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use strict;
use warnings;
use 5.010_001;

package    # hide from PAUSE
    DBIx::Squirrel::it;

=head1 NAME

DBIx::Squirrel::it - Statement iterator iterator base class

=head1 SYNOPSIS


=head1 DESCRIPTION

This module provides a base class for statement iterators. It is usable as
is, but is also subclassed by the L<DBIx::Squirrel::rs> (Results) class.

=cut

use Exporter     ();
use Scalar::Util qw(
    looks_like_number
    weaken
);
use Sub::Name 'subname';
use DBIx::Squirrel::util qw(
    cluckf
    confessf
    callbacks_args
);
use namespace::clean;

use constant E_BAD_STH   => 'Expected a statement handle object';
use constant E_BAD_SLICE => 'Slice must be a reference to an ARRAY or HASH';
use constant E_BAD_CACHE_SIZE =>
    'Maximum row count must be an integer greater than zero';
use constant W_MORE_ROWS     => 'Query would yield more than one result';
use constant E_EXP_ARRAY_REF => 'Expected an ARRAY-REF';

BEGIN {
    require DBIx::Squirrel
        unless keys %DBIx::Squirrel::;
    *DBIx::Squirrel::it::VERSION     = *DBIx::Squirrel::VERSION;
    @DBIx::Squirrel::it::ISA         = 'Exporter';
    %DBIx::Squirrel::it::EXPORT_TAGS = ( all => [
        @DBIx::Squirrel::it::EXPORT_OK = qw(
            database
            iterator
            result
            result_current
            result_first
            result_number
            result_offset
            result_original
            result_prev
            result_previous
            result_transform
            statement
        )
    ] );
    $DBIx::Squirrel::it::DEFAULT_SLICE      = [];    # Faster!
    $DBIx::Squirrel::it::DEFAULT_CACHE_SIZE = 2;     # Initial buffer size and autoscaling increment
    $DBIx::Squirrel::it::CACHE_SIZE_LIMIT   = 64;    # Absolute maximum buffersize
}

our $_DATABASE;
our $_ITERATOR;
our $_RESULT;
our $_RESULT_FIRST;
our $_RESULT_NUMBER;
our $_RESULT_OFFSET;
our $_RESULT_ORIGINAL;
our $_RESULT_PREV;
our $_STATEMENT;

sub _cache_charge {
    my( $attr, $self ) = shift->_private_state;
    my $sth = $attr->{sth};
    unless ( $sth->{Executed} ) {
        return unless defined $self->start;
    }
    return unless $sth->{Active};
    my( $slice, $cache_size ) = @{$attr}{qw(slice cache_size)};