=head1 NAME

MarpaX::xPathLike - a xPath like processor for perl data-structures (hashes and arrays)! 

=head1 VERSION

Version 0.203

=head1 Why we need another one

There are already some good approaches to xPath syntax, namely the Data::dPath 
and Data::Path. 
Nevertheless we still missing some of powerfull constructions as provided by 
xPath.
Suppose, for example, we have an array of invoices with Total, Amount and Tax 
and need to check which one does not comply to the rule "Total = Amount * (1+Tax)".

For the data structure below we can easily achieve it with this code:


     use MarpaX::xPathLike;
     use Data::Dumper;

     ($\,$,) = (qq|\n|, q|,|);
     my $data = MarpaX::xPathLike->data([
             {invoice => {
                             Amount => 100,
                             Tax => 0.2,
                             Total => 120
                     }
             },
             {invoice => {
                             Amount => 200,
                             Tax => 0.15,
                             Total => 240
                     }       
             },
             receipt =>{ 
             }
     ]);

     print Dumper $data->query(q$
             //invoice[Total != Amount * (1 + Tax)]
     $)->getvalues();


The xPathLike uses the xPath 1.0 syntax to query any set of complex perl 
data structures, using keys or indexes for defining the path.
Examples:


     /0/invoice/Total
     /2
     /*/invoice[Total>100]/Total
     //Tax
     //Total[../Tax = .2]
     //*[count(itens/*) > 1][1]
     sum(//Total)


Like as in xPath it's also possible to query a function.


=head1 SYNOPSIS

How to use it.

     use strict;
     use MarpaX::xPathLike;
     use Data::Dumper;

     ($\,$,) = ("\n",",");
     my $d = {
          drinks => {
               q|Alcoholic beverage| => 'not allowed',
               q|Soft drinks| => [qw|Soda Coke|]
          },
          food => { 
               fruit => [qw|bananas apples oranges pears|], 
               vegetables  => [qw|potatoes  carrots tomatoes|]
          } 
     };

     my $data = MarpaX::xPathLike->data($d);
     my $results = $data->query(q|/*/*/0|);
     my @values = $results->getvalues();
     print @values;                         
     #Soda,bananas,potatoes

     my $ref = $results->getref();
     $$ref = 'Tonic';
     print $d->{drinks}->{q|Soft drinks|}->[0];     
     #Tonic

To get values we can invoke the getvalues ou getvalue methods to obtain a 
list/element matched. If what we need is to change the values we can use
getrefs or getref methods to obtain a reference to the matched 
data-structures. The getref(s) methods always returns a reference to 
matched data-structure. If the matched element is a scalar a reference to 
that scalar is returned. If the matched element is a reference array (or 
hash) a reference to that reference is returned, so we can change it and 
not only nested data-structures.


=head1 DESCRIPTION

It looks for complex perl data-structures which match the xPathLike expression 
and returns a list of matched data-structures.


Like xPath it is possible to deal with any logical or arithmetic 
expressions, ex: 

    *{count(a) == count(c) / 2 * (1 + count(b)) or d}

, or even 
query xPath functions ex: 

    count(//*)
    name(//*[last()])
    sum(//[*])


Additionally some extensions are implemented to deal with perl data-structures,
namely to choose between arrays and hashes.

Example:

Get all structures but only one which are arrays

     //[*]

Similarly to get all of hash structures, we can write

     //{*}

Besides that, some extra functions are also provide to check data type in
predicates, ex: 

     //*[isScalar()]


=head1 METHODS

The MarpaX::xPathLike just provides two useful methods, compile and data. 
The first is used to compile a xPathLike expression and the second is used
to prepare data to be queried. 

=head2 MarpaX::xPathLike methods

=head3 new()

Used only internally!!! Do nothing;

=head3 compile(xPathLikeString)

     my $query = MarpaX::xPathLike->compile('*');                #compile the query
     
     my @values1 = $query->data({fruit => 'bananas'})->getvalues();
     # @values1 = (bananas)

     my @values2 = $query->data({
          fruit => 'bananas', 
          vegetables => 'orions'
     })->getvalues();
     # @values2 = (bananas, orions)

     my @values3 = $query->data({
          food => {fruit => 'bananas'}
     })->getvalues();
     # @values3 = ({fruit => 'bananas'})

The compile method receives a xPathLike string, compiles it and returns a MarpaX::xPathLike::Data object.
This is the prefered method to run the same query over several data-structures.

=head3 data(dataRef)


    my $data = MarpaX::xPathLike->data({
           food => {
                   fruit => 'bananas',
                   vegetables => 'unions'
           },
           drinks => {
                   wine => 'Porto',
                   water => 'Evian'
           }
    });


    my @values1 = $data->query('/*/*')->getvalues();
    print @values1; # Evian,Porto,bananas,unions

    my @values2 = $data->query('/*/wine')->getvalues();
    print @values2; #Porto

    #using a predicate, to get only first level entry which contains a fruit key
    my @values3 = $data->query('/*[fruit]/*')->getvalues();
    print @values3; #bananas,unions
    #using another filter to return only elements which have the value matching 
    #a /an/ pattern
    my @values4 = $data->query('/*/*[. ~ "an"]')->getvalues();
    print @values4;# Evian,bananas

    my @values5 = $data->query('//*[isScalar()]')->getvalues();
    print @values5;#Evian,Porto,bananas,unions

                  

The method data receives a hash (or array) reference and returns a MarpaX::xPathLike::Compile object. 
This is the prefered method to run several query over same data.

=head2 MarpaX::xPathLike::Data methods

=head3 data(data)

Executes the query over data and returns a MarpaX::xPathLike::Results object

=head2 MarpaX::xPathLike::Compiler methods

=head3 query(xPathLikeString)

Compile a xPathLike string, query the data and returns a MarpaX::xPathLike::Results object

=head2 MarpaX::xPathLike::Results methods

=head3 getrefs()

Returns a list os references for each matched data;

=head3 getref()

Returns a reference for first matched data;

=head3 getvalues()

Returns a list of values for each matched data;

=head3 getvalue()

Returns the value of first matched data;


=head1 xPath Compability

Unless some xPath functions, not yet implemented, and xPath axis preceding:: 
and following:: directions everything else is implemented. Probably buggly, 
sorry. I hope to fixe them as soon someone (?) identify them.

=head2 Supported axis 

=over 4

=item self::

=item child::

=item parent::

=item ancestor::

=item ancestor-or-self::

=item descendant::

=item descendant-or-self::

=item preceding-sibling::

=item following::sibling::

=back

=head2 Supported Functions

=over 4

=item count(path?)

=item sum(path)

=item name(path?)

=item position(path?)

=item last()

=item not(expr)

=item names(path?)*

=item values(path?)*

=item value(path?)*

=back

(*) not a xPath 1.0 function. 

names is like name but returns a list of names.

We don't support the C<text()> funcions as we don't know what that should mean 
in perl data-structures context, but the C<value()> and C<values()> functions 
are provided to return the value/values of current context if path argument is 
missing or the value/values of matched data-structures. That/those value/values 
could be scalar(s) or hash/array reference(s).



=head2 Supported operators

The xPath supported operators are the following: 

    +, -, *, div, %, =, !=, (), "", '', +, -, ., .., /, //, ::, <, <=, >, >=, [], and, or 
      and 
    | (paths union)

Addicionaly xPathLike also supports the following operators

    eq, ne, lt, le, gt, ge and ~ 

The ~ is the matching operator   

=head2 Support for data types

In xPathLike path expression, a digit step could mean a array index or a hash's key name.
ex:

    /a/0/b

may refere to a C<$d-E<gt>{a}-E<gt>[0]-E<gt>{b}> or to a C<$d-E<gt>{a}-E<gt>{0}-E<gt>{b}>. 
If a restriction is required for select only array's index 0
the xPathLike expression should be       

    /a/[0]/b

And similarly for hash' key '0'    

    /a/{0}/b

The curly bracket could also be useful to refere to keys with spaces or any special 
character with the help of quotes (singles or doubles). Some examples

    /{'five words as a keys'}//{"key with a / or a +"}/*

The curly and square brackets could also be used with axis and wildcard *. Examples:

    //{*}
    //[*]
    //*/parent::[b]
    //a//parent::{*}
    //*[self::{*} = 3 or self::[*] > 10]
    /1/[*][4]/child::[*][1]/{a}/following-sibling::*[last()]

If a hash key is just a * (or any other special character) the path expression could be something like this

    //{"*"}/b
    //a/{'*'}
    //{"+"}/b
    //a/{'/'}
    //{"}"}/b
    //a/{'"'}


=head1 AUTHOR

Isidro Vila Verde, C<< <jvverde at gmail.com> >>

=head1 BUGS

Send email to C<< <jvverde at gmail.com> >> with subject MarpaX::xPathLike
or report any bugs or feature requests to C<bug-data-xPathLike at rt.cpan.org>, or through
the web interface at L<http://rt.cpan.org/NoAuth/ReportBug.html?Queue=MarpaX-xPathLike>.  I will be notified, and then you'll
automatically be notified of progress on your bug as I make changes.


=head1 SUPPORT

You can find documentation for this module with the perldoc command.

    perldoc MarpaX::xPathLike


You can also look for information at:

=over 4

=item * RT: CPAN's request tracker (report bugs here)

L<http://rt.cpan.org/NoAuth/Bugs.html?Dist=MarpaX-xPathLike>

=item * AnnoCPAN: Annotated CPAN documentation

L<http://annocpan.org/dist/MarpaX-xPathLike>

=item * CPAN Ratings

L<http://cpanratings.perl.org/d/MarpaX-xPathLike>

=item * Search CPAN

L<http://search.cpan.org/dist/MarpaX-xPathLike/>

=back


=head1 ACKNOWLEDGEMENTS

I would like to say thanks to amon / Lukas Atkinson for scrutinized the code give me such valuable feedback. 
To Ron Savage for introduce me to the Marpa::R2 and all your help with UTF8 problems and good advices.
To Jean-Damien to point me some importante issues on first release.
And final a big Thank you to Jeffrey Kegler for creating the Marpa::R2.


=head1 LICENSE AND COPYRIGHT

Copyright 2013 Isidro Vila Verde.

This program is free software; you can redistribute it and/or modify it
under the terms of the the Artistic License (2.0). You may obtain a
copy of the full license at:

L<http://www.perlfoundation.org/artistic_license_2_0>

Any use, modification, and distribution of the Standard or Modified
Versions is governed by this Artistic License. By using, modifying or
distributing the Package, you accept this license. Do not use, modify,
or distribute the Package, if you do not accept this license.

If your Modified Version has been derived from a Modified Version made
by someone other than you, you are nevertheless required to ensure that
your Modified Version complies with the requirements of this license.

This license does not grant you the right to use any trademark, service
mark, tradename, or logo of the Copyright Holder.

This license includes the non-exclusive, worldwide, free-of-charge
patent license to make, have made, use, offer to sell, sell, import and
otherwise transfer the Package with respect to any patent claims
licensable by the Copyright Holder that are necessarily infringed by the
Package. If you institute patent litigation (including a cross-claim or
counterclaim) against any party alleging that the Package constitutes
direct or contributory patent infringement, then this Artistic License
to you shall terminate on the date that such litigation is filed.

Disclaimer of Warranty: THE PACKAGE IS PROVIDED BY THE COPYRIGHT HOLDER
AND CONTRIBUTORS "AS IS' AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES.
THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
PURPOSE, OR NON-INFRINGEMENT ARE DISCLAIMED TO THE EXTENT PERMITTED BY
YOUR LOCAL LAW. UNLESS REQUIRED BY LAW, NO COPYRIGHT HOLDER OR
CONTRIBUTOR WILL BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, OR
CONSEQUENTIAL DAMAGES ARISING IN ANY WAY OUT OF THE USE OF THE PACKAGE,
EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.


=cut

