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#============================================================= -*-Perl-*-
#
# Template::Iterator
#
# DESCRIPTION
#
#   Module defining an iterator class which is used by the FOREACH
#   directive for iterating through data sets.  This may be
#   sub-classed to define more specific iterator types.
#
# AUTHOR
#   Andy Wardley   <abw@wardley.org>
#
# COPYRIGHT
#   Copyright (C) 1996-2007 Andy Wardley.  All Rights Reserved.
#
#   This module is free software; you can redistribute it and/or
#   modify it under the same terms as Perl itself.
#
#============================================================================
package Template::Iterator;
use strict;
use warnings;
use base 'Template::Base';
use Template::Constants;
use Template::Exception;
use Scalar::Util qw(blessed);
use constant ODD  => 'odd';
use constant EVEN => 'even';
our $VERSION = '3.100';
our $DEBUG   = 0 unless defined $DEBUG;
our $AUTOLOAD;
#========================================================================
#                      -----  CLASS METHODS -----
#========================================================================
#------------------------------------------------------------------------
# new(\@target, \%options)
#
# Constructor method which creates and returns a reference to a new 
# Template::Iterator object.  A reference to the target data (array
# or hash) may be passed for the object to iterate through.
#------------------------------------------------------------------------
sub new {
    my $class  = shift;
    my $data   = shift || [ ];
    my $params = shift || { };
    if (ref $data eq 'HASH') {
        # map a hash into a list of { key => ???, value => ??? } hashes,
        # one for each key, sorted by keys
        $data = [ map { { key => $_, value => $data->{ $_ } } }
                  sort keys %$data ];
    }
    elsif (blessed($data) && $data->can('as_list')) {
        $data = $data->as_list();
    }
    elsif (ref $data ne 'ARRAY') {
        # coerce any non-list data into an array reference
        $data  = [ $data ] ;
    }
    bless {
        _DATA  => $data,
        _ERROR => '',
    }, $class;
}
#========================================================================
#                   -----  PUBLIC OBJECT METHODS -----
#========================================================================
#------------------------------------------------------------------------
# get_first()
#
# Initialises the object for iterating through the target data set.  The 
# first record is returned, if defined, along with the STATUS_OK value.
# If there is no target data, or the data is an empty set, then undef 
# is returned with the STATUS_DONE value.  
#------------------------------------------------------------------------
sub get_first {
    my $self  = shift;
    my $data  = $self->{ _DATA };
    $self->{ _DATASET } = $self->{ _DATA };
    my $size = scalar @$data;
    my $index = 0;
     
    return (undef, Template::Constants::STATUS_DONE) unless $size;
    # initialise various counters, flags, etc.
    @$self{ qw( SIZE MAX INDEX COUNT FIRST LAST ) } 
            = ( $size, $size - 1, $index, 1, 1, $size > 1 ? 0 : 1, undef );
    @$self{ qw( PREV NEXT ) } = ( undef, $self->{ _DATASET }->[ $index + 1 ]);
    return $self->{ _DATASET }->[ $index ];
}
#------------------------------------------------------------------------
# get_next()
#
# Called repeatedly to access successive elements in the data set.
# Should only be called after calling get_first() or a warning will 
# be raised and (undef, STATUS_DONE) returned.
#------------------------------------------------------------------------
sub get_next {
    my ( $max, $index ) = @{ $_[0] }{qw( MAX INDEX )};
    # warn about incorrect usage
    if ( !defined $index ) {
        my ( $pack, $file, $line ) = caller();
        warn("iterator get_next() called before get_first() at $file line $line\n");
        return ( undef, Template::Constants::STATUS_DONE );    ## RETURN ##
    }
    # if there's still some data to go...
    elsif ( $index >= $max ) {
        return ( undef, Template::Constants::STATUS_DONE );    ## RETURN ##
    }
    my $self = shift;
    my $dataset = $self->{_DATASET};
     
    $index++;
    # update counters and flags
    @$self{qw( INDEX COUNT FIRST LAST PREV NEXT )} = (
        $index,                                            # INDEX
        $index + 1,                                        # COUNT
        0,                                                 # FIRST
        $index == $max ? 1 : 0,                            # LAST
        @$dataset[ $index - 1, $index + 1 ]                # PREV, NEXT
    );
    return $dataset->[ $index ];                           ## RETURN ##
}
#------------------------------------------------------------------------
# get_all()
#
# Method which returns all remaining items in the iterator as a Perl list
# reference.  May be called at any time in the life-cycle of the iterator.
# The get_first() method will be called automatically if necessary, and
# then subsequent get_next() calls are made, storing each returned 
# result until the list is exhausted.  
#------------------------------------------------------------------------
sub get_all {
    my $self = shift;
    my ($max, $index) = @$self{ qw( MAX INDEX ) };
    my @data;
    # handle cases where get_first() has yet to be called.
    unless (defined $index) {
        my ($first, $status) = $self->get_first;
        # refresh $max and $index, after get_first updates MAX and INDEX
        ($max, $index) = @$self{ qw( MAX INDEX ) };
        # empty lists are handled here.
        if ($status && $status == Template::Constants::STATUS_DONE) {
            return (undef, Template::Constants::STATUS_DONE);   ## RETURN ##
        }
        push @data, $first;
        ## if there's nothing left in the iterator, return the single value.
        unless ($index < $max) {
            return \@data;
        }
    }
    # if there's still some data to go...
    if ($index < $max) {
        $index++;
        push @data, @{ $self->{ _DATASET } } [ $index..$max ];
         
        # update counters and flags
        @$self{ qw( INDEX COUNT FIRST LAST ) }
        = ( $max, $max + 1, 0, 1 );
        return \@data;                                      ## RETURN ##
    }
    else {
        return (undef, Template::Constants::STATUS_DONE);   ## RETURN ##
    }
}
sub odd {
    shift->{ COUNT } % 2 ? 1 : 0
}
sub even {
    shift->{ COUNT } % 2 ? 0 : 1
}
sub parity {
    shift->{ COUNT } % 2 ? ODD : EVEN;
}
sub index {
    return $_[0]->{INDEX};
}
sub count {
    return $_[0]->{COUNT};
}
sub number { # This is here for backward compatibility per sub AUTOLOAD
    return $_[0]->{COUNT};
}
sub first {
    return $_[0]->{FIRST};
}
sub last {
    return $_[0]->{LAST};
}
sub size {
    return $_[0]->{SIZE};
}
#------------------------------------------------------------------------
# AUTOLOAD
#
# Provides access to internal fields (e.g. prev, next, etc)
#------------------------------------------------------------------------
sub AUTOLOAD {
    my $self = shift;
    my $item = $AUTOLOAD;
    $item =~ s/.*:://;
    return if $item eq 'DESTROY';
    # alias NUMBER to COUNT for backwards compatibility
    $item = 'COUNT' if CORE::index(uc $item,'NUMBER') > -1;
    return $self->{ uc $item };
}
1;
__END__
HideShow 235 lines of Pod
=head1 NAME
Template::Iterator - Data iterator used by the FOREACH directive
=head1 SYNOPSIS
    my $iter = Template::Iterator->new(\@data, \%options);
=head1 DESCRIPTION
The C<Template::Iterator> module defines a generic data iterator for use 
by the C<FOREACH> directive.  
It may be used as the base class for custom iterators.
=head1 PUBLIC METHODS
=head2 new($data) 
Constructor method.  A reference to a list of values is passed as the
first parameter.  Subsequent calls to L<get_first()> and L<get_next()> calls 
will return each element from the list.
    my $iter = Template::Iterator->new([ 'foo', 'bar', 'baz' ]);
The constructor will also accept a reference to a hash array and will 
expand it into a list in which each entry is a hash array containing
a 'C<key>' and 'C<value>' item, sorted according to the hash keys.
    my $iter = Template::Iterator->new({ 
        foo => 'Foo Item',
        bar => 'Bar Item',
    });
This is equivalent to:
    my $iter = Template::Iterator->new([
        { key => 'bar', value => 'Bar Item' },
        { key => 'foo', value => 'Foo Item' },
    ]);
When passed a single item which is not an array reference, the constructor
will automatically create a list containing that single item.
    my $iter = Template::Iterator->new('foo');
This is equivalent to:
    my $iter = Template::Iterator->new([ 'foo' ]);
Note that a single item which is an object based on a blessed ARRAY 
references will NOT be treated as an array and will be folded into 
a list containing that one object reference.
    my $list = bless [ 'foo', 'bar' ], 'MyListClass';
    my $iter = Template::Iterator->new($list);
equivalent to:
    my $iter = Template::Iterator->new([ $list ]);
If the object provides an C<as_list()> method then the L<Template::Iterator>
constructor will call that method to return the list of data.  For example:
    package MyListObject;
     
    sub new {
        my $class = shift;
        bless [ @_ ], $class;
    }
    package main;
     
    my $list = MyListObject->new('foo', 'bar');
    my $iter = Template::Iterator->new($list);
This is then functionally equivalent to:
    my $iter = Template::Iterator->new([ $list ]);
The iterator will return only one item, a reference to the C<MyListObject>
object, C<$list>.
By adding an C<as_list()> method to the C<MyListObject> class, we can force
the C<Template::Iterator> constructor to treat the object as a list and 
use the data contained within.
    package MyListObject;
     
    ...
     
    sub as_list {
        my $self = shift;
        return $self;
    }
     
    package main;
     
    my $list = MyListObject->new('foo', 'bar');
    my $iter = Template::Iterator->new($list);
The iterator will now return the two items, 'C<foo>' and 'C<bar>', which the 
C<MyObjectList> encapsulates.
=head2 get_first()
Returns a C<($value, $error)> pair for the first item in the iterator set.
The C<$error> returned may be zero or undefined to indicate a valid datum
was successfully returned.  Returns an error of C<STATUS_DONE> if the list 
is empty.
=head2 get_next()
Returns a C<($value, $error)> pair for the next item in the iterator set.
Returns an error of C<STATUS_DONE> if all items in the list have been 
visited.
=head2 get_all()
Returns a C<(\@values, $error)> pair for all remaining items in the iterator 
set.  Returns an error of C<STATUS_DONE> if all items in the list have been 
visited.
=head2 size()
Returns the size of the data set or undef if unknown.
=head2 max()
Returns the maximum index number (i.e. the index of the last element) 
which is equivalent to L<size()> - C<1>.
=head2 index()
Returns the current index number which is in the range C<0> to L<max()>.
=head2 count()
Returns the current iteration count in the range C<1> to L<size()>.  This is
equivalent to L<index()> + C<1>.  
=head2 first()
Returns a boolean value to indicate if the iterator is currently on 
the first iteration of the set.
=head2 last()
Returns a boolean value to indicate if the iterator is currently on
the last iteration of the set.
=head2 prev()
Returns the previous item in the data set, or C<undef> if the iterator is
on the first item.
=head2 next()
Returns the next item in the data set or C<undef> if the iterator is on the 
last item.
=head2 number()
This is an alias to 'count' to provide backward compatibility.
View L<count>.
=head2 parity()
Returns the text string C<even> or C<odd> to indicate the parity of the 
current iteration count (starting at 1).  This is typically used to create
striped I<zebra tables>.
    <table>
    [% FOREACH name IN ['Arthur', 'Ford', 'Trillian'] -%]
      <tr class="[% loop.parity %]">
        <td>[% name %]</td>
      </tr>
    [% END %]
    </table>
This will produce the following output:
    <table>
      <tr class="odd">
        <td>Arthur</td>
      </tr>
      <tr class="even">
        <td>Ford</td>
      </tr>
      <tr class="odd">
        <td>Trillian</td>
      </tr>
    </table>
You can then style the C<tr.odd> and C<tr.even> elements using CSS:
    tr.odd td {
        background-color: black;
        color: white;
    }
     
    tr.even td {
        background-color: white;
        color: black;
    }
=head2 odd()
Returns a boolean (0/1) value to indicate if the current iterator count
(starting at 1) is an odd number. In other words, this will return a true
value for the first iterator, the third, fifth, and so on.
=head2 even()
Returns a boolean (0/1) value to indicate if the current iterator count
(starting at 1) is an even number. In other words, this will return a true
value for the second iteration, the fourth, sixth, and so on.
=head1 AUTHOR
Andy Wardley E<lt>abw@wardley.orgE<gt> L<http://wardley.org/>
=head1 COPYRIGHT
Copyright (C) 1996-2007 Andy Wardley.  All Rights Reserved.
This module is free software; you can redistribute it and/or
modify it under the same terms as Perl itself.
=head1 SEE ALSO
L<Template>
=cut
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