--- /dev/null
+package DBIx::Class::DeploymentHandler::VersionHandler::Monotonic;
+use Moose;
+use Carp 'croak';
+
+with 'DBIx::Class::DeploymentHandler::HandlesVersioning';
+
+has schema_version => (
+ isa => 'Int',
+ is => 'ro',
+ required => 1,
+);
+
+has database_version => (
+ isa => 'Int',
+ is => 'ro',
+ required => 1,
+);
+
+has to_version => (
+ isa => 'Int',
+ is => 'ro',
+ lazy_build => 1,
+);
+
+sub _build_to_version { $_[0]->schema_version }
+
+has _version => (
+ is => 'rw',
+ isa => 'Int',
+ lazy_build => 1,
+);
+
+sub BUILD {
+ croak "you are trying to upgrade and your current version is greater\n".
+ "than the version you are trying to upgrade to. Either downgrade\n".
+ "or update your schema" if $_[0]->to_version < $_[0]->_version;
+}
+
+sub _inc_version { $_[0]->_version($_[0]->_version + 1 ) }
+sub _dec_version { $_[0]->_version($_[0]->_version - 1 ) }
+
+sub _build__version { $_[0]->database_version }
+
+sub previous_version_set {
+ my $self = shift;
+ return undef
+ if $self->to_version == $self->_version;
+
+ $self->_dec_version;
+ return [$self->_version, $self->_version + 1];
+}
+
+sub next_version_set {
+ my $self = shift;
+ return undef
+ if $self->to_version == $self->_version;
+
+ $self->_inc_version;
+ return [$self->_version - 1, $self->_version];
+}
+
+__PACKAGE__->meta->make_immutable;
+
+1;
+
+__END__
+
+vim: ts=2 sw=2 expandtab
--- /dev/null
+#!perl
+
+use Test::More;
+use Test::Exception;
+
+use lib 't/lib';
+use aliased
+ 'DBIx::Class::DeploymentHandler::VersionHandler::Monotonic';
+
+{
+ my $vh = Monotonic->new({
+ schema_version => 2,
+ database_version => 1,
+ });
+
+ ok $vh, 'VersionHandler gets instantiated';
+
+ ok(
+ eq_array($vh->next_version_set, [1,2]),
+ 'first version pair works'
+ );
+ ok(
+ !$vh->next_version_set,
+ 'next version set returns undef when we are done'
+ );
+}
+
+{
+ my $vh = Monotonic->new({
+ to_version => 1,
+ schema_version => 1,
+ database_version => 1,
+ });
+
+ ok $vh, 'VersionHandler gets instantiated';
+
+ ok(
+ !$vh->next_version_set,
+ 'next version set returns undef if we are at the version requested'
+ );
+}
+
+{
+ my $vh = Monotonic->new({
+ to_version => 5,
+ schema_version => 1,
+ database_version => 1,
+ });
+
+ ok $vh, 'VersionHandler gets instantiated';
+ ok(
+ eq_array($vh->next_version_set, [1,2]),
+ 'first version pair works'
+ );
+ ok(
+ eq_array($vh->previous_version_set, [1,2]),
+ 'doing previous version works'
+ );
+ ok(
+ eq_array($vh->next_version_set, [1,2]),
+ 'first version pair works again'
+ );
+ ok(
+ eq_array($vh->next_version_set, [2,3]),
+ 'second version pair works'
+ );
+ ok(
+ eq_array($vh->next_version_set, [3,4]),
+ 'third version pair works'
+ );
+ ok(
+ eq_array($vh->next_version_set, [4,5]),
+ 'fourth version pair works'
+ );
+ ok( !$vh->next_version_set, 'no more versions after final pair' );
+ ok( !$vh->next_version_set, 'still no more versions after final pair' );
+}
+
+dies_ok {
+ my $vh = Monotonic->new({
+ schema_version => 2,
+ database_version => '1.1',
+ });
+ $vh->next_vesion_set
+} 'dies if database version not an Int';
+
+dies_ok {
+ my $vh = Monotonic->new({
+ to_version => 0,
+ schema_version => 1,
+ database_version => 1,
+ });
+} 'cannot request a version before the current version';
+
+done_testing;
+#vim: ts=2 sw=2 expandtab