<?php


namespace Database;


use Snowflake\Abstracts\Component;
use Closure;
use Exception;

/**
 * Class Pagination
 * @package Database
 */
class Pagination extends Component
{

	/** @var ActiveQuery */
	private $activeQuery;

	/** @var int 从第几个开始查 */
	private $_offset = 0;

	/** @var int 每页数量 */
	private $_limit = 100;

	/** @var int 最大查询数量 */
	private $_max = 0;

	/** @var int 当前已查询数量 */
	private $_length = 0;

	/** @var Closure */
	private $_callback;

	/**
	 * PaginationIteration constructor.
	 * @param ActiveQuery $activeQuery
	 * @param array $config
	 */
	public function __construct(ActiveQuery $activeQuery, array $config = [])
	{
		parent::__construct($config);
		$this->activeQuery = $activeQuery;
	}


	/**
	 * @param Closure|array $callback
	 * @throws Exception
	 */
	public function setCallback($callback)
	{
		if (!is_callable($callback, true)) {
			throw new Exception('非法回调函数~');
		}
		$this->_callback = $callback;
	}


	/**
	 * @param int $number
	 */
	public function setOffset(int $number)
	{
		if ($number < 0) {
			$number = 0;
		}
		$this->_offset = $number;
	}


	/**
	 * @param int $number
	 */
	public function setLimit(int $number)
	{
		if ($number < 1) {
			$number = 100;
		} else if ($number > 5000) {
			$number = 5000;
		}
		$this->_limit = $number;
	}


	/**
	 * @param int $number
	 */
	public function setMax(int $number)
	{
		if ($number < 0) {
			return;
		}
		$this->_max = $number;
	}


	/**
	 * @param array $param
	 */
	public function search($param = [])
	{
		if ($this->_length >= $this->_max) {
			return;
		}
		[$length, $data] = $this->load();
		if ($param !== null) {
			call_user_func($this->_callback, $data, $param);
		} else {
			call_user_func($this->_callback, $data);
		}
		unset($data);
		if ($length < $this->_limit) {
			return;
		}
		$this->search($param);
	}


	/**
	 * @return array|Collection
	 */
	private function load()
	{
		if ($this->_length + $this->_limit > $this->_max) {
			$this->_limit = $this->_length + $this->_limit - $this->_max;
		}
		$data = $this->activeQuery->limit($this->_offset, $this->_limit)->get();
		$this->_offset += $this->_limit;
		$this->_length += $data->size();
		return [$data->size(), $data];
	}

}