package DBIx::Custom::Where;

use strict;

use warnings;

use base 'Object::Simple';

use overload 'bool' => sub {1}, fallback => 1;

use overload '""' => sub { shift->to_string }, fallback => 1;

use Carp 'croak';

# Carp trust relationship

push @DBIx::Custom::CARP_NOT, __PACKAGE__;

__PACKAGE__->attr(

    [qw/param query_builder safety_character/],

    clause => sub { [] },

);

sub to_string {

    my $self = shift;

    # Clause

    my $clause = $self->clause;

    $clause = ['and', $clause] unless ref $clause eq 'ARRAY';

    $clause->[0] = 'and' unless @$clause;

    # Parse

    my $where = [];

    my $count = {};

    $self->_parse($clause, $where, $count, 'and');

    # Stringify

    unshift @$where, 'where' if @$where;

    return join(' ', @$where);

}

our %VALID_OPERATIONS = map { $_ => 1 } qw/and or/;

sub _parse {

    my ($self, $clause, $where, $count, $op) = @_;

    # Array

    if (ref $clause eq 'ARRAY') {

        # Start

        push @$where, '(';

        # Operation

        my $op = $clause->[0] || '';

        croak qq{"$op" is invalid operation}

          unless $VALID_OPERATIONS{$op};

        # Parse internal clause

        for (my $i = 1; $i < @$clause; $i++) {

            my $pushed = $self->_parse($clause->[$i], $where, $count, $op);

            push @$where, $op if $pushed;

        }

        pop @$where if $where->[-1] eq $op;

        # Undo

        if ($where->[-1] eq '(') {

            pop @$where;

            pop @$where;

        }

        # End

        else { push @$where, ')' }

    }

    # String

    else {

        # Column

        my $columns = $self->query_builder->build_query($clause)->columns;

        croak qq{Each tag contains one column name: tag "$clause"}

          unless @$columns == 1;

        my $column = $columns->[0];

        my $safety = $self->safety_character;

        croak qq{"$column" is not safety column name}

          unless $column =~ /^[$safety\.]+$/;

        # Column count up

        my $count = ++$count->{$column};

        # Push

        my $param = $self->param;

        my $pushed;

        if (ref $param eq 'HASH') {

            if (exists $param->{$column}) {

                if (ref $param->{$column} eq 'ARRAY') {

                    $pushed = 1

                      if  exists $param->{$column}->[$count - 1]

                       && ref $param->{$column}->[$count - 1] ne 'DBIx::Custom::NotExists';

                } 

                elsif ($count == 1) {

                    $pushed = 1;

                }

            }

            push @$where, $clause if $pushed;

        }

        elsif (!defined $param) {

            push @$where, $clause;

            $pushed = 1;

        }

        else { croak "Parameter must be hash reference or undfined value" }

        return $pushed;

    }

}

1;

=head1 NAME

DBIx::Custom::Where - Where clause EXPERIMENTAL

=head1 SYNOPSYS

    my $where = DBIx::Custom::Where->new;

=head1 ATTRIBUTES

=head2 C<clause>

    $where->clause(

        ['and', '{= title}', ['or', '{< date}', '{> date}']]

    );

Where clause. Above one is expanded to the following SQL by to_string

If all parameter names is exists.

    "where ( {= title} and ( {< date} or {> date} ) )"

=head2 C<param>

    my $param = $where->param;

    $where    = $where->param({title => 'Perl',

                               date => ['2010-11-11', '2011-03-05']},

                               name => ['Ken', 'Taro']);

=head2 C<safety_character>

    my $safety_character = $self->safety_character;

    $dbi                 = $self->safety_character($name);

=head1 METHODS

=head2 C<to_string>

    $where->to_string;

Convert where clause to string correspoinding to param name.