# this timestamp can be used on either a single element, like so:
#		<element><name>test_ts</name><macro>timestamp</macro></element>
#	(which just records in comma internals that you are using a
#	 timestamp, only useful for introspection stuff, so far...)
# OR, at the top level of a def, like one of the below:
#	<macro>timestamp: [ @stores ], 'created_ts'</macro>
#	<macro>timestamp: [ @stores ], 'created_ts', 'last_modified_ts'</macro>
# these means that for each stores, update created_ts whenever a doc is
# created, and (in the latter usage), update last_modified_ts whenever
# a doc is modified.

if($self->tag eq 'DocumentDefinition') {
	#macro used in def context:
	my ( $stores, $created, $last_modified ) = @macro_args;

	die "timestamp macro needs a list of stores\n" unless ref($stores) eq 'ARRAY';
	die "timestamp macro needs the name of a 'created' element\n" unless $created;

	if ( $created ) {
		#add the element
		my $el = $self->add_element ( 'element' );
		$el->add_element ( 'name' )->set ( $created );
		#keep some info in the def about which elements are timestamps
		push @{$el->{_Def_macro_names}}, 'timestamp';
		push @{$el->{_Def_macro_names}}, 'timestamp_created';

		foreach my $store_name ( @$stores ) {
			my $store = $self->get_store($store_name );
			$store->add_hook ( 'pre_store_hook',
				sub {
					my $doc = shift;
					$doc->element ( $created )->set ( time() )
					unless $doc->element ( $created )->get();
				}
			);
		}
	}

	if ( $last_modified ) {
		#add the element
		my $el = $self->add_element ( 'element' );
		$el->add_element ( 'name' )->set ( $last_modified );
		#keep some info in the def about which elements are timestamps
		push @{$el->{_Def_macro_names}}, 'timestamp';
		push @{$el->{_Def_macro_names}}, 'timestamp_last_modified';

		foreach my $store_name ( @$stores ) {
			my $store = $self->get_store($store_name);
			$store->add_hook ( 'pre_store_hook',
				sub {
					my ( $self, $store, $args ) = @_;
					return  if  $args->{no_mtime};
					$self->element ( $last_modified )->set ( time() );
				}
			);
		}
	}
} elsif($self->tag eq 'element') {
	#macro is used in element context:
	#a no-op. but this call adds to applied_macros();
} else {
	#unknown context, error out
	die "you must use the timestamp macro on a def or a single element";
}

1;