<?php
    
    class Page{
        protected $number;//每页显示多少条数据
        protected $totalCount;//一共有多少条数据
        protected $page;//当前页
        protected $totalPage;//总页数
        protected $url;

        public function __construct($number,$totalCount){
            $this->number = $number;
            $this->totalCount = $totalCount;
            //得到总页数
            $this->totalPage = $this->getTotalPage();
            //得到当前页数
            $this->page = $this->getPage();
            //得到url
            $this->url = $this->getUrl();
            
        }
        protected function getTotalPage(){
            return ceil($this->totalCount/$this->number);
        }
        protected function getPage(){
            if(empty($_GET['page'])){
                $page  = 1;
            }else if($_GET['page'] > $this->totalPage){
                $page = $this->totalPage;
            }else{
                $page = $_GET['page'];
            }
            return $page;
        }

        protected function getUrl(){
            $scheme = $_SERVER['REQUEST_SCHEME'];//协议
            $host = $_SERVER['SERVER_NAME'];//主机名
            $port = $_SERVER['SERVER_PORT'];//端口号
            $uri = $_SERVER['REQUEST_URI'];//得到路径和请求字符串
            //清除原来page的参数
            $uriArray = parse_url($uri);
            $path = $uriArray['path'];
            if(!empty($uriArray['query'])){
                //将请求字符串变成关联数组
                parse_str($uriArray['query'],$arr);
                //清除关联数组中的page键值对
                unset($arr['page']);
                //将剩下额参数拼接为请求字符串
                $query = http_build_query($arr);
                //再将请求字符串拼接到路径后面
                if($query != ''){
                    $path = $path.'?'.$query;
                }
            }
            return $scheme.'://'.$host.':'.$port.$path;


        }

        protected function setUrl($str){
            if(strstr($this->url,'?')){
                $url = $this->url.'&'.$str;
            }else{
                $url = $this->url.'?'.$str;
            }   
            return $url;
        }

        public function allUrl(){
            return [
            'first' => $this->first(),
            'prev' => $this->prev(),
            'next' => $this->next(),
            'end' => $this->end(),

            ];
        }
        public function first(){

            return $this->setUrl('page=1');
        }

        public function end(){
            return $this->setUrl('page='.$this->totalPage);
        }
        public function prev(){

            if($this->page -1 < 1){
                $page = 1;
            }else{
                $page = $this->page -1;
            }
            return $this->setUrl('page='.$page);
        }
        public function next(){
            if($this->page+1 > $this->totalPage){
                $page = $this->totalPage;
            }else{
                $page= $this->page +1;
            }
            return $this->setUrl('page='.$page);

        }

        public function limit(){
            $offset= ($this->page -1)*$this->number;
            return $offset.','.$this->number;

        }

    }