<?php namespace Illuminate\Pagination;

use Illuminate\Contracts\Pagination\LengthAwarePaginator as PaginatorContract;

class UrlWindow {

	/**
	 * The paginator implementation.
	 *
	 * @var \Illuminate\Contracts\Pagination\LengthAwarePaginator
	 */
	protected $paginator;

	/**
	 * Create a new URL window instance.
	 *
	 * @param  \Illuminate\Contracts\Pagination\LengthAwarePaginator  $paginator
	 * @return void
	 */
	public function __construct(PaginatorContract $paginator)
	{
		$this->paginator = $paginator;
	}

	/**
	 * Create a new URL window instance.
	 *
	 * @param  \Illuminate\Contracts\Pagination\LengthAwarePaginator  $paginator
	 * @param  int  $onEachSide
	 * @return array
	 */
	public static function make(PaginatorContract $paginator, $onEachSide = 3)
	{
		return (new static($paginator))->get($onEachSide);
	}

	/**
	 * Get the window of URLs to be shown.
	 *
	 * @param  int  $onEachSide
	 * @return array
	 */
	public function get($onEachSide = 3)
	{
		if ($this->paginator->lastPage() < ($onEachSide * 2) + 6)
		{
			return $this->getSmallSlider();
		}

		return $this->getUrlSlider($onEachSide);
	}

	/**
	 * Get the slider of URLs there are not enough pages to slide.
	 *
	 * @return array
	 */
	protected function getSmallSlider()
	{
		return [
			'first'  => $this->paginator->getUrlRange(1, $this->lastPage()),
			'slider' => null,
			'last'   => null,
		];
	}

	/**
	 * Create a URL slider links.
	 *
	 * @param  int  $onEachSide
	 * @return array
	 */
	protected function getUrlSlider($onEachSide)
	{
		$window = $onEachSide * 2;

		if ( ! $this->hasPages())
		{
			return [
				'first'  => null,
				'slider' => null,
				'last'   => null,
			];
		}

		// If the current page is very close to the beginning of the page range, we will
		// just render the beginning of the page range, followed by the last 2 of the
		// links in this list, since we will not have room to create a full slider.
		if ($this->currentPage() <= $window)
		{
			return $this->getSliderTooCloseToBeginning($window);
		}

		// If the current page is close to the ending of the page range we will just get
		// this first couple pages, followed by a larger window of these ending pages
		// since we're too close to the end of the list to create a full on slider.
		elseif ($this->currentPage() > ($this->lastPage() - $window))
		{
			return $this->getSliderTooCloseToEnding($window);
		}

		// If we have enough room on both sides of the current page to build a slider we
		// will surround it with both the beginning and ending caps, with this window
		// of pages in the middle providing a Google style sliding paginator setup.
		return $this->getFullSlider($onEachSide);
	}

	/**
	 * Get the slider of URLs when too close to beginning of window.
	 *
	 * @param  int  $window
	 * @return array
	 */
	protected function getSliderTooCloseToBeginning($window)
	{
		return [
			'first'  => $this->paginator->getUrlRange(1, $window + 2),
			'slider' => null,
			'last'   => $this->getFinish(),
		];
	}

	/**
	 * Get the slider of URLs when too close to ending of window.
	 *
	 * @param  int  $window
	 * @return array
	 */
	protected function getSliderTooCloseToEnding($window)
	{
		$last = $this->paginator->getUrlRange(
			$this->lastPage() - ($window + 2),
			$this->lastPage()
		);

		return [
			'first'  => $this->getStart(),
			'slider' => null,
			'last'   => $last,
		];
	}

	/**
	 * Get the slider of URLs when a full slider can be made.
	 *
	 * @param  int  $onEachSide
	 * @return array
	 */
	protected function getFullSlider($onEachSide)
	{
		return [
			'first'  => $this->getStart(),
			'slider' => $this->getAdjacentUrlRange($onEachSide),
			'last'   => $this->getFinish(),
		];
	}

	/**
	 * Get the page range for the current page window.
	 *
	 * @param  int  $onEachSide
	 * @return array
	 */
	public function getAdjacentUrlRange($onEachSide)
	{
		return $this->paginator->getUrlRange(
			$this->currentPage() - $onEachSide,
			$this->currentPage() + $onEachSide
		);
	}

	/**
	 * Get the starting URLs of a pagination slider.
	 *
	 * @return array
	 */
	public function getStart()
	{
		return $this->paginator->getUrlRange(1, 2);
	}

	/**
	 * Get the ending URLs of a pagination slider.
	 *
	 * @return array
	 */
	public function getFinish()
	{
		return $this->paginator->getUrlRange(
			$this->lastPage() - 1,
			$this->lastPage()
		);
	}

	/**
	 * Determine if the underlying paginator being presented has pages to show.
	 *
	 * @return bool
	 */
	public function hasPages()
	{
		return $this->paginator->lastPage() > 1;
	}

	/**
	 * Get the current page from the paginator.
	 *
	 * @return int
	 */
	protected function currentPage()
	{
		return $this->paginator->currentPage();
	}

	/**
	 * Get the last page from the paginator.
	 *
	 * @return int
	 */
	protected function lastPage()
	{
		return $this->paginator->lastPage();
	}

}
