package fds

import (
	"fmt"
)

type FdsDate struct {
	Year  int
	Month int
	Day   int
}

func NewFdsDate(raw []byte) (*FdsDate, error) {
	if len(raw) != 3 {
		return nil, fmt.Errorf("Must be three bytes")
	}

	if raw[1] == 0x00 || raw[1] > 0x12 || (raw[1] > 0x09 && raw[1] < 0x10) {
		return nil, fmt.Errorf("Invalid month: %02X", raw[1])
	}

	if raw[2] == 0x00 || raw[2] > 0x31 ||
	   (raw[2] > 0x09 && raw[2] < 0x10) ||
	   (raw[2] > 0x19 && raw[2] < 0x20) ||
	   (raw[2] > 0x29 && raw[2] < 0x30) {

		return nil, fmt.Errorf("Invalid day: %02X", raw[1])
	}

	return &FdsDate{
		Year:  bcdToDec(raw[0]),
		Month: bcdToDec(raw[1]),
		Day:   bcdToDec(raw[2]),
	}, nil
}

func bcdToDec(val byte) int {
	v := int(val)
	return (v>>4)*10 + (v&0x0F)
}

func (date *FdsDate) String() string {
	return fmt.Sprintf("Years: %04d/%04d/%04d Month: %d Day: %d",
		date.Year+1926,
		date.Year+1989,
		date.Year+1900,
		date.Month,
		date.Day,
	)
}

//func (date *FdsDate) Raw() []byte {
//}