use strict;
use warnings;

package DBIx::Class::DynamicDefault;

use parent 'DBIx::Class';

our $VERSION = '0.03';

__PACKAGE__->mk_classdata(
    __column_dynamic_default_triggers => {
        on_update => [], on_create => [],
    },
);

=head1 NAME

DBIx::Class::DynamicDefault - Automatically set and update fields

=head1 SYNOPSIS

  package My::Schema::SomeTable;

  __PACKAGE__->load_components(qw/DynamicDefault ... Core/);

  __PACKAGE__->add_columns(
          quux          => { data_type => 'integer' },
          quux_plus_one => { data_type => 'integer',
                             dynamic_default_on_create => \&quux_plus_one_default,
                             dynamic_default_on_update => 'quux_plus_one_default', },
          last_changed  => { data_type => 'integer',
                             dynamic_default_on_create => 'now',
                             dynamic_default_on_update => 'now, },
  );

  sub quux_plus_one_default {
      my ($self) = @_;
      return $self->quux + 1;
  }

  sub now {
      return DateTime->now->epoch;
  }

Now, any update or create actions will set the specified columns to the value
returned by the callback you specified as a method name or code reference.

=head1 DESCRIPTION

Automatically set and update fields with values calculated at runtime.

=cut

sub add_columns {
    my $self = shift;

    $self->next::method(@_);

    my @update_columns;
    my @create_columns;

    for my $column ($self->columns) {
        my $info = $self->column_info($column);

        my $update_trigger = $info->{dynamic_default_on_update};
        push @update_columns, [$column => $update_trigger, $info->{always_update} || 0]
            if $update_trigger;

        my $create_trigger = $info->{dynamic_default_on_create};
        push @create_columns, [$column => $create_trigger]
            if $create_trigger;
    }

    if (@update_columns || @create_columns) {
        $self->__column_dynamic_default_triggers({
            on_update => [sort { $b->[2] <=> $a->[2] } @update_columns],
            on_create => \@create_columns,
        });
    }
}

sub insert {
    my $self = shift;

    my @columns = @{ $self->__column_dynamic_default_triggers->{on_create} };
    for my $column (@columns) {
        my $column_name = $column->[0];
        next if defined $self->get_column($column_name);

        my $meth = $column->[1];
        my $default_value = $self->$meth;

        my $accessor = $self->column_info($column_name)->{accessor} || $column_name;
        $self->$accessor($default_value);
    }

    return $self->next::method(@_);
}

sub update {
    my ($self, $upd) = @_;

    $self->set_inflated_columns($upd) if $upd;
    my %dirty = $self->get_dirty_columns;

    my @columns = @{ $self->__column_dynamic_default_triggers->{on_update} };
    for my $column (@columns) {
        my $column_name = $column->[0];
        next if !%dirty && !$column->[2];
        next if exists $dirty{$column_name};

        my $meth = $column->[1];
        my $default_value = $self->$meth;

        my $accessor = $self->column_info($column_name)->{accessor} || $column_name;
        $self->$accessor($default_value);

        $dirty{$column_name} = 1;
    }

    return $self->next::method;
}

=head1 OPTIONS

=head2 dynamic_default_on_create

  dynamic_default_on_create => sub { ... }

  dynamic_default_on_create => 'method_name'

When inserting a new row all columns with the C<dynamic_default_on_create>
option will be set to the return value of the specified callback unless the
columns value has been explicitly set. The callback, that'll be invoked with
the row object as its only argument, may be a code reference or a method name.

=head2 dynamic_default_on_update

  dynamic_default_on_update => sub { ... }

  dynamic_default_on_update => 'method_name'

When updating a row all columns with the C<dynamic_default_on_update> option
will be set to the return value of the specified callback unless the columns
value has been explicitly set.

Columns will only be altered if other dirty columns exist. See C<always_update>
on how to change this.

=head2 always_update

  always_update => 1

When setting C<always_update> to 1 C<dynamic_default_on_update> callbacks will
always be invoked, even if no other columns are dirty.

=head1 AUTHOR

Florian Ragwitz E<lt>rafl@debian.orgE<gt>

=head1 LICENSE

This software is copyright (c) 2008 by Florian Ragwitz.

This is free software; you can redistribute it and/or modify it under
the same terms as perl itself.

=cut

1;
