package main

import "time"

type YMD uint32
type YM uint32

// YYYYMM max 6 digits.
// YYYYMMDD max 8 digits.  int32.
//
// Store dates as uint32
// YYYYMMDD
//
// So: Jan 21, 2022 => 20220121
//     Jan 2022     => 202201
//

func (d *YMD) Year() int {
	return int(*d) / 10000
}

func (d *YMD) Month() int {
	return (int(*d) / 100) % 100
}

func (d *YMD) Day() int {
	return int(*d) % 100
}

func (d *YMD) YM() YM {
	return YM(int(*d) / 100)
}

// Set day - does no validation
func (d *YMD) SetDay(day int) {
	var i int = int(*d)
	i -= (i % 100)
	i += day
	*d = YMD(i)
}

// Make the first of the month
func (d *YMD) First() {
	d.SetDay(1)
}

// Make end of month
func (d *YMD) Last() {
	var value int = int(*d)
	// time.Date will normalize the date for us.
	// set Month +1, and day to 0 (gives us last day of previous month)
	var lastDay time.Time = time.Date(value/10000,
		time.Month((value/100)%100)+1,
		0, 4, 3, 2, 1, time.Local)
	*d = YMD(lastDay.Year()*10000 +
		int(lastDay.Month())*100 + lastDay.Day())
}

func NewYMD(year, month, day int) YMD {
	return YMD(year*10000 + month*100 + day)
}

func (d *YMD) YMD() (int, int, int) {
	var i int = int(*d)
	return i / 10000, (i / 100) % 100, i % 100
}

func (d *YMD) Time() time.Time {
	var value int = int(*d)
	return time.Date(value/10000,
		time.Month((value/100)%100),
		value%100, 2, 2, 2, 0, time.Local)
}

// Convert time.Time to DBDate
func NewYMDFromTime(point time.Time) YMD {
	return YMD(point.Year()*10000 +
		int(point.Month())*100 + point.Day())
}

// Convert DBDate to time.Time
func ToTime(point YMD) time.Time {
	// I'm not sure about hours, minutes, seconds.

	var value int = int(point)
	var result time.Time = time.Date(value/10000,
		time.Month((value/100)%100),
		value%100, 2, 2, 2, 0, time.Local)
	return result
}

func NewYM(year, month int) YM {
	return YM(year*100 + month)
}

func (d *YM) Year() int {
	return int(*d) / 100
}

func (d *YM) Month() int {
	return int(*d) % 100
}

func (d *YM) YMD() YMD {
	return YMD(int(*d)*100 + 1)
}