<?php

namespace DbCopy;

class Cursor implements ICursor
{
	private $_closed;
	private $_buffer;
	private $_callback;

	public function __construct(callable $callback)
	{
		$this->_callback = $callback;
		$this->_closed = false;
		$this->_buffer = [];
	}

	public function closed(): bool
	{
		return $this->_closed;
	}

	public function get(): ?array
	{
		if ($this->_closed)
		{
			return null;
		}

		if (sizeof($this->_buffer) == 0)
		{
			// Fill more data
			$callback = $this->_callback;
			$this->_buffer = $callback();
			if (sizeof($this->_buffer) == 0)
			{
				$this->_closed = true;
				return null;
			}
		}

		return array_shift($this->_buffer);
	}
}