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package inc::latest;
use strict;
use vars qw($VERSION);
$VERSION = '0.4005';
$VERSION = eval $VERSION;

use Carp;
use File::Basename  ();
use File::Spec      ();
use File::Path      ();
use IO::File        ();
use File::Copy      ();

# track and return modules loaded by inc::latest
my @loaded_modules;
sub loaded_modules {@loaded_modules}

# must ultimately "goto" the import routine of the module to be loaded
# so that the calling package is correct when $mod->import() runs.
sub import {
  my ($package, $mod, @args) = @_;
  return unless(defined $mod);

my $private_path = 'inc/latest/private.pm';
  if(-e $private_path) {
    # user mode - delegate work to bundled private module
    require $private_path;
    splice( @_, 0, 1, 'inc::latest::private');
    goto \&inc::latest::private::import;
  }

# author mode - just record and load the modules
  push(@loaded_modules, $mod);
  require inc::latest::private;
  goto \&inc::latest::private::_load_module;
}

sub write {
  my $package = shift;
  my ($where, @preload) = @_;

warn "should really be writing in inc/" unless $where =~ /inc$/;

# write inc/latest.pm
  File::Path::mkpath( $where );
  my $fh = IO::File->new( File::Spec->catfile($where,'latest.pm'), "w" );
  print {$fh} "# This stub created by inc::latest $VERSION\n";
  print {$fh} <<'HERE';
package inc::latest;
use strict;
use vars '@ISA';
require inc::latest::private;
@ISA = qw/inc::latest::private/;
HERE
  if (@preload) {
    print {$fh} "\npackage inc::latest::preload;\n";
    for my $mod (@preload) {
      print {$fh} "inc::latest->import('$mod');\n";
    }
  }
  print {$fh} "\n1;\n";
  close $fh;

# write inc/latest/private;
  require inc::latest::private;
  File::Path::mkpath( File::Spec->catdir( $where, 'latest' ) );
  my $from = $INC{'inc/latest/private.pm'};
  my $to = File::Spec->catfile($where,'latest','private.pm');
  File::Copy::copy( $from, $to ) or die "Couldn't copy '$from' to '$to': $!";

return 1;
}

sub bundle_module {
  my ($package, $module, $where) = @_;

# create inc/inc_$foo
  (my $dist = $module) =~ s{::}{-}g;
  my $inc_lib = File::Spec->catdir($where,"inc_$dist");
  File::Path::mkpath $inc_lib;

# get list of files to copy
  require ExtUtils::Installed;
  # workaround buggy EU::Installed check of @INC
  my $inst = ExtUtils::Installed->new(extra_libs => [@INC]);
  my $packlist = $inst->packlist( $module ) or die "Couldn't find packlist";
  my @files = grep { /\.pm$/ } keys %$packlist;

# figure out prefix
  my $mod_path = quotemeta $package->_mod2path( $module );
  my ($prefix) = grep { /$mod_path$/ } @files;
  $prefix =~ s{$mod_path$}{};

# copy files
  for my $from ( @files ) {
    next unless $from =~ /\.pm$/;
    (my $mod_path = $from) =~ s{^\Q$prefix\E}{};
    my $to = File::Spec->catfile( $inc_lib, $mod_path );
    File::Path::mkpath(File::Basename::dirname($to));
    File::Copy::copy( $from, $to ) or die "Couldn't copy '$from' to '$to': $!";
  }
  return 1;
}

# Translate a module name into a directory/file.pm to search for in @INC
sub _mod2path {
  my ($self, $mod) = @_;
  my @parts = split /::/, $mod;
  $parts[-1] .= '.pm';
  return $parts[0] if @parts == 1;
  return File::Spec->catfile(@parts);
}

=head1 NAME

inc::latest - use modules bundled in inc/ if they are newer than installed ones

=head1 SYNOPSIS

# in Build.PL
  use inc::latest 'Module::Build';

=head1 DESCRIPTION

The C<inc::latest> module helps bootstrap configure-time dependencies for CPAN
distributions.  These dependencies get bundled into the C<inc> directory within
a distribution and are used by Build.PL (or Makefile.PL).

Arguments to C<inc::latest> are module names that are checked against both the
current C<@INC> array and against specially-named directories in C<inc>.  If
the bundled version is newer than the installed one (or the module isn't
installed, then, the bundled directory is added to the start of <@INC> and the
module is loaded from there.

There are actually two variations of C<inc::latest> -- one for authors and one
for the C<inc> directory.  For distribution authors, the C<inc::latest>
installed in the system will record modules loaded via C<inc::latest> and can
be used to create the bundled files in C<inc>, including writing the second
variation as C<inc/latest.pm>.

This second C<inc::latest> is the one that is loaded in a distribution being
installed (e.g. from Build.PL).  This bundled C<inc::latest> is the one
that determines which module to load.

=head2 Special notes on bundling

The C<inc::latest> module creates bundled directories based on the packlist
file of an installed distribution.  Even though C<inc::latest> takes module
name arguments, it is better to think of it as bundling and making available
entire I<distributions>.  When a module is loaded through C<inc::latest>,
it looks in all bundled distributions in C<inc/> for a newer module than
can be found in the existing C<@INC> array.

Thus, the module-name provided should usually be the "top-level" module name of
a distribution, though this is not strictly required.  For example,
L<Module::Build> has a number of heuristics to map module names to packlists,
allowing users to do things like this:

use inc::latest 'Devel::AssertOS::Unix';

even though Devel::AssertOS::Unix is contained within the Devel-CheckOS
distribution.

At the current time, packlists are required.  Thus, bundling dual-core modules
may require a 'forced install' over versions in the latest version of perl
in order to create the necessary packlist for bundling.

=head1 USAGE

When calling C<use>, the bundled C<inc::latest> takes a single module name and
optional arguments to pass to that module's own import method.

use 'inc::latest' 'Foo::Bar' qw/foo bar baz/;

=head2 Author-mode

You are in author-mode inc::latest if any of the Author-mode methods are
available.  For example:

if ( inc::latest->can('write') ) {
    inc::latest->write('inc');
  }

=over 4

=item loaded_modules()

my @list = inc::latest->loaded_modules;

This takes no arguments and always returns a list of module names requested for
loading via "use inc::latest 'MODULE'", regardless of whether the load was
successful or not.

=item write()

inc::latest->write( 'inc' );

This writes the bundled version of inc::latest to the directory name given as an
argument.  It almost all cases, it should be 'C<inc>'.

=item bundle_module()

for my $mod ( inc::latest->loaded_modules ) {
    inc::latest->bundle_module($mod, $dir);
  }

If $mod corresponds to a packlist, then this function creates a specially-named
directory in $dir and copies all .pm files from the modlist to the new
directory (which almost always should just be 'inc').  For example, if Foo::Bar
is the name of the module, and $dir is 'inc', then the directory would be
'inc/inc_Foo-Bar' and contain files like this:

inc/inc_Foo-Bar/Foo/Bar.pm

Currently, $mod B<must> have a packlist.  If this is not the case (e.g. for a
dual-core module), then the bundling will fail.  You may be able to create a
packlist by forced installing the module on top of the version that came with
core Perl.

=back

=head2 As bundled in inc/

All methods are private.  Only the C<import> method is public.

=head1 AUTHOR

Eric Wilhelm <ewilhelm@cpan.org>, David Golden <dagolden@cpan.org>

=head1 COPYRIGHT

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

=head1 SEE ALSO

L<Module::Build>

=cut

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