eval '(exit $?0)' && eval 'exec perl -wS "$0" "$@"'
  & eval 'exec perl -wS "$0" $argv:q'
    if 0;

# This file is part of GNU Mailutils.
# Copyright (C) 2017 Free Software Foundation, Inc.
#
# GNU Mailutils is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License as
# published by the Free Software Foundation; either version 3, or (at
# your option) any later version.
#
# GNU Mailutils is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with GNU Mailutils.  If not, see <http://www.gnu.org/licenses/>.

use strict;
use warnings;
use Getopt::Long qw(:config gnu_getopt no_ignore_case require_order auto_version);
use File::Basename;
use File::Temp qw(tempdir);
use Pod::Man;
use Pod::Usage;
use Cwd 'abs_path';
use List::Regexp;

=head1 NAME

gylwrap - wrapper for yacc, lex and similar programs

=head1 SYNOPSIS

B<gylwrap>
[B<-c?>]
[B<--compatibility>]    
[B<--yyrepl=>I<PREFIX>]
[B<--yysym=>I<STRING>]
[B<--stdout>]
[B<--help>]
[B<--version>]    
I<COMMAND>
I<INPUT>
I<OUTPUT> I<DESIRED>...

B<ylwrap>
[B<-?>]    
[B<--yyrepl=>I<PREFIX>]
[B<--yysym=>I<STRING>]
[B<--stdout>]
[B<--help>]
[B<--version>]    
I<INPUT>
[I<OUTPUT> I<DESIRED>]...
B<--> I<PROGRAM> [I<ARGS>]    

=head1 DESCRIPTION

Wraps B<lex> and B<yacc> invocations to rename their output files.  
It also ensures that multiple I<COMMAND> instances can be invoked
in a single directory in parallel and allows for renaming global
symbols to avoid clashes when multiple parsers and/or lexers are
linked in a single executable.

To achieve this, B<gylwrap> creates a temporary directory, changes
to it, and runs I<COMMAND> (which may contain arguments and options)
with I<INPUT> as its last argument.  Upon successful exit, it processes
the I<OUTPUT> I<DESIRED> pairs.  Each I<OUTPUT> file is then renamed
to the file I<DESIRED>, taking care to fix up any eventual B<#line>
directives.

If B<--yyrepl=I<PREFIX>> is given, the global symbols that can cause
name clashes are renamed by replacing the initial B<yy> with I<PREFIX>.
For a list of symbols that are subject for replacement, inspect the
B<@sym> variable at the start of the script.  Additional names can be
added to this list using the B<--yysym> option.

If given the B<--compatibility> option or if invoked as B<ylwrap>,
the tool runs in compatibility mode, mimicking the behavior of the
standard B<ylwrap> utility from GNU Automake.  Command line arguments
consist of two lists, separated by B<-->.  The left-hand side list
supplies the I<OUTPUT>,I<DESIRED> pairs, and the right-hand side one
supplies the command and its arguments.

In both modes, prior to running the command, the program looks for file
B<gylwrap.conf> in the same directory as the I<INPUT> file.  If found,
the file is sourced.  Empty lines and comments (introduced by the hash
sign) are ignored.  Rest of lines are either option assignements, or
section headings.

Option assignements have the form B<I<OPTION> = I<VALUE>>, and generally,
have the same meaning as the corresponding command line option without
the leading two dashes:

=over 4

=item B<yyrepl => I<PREFIX>

Replace the B<yy> prefix with I<PREFIX> in the identifiers.

=item B<stdout = 1>

Enable the B<--stdout> option.

=item B<yysym => I<NAME>

Add I<NAME> to the list of symbols suitable for prefix replacement.
This keyword can appear multiple times.

=item B<flags => I<STRING>

Add I<STRING> to the invocation of I<COMMAND>.  This is useful, if you
have several parsers in the same directory, and some of them require
the B<-d> option, while others don't.    
    
=back

Section headers have the form B<[I<FILE>]>.  The settings under a
section header have effect only if I<FILE> is the same as the I<INPUT>
command line argument.    
    
=head1 OPTIONS

=over 4

=item B<-c>, B<--compatibility>

Run in compatibility mode.
    
=item B<--stdout>

Redirect I<COMMAND>'s standard output to the first I<OUTPUT>.

=item B<--yyrepl=>I<PREFIX>

Replace the B<yy> prefix in global symbols with I<PREFIX>.

=item B<--yysym=>I<SYMBOL>

Add I<SYMBOL> to the list of symbols subject for replacement.

=item B<-?>, B<--help>

Displays help text and exit

=item B<--version>

Displays program version and exits.
    
=back

=head1 NOTE

This script is an improved version of the B<ylwrap> script, included
in the GNU Automake distribution.    
    
=cut    

# List of symbols suitable for prefix replacements.  See the
# options --yyrepl and --yysym, and similar statements in the configuration
# file.
my @yysym = qw(
     yymaxdepth 
     yyparse 
     yylex   
     yyerror 
     yylval  
     yychar  
     yydebug 
     yypact  
     yyr1    
     yyr2    
     yydef   
     yychk   
     yypgo   
     yyact   
     yyexca  
     yyerrflag
     yynerrs 
     yyps    
     yypv    
     yys     
     yy_yys  
     yystate 
     yytmp   
     yyv     
     yy_yyv  
     yyval   
     yylloc  
     yyreds  
     yytoks  
     yylhs   
     yylen   
     yydefred 
     yydgoto  
     yysindex 
     yyrindex 
     yygindex 
     yytable  
     yycheck  
     yyname   
     yyrule

     yy_create_buffer
     yy_delete_buffer
     yy_flex_debug
     yy_init_buffer
     yy_flush_buffer
     yy_load_buffer_state
     yy_switch_to_buffer
     yyin
     yyleng
     yylex
     yylineno
     yyout
     yyrestart
     yytext
     yywrap
     yyalloc
     yyrealloc
     yyfree
);

our $VERSION = '1.00';

# If prefix replacement is requested, the list above is assembled into
# a single regular expression, stored here.
my $yyrx;

# String to replace the "yy" prefix with.
my $yyrepl;

# If set, redirect the stdout from the command to the first output file.
my $stdout;

# Input directory with special characters escaped, for "#line" directive
# fixup.
my $input_rx;

# Configuration settings from the "gylwrap.conf" file.  Indexed by
# input file name.  Default entry is ''.
my %config;

# Name of the first output file.  This is used in compatibility mode to
# avoid bailing out if one of the output files (except the principal one)
# does not exist.
my $parser;

# Name this program was invoked as.
my $progname = basename($0);
my $compat = $progname eq 'ylwrap'; # True if running in compatibility mode

# List of files created during the run, for cleanup purposes.
my @created;

sub filter {
    my ($from, $to) = @_;
    my $target = basename($to);
    my $ifd;
    unless (open($ifd, '<', $from)) {
	if ($compat) {
	    return if $from ne $parser;
	}
	die "can't open input file $from: $!";
    }
    open(my $ofd, '>', $to)
	or die "can't open output file $to: $!";
    push @created, $to;
    while (<$ifd>) {
	if (/^#/) {
	    s{$input_rx/}{};
	    s{"$from"}{"$target"};
	}
	if ($yyrx) {
	    s{\byy($yyrx)\b}{${yyrepl}$1}g;
	}
	print $ofd $_
    }
    close $ifd;
    close $ofd;
}

sub readconf {
    my $file = shift;
    open(my $fd, '<', $file)
	or die "can't open $file: $!";
    my $key = '';
    while (<$fd>) {
	chomp;
	s/^\s+//;
	if (/^#/ || /^$/) {
	    next;
	} elsif (/^\[(.+)\]/) {
	    $key = $1;
	} elsif (m/(.+?)\s*=\s*(.+)$/) {
	    if ($1 eq 'yysym') {
		push @{$config{$key}{$1}}, $2;
	    } else {
		$config{$key}{$1} = $2;
	    }
	} else {
	    print STDERR "$file:$.: unrecognized line\n";
	}
    }
    close($fd);
}

my ($command, $input, @output);

GetOptions("yyrepl=s" => \$yyrepl,
	   "yysym=s@" => \@yysym,
	   "stdout" => \$stdout,
	   "compatibility|c" => \$compat,
	   "help|?" => sub {
	       pod2usage(-exitstatus => 0, -verbose => 2);
	   }	   
    ) or exit(1);

if ($compat) {
    $input = shift @ARGV;
    while (my $arg = shift @ARGV) {
	last if ($arg eq '--');
	push @output, $arg;
    }
    $command = join(' ', @ARGV); 
} else {
    pod2usage(-exitstatus => 1, -verbose => 0, -output => \*STDERR)
	unless @ARGV >= 2;
    ($command, $input, @output) = @ARGV;
}

pod2usage(-exitstatus => 1, -verbose => 0, -output => \*STDERR)
    unless (@output && (@output % 2) == 0);

# Make sure input file name is absolute
$input = abs_path($input);

my $input_dir = dirname($input);
$input_rx = qr($input_dir);

my $confile = "$input_dir/gylwrap.conf";
readconf($confile) if -r $confile;    

my $input_base = basename($input);
unless ($stdout) {
    $stdout = $config{$input_base}{stdout} || $config{''}{stdout};
}
unless ($yyrepl) {
    $yyrepl = $config{$input_base}{yyrepl} || $config{''}{yyrepl};
}
if ($yyrepl) {
    push @yysym, @{$config{$input_base}{yysym}}
        if exists $config{$input_base}{yysym};
    push @yysym, @{$config{''}{yysym}}
        if exists $config{''}{yysym};
    if ($yyrepl) {
	$yyrx = regexp_opt({ type => 'pcre' }, map { s/^yy//; $_ } @yysym);
    }
}

my $prog = $command;
$prog =~ s/\s.*$//;

if (my $flags = $config{$input_base}{flags} || $config{''}{flags}) {
    $command .= ' ' . $flags;
}

$parser = $output[0];

$command .= ' '.$input;
if ($stdout) {
    $command .= '>'.$parser;
}    

# Create working directory
my $wd = tempdir("ylXXXXXX", DIR => '.', CLEANUP => 1)
    or die "cannot create temporary directory";
chdir $wd
    or die "cannot change to the temporary directory";
END {
    if ($?) {
	unlink @created;
    }
    chdir "..";
}

system($command);
if ($? == -1) {
    print STDERR "$prog: $!\n";
    exit(127);
} elsif ($? & 127) {
    print STDERR "$prog died with signal ".($? & 127)."\n";
    exit(127);
} else {
    my $code = $? >> 8;
    exit($code) if $code;
}

while (my $from = shift @output) {
    my $to = shift @output;
    $to = '../' . $to unless $to =~ m{^/};
    filter($from, $to);
}
    
exit 0;

# Local Variables:
# mode: perl
# End: