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use warnings;
use strict;
use Carp;

=head1 NAME

Algorithm::IncludeExclude - build and evaluate include/exclude lists

=head1 VERSION

Version 0.01

=cut

our $VERSION = '0.01';

=head1 SYNOPSIS

Algorithm::IncludeExclude lets you define a tree of include / exclude
rules and then allows you to determine the best rule for a given path.

For example, to include everything, then exclude everything under
C<bar> or C<baz> but then include everything under C<foo baz>, you
could write:

   my $ie = Algorithm::IncludeExclude->new;
   
   # setup rules
   $ie->include();                      # default to include
   $ie->exclude('foo');
   $ie->exclude('bar');
   $ie->include(qw/foo baz/);

   # evaluate candidates
   $ie->evaluate(qw/foo bar/);          # exclude (due to 'foo' rule)
   $ie->evaluate(qw/bar baz/);          # exclude (due to 'bar' rule)
   $ie->evaluate(qw/quux foo bar/);     # include (due to '' rule)
   $ie->evaluate(qw/foo baz quux/);     # include (due to 'foo/baz' rule)

You can also match against regexes.  Let's imagine you want to exclude
everything in the C<admin> directory, as well as all files that end
with a C<.protected> extension.

Here's how to implement that:

   my $ie = Algorithm::IncludeExclude->new;
   $ie->exclude('admin');
   $ie->exclude(qr/[.]protected$/);

   $ie->evaluate(qw/admin let me in/);  # exclude (due to 'admin' rule)
   $ie->evaluate(qw/a path.protected/); # exclude (due to regex)
   $ie->evaluate(qw/foo bar/);          # undefined (no rule matches)

   $ie->include(qw/foo bar/);
   $ie->evaluate(qw/foo bar/);          # now it's included

If you wanted to include files inside the C<admin> path ending in C<.ok>,
you could just add this rule:

   $ie->include('admin', qr/[.]ok$/);
   $ie->evaluate(qw/admin super public records.ok/); # included

The most specific match always wins -- if there's not an exact match,
the nearest match is chosen instead.

=head1 NOTES

=over 4

=item *

Regexes can only appear as the last element in a rule:

   $ie->include(qr/foo/, qr/bar/);
   $ie->exclude(qr/foo/, qr/bar/);

If regexes were allowed anywhere, things could get very confusing,
very quickly.

=item *

Regexes are matched against any remaining path elements when they are
first encountered.  In the following example:

   $ie->include('foo', qr/bar/);
   $ie->evaluate('foo', 'baz', 'quux', 'bar'); # include

The match works like this.  First, 'foo' (from the include rule) and
'foo' (from the path being evaluated) are compared.  Since there's a
match, the next element in the path is examined against C<foo>'s
subtree.  The only remaining item in the rule tree is a regex, so the
regex is compared to the rest of the path being evaluated, joined by
the C<join> argument to new (see L</METHODS/new>); namely:

   baz/quux/bar

Since the regular expression matches this string, the include rule is
matched.

=item *

Regex rules are checked before non-regex rules.  For example:

  $ie->exclude('foo', 'bar');
  $ie->include(qr/bar/);

  $ie->evaluate('foo', 'bar'); # include, due to regex

=item *

If two or more regular expressions at the same level match a path, the
result is undefined:

  $ie->include(qr/foo/);
  $ie->exclude(qr/bar/);
 
  $ie->evaluate('foobar'); # undef is returned

=back

=cut