use 5.008001;
use strict;
use warnings;

package Path::Iterator::Rule;
# ABSTRACT: Iterative, recursive file finder
our $VERSION = '1.014';

# Register warnings category
use warnings::register;

use if $] ge '5.010000', 're', 'regexp_pattern';

# Dependencies
use Carp           ();
use File::Basename ();
use File::Spec     ();
use List::Util     ();
use Number::Compare 0.02;
use Scalar::Util ();
use Text::Glob   ();
use Try::Tiny;

#--------------------------------------------------------------------------#
# constructors and meta methods
#--------------------------------------------------------------------------#

sub new {
    my $class = shift;
    $class = ref $class if ref $class;
    return bless { rules => [] }, $class;
}

sub clone {
    my $self = shift;
    return bless _my_clone( {%$self} ), ref $self;
}

# avoid XS/buggy dependencies for a simple recursive clone; we clone
# fully instead of just 'rules' in case we get subclassed and they
# add attributes
sub _my_clone {
    my $d = shift;
    if ( ref $d eq 'HASH' ) {
        return {
            map { ; my $v = $d->{$_}; $_ => ( ref($v) ? _my_clone($v) : $v ) }
              keys %$d
        };
    }
    elsif ( ref $d eq 'ARRAY' ) {
        return [ map { ref($_) ? _my_clone($_) : $_ } @$d ];
    }
    else {
        return $d;
    }
}

sub add_helper {
    my ( $class, $name, $coderef, $skip_negation ) = @_;
    $class = ref $class if ref $class;
    if ( !$class->can($name) ) {
        no strict 'refs'; ## no critic
        *$name = sub {
            my $self = shift;
            my $rule = $coderef->(@_);
            $self->and($rule);
        };
        if ( !$skip_negation ) {
            *{"not_$name"} = sub {
                my $self = shift;
                my $rule = $coderef->(@_);
                $self->not($rule);
            };
        }
    }
    else {
        Carp::croak("Can't add rule '$name' because it conflicts with an existing method");
    }
}

#--------------------------------------------------------------------------#
# Implementation-specific method; these may be overridden by subclasses
# to test/return results of file wrappers like Path::Class or IO::All
# or to provide custom error handler, visitors or other features
#--------------------------------------------------------------------------#

sub _objectify {
    my ( $self, $path ) = @_;
    return "$path";
}

## We inline this below, but a subclass equivalent would be this:
##sub _children {
##    my $self = shift;
##    my $path = "" . shift; # stringify objects
##    opendir( my $dh, $path );
##    return map { [ $_, "$path/$_" ] } grep { $_ ne "." && $_ ne ".." } readdir $dh;
##}

# The _stringify option controls whether the string form of an object is cached
# for iteration control.  This is generally a good idea to avoid extra overhead,
# but subclasses can override this if necessary

sub _defaults {
    return (
        _stringify      => 1,
        follow_symlinks => 1,
        depthfirst      => 0,
        sorted          => 1,
        loop_safe       => ( $^O eq 'MSWin32' ? 0 : 1 ),       # No inode #'s on Windows
        error_handler   => sub { die sprintf( "%s: %s", @_ ) },
        visitor         => undef,
    );
}

sub _fast_defaults {
    return (
        _stringify      => 1,
        follow_symlinks => 1,
        depthfirst      => -1,
        sorted          => 0,
        loop_safe       => 0,
        error_handler   => undef,
        visitor         => undef,
    );
}

#--------------------------------------------------------------------------#
# iteration methods
#--------------------------------------------------------------------------#

sub iter {
    my $self = shift;
    $self->_iter( { $self->_defaults }, @_ );
}

sub iter_fast {
    my $self = shift;
    $self->_iter( { $self->_fast_defaults }, @_ );
}

sub _iter {
    my $self     = shift;
    my $defaults = shift;
    my $args =
        ref( $_[0] )  && !Scalar::Util::blessed( $_[0] )  ? shift
      : ref( $_[-1] ) && !Scalar::Util::blessed( $_[-1] ) ? pop
      :                                                     {};
    my %opts = ( %$defaults, %$args );

    # unroll these for efficiency
    my $opt_stringify       = $opts{_stringify};
    my $opt_depthfirst      = $opts{depthfirst};
    my $opt_follow_symlinks = $opts{follow_symlinks};
    my $opt_sorted          = $opts{sorted};
    my $opt_loop_safe       = $opts{loop_safe};
    my $opt_error_handler   = $opts{error_handler};
    my $opt_relative        = $opts{relative};
    my $opt_visitor         = $opts{visitor};
    my $has_rules           = @{ $self->{rules} };
    my $stash               = {};

    my $opt_report_symlinks =
      defined( $opts{report_symlinks} )
      ? $opts{report_symlinks}
      : $opts{follow_symlinks};

    # if not subclassed, we want to inline
    my $can_children = $self->can("_children");

    # queue structure: flat list of (unnested) tuples of 4 (object,
    # basename, depth, origin).  If object is a coderef, it's a deferred
    # directory list.  If the object is an arrayref, then that's a special
    # case signal that it was already of interest and can finally be
    # returned for postorder searches
    my @queue =
      map {
        my $i = $self->_objectify($_);
        ( $i, File::Basename::basename("$_"), 0, $i )
      } @_ ? @_ : '.';

    return sub {
        LOOP: {
            my ( $item, $base, $depth, $origin ) = splice( @queue, 0, 4 );
            return unless $item;
            if ( ref $item eq 'CODE' ) {
                # replace placeholder with children
                unshift @queue, $item->();
                redo LOOP;
            }
            return $item->[0] if ref $item eq 'ARRAY'; # deferred for postorder
            my $string_item = $opt_stringify ? "$item" : $item;

            # by default, we're interested in everything and prune nothing
            my ( $interest, $prune ) = ( 1, 0 );

            if ( -l $string_item ) {
                $prune = 1 if !$opt_follow_symlinks;
                redo LOOP if !$opt_report_symlinks;
            }

            if ($has_rules) {
                local $_ = $item;
                $stash->{_depth} = $depth;
                if ($opt_error_handler) {
                    $interest = try { $self->test( $item, $base, $stash ) }
                    catch { $opt_error_handler->( $item, $_ ) };
                }
                else {
                    $interest = $self->test( $item, $base, $stash );
                }
                # New way to signal prune is returning a reference to a scalar.
                # Value of the scalar indicates if it should be returned by the
                # iterator or not
                if ( ref $interest eq 'SCALAR' ) {
                    $prune    = 1;
                    $interest = $$interest;
                }
            }

            # if we have a visitor, we call it like a custom rule
            if ( $opt_visitor && $interest ) {
                local $_ = $item;
                $stash->{_depth} = $depth;
                $opt_visitor->( $item, $base, $stash );
            }

            # if it's a directory, maybe add children to the queue
            if (   ( -d $string_item )
                && ( !$prune )
                && ( !$opt_loop_safe || $self->_is_unique( $string_item, $stash ) ) )
            {
                if ( !-r $string_item ) {
                    warnings::warnif("Directory '$string_item' is not readable. Skipping it");
                }
                else {
                    my $depth_p1 = $depth + 1;
                    my $next;
                    if ($can_children) {
                        $next = sub {
                            my @paths = $can_children->( $self, $item );
                            if ($opt_sorted) {
                                @paths = sort { "$a->[0]" cmp "$b->[0]" } @paths;
                            }
                            map { ( $_->[1], $_->[0], $depth_p1, $origin ) } @paths;
                        };
                    }
                    else {
                        $next = sub {
                            opendir( my $dh, $string_item );
                            if ($opt_sorted) {
                                map { ( "$string_item/$_", $_, $depth_p1, $origin ) }
                                  sort { $a cmp $b } grep { $_ ne "." && $_ ne ".." } readdir $dh;
                            }
                            else {
                                map { ( "$string_item/$_", $_, $depth_p1, $origin ) }
                                  grep { $_ ne "." && $_ ne ".." } readdir $dh;
                            }
                        };
                    }

                    if ($opt_depthfirst) {
                        # either preorder (parents before kids) or
                        # postorder (parents after kids); for postorder,
                        # requeue current item as a reference to signal it
                        # can be returned without being retested
                        unshift @queue,
                          [
                            (
                                  $opt_relative
                                ? $self->_objectify( File::Spec->abs2rel( $string_item, $origin ) )
                                : $item
                            )
                          ],
                          undef, undef, undef
                          if $interest && $opt_depthfirst > 0;
                        unshift @queue, $next, undef, undef, undef;
                        redo LOOP if $opt_depthfirst > 0;
                    }
                    else {
                        # breadth-first: add placeholder for children at the end
                        push @queue, $next, undef, undef, undef;
                    }
                }
            } # end of "is directory maybe with children"
            return (
                  $opt_relative
                ? $self->_objectify( File::Spec->abs2rel( $string_item, $origin ) )
                : $item
            ) if $interest;
            redo LOOP;
        }
    };
}

sub all {
    my $self = shift;
    return $self->_all( $self->iter(@_) );
}

sub all_fast {
    my $self = shift;
    return $self->_all( $self->iter_fast(@_) );
}

sub _all {
    my $self = shift;
    my $iter = shift;
    if (wantarray) {
        my @results;
        while ( defined( my $item = $iter->() ) ) {
            push @results, $item;
        }
        return @results;
    }
    elsif ( defined wantarray ) {
        my $count = 0;
        $count++ while defined $iter->();
        return $count;
    }
    else {
        1 while defined $iter->();
    }
}

#--------------------------------------------------------------------------#
# logic methods
#--------------------------------------------------------------------------#

sub and {
    my $self = shift;
    push @{ $self->{rules} }, $self->_rulify(@_);
    return $self;
}

sub or {
    my $self    = shift;
    my @rules   = $self->_rulify(@_);
    my $coderef = sub {
        my ( $result, $prune );
        for my $rule (@rules) {
            $result = $rule->(@_);
            # once any rule says to prune, we remember that
            $prune ||= ref($result) eq 'SCALAR';
            # extract whether constraint was met
            $result = $$result if ref($result) eq 'SCALAR';
            # shortcut if met, propagating prune state
            return ( $prune ? \1 : 1 ) if $result;
        }
        return ( $prune ? \$result : $result )
          ; # may or may not be met, but propagate prune state
    };
    return $self->and($coderef);
}

sub not {
    my $self    = shift;
    my $obj     = $self->new->and(@_);
    my $coderef = sub {
        my $result = $obj->test(@_);
        return ref($result) ? \!$$result : !$result; # invert, but preserve prune
    };
    return $self->and($coderef);
}

sub skip {
    my $self    = shift;
    my @rules   = @_;
    my $obj     = $self->new->or(@rules);
    my $coderef = sub {
        my $result = $obj->test(@_);
        my ( $prune, $interest );
        if ( ref($result) eq 'SCALAR' ) {
            # test told us to prune, so make that sticky
            # and also skip it
            $prune    = 1;
            $interest = 0;
        }
        else {
            # prune if test was true
            $prune = $result;
            # negate test result
            $interest = !$result;
        }
        return $prune ? \$interest : $interest;
    };
    return $self->and($coderef);
}

sub test {
    my ( $self, $item, $base, $stash ) = @_;
    my ( $result, $prune );
    for my $rule ( @{ $self->{rules} } ) {
        $result = $rule->( $item, $base, $stash ) || 0;
        if ( !ref($result) && $result eq '0 but true' ) {
            Carp::croak("0 but true no longer supported by custom rules");
        }
        # once any rule says to prune, we remember that
        $prune ||= ref($result) eq 'SCALAR';
        # extract whether constraint was met
        $result = $$result if ref($result) eq 'SCALAR';
        # shortcut if not met, propagating prune state
        return ( $prune ? \0 : 0 ) if !$result;
    }
    return ( $prune ? \1 : 1 ); # all constraints met, but propagate prune state
}

#--------------------------------------------------------------------------#
# private methods
#--------------------------------------------------------------------------#

sub _rulify {
    my ( $self, @args ) = @_;
    my @rules;
    for my $arg (@args) {
        my $rule;
        if ( Scalar::Util::blessed($arg) && $arg->isa("Path::Iterator::Rule") ) {
            $rule = sub { $arg->test(@_) };
        }
        elsif ( ref($arg) eq 'CODE' ) {
            $rule = $arg;
        }
        else {
            Carp::croak("Rules must be coderef or Path::Iterator::Rule");
        }
        push @rules, $rule;
    }
    return @rules;
}

sub _is_unique {
    my ( $self, $string_item, $stash ) = @_;
    my $unique_id;
    my @st = eval { stat $string_item };
    @st = eval { lstat $string_item } unless @st;
    if (@st) {
        $unique_id = join( ",", $st[0], $st[1] );
    }
    else {
        my $type = -d $string_item ? 'directory' : 'file';
        warnings::warnif("Could not stat $type '$string_item'");
        $unique_id = $string_item;
    }
    return !$stash->{_seen}{$unique_id}++;
}

#--------------------------------------------------------------------------#
# built-in helpers
#--------------------------------------------------------------------------#

sub _regexify {
    my ( $re, $add ) = @_;
    $add ||= '';
    my $new = ref($re) eq 'Regexp' ? $re : Text::Glob::glob_to_regex($re);
    return $new unless $add;
    my ( $pattern, $flags ) = _split_re($new);
    my $new_flags = $add ? _reflag( $flags, $add ) : "";
    return qr/$new_flags$pattern/;
}

sub _split_re {
    my $value = shift;
    if ( $] ge 5.010 ) {
        return re::regexp_pattern($value);
    }
    else {
        $value =~ s/^\(\?\^?//;
        $value =~ s/\)$//;
        my ( $opt, $re ) = split( /:/, $value, 2 );
        $opt =~ s/\-\w+$//;
        return ( $re, $opt );
    }
}

sub _reflag {
    my ( $orig, $add ) = @_;
    $orig ||= "";

    if ( $] >= 5.014 ) {
        return "(?^$orig$add)";
    }
    else {
        my ( $pos, $neg ) = split /-/, $orig;
        $pos ||= "";
        $neg ||= "";
        $neg =~ s/i//;
        $neg = "-$neg" if length $neg;
        return "(?$add$pos$neg)";
    }
}

# "simple" helpers take no arguments
my %simple_helpers = (
    directory => sub { -d $_ },           # see also -d => dir below
    dangling => sub { -l $_ && !stat $_ },
);

while ( my ( $k, $v ) = each %simple_helpers ) {
    __PACKAGE__->add_helper( $k, sub { return $v } );
}

sub _generate_name_matcher {
    my (@patterns) = @_;
    if ( @patterns > 1 ) {
        return sub {
            my $name = "$_[1]";
            return ( List::Util::first { $name =~ $_ } @patterns ) ? 1 : 0;
          }
    }
    else {
        my $pattern = $patterns[0];
        return sub {
            my $name = "$_[1]";
            return $name =~ $pattern ? 1 : 0;
          }
    }
}

# "complex" helpers take arguments
my %complex_helpers = (
    name => sub {
        Carp::croak("No patterns provided to 'name'") unless @_;
        _generate_name_matcher( map { _regexify($_) } @_ );
    },
    iname => sub {
        Carp::croak("No patterns provided to 'iname'") unless @_;
        _generate_name_matcher( map { _regexify( $_, "i" ) } @_ );
    },
    min_depth => sub {
        Carp::croak("No depth argument given to 'min_depth'") unless @_;
        my $min_depth = 0+ shift; # if this warns, do here and not on every file
        return sub {
            my ( $f, $b, $stash ) = @_;
            return $stash->{_depth} >= $min_depth;
          }
    },
    max_depth => sub {
        Carp::croak("No depth argument given to 'max_depth'") unless @_;
        my $max_depth = 0+ shift; # if this warns, do here and not on every file
        return sub {
            my ( $f, $b, $stash ) = @_;
            return 1  if $stash->{_depth} < $max_depth;
            return \1 if $stash->{_depth} == $max_depth;
            return \0;
          }
    },
    shebang => sub {
        Carp::croak("No patterns provided to 'shebang'") unless @_;
        my @patterns = map { _regexify($_) } @_;
        return sub {
            my $f = shift;
            return unless !-d $f;
            open my $fh, "<", $f;
            my $shebang = <$fh>;
            return unless defined $shebang;
            return ( List::Util::first { $shebang =~ $_ } @patterns ) ? 1 : 0;
        };
    },
    contents_match => sub {
        my @regexp = @_;
        my $filter = ':encoding(UTF-8)';
        $filter = shift @regexp unless ref $regexp[0];
        return sub {
            my $f = shift;
            return unless !-d $f;
            my $contents = do {
                local $/ = undef;
                open my $fh, "<$filter", $f;
                <$fh>;
            };
            for my $re (@regexp) {
                return 1 if $contents =~ $re;
            }
            return 0;
        };
    },
    line_match => sub {
        my @regexp = @_;
        my $filter = ':encoding(UTF-8)';
        $filter = shift @regexp unless ref $regexp[0];
        return sub {
            my $f = shift;
            return unless !-d $f;
            open my $fh, "<$filter", $f;
            while ( my $line = <$fh> ) {
                for my $re (@regexp) {
                    return 1 if $line =~ $re;
                }
            }
            return 0;
        };
    },
);

while ( my ( $k, $v ) = each %complex_helpers ) {
    __PACKAGE__->add_helper( $k, $v );
}

# skip_dirs
__PACKAGE__->add_helper(
    skip_dirs => sub {
        Carp::croak("No patterns provided to 'skip_dirs'") unless @_;
        my $name_check = Path::Iterator::Rule->new->name(@_);
        return sub {
            return \0 if -d $_[0] && $name_check->test(@_);
            return 1; # otherwise, like a null rule
          }
      } => 1 # don't create not_skip_dirs
);

__PACKAGE__->add_helper(
    skip_subdirs => sub {
        Carp::croak("No patterns provided to 'skip_subdirs'") unless @_;
        my $name_check = Path::Iterator::Rule->new->name(@_);
        return sub {
            my ( $f, $b, $stash ) = @_;
            return \0 if -d $f && $stash->{_depth} && $name_check->test(@_);
            return 1; # otherwise, like a null rule
          }
      } => 1 # don't create not_skip_dirs
);

# X_tests adapted from File::Find::Rule
#<<< do not perltidy this
my %X_tests = (
    -r  =>  readable           =>  -R  =>  r_readable      =>
    -w  =>  writeable          =>  -W  =>  r_writeable     =>
    -w  =>  writable           =>  -W  =>  r_writable      =>
    -x  =>  executable         =>  -X  =>  r_executable    =>
    -o  =>  owned              =>  -O  =>  r_owned         =>

    -e  =>  exists             =>  -f  =>  file            =>
    -z  =>  empty              =>  -d  =>  dir             =>
    -s  =>  nonempty           =>  -l  =>  symlink         =>
                               =>  -p  =>  fifo            =>
    -u  =>  setuid             =>  -S  =>  socket          =>
    -g  =>  setgid             =>  -b  =>  block           =>
    -k  =>  sticky             =>  -c  =>  character       =>
                               =>  -t  =>  tty             =>
    -T  =>  ascii              =>
    -B  =>  binary             =>
);
#>>>

while ( my ( $op, $name ) = each %X_tests ) {
    my $coderef = eval "sub { $op \$_ }"; ## no critic
    __PACKAGE__->add_helper( $name, sub { return $coderef } );
}

my %time_tests = ( -A => accessed => -M => modified => -C => changed => );

while ( my ( $op, $name ) = each %time_tests ) {
    my $filetest = eval "sub { $op \$_ }"; ## no critic
    my $coderef  = sub {
        Carp::croak("The '$name' test requires a single argument") unless @_ == 1;
        my $comparator = Number::Compare->new(shift);
        return sub { return $comparator->( $filetest->() ) };
    };
    __PACKAGE__->add_helper( $name, $coderef );
}

# stat tests adapted from File::Find::Rule
my @stat_tests = qw(
  dev ino mode nlink uid gid rdev size atime mtime ctime blksize blocks
);

for my $i ( 0 .. $#stat_tests ) {
    my $name    = $stat_tests[$i];
    my $coderef = sub {
        Carp::croak("The '$name' test requires a single argument") unless @_ == 1;
        my $comparator = Number::Compare->new(shift);
        return sub { return $comparator->( ( stat($_) )[$i] ) };
    };
    __PACKAGE__->add_helper( $name, $coderef );
}

# VCS rules adapted from File::Find::Rule::VCS
my %vcs_rules = (
    skip_cvs => sub {
        return Path::Iterator::Rule->new->skip_dirs('CVS')->not_name(qr/\.\#$/);
    },
    skip_rcs => sub {
        return Path::Iterator::Rule->new->skip_dirs('RCS')->not_name(qr/,v$/);
    },
    skip_git => sub {
        return Path::Iterator::Rule->new->skip_dirs('.git');
    },
    skip_svn => sub {
        return Path::Iterator::Rule->new->skip_dirs(
            ( $^O eq 'MSWin32' ) ? ( '.svn', '_svn' ) : ('.svn') );
    },
    skip_bzr => sub {
        return Path::Iterator::Rule->new->skip_dirs('.bzr');
    },
    skip_hg => sub {
        return Path::Iterator::Rule->new->skip_dirs('.hg');
    },
    skip_darcs => sub {
        return Path::Iterator::Rule->new->skip_dirs('_darcs');
    },
    skip_vcs => sub {
        return Path::Iterator::Rule->new->skip_dirs(qw/.git .bzr .hg _darcs CVS RCS/)
          ->skip_svn->not_name( qr/\.\#$/, qr/,v$/ );
    },
);

while ( my ( $name, $coderef ) = each %vcs_rules ) {
    __PACKAGE__->add_helper( $name, $coderef, 1 ); # don't create not_*
}

# perl rules adapted from File::Find::Rule::Perl
my %perl_rules = (
    perl_module    => sub { return Path::Iterator::Rule->new->file->name('*.pm') },
    perl_pod       => sub { return Path::Iterator::Rule->new->file->name('*.pod') },
    perl_test      => sub { return Path::Iterator::Rule->new->file->name('*.t') },
    perl_installer => sub {
        return Path::Iterator::Rule->new->file->name( 'Makefile.PL', 'Build.PL' );
    },
    perl_script => sub {
        return Path::Iterator::Rule->new->file->or(
            Path::Iterator::Rule->new->name('*.pl'),
            Path::Iterator::Rule->new->shebang(qr/#!.*\bperl\b/),
        );
    },
    perl_file => sub {
        return Path::Iterator::Rule->new->or(
            Path::Iterator::Rule->new->perl_module, Path::Iterator::Rule->new->perl_pod,
            Path::Iterator::Rule->new->perl_test,   Path::Iterator::Rule->new->perl_installer,
            Path::Iterator::Rule->new->perl_script,
        );
    },
);

while ( my ( $name, $coderef ) = each %perl_rules ) {
    __PACKAGE__->add_helper( $name, $coderef );
}

1;


# vim: ts=4 sts=4 sw=4 et:

__END__

=pod

=encoding UTF-8

=head1 NAME

Path::Iterator::Rule - Iterative, recursive file finder

=head1 VERSION

version 1.014

=head1 SYNOPSIS

  use Path::Iterator::Rule;

  my $rule = Path::Iterator::Rule->new; # match anything
  $rule->file->size(">10k");         # add/chain rules

  # iterator interface
  my $next = $rule->iter( @dirs );
  while ( defined( my $file = $next->() ) ) {
    ...
  }

  # list interface
  for my $file ( $rule->all( @dirs ) ) {
    ...
  }

=head1 DESCRIPTION

This module iterates over files and directories to identify ones matching a
user-defined set of rules.  The API is based heavily on L<File::Find::Rule>,
but with more explicit distinction between matching rules and options that
influence how directories are searched.  A C<Path::Iterator::Rule> object is a
collection of rules (match criteria) with methods to add additional criteria.
Options that control directory traversal are given as arguments to the method
that generates an iterator.

Here is a summary of features for comparison to other file finding modules:

=over 4

=item *

provides many "helper" methods for specifying rules

=item *

offers (lazy) iterator and flattened list interfaces

=item *

custom rules implemented with callbacks

=item *

breadth-first (default) or pre- or post-order depth-first searching

=item *

follows symlinks (by default, but can be disabled)

=item *

directories visited only once (no infinite loop; can be disabled)

=item *

doesn't chdir during operation

=item *

provides an API for extensions

=back

As a convenience, the L<PIR> module is an empty subclass of this one
that is less arduous to type for one-liners.

B<Note>: paths are constructed with unix-style forward-slashes for
efficiency rather than using L<File::Spec>.  If proper path separators are
needed, call L<canonpath|File::Spec/canonpath> on the search results.

=head1 USAGE

=head2 Constructors

=head3 C<new>

  my $rule = Path::Iterator::Rule->new;

Creates a new rule object that matches any file or directory.  It takes
no arguments. For convenience, it may also be called on an object, in which
case it still returns a new object that matches any file or directory.

=head3 C<clone>

  my $common      = Path::Iterator::Rule->new->file->not_empty;
  my $big_files   = $common->clone->size(">1M");
  my $small_files = $common->clone->size("<10K");

Creates a copy of a rule object.  Useful for customizing different
rule objects against a common base.

=head2 Matching and iteration

=head3 C<iter>

  my $next = $rule->iter( @dirs, \%options);
  while ( defined( my $file = $next->() ) ) {
    ...
  }

Creates a subroutine reference iterator that returns a single result
when dereferenced.  This iterator is "lazy" -- results are not
pre-computed.

It takes as arguments a list of directories to search and an optional hash
reference of control options.  If no search directories are provided, the
current directory is used (C<".">).  Valid options include:

=over 4

=item *

C<depthfirst> -- Controls order of results.  Valid values are "1" (post-order, depth-first search), "0" (breadth-first search) or "-1" (pre-order, depth-first search). Default is 0.

=item *

C<error_handler> -- Catches errors during execution of rule tests. Default handler dies with the filename and error. If set to undef, error handling is disabled.

=item *

C<follow_symlinks> -- Follow directory symlinks when true. Default is 1.

=item *

C<report_symlinks> -- Includes symlinks in results when true. Default is equal to C<follow_symlinks>.

=item *

C<loop_safe> -- Prevents visiting the same directory more than once when true.  Default is 1.

=item *

C<relative> -- Return matching items relative to the search directory. Default is 0.

=item *

C<sorted> -- Whether entries in a directory are sorted before processing. Default is 1.

=item *

C<visitor> -- An optional coderef that will be called on items matching all rules.

=back

Filesystem loops might exist from either hard or soft links.  The C<loop_safe>
option prevents infinite loops, but adds some overhead by making C<stat> calls.
Because directories are visited only once when C<loop_safe> is true, matches
could come from a symlinked directory before the real directory depending on
the search order.

To get only the real files, turn off C<follow_symlinks>.  You can have
symlinks included in results, but not descend into symlink directories if
you turn off C<follow_symlinks>, but turn on C<report_symlinks>.

Turning C<loop_safe> off and leaving C<follow_symlinks> on avoids C<stat> calls
and will be fastest, but with the risk of an infinite loop and repeated files.
The default is slow, but safe.

The C<error_handler> parameter must be a subroutine reference.  It will be
called when a rule test throws an exception.  The first argument will be
the file name being inspected and the second argument will be
the exception.

The optional C<visitor> parameter must be a subroutine reference.  If set,
it will be called for any result that matches.  It is called the same way
a custom rule would be (see L</EXTENDING>) but its return value is ignored.
It is called when an item is first inspected -- "postorder" is not respected.

The paths inspected and returned will be relative to the search directories
provided.  If these are absolute, then the paths returned will have absolute
paths.  If these are relative, then the paths returned will have relative
paths.

If the search directories are absolute and the C<relative> option is true,
files returned will be relative to the search directory.  Note that if the
search directories are not mutually exclusive (whether containing
subdirectories like C<@INC> or symbolic links), files found could be returned
relative to different initial search directories based on C<depthfirst>,
C<follow_symlinks> or C<loop_safe>.

When the iterator is exhausted, it will return undef.

=head3 C<iter_fast>

This works just like C<iter>, except that it optimizes for speed over
safety. Don't do this unless you're sure you need it and accept
the consequences.  See L</PERFORMANCE> for details.

=head3 C<all>

  my @matches = $rule->all( @dir, \%options );

Returns a list of paths that match the rule.  It takes the same arguments and
has the same behaviors as the C<iter> method.  The C<all> method uses C<iter>
internally to fetch all results.

In scalar context, it will return the count of matched paths.

In void context, it is optimized to iterate over everything, but not store
results.  This is most useful with the C<visitor> option:

    $rule->all( $path, { visitor => \&callback } );

=head3 C<all_fast>

This works just like C<all>, except that it optimizes for speed over
safety. Don't do this unless you're sure you need it and accept
the consequences.  See L</PERFORMANCE> for details.

=head3 C<test>

  if ( $rule->test( $path, $basename, $stash ) ) { ... }

Test a file path against a rule.  Used internally, but provided should
someone want to create their own, custom iteration algorithm.

=head2 Logic operations

C<Path::Iterator::Rule> provides three logic operations for adding rules to the
object.  Rules may be either a subroutine reference with specific semantics
(described below in L</EXTENDING>) or another C<Path::Iterator::Rule> object.

=head3 C<and>

  $rule->and( sub { -r -w -x $_ } ); # stacked filetest example
  $rule->and( @more_rules );

Adds one or more constraints to the current rule. E.g. "old rule AND
new1 AND new2 AND ...".  Returns the object to allow method chaining.

=head3 C<or>

  $rule->or(
    $rule->new->name("foo*"),
    $rule->new->name("bar*"),
    sub { -r -w -x $_ },
  );

Takes one or more alternatives and adds them as a constraint to the current
rule. E.g. "old rule AND ( new1 OR new2 OR ... )".  Returns the object to allow
method chaining.

=head3 C<not>

  $rule->not( sub { -r -w -x $_ } );

Takes one or more alternatives and adds them as a negative constraint to the
current rule. E.g. "old rule AND NOT ( new1 AND new2 AND ...)".  Returns the
object to allow method chaining.

=head3 C<skip>

  $rule->skip(
    $rule->new->dir->not_writeable,
    $rule->new->dir->name("foo"),
  );

Takes one or more alternatives and will prune a directory if any of the
criteria match or if any of the rules already indicate the directory should be
pruned.  Pruning means the directory will not be returned by the iterator and
will not be searched.

For files, it is equivalent to C<< $rule->not($rule->or(@rules)) >>.  Returns
the object to allow method chaining.

This method should be called as early as possible in the rule chain.
See L</skip_dirs> below for further explanation and an example.

=head1 RULE METHODS

Rule methods are helpers that add constraints.  Internally, they generate a
closure to accomplish the desired logic and add it to the rule object with the
C<and> method.  Rule methods return the object to allow for method chaining.

=head2 File name rules

=head3 C<name>

  $rule->name( "foo.txt" );
  $rule->name( qr/foo/, "bar.*");

The C<name> method takes one or more patterns and creates a rule that is true
if any of the patterns match the B<basename> of the file or directory path.
Patterns may be regular expressions or glob expressions (or literal names).

=head3 C<iname>

  $rule->iname( "foo.txt" );
  $rule->iname( qr/foo/, "bar.*");

The C<iname> method is just like the C<name> method, but matches
case-insensitively.

=head3 C<skip_dirs>

  $rule->skip_dirs( @patterns );

The C<skip_dirs> method skips directories that match one or more patterns.
Patterns may be regular expressions or globs (just like C<name>).  Directories
that match will not be returned from the iterator and will be excluded from
further search.  B<This includes the starting directories.>  If that isn't
what you want, see L</skip_subdirs> instead.

B<Note:> this rule should be specified early so that it has a chance to
operate before a logical shortcut.  E.g.

  $rule->skip_dirs(".git")->file; # OK
  $rule->file->skip_dirs(".git"); # Won't work

In the latter case, when a ".git" directory is seen, the C<file> rule
shortcuts the rule before the C<skip_dirs> rule has a chance to act.

=head3 C<skip_subdirs>

  $rule->skip_subdirs( @patterns );

This works just like C<skip_dirs>, except that the starting directories
(depth 0) are not skipped and may be returned from the iterator
unless excluded by other rules.

=head2 File test rules

Most of the C<-X> style filetest are available as boolean rules.  The table
below maps the filetest to its corresponding method name.

   Test | Method               Test |  Method
  ------|-------------        ------|----------------
    -r  |  readable             -R  |  r_readable
    -w  |  writeable            -W  |  r_writeable
    -w  |  writable             -W  |  r_writable
    -x  |  executable           -X  |  r_executable
    -o  |  owned                -O  |  r_owned
        |                           |
    -e  |  exists               -f  |  file
    -z  |  empty                -d  |  directory, dir
    -s  |  nonempty             -l  |  symlink
        |                       -p  |  fifo
    -u  |  setuid               -S  |  socket
    -g  |  setgid               -b  |  block
    -k  |  sticky               -c  |  character
        |                       -t  |  tty
    -T  |  ascii
    -B  |  binary

For example:

  $rule->file->nonempty; # -f -s $file

The -X operators for timestamps take a single argument in a form that
L<Number::Compare> can interpret.

   Test | Method
  ------|-------------
    -A  |  accessed
    -M  |  modified
    -C  |  changed

For example:

  $rule->modified(">1"); # -M $file > 1

=head2 Stat test rules

All of the C<stat> elements have a method that takes a single argument in
a form understood by L<Number::Compare>.

  stat()  |  Method
 --------------------
       0  |  dev
       1  |  ino
       2  |  mode
       3  |  nlink
       4  |  uid
       5  |  gid
       6  |  rdev
       7  |  size
       8  |  atime
       9  |  mtime
      10  |  ctime
      11  |  blksize
      12  |  blocks

For example:

  $rule->size(">10K")

=head2 Depth rules

  $rule->min_depth(3);
  $rule->max_depth(5);

The C<min_depth> and C<max_depth> rule methods take a single argument and limit
the paths returned to a minimum or maximum depth (respectively) from the
starting search directory.  A depth of 0 means the starting directory itself.
A depth of 1 means its children.  (This is similar to the Unix C<find> utility.)

=head2 Perl file rules

  # All perl rules
  $rule->perl_file;

  # Individual perl file rules
  $rule->perl_module;     # .pm files
  $rule->perl_pod;        # .pod files
  $rule->perl_test;       # .t files
  $rule->perl_installer;  # Makefile.PL or Build.PL
  $rule->perl_script;     # .pl or 'perl' in the shebang

These rule methods match file names (or a shebang line) that are typical
of Perl distribution files.

=head2 Version control file rules

  # Skip all known VCS files
  $rule->skip_vcs;

  # Skip individual VCS files
  $rule->skip_cvs;
  $rule->skip_rcs;
  $rule->skip_svn;
  $rule->skip_git;
  $rule->skip_bzr;
  $rule->skip_hg;
  $rule->skip_darcs;

Skips files and/or prunes directories related to a version control system.
Just like C<skip_dirs>, these rules should be specified early to get the
correct behavior.

=head2 File content rules

=head3 C<contents_match>

  $rule->contents_match(qr/BEGIN .* END/xs);

The C<contents_match> rule takes a list of regular expressions and returns
files that match one of the expressions.

The expressions are applied to the file's contents as a single string. For
large files, this is likely to take significant time and memory.

Files are assumed to be encoded in UTF-8, but alternative Perl IO layers can
be passed as the first argument:

  $rule->contents_match(":encoding(iso-8859-1)", qr/BEGIN .* END/xs);

See L<perlio> for further details.

=head3 C<line_match>

  $rule->line_match(qr/^new/i, qr/^Addition/);

The C<line_match> rule takes a list of regular expressions and returns
files with at least one line that matches one of the expressions.

Files are assumed to be encoded in UTF-8, but alternative Perl IO layers can
be passed as the first argument.

=head3 C<shebang>

  $rule->shebang(qr/#!.*\bperl\b/);

The C<shebang> rule takes a list of regular expressions or glob patterns and
checks them against the first line of a file.

=head2 Other rules

=head3 C<dangling>

  $rule->symlink->dangling;
  $rule->not_dangling;

The C<dangling> rule method matches dangling symlinks.  Use it or its inverse
to control how dangling symlinks should be treated.

=head2 Negated rules

Most rule methods have a negated form preceded by "not_".

  $rule->not_name("foo.*")

Because this happens automatically, it includes somewhat silly ones like
C<not_nonempty> (which is thus a less efficient way of saying C<empty>).

Rules that skip directories or version control files do not have a negated
version.

=head1 EXTENDING

=head2 Custom rule subroutines

Rules are implemented as (usually anonymous) subroutine callbacks that return
a value indicating whether or not the rule matches.  These callbacks are called
with three arguments.  The first argument is a path, which is
also locally aliased as the C<$_> global variable for convenience in simple
tests.

  $rule->and( sub { -r -w -x $_ } ); # tests $_

The second argument is the basename of the path, which is useful for certain
types of name checks:

  $rule->and( sub { $_[1] =~ /foo|bar/ } ); "foo" or "bar" in basename;

The third argument is a hash reference that can be used to maintain state.
Keys beginning with an underscore are B<reserved> for C<Path::Iterator::Rule>
to provide additional data about the search in progress.
For example, the C<_depth> key is used to support minimum and maximum
depth checks.

The custom rule subroutine must return one of four values:

=over 4

=item *

A true value -- indicates the constraint is satisfied

=item *

A false value -- indicates the constraint is not satisfied

=item *

C<\1> -- indicate the constraint is satisfied, and prune if it's a directory

=item *

C<\0> -- indicate the constraint is not satisfied, and prune if it's a directory

=back

A reference is a special flag that signals that a directory should not be
searched recursively, regardless of whether the directory should be
returned by the iterator or not.

The legacy "0 but true" value used previously for pruning is no longer valid
and will throw an exception if it is detected.

Here is an example.  This is equivalent to the "max_depth" rule method with
a depth of 3:

  $rule->and(
    sub {
      my ($path, $basename, $stash) = @_;
      return 1 if $stash->{_depth} < 3;
      return \1 if $stash->{_depth} == 3;
      return \0; # should never get here
    }
  );

Files and directories and directories up to depth 3 will be returned and
directories will be searched.  Files of depth 3 will be returned. Directories
of depth 3 will be returned, but their contents will not be added to the
search.

Returning a reference is "sticky" -- they will propagate through "and" and "or"
logic.

    0 && \0 = \0    \0 && 0 = \0    0 || \0 = \0    \0 || 0 = \0
    0 && \1 = \0    \0 && 1 = \0    0 || \1 = \1    \0 || 1 = \1
    1 && \0 = \0    \1 && 0 = \0    1 || \0 = \1    \1 || 0 = \1
    1 && \1 = \1    \1 && 1 = \1    1 || \1 = \1    \1 || 1 = \1

Once a directory is flagged to be pruned, it will be pruned regardless of
subsequent rules.

    $rule->max_depth(3)->name(qr/foo/);

This will return files or directories with "foo" in the name, but all
directories at depth 3 will be pruned, regardless of whether they match the
name rule.

Generally, if you want to do directory pruning, you are encouraged to use the
L</skip> method instead of writing your own logic using C<\0> and C<\1>.

=head2 Extension modules and custom rule methods

One of the strengths of L<File::Find::Rule> is the many CPAN modules
that extend it.  C<Path::Iterator::Rule> provides the C<add_helper> method
to provide a similar mechanism for extensions.

The C<add_helper> class method takes three arguments, a C<name> for the rule
method, a closure-generating callback, and a flag for not generating a negated
form of the rule.  Unless the flag is true, an inverted "not_*" method is
generated automatically.  Extension classes should call this as a class method
to install new rule methods.  For example, this adds a "foo" method that checks
if the filename is "foo":

  package Path::Iterator::Rule::Foo;

  use Path::Iterator::Rule;

  Path::Iterator::Rule->add_helper(
    foo => sub {
      my @args = @_; # do this to customize closure with arguments
      return sub {
        my ($item, $basename) = @_;
        return if -d "$item";
        return $basename =~ /^foo$/;
      }
    }
  );

  1;

This allows the following rule methods:

  $rule->foo;
  $fule->not_foo;

The C<add_helper> method will warn and ignore a helper with the same name as
an existing method.

=head2 Subclassing

Instead of processing and returning strings, this module may be subclassed
to operate on objects that represent files.  Such objects B<must> stringify
to a file path.

The following private implementation methods must be overridden:

=over 4

=item *

_objectify -- given a path, return an object

=item *

_children -- given a directory, return an (unsorted) list of [ basename, full path ] entries within it, excluding "." and ".."

=back

Note that C<_children> should return a I<list> of I<tuples>, where the tuples
are array references containing basename and full path.

See L<Path::Class::Rule> source for an example.

=head1 LEXICAL WARNINGS

If you run with lexical warnings enabled, C<Path::Iterator::Rule> will issue
warnings in certain circumstances (such as an unreadable directory that must be
skipped).  To disable these categories, put the following statement at the
correct scope:

  no warnings 'Path::Iterator::Rule';

=head1 PERFORMANCE

By default, C<Path::Iterator::Rule> iterator options are "slow but safe".  They
ensure uniqueness, return files in sorted order, and throw nice error messages
if something goes wrong.

If you want speed over safety, set these options:

    %options = (
        loop_safe => 0,
        sorted => 0,
        depthfirst => -1,
        error_handler => undef
    );

Alternatively, use the C<iter_fast> and C<all_fast> methods instead, which set
these options for you.

    $iter = $rule->iter( @dirs, \%options );

    $iter = $rule->iter_fast( @dirs ); # same thing

Depending on the file structure being searched, C<< depthfirst => -1 >> may or
may not be a good choice. If you have lots of nested directories and all the
files at the bottom, a depth first search might do less work or use less
memory, particularly if the search will be halted early (e.g. finding the first
N matches.)

Rules will shortcut on failure, so be sure to put rules likely to fail
early in a rule chain.

Consider:

    $r1 = Path::Iterator::Rule->new->name(qr/foo/)->file;
    $r2 = Path::Iterator::Rule->new->file->name(qr/foo/);

If there are lots of files, but only a few containing "foo", then
C<$r1> above will be faster.

Rules are implemented as code references, so long chains have
some overhead.  Consider testing with a custom coderef that
combines several tests into one.

Consider:

    $r3 = Path::Iterator::Rule->new->and( sub { -x -w -r $_ } );
    $r4 = Path::Iterator::Rule->new->executable->writeable->readable;

Rule C<$r3> above will be much faster, not only because it stacks
the file tests, but because it requires only a single code reference.

=head1 CAVEATS

Some features are still unimplemented:

=over 4

=item *

Untainting options

=item *

Some L<File::Find::Rule> helpers (e.g. C<grep>)

=item *

Extension class loading via C<import()>

=back

Filetest operators and stat rules are subject to the usual portability
considerations.  See L<perlport> for details.

=head1 SEE ALSO

There are many other file finding modules out there.  They all have various
features/deficiencies, depending on your preferences and needs.  Here is an
(incomplete) list of alternatives, with some comparison commentary.

L<Path::Class::Rule> and L<IO::All::Rule> are subclasses of
C<Path::Iterator::Rule> and operate on L<Path::Class> and L<IO::All> objects,
respectively.  Because of this, they are substantially slower on
large directory trees than just using this module directly.

L<File::Find> is part of the Perl core.  It requires the user to write a
callback function to process each node of the search.  Callbacks must use
global variables to determine the current node.  It only supports depth-first
search (both pre- and post-order). It supports pre- and post-processing
callbacks; the former is required for sorting files to process in a directory.
L<File::Find::Closures> can be used to help create a callback for
L<File::Find>.

L<File::Find::Rule> is an object-oriented wrapper around L<File::Find>.  It
provides a number of helper functions and there are many more
C<File::Find::Rule::*> modules on CPAN with additional helpers.  It provides
an iterator interface, but precomputes all the results.

L<File::Next> provides iterators for file, directories or "everything".  It
takes two callbacks, one to match files and one to decide which directories to
descend.  It does not allow control over breadth/depth order, though it does
provide means to sort files for processing within a directory. Like
L<File::Find>, it requires callbacks to use global variables.

L<Path::Class::Iterator> walks a directory structure with an iterator.  It is
implemented as L<Path::Class> subclasses, which adds a degree of extra
complexity. It takes a single callback to define "interesting" paths to return.
The callback gets a L<Path::Class::Iterator::File> or
L<Path::Class::Iterator::Dir> object for evaluation.

L<File::Find::Object> and companion L<File::Find::Object::Rule> are like
File::Find and File::Find::Rule, but without File::Find inside.  They use an
iterator that does not precompute results. They can return
L<File::Find::Object::Result> objects, which give a subset of the utility
of Path::Class objects.  L<File::Find::Object::Rule> appears to be a literal
translation of L<File::Find::Rule>, including oddities like making C<-M> into a
boolean.

L<File::chdir::WalkDir> recursively descends a tree, calling a callback on each
file.  No iterator.  Supports exclusion patterns.  Depth-first post-order by
default, but offers pre-order option. Does not process symlinks.

L<File::Find::Iterator> is based on iterator patterns in Higher Order Perl.  It
allows a filtering callback. Symlinks are followed automatically without
infinite loop protection. No control over order. It offers a "state file"
option for resuming interrupted work.

L<File::Find::Declare> has declarative helper rules, no iterator, is
Moose-based and offers no control over ordering or following symlinks.

L<File::Find::Node> has no iterator, does matching via callback and offers
no control over ordering.

L<File::Set> builds up a set of files to operate on from a list of directories
to include or exclude, with control over recursion.  A callback is applied to
each file (or directory) in the set.  There is no iterator.  There is no
control over ordering.  Symlinks are not followed.  It has several extra
features for checksumming the set and creating tarballs with F</bin/tar>.

=head1 THANKS

Thank you to Ricardo Signes (rjbs) for inspiring me to write yet another file
finder module, for writing file finder optimization benchmarks, and tirelessly
running my code over and over to see if it got faster.

=over 4

=item *

See L<the speed of Perl file finders|http://rjbs.manxome.org/rubric/entry/1981>

=back

=for :stopwords cpan testmatrix url annocpan anno bugtracker rt cpants kwalitee diff irc mailto metadata placeholders metacpan

=head1 SUPPORT

=head2 Bugs / Feature Requests

Please report any bugs or feature requests through the issue tracker
at L<https://github.com/dagolden/Path-Iterator-Rule/issues>.
You will be notified automatically of any progress on your issue.

=head2 Source Code

This is open source software.  The code repository is available for
public review and contribution under the terms of the license.

L<https://github.com/dagolden/Path-Iterator-Rule>

  git clone https://github.com/dagolden/Path-Iterator-Rule.git

=head1 AUTHOR

David Golden <dagolden@cpan.org>

=head1 CONTRIBUTORS

=for stopwords David Steinbrunner Diab Jerius Edward Betts Gian Piero Carrubba Graham Knop Ricardo Signes Slaven Rezic Toby Inkster

=over 4

=item *

David Steinbrunner <dsteinbrunner@pobox.com>

=item *

Diab Jerius <djerius@cfa.harvard.edu>

=item *

Edward Betts <edward@4angle.com>

=item *

Gian Piero Carrubba <gpiero@butterfly.fdc.rm-rf.it>

=item *

Graham Knop <haarg@cpan.org>

=item *

Ricardo Signes <rjbs@cpan.org>

=item *

Slaven Rezic <slaven.rezic@idealo.de>

=item *

Toby Inkster <tobyink@cpan.org>

=back

=head1 COPYRIGHT AND LICENSE

This software is Copyright (c) 2013 by David Golden.

This is free software, licensed under:

  The Apache License, Version 2.0, January 2004

=cut