package utils

import (
	"fmt"
	"github.com/gogf/gf/v2/errors/gcode"
	"github.com/gogf/gf/v2/errors/gerror"
	"reflect"
	"time"
)

// ValidStructPtr 验证是否为结构体指针
func ValidStructPtr(req any) (err error) {
	//验证请求参数必须为指针
	var (
		reflectValue reflect.Value
		reflectKind  reflect.Kind
	)
	if v, ok := req.(reflect.Value); ok {
		reflectValue = v
	} else {
		reflectValue = reflect.ValueOf(req)
	}

	reflectKind = reflectValue.Kind()
	if reflectKind != reflect.Ptr {
		err = gerror.NewCode(gcode.CodeInvalidParameter, `the parameter "req" for function Find should type of *struct/*[]struct`)
	}
	return
}

// GetMonthToday 获取N个月前的某日
func GetMonthToday(t time.Time, month int) time.Time {
	// today
	fmt.Printf("today: [%s]\n", t)
	// 判断天数范围 小于等于28天的计算,覆盖大多数情况
	if t.Day() <= 28 {
		return t.AddDate(0, -month, 0)
	}
	// 月份的天数数组
	monthDay := [13]int{0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}
	// 计算目标所在日期
	target := t.AddDate(0, 0, 1-t.Day()).AddDate(0, -month, 0)
	// 计算当月最大天数
	targetDay := monthDay[target.Month()]
	// 计算闰年
	if target.Month() == time.February && (target.Year()%400 == 0 || (target.Year()%100 != 0 && target.Year()%4 == 0)) {
		targetDay++
	}
	if t.Day() > targetDay {
		return target.AddDate(0, 0, targetDay-1)
	}
	return target.AddDate(0, 0, t.Day()-1)
}