<?php

/**
 * 日曆類
 * Class Calendar
 * @author fengzi
 * @date   2022-05-05 15:42
 */
class Calendar{
    protected $table = '';
    protected $year;
    protected $month;
    protected $day;
    protected $days;
    protected $currentDate;
    protected $space;
    protected $daysUp;
    protected $daysDown
 
;

    function __construct() {
        date_default_timezone_set('PRC');
        $this->year = isset($_GET['y']) ? $_GET['y'] : date('Y', time());   //變動的年份

        $this->month = isset($_GET['m']) ? $_GET['m'] : date('n', time());  //變動的月份
        if ( intval($this->month) > 12) {
            
 
$this->month = 1;
            $this->year++;
        }
        if ( intval($this->month) < 1) {
            $this->month = 12;
            $this->year--;
        }

        $this->day = date('j', time());     //當月第幾天
        $this->months = date('n', time());      //當前月份
        $this
 
->currentDate = $this->year." 年 ".$this->month." 月";
        $this->space = date('w', mktime(0, 0, 0, $this->month, 1, $this->year)); //每月的 1號 是星期幾
        $this->days = date("t",mktime(0,0,0,$this->month,1,$this->year));//得到給定的月份應有的天數
        $this->daysUp = date("t",mktime(0,0,0,$this->month-1,1,$this->year));//得到給定的月份上一個月的應有的天數
        $this->daysDown = date("t",mktime(0,0,0,$this->month+1,1,$this->year));//得到給定的月份下一個月的應有的天數
    }


    //拼接表
    protected function mosaicTable() {
        $this->table .= "<table><thead><tr align='center'><th colspan='7'>".$this->currentDate."</th></tr></thead>";
        $this->table .= "<tbody><tr>";
        $this->table .= "<td style='color:red;'>星期日</td>";
        $this->table .= "<td>星期一</td>";
        $this->table .= "<td>星期二</td>";
        $this->table .= "<td>星期三</td>";
        $this->table .= "<td>星期四</td>";
        $this->table .= "<td>星期五</td>";
        $this->table .= "<td style='color:red;'>星期六</td>";
        $this->table .= "</tr>";
    }


    //填日期
    protected function fillingDate() {
        $this->table .= "<tr>";

        //補足第一行前面淡色部分
        $up = $this->daysUp - $this->space + 1;
        if ( (int)$this->space !== 0 ) {
            for ($i=0; $i < $this->space; $i++) {
                $this->table .= "<td style='color:#aaa;'>$up</td>";
                $up++;
            }
        }

        $nums = $this->space;
        for ($i=1; $i <= $this->days; $i++) {
            if ( $nums % 7 != 0 ) {
                if ($i == (int)$this->day && $this->month == $this->months) {
                    $this->table .= "<td style='color:red;'>$i</td>";
                } else {
                    $this->table .= "<td>$i</td>";
                }
            } else {
                if ($i == (int)$this->day && $this->month == $this->months) {
                    $this->table .= "</tr><tr><td style='color:red;'>$i</td>";
                } else {
                    $this->table .= "</tr><tr><td>$i</td>";
                }
            }

            $nums++;
        }

        //補足最後一行後面淡色部分
        $down = 6 - ($nums % 7) + 1;
        if ( ($nums % 7) != 0 ) {
            for ($i=1; $i <= $this->daysDown; $i++) {
                if ( $i > $down) {
                    break;
                }
                $this->table .= "<td style='color:#aaa;'>$i</td>";
            }
        }

        $this->table .= "</tr></tbody></table>";
    }


    //增減月份
    protected function increaseAndDecreaseMonth() {
        $this->table .= "<h3><a href='?y=".($this->year)."&m=".($this->month-1)."'>上一月</a> ";
        $this->table .= "<a href='?y=".($this->year)."&m=".($this->month+1)."'>下一月</a></h3>";
    }


    //顯示日曆表
    public function showTable() {
        $this->mosaicTable();
        $this->fillingDate();
        $this->increaseAndDecreaseMonth();
        echo $this->table;
    }
}

$Calendar = new Calendar();
$Calendar->showTable();