<?php

use SilverStripe\ORM\SS_Limitable;
use SilverStripe\ORM\SS_List;
use SilverStripe\ORM\UnsavedRelationList;
/**
 * GridFieldPaginator paginates the {@link GridField} list and adds controls
 * to the bottom of the {@link GridField}.
 *
 * @package forms
 * @subpackage fields-gridfield
 */
class GridFieldPaginator implements GridField_HTMLProvider, GridField_DataManipulator, GridField_ActionProvider {

	/**
	 * Specifies default items per page
	 *
	 * @config
	 * @var int
	 */
	private static $default_items_per_page = 15;

	/**
	 * @var int
	 */
	protected $itemsPerPage;

	/**
	 * See {@link setThrowExceptionOnBadDataType()}
	 */
	protected $throwExceptionOnBadDataType = true;

	/**
	 *
	 * @param int $itemsPerPage - How many items should be displayed per page
	 */
	public function __construct($itemsPerPage=null) {
		$this->itemsPerPage = $itemsPerPage
			?: Config::inst()->get('GridFieldPaginator', 'default_items_per_page');
	}

	/**
	 * Determine what happens when this component is used with a list that isn't {@link SS_Filterable}.
	 *
	 *  - true: An exception is thrown
	 *  - false: This component will be ignored - it won't make any changes to the GridField.
	 *
	 * By default, this is set to true so that it's clearer what's happening, but the predefined
	 * {@link GridFieldConfig} subclasses set this to false for flexibility.
	 */
	public function setThrowExceptionOnBadDataType($throwExceptionOnBadDataType) {
		$this->throwExceptionOnBadDataType = $throwExceptionOnBadDataType;
	}

	/**
	 * See {@link setThrowExceptionOnBadDataType()}
	 */
	public function getThrowExceptionOnBadDataType() {
		return $this->throwExceptionOnBadDataType;
	}

	/**
	 * Check that this dataList is of the right data type.
	 * Returns false if it's a bad data type, and if appropriate, throws an exception.
	 */
	protected function checkDataType($dataList) {
		if($dataList instanceof SS_Limitable) {
			return true;
		} else {
			if($this->throwExceptionOnBadDataType) {
				throw new LogicException(
					get_class($this) . " expects an SS_Limitable list to be passed to the GridField.");
			}
			return false;
		}
	}

	/**
	 *
	 * @param GridField $gridField
	 * @return array
	 */
	public function getActions($gridField) {
		if(!$this->checkDataType($gridField->getList())) return;

		return array('paginate');
	}

	/**
	 *
	 * @param GridField $gridField
	 * @param string $actionName
	 * @param string $arguments
	 * @param array $data
	 * @return void
	 */
	public function handleAction(GridField $gridField, $actionName, $arguments, $data) {
		if(!$this->checkDataType($gridField->getList())) return;

		if($actionName !== 'paginate') {
			return;
		}
		$state = $this->getGridPagerState($gridField);
		$state->currentPage = (int)$arguments;
	}

	protected $totalItems = 0;

	/**
	 * Retrieves/Sets up the state object used to store and retrieve information
	 * about the current paging details of this GridField
	 * @param GridField $gridField
	 * @return GridState_Data
	 */
	protected function getGridPagerState(GridField $gridField) {
		$state = $gridField->State->GridFieldPaginator;

		// Force the state to the initial page if none is set
		$state->currentPage(1);

		return $state;
	}

	/**
	 *
	 * @param GridField $gridField
	 * @param SS_List $dataList
	 * @return SS_List
	 */
	public function getManipulatedData(GridField $gridField, SS_List $dataList) {
		if(!$this->checkDataType($dataList)) return $dataList;

		$state = $this->getGridPagerState($gridField);

		// Update item count prior to filter. GridFieldPageCount will rely on this value
		$this->totalItems = $dataList->count();

		$startRow = $this->itemsPerPage * ($state->currentPage - 1);

		// Prevent visiting a page with an offset higher than the total number of items
		if($startRow >= $this->totalItems) {
			$state->currentPage = 1;
			$startRow = 0;
		}

		if(!($dataList instanceof SS_Limitable) || ($dataList instanceof UnsavedRelationList)) {
			return $dataList;
		}

		return $dataList->limit((int)$this->itemsPerPage, (int)$startRow);
	}

	/**
	 * Determines arguments to be passed to the template for building this field
	 * @return ArrayData|null If paging is available this will be an ArrayData
	 * object of paging details with these parameters:
	 * <ul>
	 *	<li>OnlyOnePage:				boolean - Is there only one page?</li>
	 *  <li>FirstShownRecord:			integer - Number of the first record displayed</li>
	 *  <li>LastShownRecord:			integer - Number of the last record displayed</li>
	 *  <li>NumRecords:					integer - Total number of records</li>
	 *	<li>NumPages:					integer - The number of pages</li>
	 *	<li>CurrentPageNum (optional):	integer - If OnlyOnePage is false, the number of the current page</li>
	 *  <li>FirstPage (optional):		GridField_FormAction - Button to go to the first page</li>
	 *	<li>PreviousPage (optional):	GridField_FormAction - Button to go to the previous page</li>
	 *	<li>NextPage (optional):		GridField_FormAction - Button to go to the next page</li>
	 *	<li>LastPage (optional):		GridField_FormAction - Button to go to last page</li>
	 * </ul>
	 */
	public function getTemplateParameters(GridField $gridField) {
		if(!$this->checkDataType($gridField->getList())) return null;

		$state = $this->getGridPagerState($gridField);

		// Figure out which page and record range we're on
		$totalRows = $this->totalItems;
		if(!$totalRows) return null;

		$totalPages = (int)ceil($totalRows/$this->itemsPerPage);
		if($totalPages == 0)
			$totalPages = 1;
		$firstShownRecord = ($state->currentPage - 1) * $this->itemsPerPage + 1;
		if($firstShownRecord > $totalRows)
			$firstShownRecord = $totalRows;
		$lastShownRecord = $state->currentPage * $this->itemsPerPage;
		if($lastShownRecord > $totalRows)
			$lastShownRecord = $totalRows;

		// If there is only 1 page for all the records in list, we don't need to go further
		// to sort out those first page, last page, pre and next pages, etc
		// we are not render those in to the paginator.
		if($totalPages === 1){
			return new ArrayData(array(
				'OnlyOnePage' => true,
				'FirstShownRecord' => $firstShownRecord,
				'LastShownRecord' => $lastShownRecord,
				'NumRecords' => $totalRows,
				'NumPages' => $totalPages
			));
		} else {
			// First page button
			$firstPage = new GridField_FormAction($gridField, 'pagination_first', 'First', 'paginate', 1);
			$firstPage->addExtraClass('btn btn-secondary btn--no-text font-icon-angle-double-left ss-gridfield-firstpage');
			if($state->currentPage == 1)
				$firstPage = $firstPage->performDisabledTransformation();

			// Previous page button
			$previousPageNum = $state->currentPage <= 1 ? 1 : $state->currentPage - 1;
			$previousPage = new GridField_FormAction($gridField, 'pagination_prev', 'Previous',
				'paginate', $previousPageNum);
			$previousPage->addExtraClass('btn btn-secondary btn--no-text font-icon-angle-left ss-gridfield-previouspage');
			if($state->currentPage == 1)
				$previousPage = $previousPage->performDisabledTransformation();

			// Next page button
			$nextPageNum = $state->currentPage >= $totalPages ? $totalPages : $state->currentPage + 1;
			$nextPage = new GridField_FormAction($gridField, 'pagination_next', 'Next',
				'paginate', $nextPageNum);
			$nextPage->addExtraClass('btn btn-secondary btn--no-text font-icon-angle-right ss-gridfield-nextpage');
			if($state->currentPage == $totalPages)
				$nextPage = $nextPage->performDisabledTransformation();

			// Last page button
			$lastPage = new GridField_FormAction($gridField, 'pagination_last', 'Last', 'paginate', $totalPages);
			$lastPage->addExtraClass('btn btn-secondary btn--no-text font-icon-angle-double-right ss-gridfield-lastpage');
			if($state->currentPage == $totalPages)
				$lastPage = $lastPage->performDisabledTransformation();

			// Render in template
			return new ArrayData(array(
				'OnlyOnePage' => false,
				'FirstPage' => $firstPage,
				'PreviousPage' => $previousPage,
				'CurrentPageNum' => $state->currentPage,
				'NumPages' => $totalPages,
				'NextPage' => $nextPage,
				'LastPage' => $lastPage,
				'FirstShownRecord' => $firstShownRecord,
				'LastShownRecord' => $lastShownRecord,
				'NumRecords' => $totalRows
			));
		}
	}

	/**
	 *
	 * @param GridField $gridField
	 * @return array
	 */
	public function getHTMLFragments($gridField) {
		$forTemplate = $this->getTemplateParameters($gridField);
		if(!$forTemplate) {
			return null;
		}
		$template = SSViewer::get_templates_by_class($this, '_Row', __CLASS__);
		return array(
			'footer' => $forTemplate->renderWith(
				$template,
				array('Colspan' => count($gridField->getColumns()))
			)
		);
	}

	/**
	 * @param int $num
	 * @return $this
	 */
	public function setItemsPerPage($num) {
		$this->itemsPerPage = $num;
		return $this;
	}

	/**
	 * @return Int
	 */
	public function getItemsPerPage() {
		return $this->itemsPerPage;
	}

}