package Module::Path;
# ABSTRACT: get the full path to a locally installed module
$Module::Path::VERSION = '0.18';
use 5.006;
use strict;
use warnings;
use File::Basename 'dirname';
use Cwd qw/ abs_path /;

require Exporter;

our @ISA       = qw(Exporter);
our @EXPORT_OK = qw(module_path);

my $SEPARATOR;

BEGIN {
    if ($^O =~ /^(dos|os2)/i) {
        $SEPARATOR = '\\';
    } elsif ($^O =~ /^MacOS/i) {
        $SEPARATOR = ':';
    } else {
        $SEPARATOR = '/';
    }
}

sub module_path
{
    my $module = shift;
    my $relpath;
    my $fullpath;

    ($relpath = $module) =~ s/::/$SEPARATOR/g;
    $relpath .= '.pm' unless $relpath =~ m!\.pm$!;

    DIRECTORY:
    foreach my $dir (@INC) {
        next DIRECTORY if not defined($dir);

        # see 'perldoc -f require' on why you might find
        # a reference in @INC
        next DIRECTORY if ref($dir);

        next unless -d $dir && -r $dir && -x $dir;

        # The directory path might have a symlink somewhere in it,
        # so we get an absolute path (ie resolve any symlinks).
        # The previous attempt at this only dealt with the case
        # where the final directory in the path was a symlink,
        # now we're trying to deal with symlinks anywhere in the path.
        my $abs_dir = $dir;
        eval { $abs_dir = abs_path($abs_dir); };
        next DIRECTORY if $@ || !defined($abs_dir);

        $fullpath = $abs_dir.$SEPARATOR.$relpath;
        return $fullpath if -f $fullpath;
    }

    return undef;
}

1;

=head1 NAME

Module::Path - get the full path to a locally installed module

=head1 SYNOPSIS

 use Module::Path 'module_path';
 
 $path = module_path('Test::More');
 if (defined($path)) {
   print "Test::More found at $path\n";
 } else {
   print "Danger Will Robinson!\n";
 }

=head1 DESCRIPTION

This module provides a single function, C<module_path()>,
which takes a module name and finds the first directory in your C<@INC> path
where the module is installed locally.
It returns the full path to that file, resolving any symlinks.
It is portable and only depends on core modules.

It works by looking in all the directories in C<@INC>
for an appropriately named file:

=over 4

=item

Foo::Bar becomes C<Foo/Bar.pm>, using the correct directory path
separator for your operating system.

=item

Iterate over C<@INC>, ignoring any references
(see L<"perlfunc"/"require"> if you're surprised to hear
that you might find references in C<@INC>).

=item

For each directory in C<@INC>, append the partial path (C<Foo/Bar.pm>),
again using the correct directory path separator.
If the resulting file exists, return this path.

=item

If a directory in C<@INC> is a symlink, then we resolve the path,
and return a path containing the linked-to directory.

=item

If no file was found, return C<undef>.

=back

I wrote this module because I couldn't find an alternative
which dealt with the points listed above, and didn't pull in
what seemed like too many dependencies to me.

The distribution for C<Module::Path> includes the C<mpath>
script, which lets you get the path for a module from the command-line:

 % mpath Module::Path

The C<module_path()> function will also cope if the module name includes C<.pm>;
this means you can pass a partial path, such as used as the keys in C<%INC>:

  module_path('Test/More.pm') eq $INC{'Test/More.pm'}

The above is the basis for one of the tests.

=head1 BUGS

Obviously this only works where the module you're after has its own C<.pm>
file. If a file defines multiple packages, this won't work.

This also won't find any modules that are being loaded in some special
way, for example using a code reference in C<@INC>, as described
in L<"perlfunc"/"require">.


=head1 SEE ALSO

There are a number of other modules on CPAN which provide the
same or similar functionality:
L<App::whichpm>,
L<Class::Inspector>,
L<Module::Data>,
L<Module::Filename>,
L<Module::Finder>,
L<Module::Info>,
L<Module::Locate>,
L<Module::Mapper>,
L<Module::Metadata>,
L<Module::Runtime>,
L<Module::Util>,
and L<Path::ScanINC>.

I've written a review of all such modules that I'm aware of:

=over 4

L<http://neilb.org/reviews/module-path.html>

=back

Module::Path was written to be fast, portable, and have a low number of
core-only runtime dependencies. It you only want to look up the path to
a module, it's a good choice.

If you want more information, such as the module's version, what functions
are provided, etc, then start by looking at L<Module::Info>,
L<Module::Metadata>, and L<Class::Inspector>.

The following scripts can also give you the path:
L<perldoc>,
L<whichpm|https://www.metacpan.org/module/whichpm>.


=head1 REPOSITORY

L<https://github.com/neilbowers/Module-Path>

=head1 AUTHOR

Neil Bowers E<lt>neilb@cpan.orgE<gt>

=head1 COPYRIGHT AND LICENSE

This software is copyright (c) 2012 by Neil Bowers <neilb@cpan.org>.

This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.