann(
        erl_syntax:text("."), [expression_dot]).

%% ---------------------------------------------------------------------
%% Quick scanning/parsing - deletes macro definitions and other
%% preprocessor directives, and replaces all macro calls with atoms.

quick_parser(Ts, _Opt) ->
    filter_form(parse_tokens(quickscan_form(Ts))).

quickscan_form([{'-', _Anno}, {atom, AnnoA, define} | _Ts]) ->
    kill_form(AnnoA);
quickscan_form([{'-', _Anno}, {atom, AnnoA, undef} | _Ts]) ->
    kill_form(AnnoA);
quickscan_form([{'-', _Anno}, {atom, AnnoA, include} | _Ts]) ->
    kill_form(AnnoA);
quickscan_form([{'-', _Anno}, {atom, AnnoA, include_lib} | _Ts]) ->
    kill_form(AnnoA);
quickscan_form([{'-', _Anno}, {atom, AnnoA, ifdef} | _Ts]) ->
    kill_form(AnnoA);
quickscan_form([{'-', _Anno}, {atom, AnnoA, ifndef} | _Ts]) ->
    kill_form(AnnoA);
quickscan_form([{'-', _Anno}, {'if', AnnoA} | _Ts]) ->
    kill_form(AnnoA);
quickscan_form([{'-', _Anno}, {atom, AnnoA, elif} | _Ts]) ->
    kill_form(AnnoA);
quickscan_form([{'-', _Anno}, {atom, AnnoA, 'else'} | _Ts]) ->
    kill_form(AnnoA);
quickscan_form([{'-', _Anno}, {'else', AnnoA} | _Ts]) ->
    kill_form(AnnoA);
quickscan_form([{'-', _Anno}, {atom, AnnoA, endif} | _Ts]) ->
    kill_form(AnnoA);
quickscan_form([{'-', _Anno}, {atom, AnnoA, feature} | _Ts]) ->
    kill_form(AnnoA);
quickscan_form([{'-', Anno}, {'?', _}, {Type, _, _} = N | [{'(', _} | _] = Ts])
    when Type =:= atom; Type =:= var ->
    %% minus, macro and open parenthesis at start of form - assume that
    %% the macro takes no arguments; e.g. `-?foo(...).'
    do_quickscan_macros(N, Ts, [{'-', Anno}]);
quickscan_form([{'?', _Anno}, {Type, _, _} = N | [{'(', _} | _] = Ts])
    when Type =:= atom; Type =:= var ->
    %% macro and open parenthesis at start of form - assume that the
    %% macro takes no arguments (see scan_macros for details)
    do_quickscan_macros(N, Ts, []);
quickscan_form(Ts) ->
    quickscan_macros(Ts).

kill_form(A) ->
    [{atom, A, ?pp_form}, {'(', A}, {')', A}, {'->', A}, {atom, A, kill}, {dot, A}].

quickscan_macros(Ts) ->
    quickscan_macros(Ts, []).

quickscan_macros([{'?', _}, {Type, _, A} | Ts], [{string, AnnoS, S} | As])
  when Type =:= atom; Type =:= var ->
    %% macro after a string literal: change to a single string
    {_, Ts1} = skip_macro_args(Ts),
    S1 = S ++ quick_macro_string(A),
    quickscan_macros(Ts1, [{string, AnnoS, S1} | As]);
quickscan_macros([{'?', _}, {Type, _, _} = N | [{'(', _} | _] = Ts], [{':', _} | _] = As)
    when Type =:= atom; Type =:= var ->
    %% macro and open parenthesis after colon - check the token
    %% following the arguments (see scan_macros for details)
    Ts1 = case skip_macro_args(Ts) of
              {_, [{'->', _} | _] = Ts2} ->
                  Ts2;
              {_, [{'when', _} | _] = Ts2} ->
                  Ts2;
              _ ->
                  Ts    %% assume macro without arguments
          end,
    do_quickscan_macros(N, Ts1, As);
quickscan_macros([{'?', _}, {Type, _, _} = N | Ts], As)
    when Type =:= atom; Type =:= var ->
    %% macro with or without arguments
    {_, Ts1} = skip_macro_args(Ts),
    do_quickscan_macros(N, Ts1, As);
quickscan_macros([T | Ts], As) ->
    quickscan_macros(Ts, [T | As]);
quickscan_macros([], As) ->
    lists:reverse(As).

%% (after a macro has been found and the arglist skipped, if any)
do_quickscan_macros({_Type, _, A}, [{string, AnnoS, S} | Ts], As) ->
    %% string literal following macro: change to single string
    S1 = quick_macro_string(A) ++ S,
    quickscan_macros(Ts, [{string, AnnoS, S1} | As]);
do_quickscan_macros({_Type, AnnoA, A}, Ts, As) ->
    %% normal case - just replace the macro with an atom
    quickscan_macros(Ts, [{atom, AnnoA, quick_macro_atom(A)} | As]).

quick_macro_atom(A) ->
    list_to_atom("?" ++ atom_to_list(A)).

quick_macro_string(A) ->
    "(?" ++ atom_to_list(A) ++ ")".

%% Skipping to the end of a macro call, tracking open/close constructs.

-spec skip_macro_args(Tokens :: term()) -> {Skipped :: list(), Rest :: term()}.

skip_macro_args([{'(', _} = T | Ts]) ->
    skip_macro_args(Ts, [')'], [T]);
skip_macro_args(Ts) ->
    {[], Ts}.

skip_macro_args([{'(', _} = T | Ts], Es, As) ->
    skip_macro_args(Ts, [')' | Es], [T | As]);
skip_macro_args([{'{', _} = T | Ts], Es, As) ->
    skip_macro_args(Ts, ['}' | Es], [T | As]);
skip_macro_args([{'[', _} = T | Ts], Es, As) ->
    skip_macro_args(Ts, [']' | Es], [T | As]);
skip_macro_args([{'<<', _} = T | Ts], Es, As) ->
    skip_macro_args(Ts, ['>>' | Es], [T | As]);
skip_macro_args([{'begin', _} = T | Ts], Es, As) ->
    skip_macro_args(Ts, ['end' | Es], [T | As]);
skip_macro_args([{'if', _} = T | Ts], Es, As) ->
    skip_macro_args(Ts, ['end' | Es], [T | As]);
skip_macro_args([{'case', _} = T | Ts], Es, As) ->
    skip_macro_args(Ts, ['end' | Es], [T | As]);
skip_macro_args([{'receive', _} = T | Ts], Es, As) ->
    skip_macro_args(Ts, ['end' | Es], [T | As]);
skip_macro_args([{'try', _} = T | Ts], Es, As) ->
    skip_macro_args(Ts, ['end' | Es], [T | As]);
skip_macro_args([{E, _} = T | Ts], [E], As) -> %final close
    {lists:reverse([T | As]), Ts};
skip_macro_args([{E, _} = T | Ts], [E | Es], As) -> %matching close
    skip_macro_args(Ts, Es, [T | As]);
skip_macro_args([T | Ts], Es, As) ->
    skip_macro_args(Ts, Es, [T | As]);
skip_macro_args([], _Es, _As) ->
    throw({error, macro_args}).

filter_form({function, _, ?pp_form, _, [{clause, _, [], [], [{atom, _, kill}]}]}) ->
    none;
filter_form(T) ->
    T.

%% ---------------------------------------------------------------------
%% Normal parsing - try to preserve all information

normal_parser(Ts0, Opt) ->
    case scan_form(Ts0, Opt) of
        Ts when is_list(Ts) ->
            rewrite_form(parse_tokens(Ts,
                                      normal_parser_prefix(Opt),
                                      fun fix_form/1,
                                      Opt#opt.post_fixer));
        Node ->
            Node
    end.

normal_parser_prefix(#opt{pre_fixer = PreFixer} = Opt) ->
    DefaultPrefix = default_prefix(Opt),
    fun(Ts) ->
       case PreFixer(Ts) of
           no_fix ->
               DefaultPrefix(Ts);
           {retry, Ts1} ->
               case DefaultPrefix(Ts1) of
                   no_fix ->
                       {retry, Ts1};
                   Other ->
                       Other
               end
       end
    end.

default_prefix(#opt{parse_macro_definitions = true, compact_strings = false}) ->
    fun no_fix/1;
default_prefix(#opt{parse_macro_definitions = true, compact_strings = true}) ->
    fun fix_contiguous_strings/1;
default_prefix(#opt{parse_macro_definitions = false, compact_strings = false}) ->
    fun fix_define/1;
default_prefix(#opt{parse_macro_definitions = false, compact_strings = true}) ->
    fun(Ts) ->
       case fix_contiguous_strings(Ts) of
           no_fix ->
               fix_define(Ts);
           {retry, Ts1} ->
               case fix_define(Ts1) of
                   no_fix ->
                       {retry, Ts1};
                   Other ->
                       Other
               end
       end
    end.

scan_form([{'-', _Anno}, {atom, AnnoA, define} | Ts], #opt{parse_macro_definitions = false}) ->
    [
        {atom, AnnoA, ?pp_form},
        {'(', AnnoA},
        {')', AnnoA},
        {'->', AnnoA},
        {atom, AnnoA, define}
    | Ts];
scan_form([{'-', _Anno}, {atom, AnnoA, define} | Ts], Opt) ->
    [{atom, AnnoA, ?pp_form}, {'(', AnnoA}, {')', AnnoA}, {'->', AnnoA}, {atom, AnnoA, define}
     | scan_macros(Ts, Opt)];
scan_form([{'-', _Anno}, {atom, AnnoA, undef} | Ts], Opt) ->
    [{atom, AnnoA, ?pp_form}, {'(', AnnoA}, {')', AnnoA}, {'->', AnnoA}, {atom, AnnoA, undef}
     | scan_macros(Ts, Opt)];
scan_form([{'-', _Anno}, {atom, AnnoA, include} | Ts], Opt) ->
    [{atom, AnnoA, ?pp_form}, {'(', AnnoA}, {')', AnnoA}, {'->', AnnoA}, {atom, AnnoA, include}
     | scan_macros(Ts, Opt)];
scan_form([{'-', _Anno}, {atom, AnnoA, include_lib} | Ts], Opt) ->
    [{atom, AnnoA, ?pp_form}, {'(', AnnoA}, {')', AnnoA}, {'->', AnnoA}, {atom, AnnoA, include_lib}
     | scan_macros(Ts, Opt)];
scan_form([{'-', _Anno}, {atom, AnnoA, ifdef} | Ts], Opt) ->
    [{atom, AnnoA, ?pp_form}, {'(', AnnoA}, {')', AnnoA}, {'->', AnnoA}, {atom, AnnoA, ifdef}
     | scan_macros(Ts, Opt)];
scan_form([{'-', _Anno}, {atom, AnnoA, ifndef} | Ts], Opt) ->
    [{atom, AnnoA, ?pp_form}, {'(', AnnoA}, {')', AnnoA}, {'->', AnnoA}, {atom, AnnoA, ifndef}
     | scan_macros(Ts, Opt)];
scan_form([{'-', _Anno}, {'if', AnnoA} | Ts], Opt) ->
    [{atom, AnnoA, ?pp_form}, {'(', AnnoA}, {')', AnnoA}, {'->', AnnoA}, {atom, AnnoA, 'if'}
     | scan_macros(Ts, Opt)];
scan_form([{'-', _Anno}, {atom, AnnoA, elif} | Ts], Opt) ->
    [{atom, AnnoA, ?pp_form}, {'(', AnnoA}, {')', AnnoA}, {'->', AnnoA}, {atom, AnnoA, elif}
     | scan_macros(Ts, Opt)];
scan_form([{'-', _Anno}, {atom, AnnoA, 'else'} | Ts], Opt) ->
    [{atom, AnnoA, ?pp_form}, {'(', AnnoA}, {')', AnnoA}, {'->', AnnoA}, {atom, AnnoA, 'else'}
     | scan_macros(Ts, Opt)];
scan_form([{'-', Anno}, {'else', AnnoA} | Ts], Opt) ->
    %% See previous clause
    scan_form([{'-', Anno}, {atom, AnnoA, 'else'} | Ts], Opt);
scan_form([{'-', _Anno}, {atom, AnnoA, endif} | Ts], Opt) ->
    [{atom, AnnoA, ?pp_form}, {'(', AnnoA}, {')', AnnoA}, {'->', AnnoA}, {atom, AnnoA, endif}
     | scan_macros(Ts, Opt)];
scan_form([{'-', _Anno}, {atom, AnnoA, error} | Ts], _Opt) ->
    Desc = build_info_string("-error", Ts),
    ErrorInfo = {erl_anno:location(AnnoA), ?MODULE, {error, Desc}},
    erl_syntax:error_marker(ErrorInfo);
scan_form([{'-', _Anno}, {atom, AnnoA, warning} | Ts], _Opt) ->
    Desc = build_info_string("-warning", Ts),
    ErrorInfo = {erl_anno:location(AnnoA), ?MODULE, {warning, Desc}},
    erl_syntax:error_marker(ErrorInfo);
scan_form([{'-', A}, {'?', A1}, {Type, _, _} = N | [{'(', _} | _] = Ts], Opt)
    when Type =:= atom; Type =:= var ->
    %% minus, macro and open parenthesis at start of form - assume that
    %% the macro takes no arguments; e.g. `-?foo(...).'
    macro(A1, N, Ts, [{'-', A}], Opt);
scan_form([{'?', A}, {Type, _, _} = N | [{'(', _} | _] = Ts], Opt)
    when Type =:= atom; Type =:= var ->
    %% macro and open parenthesis at start of form - assume that the
    %% macro takes no arguments; probably a function declaration on the
    %% form `?m(...) -> ...', which will not parse if it is rewritten as
    %% `(?m(...)) -> ...', so it must be handled as `(?m)(...) -> ...'
    macro(A, N, Ts, [], Opt);
scan_form(Ts, Opt) ->
    scan_macros(Ts, Opt).

build_info_string(Prefix, Ts0) ->
    Ts = lists:droplast(Ts0),
    String = lists:droplast(tokens_to_string(Ts)),
    Prefix ++ " " ++ String ++ ".".

scan_macros(Ts, Opt) ->
    scan_macros(Ts, [], Opt).

scan_macros([{'?', _} = M, {Type, _, _} = N | Ts],
            [{string, AnnoS, _} = S | As],
            #opt{clever = true} = Opt)
    when Type =:= atom; Type =:= var ->
    %% macro after a string literal: be clever and insert ++
    scan_macros([M, N | Ts], [{'++', AnnoS}, S | As], Opt);
scan_macros([{'?', Anno}, {Type, _, _} = N | [{'(', _} | _] = Ts], [{':', _} | _] = As, Opt)
    when Type =:= atom; Type =:= var ->
    %% macro and open parentheses after colon - probably a call
    %% `m:?F(...)' so the argument list might belong to the call, not
    %% the macro - but it could also be a try-clause pattern
    %% `...:?T(...) ->' - we need to check the token following the
    %% arguments to decide
    {Args, Rest} = skip_macro_args(Ts),
    case Rest of
        [{'->', _} | _] ->
            macro_call(Args, Anno, N, Rest, As, Opt);
        [{'when', _} | _] ->
            macro_call(Args, Anno, N, Rest, As, Opt);
        [{':', _} | _] ->
            macro_call(Args, Anno, N, Rest, As, Opt);
        _ ->
            macro(Anno, N, Ts, As, Opt)
    end;
scan_macros([{'?', Anno}, {Type, _, _} = N | [{'(', _} | _] = Ts], As, Opt)
    when Type =:= atom; Type =:= var ->
    %% macro with arguments
    {Args, Rest} = skip_macro_args(Ts),
    macro_call(Args, Anno, N, Rest, As, Opt);
scan_macros([{'?', Anno}, {Type, _, _} = N | Ts], As, Opt)
    when Type =:= atom; Type =:= var ->
    %% macro without arguments
    macro(Anno, N, Ts, As, Opt);
scan_macros([T | Ts], As, Opt) ->
    scan_macros(Ts, [T | As], Opt);
scan_macros([], As, _Opt) ->
    lists:reverse(As).

%% Rewriting to a tuple which will be recognized by the post-parse pass
%% (we insert parentheses to preserve the precedences when parsing).

macro(Anno, {Type, _, A}, Rest, As, Opt) ->
    do_scan_macros([], Rest, [{atom, Anno, macro_atom(Type, A)} | As], Opt).

macro_call([{'(', _}, {')', _}], Anno, {_, AnnoN, _} = N, Rest, As, Opt) ->
    {Open, Close} = parentheses(As),
    do_scan_macros([],
                  Rest,
                  lists:reverse(
                    Open ++
                    [{atom, Anno, ?macro_call}, {'(', Anno}, N, {')', AnnoN}] ++
                    Close,
                    As),
                  Opt);
macro_call([{'(', _} | Args], L, {_, Ln, _} = N, Rest, As, Opt) ->
    {Open, Close} = parentheses(As),
    %% drop closing parenthesis

    %% assert
    {')', _} = lists:last(Args),
    Args1 = lists:droplast(Args),
    %% note that we must scan the argument list; it may not be skipped
    do_scan_macros(Args1 ++ [{'}', Ln} | Close],
                  Rest,
                  lists:reverse(Open ++ [{atom, L, ?macro_call}, {'(', L}, N, {',', Ln}], As),
                  Opt).

macro_atom(atom, A) ->
    list_to_atom(?atom_prefix ++ atom_to_list(A));
macro_atom(var, A) ->
    list_to_atom(?var_prefix ++ atom_to_list(A)).

%% don't insert parentheses after a string token, to avoid turning
%% `"string" ?macro' into a "function application" `"string"(...)'
%% (see note at top of file)
parentheses([{string, _, _} | _]) ->
    {[], []};
parentheses(_) ->
    {[{'(', 0}], [{')', 0}]}.

%% (after a macro has been found and the arglist skipped, if any)
do_scan_macros(Args, [{string, AnnoS, _} | _] = Rest, As, #opt{clever = true} = Opt) ->
    %% string literal following macro: be clever and insert ++
    scan_macros(Args ++ [{'++', AnnoS} | Rest],  As, Opt);
do_scan_macros(Args, Rest, As, Opt) ->
    %% normal case - continue scanning
    scan_macros(Args ++ Rest, As, Opt).

rewrite_form({function, Anno, ?pp_form, _, [{clause, _, [], [], [{call, _, A, As}]}]}) ->
    erl_syntax:set_pos(
        erl_syntax:attribute(A, rewrite_list(As)), Anno);
rewrite_form({function, Anno, ?pp_form, _, [{clause, _, [], [], [A]}]}) ->
    erl_syntax:set_pos(
        erl_syntax:attribute(A), Anno);
rewrite_form(T) ->
    rewrite(T).

rewrite_list([T | Ts]) ->
    [rewrite(T) | rewrite_list(Ts)];
rewrite_list([]) ->
    [].

%% Note: as soon as we start using erl_syntax:subtrees/1 and similar
%% functions, we cannot assume that we know the exact representation of
%% the syntax tree anymore - we must use erl_syntax functions to analyze
%% and decompose the data.

rewrite(Node) ->
    case erl_syntax:type(Node) of
        atom ->
            case atom_to_list(erl_syntax:atom_value(Node)) of
                ?atom_prefix ++ As ->
                    A1 = list_to_atom(As),
                    N = erl_syntax:copy_pos(Node, erl_syntax:atom(A1)),
                    erl_syntax:copy_pos(Node, erl_syntax:macro(N));
                ?var_prefix ++ As ->
                    A1 = list_to_atom(As),
                    N = erl_syntax:copy_pos(Node, erl_syntax:variable(A1)),
                    erl_syntax:copy_pos(Node, erl_syntax:macro(N));
                _ ->
                    Node
            end;
        application ->
            F = erl_syntax:application_operator(Node),
            case erl_syntax:type(F) of
                atom ->
                    case erl_syntax:atom_value(F) of
                        ?macro_call ->
                            [A | As] = erl_syntax:application_arguments(Node),
                            M = erl_syntax:macro(A, rewrite_list(As)),
                            erl_syntax:copy_pos(Node, M);
                        _ ->
                            do_rewrite(Node)
                    end;
                _ ->
                    do_rewrite(Node)
            end;
        tuple ->
            case erl_syntax:tuple_elements(Node) of
                [MagicWord, A | As] ->
                    case erl_syntax:type(MagicWord) of
                        atom ->
                            case erl_syntax:atom_value(MagicWord) of
                                ?macro_call ->
                                    M = erl_syntax:macro(A, rewrite_list(As)),
                                    erl_syntax:copy_pos(Node, M);
                                _ ->
                                    do_rewrite(Node)
                            end;
                        _ ->
                            do_rewrite(Node)
                    end;
                _ ->
                    do_rewrite(Node)
            end;
        _ ->
            do_rewrite(Node)
    end.

do_rewrite(Node) ->
    case erl_syntax:subtrees(Node) of
        [] ->
            Node;
        Gs ->
            Node1 =
                erl_syntax:make_tree(
                    erl_syntax:type(Node), [[rewrite(T) || T <- Ts] || Ts <- Gs]),
            erl_syntax:copy_pos(Node, Node1)
    end.

%% attempting a rescue operation on a token sequence for a single form
%% if it could not be parsed after the normal treatment

fix_form([{atom, _, ?pp_form}, {'(', _}, {')', _}, {'->', _}, {atom, _, define}, {'(', _}
          | _] =
             Ts) ->
    case lists:reverse(Ts) of
        [{dot, _}, {')', _} | _] ->
            {retry, Ts, fun fix_stringyfied_macros/1};
        [{dot, L} | Ts1] ->
            Ts2 = lists:reverse([{dot, L}, {')', L} | Ts1]),
            {retry, Ts2, fun fix_stringyfied_macros/1};
        _ ->
            no_fix
    end;
fix_form(_Ts) ->
    no_fix.

fix_stringyfied_macros(Ts) ->
    {retry, fix_stringyfied_macros(Ts, []), fun fix_define/1}.

fix_stringyfied_macros([], Ts) ->
    lists:reverse(Ts);
fix_stringyfied_macros([{'?', Pos}, {atom, Pos, MacroName} | Rest], Ts) ->
    NextTs =
        case atom_to_list(MacroName) of
            ?var_prefix ++ Name ->
                [{atom, Pos, list_to_atom(?var_prefix ++ [$? | Name])} | Ts];
            _ ->
                [{atom, Pos, MacroName}, {'?', Pos} | Ts]
        end,
    fix_stringyfied_macros(Rest, NextTs);
fix_stringyfied_macros([Other | Rest], Ts) ->
    fix_stringyfied_macros(Rest, [Other | Ts]).

fix_define([{atom, Anno, ?pp_form},
            {'(', _},
            {')', _},
            {'->', _},
            {atom, AnnoA, define},
            {'(', _},
            N,
            {',', _}
            | Ts]) ->
    [{dot, _}, {')', _} | Ts1] = lists:reverse(Ts),
    S = tokens_to_string(lists:reverse(Ts1)),
    A = erl_syntax:set_pos(
            erl_syntax:atom(define), AnnoA),
    Txt = erl_syntax:set_pos(
              erl_syntax:text(S), AnnoA),
    {form,
     erl_syntax:set_pos(
         erl_syntax:attribute(A, [N, Txt]), Anno)};
fix_define(_Ts) ->
    no_fix.

fix_contiguous_strings(Ts) ->
    case fix_contiguous_strings(Ts, []) of
        Ts ->
            no_fix;
        NextTs ->
            {retry, NextTs}
    end.

fix_contiguous_strings([], Ts) ->
    lists:reverse(Ts);
fix_contiguous_strings([{string, L1, S1} = First, {string, L2, S2} = Second | Rest],
                       Ts) ->
    case {erl_anno:text(L1), erl_anno:text(L2)} of
        {T1, T2} when is_list(T1), is_list(T2) ->
            Separator =
                case {erl_anno:location(L1), erl_anno:location(L2)} of
                    {L, L} ->
                        $\s;
                    {_, _} ->
                        $\n % different lines
                end,
            NewL = erl_anno:set_text(T1 ++ [Separator | T2], L1),
            fix_contiguous_strings([{string, NewL, S1 ++ S2} | Rest], Ts);
        _ ->
            fix_contiguous_strings([Second | Rest], [First | Ts])
    end;
fix_contiguous_strings([Other | Rest], Ts) ->
    fix_contiguous_strings(Rest, [Other | Ts]).

no_fix(_) ->
    no_fix.

%-doc """
%Generates a string corresponding to the given token sequence.
%
%The string can be re-tokenized to yield the same token list again.
%""".
token_to_string(T) ->
    case erl_scan:text(T) of
        undefined ->
            token_to_string(erl_scan:category(T), erl_scan:symbol(T));
        Text ->
            Text
    end.

token_to_string(atom, A) ->
    io_lib:write_atom(A);
token_to_string(string, S) ->
    io_lib:write_string(S);
token_to_string(char, C) ->
    io_lib:write_char(C);
token_to_string(float, F) ->
    lists:flatten(
        io_lib:format("~p", [F]));
token_to_string(integer, N) ->
    lists:flatten(
        io_lib:format("~p", [N]));
token_to_string(var, A) ->
    atom_to_list(A);
token_to_string(dot, dot) ->
    ".\n";
% from OTP: -type af_sigil_prefix() :: {'sigil_prefix', anno(), atom()}.
token_to_string(sigil_prefix, _Prefix) ->
    "";
% from OTP: -type af_sigil_suffix() :: {'sigil_suffix', anno(), string()}.
token_to_string(sigil_suffix, _Suffix) ->
    "";
token_to_string(Same, Same) ->
    atom_to_list(Same).

-spec tokens_to_string([term()]) -> string().
tokens_to_string([T | Ts]) ->
    token_to_string(T) ++ maybe_space(erl_scan:category(T), Ts) ++ tokens_to_string(Ts);
tokens_to_string([]) ->
    "".

maybe_space(_, []) ->
    "";
maybe_space(C, [T | _]) ->
    maybe_space_between(C, erl_scan:category(T)).

maybe_space_between(dot, _) ->
    ""; % No space at the end
maybe_space_between('#', '!') ->
    ""; %  \
maybe_space_between('!', '/') ->
    ""; %   \_ No space for escript headers
maybe_space_between('/', atom) ->
    ""; %  /
maybe_space_between(atom, '/') ->
    ""; % /
maybe_space_between('#', _) ->
    ""; % No space for records and maps
maybe_space_between(atom, '{') ->
    ""; % No space for records
maybe_space_between('?', _) ->
    ""; % No space for macro names
maybe_space_between('-', atom) ->
    ""; % No space for attributes
maybe_space_between(atom, '(') ->
    ""; % No space for function calls
maybe_space_between(var, '(') ->
    ""; % No space for function calls
maybe_space_between(_, _) ->
    " ". % Space between anything else

%% @private
%% @doc Callback function for formatting error descriptors. Not for
%% normal use.

%-doc false.
-spec format_error(term()) -> string().

format_error(macro_args) ->
    errormsg("macro call missing end parenthesis");
format_error({error, Error}) ->
    Error;
format_error({warning, Error}) ->
    Error;
format_error({unknown, Reason}) ->
    errormsg(io_lib:format("unknown error: ~tP", [Reason, 15])).

errormsg(String) ->
    io_lib:format("~s: ~ts", [?MODULE, String]).

%% =====================================================================

%% See #7266: The dodger currently does not process feature attributes
%% correctly, so temporarily consider the `else` and `maybe` atoms
%% always as keywords
-spec reserved_word(Atom :: atom()) -> boolean().
reserved_word('else') -> true;
reserved_word('maybe') -> true;
reserved_word(Atom) -> erl_scan:f_reserved_word(Atom).
%% erlfmt:ignore-end