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

VERSION
    Version 0.2

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.

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.

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()]

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.

  MarpaX::xPathLike methods
    new()
    Used only internally!!! Do nothing;

    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.

    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.

  MarpaX::xPathLike::Data methods
    data(data)
    Executes the query over data and returns a MarpaX::xPathLike::Results
    object

  MarpaX::xPathLike::Compiler methods
    query(xPathLikeString)
    Compile a xPathLike string, query the data and returns a
    MarpaX::xPathLike::Results object

  MarpaX::xPathLike::Results methods
    getrefs()
    Returns a list os references for each matched data;

    getref()
    Returns a reference for first matched data;

    getvalues()
    Returns a list of values for each matched data;

    getvalue()
    Returns the value of first matched data;

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.

  Supported axis
    self::
    child::
    parent::
    ancestor::
    ancestor-or-self::
    descendant::
    descendant-or-self::
    preceding-sibling::
    following::sibling::

  Supported Functions
    count(path?)
    sum(path)
    name(path?)
    position(path?)
    last()
    not(expr)
    names(path?)*
    values(path?)*
    value(path?)*

    (*) not a xPath 1.0 function.

    names is like name but returns a list of names.

    We don't support the `text()' funcions as we don't know what that should
    mean in perl data-structures context, but the `value()' and `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).

  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

  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 `$d->{a}->[0]->{b}' or to a `$d->{a}->{0}->{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/{'"'}

AUTHOR
    Isidro Vila Verde, `<jvverde at gmail.com>'

BUGS
    Send email to `<jvverde at gmail.com>' with subject MarpaX::xPathLike or
    report any bugs or feature requests to `bug-data-xPathLike at
    rt.cpan.org', or through the web interface at
    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.

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

        perldoc MarpaX::xPathLike

    You can also look for information at:

    * RT: CPAN's request tracker (report bugs here)
        http://rt.cpan.org/NoAuth/Bugs.html?Dist=MarpaX-xPathLike

    * AnnoCPAN: Annotated CPAN documentation
        http://annocpan.org/dist/MarpaX-xPathLike

    * CPAN Ratings
        http://cpanratings.perl.org/d/MarpaX-xPathLike

    * Search CPAN
        http://search.cpan.org/dist/MarpaX-xPathLike/

ACKNOWLEDGEMENTS
    I would like to say thansk to amon / Lukas Atkinson for scrutinized the
    code i 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.

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:

    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
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    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.
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