#!/usr/bin/perl

=pod

=head1 NAME

shython - Shebang wrapper for cython


=head1 SYNOPSIS

#!/usr/bin/shython

python program

=head1 DESCRIPTION

B<shython> uses B<cython> to compile a python script into a C-file
which is then compiled and run.

It caches the compiled C-file in $XDG_CACHE_HOME/shython or
$HOME/.cache/shython, and recompiles only if the source script has a
newer timestamp.


=head1 EXAMPLE

  #!/usr/bin/shython

  import sys
  print "Hello world, ",sys.argv

=head1 EXAMPLE: Shython in $PATH

  #!/usr/bin/env shython

  import sys
  print "Hello world, ",sys.argv

=head1 AUTHOR

Copyright (C) 2017 Ole Tange,
http://ole.tange.dk and Free Software Foundation, Inc.


=head1 LICENSE

Copyright (C) 2012 Free Software Foundation, Inc.

This program 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 of the License, or
at your option any later version.

This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.


=head1 DEPENDENCIES

B<shython> uses B<cython>, B<gcc>, and B<perl>.


=head1 SEE ALSO

B<cython>


=cut

use File::Path;

my $pyfile = shift;

my $cache_home = append_shython('XDG_CACHE_HOME') ||
    $ENV{'HOME'}."/.cache/shython";
my $cachefile = $cache_home."/".$pyfile;
-d $cache_home or File::Path::mkpath($cache_home);
if (not -e $cachefile
    or
    -M $cachefile > -M $pyfile) {
    compile($pyfile,$cachefile);
}
# run
system($cachefile,@ARGV);

sub compile {
    my $pyfile = shift;
    my $cachefile = shift;
    my $cython = (which("cython3","cython"))[0];
    my $cfile = $cachefile.".tmp";
    $cfile =~ s/(.py.?)?$/.c/;
    # cython3 --embed -o hello.c hello.py
    system($cython,"--embed","-o",$cfile,$pyfile);
    my @installed_lib;
    my @installed_inc;
    for my $inc (</usr/include/python*>,</usr/local/include/python*>) {
	my $ver = $inc;
	$ver =~ s:.*/::;
	for my $lib (qw(/lib64 /lib /lib/x86_64-linux-gnu
		     /usr/lib/gcc/x86_64-linux-gnu/6 /usr/lib
		     /usr/lib/x86_64-linux-gnu /usr/local/lib)) {
	    if(-e "$lib/lib$ver.so" and -e "$lib/lib$ver.a") {
		push @installed_lib,$ver;
		push @installed_inc,$inc;
	    }
	}
    }
    my $inc = (reverse sort @installed_inc)[0];
    my $lib = (reverse sort @installed_lib)[0];
    
    system("gcc","-Os","-I",$inc,"-o",$cachefile,$cfile,"-l$lib","-lpthread","-lm","-lutil","-ldl");
    unlink $cfile;
}

sub which {
    # Input:
    #   @programs = programs to find the path to
    # Returns:
    #   @full_path = full paths to @programs. Nothing if not found
    my @which;
    for my $prg (@_) {
	push(@which, grep { not -d $_ and -x $_ }
	     map { $_."/".$prg } split(":",$ENV{'PATH'}));
    }
    return @which;
}

sub append_shython {
    my $v = shift;
    if($ENV{$v}) {
	return(map { "$_/shython" }
	       grep { -d $_ }
	       split /:/, $ENV{$v});
    } else {
	return "";
    }
}