<?php

class ViewableDataExtensions extends Extension {
	function ColumnedPos($cols=3, $startIndex = 1) {
		return $this->owner->Pos(0) % $cols + $startIndex;
	}

	function setIterator($iterator) {
		$this->iterator = $iterator;
	}

	function Prev() {
		$pos = $this->owner->Pos(0);
		if ($pos <= 0) return null;

		return $this->iterator->getOffset(-1);
	}

	function Next() {
		$pos = $this->owner->Pos(0);
		if ($pos+1 >= $this->owner->TotalItems()) return null;

		return $this->iterator->getOffset(1);
	}

	/* Some ViewableData subclasses are DataObjects, which need this function when extended. Just return null */
	function extraStatics() {
		return null;
	}
}