use 5.008;
use ExtUtils::MakeMaker;
# See lib/ExtUtils/MakeMaker.pm for details of how to influence
# the contents of the Makefile that is written.

use Carp;
use List::Util qw(first);
use File::Find;
use File::Spec;

my $GAP_path; 


if (defined($ENV{GAP})){
    
    $GAP_path= $ENV{GAP};
    print "Using gap from GAP env. variable\n";
    
} else {
    
    use File::Find;
    my @dir = split /:/, $ENV{PATH};
    sub wanted{
	if($_ eq 'gap.sh'){
	    $GAP_path = $File::Find::dir . q{/gap.sh};
	} elsif ($_ eq 'sage'){
	    $GAP_path = $File::Find::dir . q{/sage -gap};
	} elsif ($_ eq 'gap'){
	    $GAP_path = $File::Find::dir . q{/gap};

	}
    }
    find(\&wanted,@dir);
    
}


if(!defined($GAP_path)){

    print "GAP interpreter not found\n";
    $GAP_path = prompt("Absolut path to gap exec?");
    $GAP_path =~ s/^\s*//;
    $GAP_path =~ s/\s*$//;

} else {
    $GAP_path=File::Spec->rel2abs($GAP_path);
}

my $command=$GAP_path;
$command =~ s{/sage\s.*}{/sage};
if(! (-f $command) && (-x _) ) {
print <<"WARN";
**Non executable GAP interpreter
**Several tests won't be performed
**You are advised to check/fix and rerun with a correct GAP exec
WARN
}

print <<"INFO";
Will use :
$GAP_path
as default GAP interpreter
INFO


my $file;
my $module_path = q(lib/Math/GAP.pm);

open ($file,"<",$module_path)
	or croak "Can't read from $module_path: $!";
my @lines=<$file>;
close $file;

#look for 'my $$var' in line $l and set it to $value
sub change_value {
    my ($var,$value)= @_[1..2];
    if($_[0]  =~ s/
       (
	my \s+ \$$var \s+ = \s+
	)
       ('[^']*')
       (
       \s*;\s*
       #set at installation
       )
       /$1'$value'$3/x)
       {return 1;}
		 
	return 0;
}

first {change_value($_,'GAP_path',$GAP_path)} @lines
	or die "GAP path not found in $module_path!";
	

open ($file,">",$module_path)
	or croak "Can't write to $module_path : $!";
foreach my $l (@lines) {print {$file} $l;}
close $file;


WriteMakefile(
    NAME              => 'Math::GAP',
    AUTHOR            => 'Fabien Galand <galand@cpan.org>',
    VERSION_FROM      => 'lib/Math/GAP.pm', # finds $VERSION
    ABSTRACT_FROM     => 'lib/Math/GAP.pm', # retrieve abstract from module
    PREREQ_PM         => {
                        'strict'              => 0,
			'warnings'            => 0,
			'Carp'                => 0,
  			'ExtUtils::MakeMaker' => 0,
  			'File::Find'          => 0,
                        'File::Spec'          => 0,
			'List::Util'	      => 0,
  			'IO::Handle'          => 0,
  			'Scalar::Util'        => 0,
			'Socket'              => 0,
			'Test::More'          => 0,
  			    }, 
    dist               => { COMPRESS => 'gzip -9f', SUFFIX => 'gz', },
    clean              => { FILES => 'Math-GAP-*' },

);