locale_ja.go

package strftime

import (
	"fmt"
	"strconv"
	"time"

	"golang.org/x/text/language"
)

var japaneseLocale = &strftimeLocaleInfo{
	tag:      language.Japanese,
	DTfmt:    "%Y年%m月%d日 %H時%M分%S秒",
	Dfmt:     "%Y年%m月%d日",
	Tfmt:     "%H時%M分%S秒",
	Tfmt12:   "%p%I時%M分%S秒",
	DTfmtEra: "%EY%m月%d日 %H時%M分%S秒",
	DfmtEra:  "%EY%m月%d日",
	AmPm:     [...]string{"午前", "午後"},
	Eyear:    strftimeJapaneseEra,
	Oprint:   strftimeJapaneseDigit,

	AbDay:   [...]string{"日", "月", "火", "水", "木", "金", "土"},
	Day:     [...]string{"日曜日", "月曜日", "火曜日", "水曜日", "木曜日", "金曜日", "土曜日"},
	AbMonth: [...]string{" 1月", " 2月", " 3月", " 4月", " 5月", " 6月", " 7月", " 8月", " 9月", "10月", "11月", "12月"},
	Month:   [...]string{"1月", "2月", "3月", "4月", "5月", "6月", "7月", "8月", "9月", "10月", "11月", "12月"},
}

// TODO need something more generic for era
func strftimeJapaneseEra(t time.Time, r byte) string {
	era := "西暦"
	y, m, d := t.Date()

	switch {
	case (y > 2019) || ((y == 2019) && (m > 5)) || ((y == 2019) && (m == 5) && (d >= 1)):
		// Reiwa era
		era = "令和"
		y -= 2018
	case (y > 1989) || ((y == 1989) && (m > 1)) || ((y == 1989) && (m == 1) && (d >= 8)):
		// Heisei era
		era = "平成"
		y -= 1988
	case (y > 1926) || ((y == 1926) && (m > 12)) || ((y == 1926) && (m == 12) && (d >= 25)):
		// Showa era
		era = "昭和"
		y -= 1925
	case (y > 1912) || ((y == 1912) && (m > 7)) || ((y == 1912) && (m == 7) && (d >= 30)):
		// Taisho era
		era = "大正"
		y -= 1911
	case (y > 1868) || ((y == 1868) && (m > 10)) || ((y == 1868) && (m == 10) && (d >= 23)):
		// Meiji era
		era = "明治"
		y -= 1867
	}

	switch r {
	case 'C':
		return era
	case 'y':
		return strconv.FormatInt(int64(y), 10)
	case 'Y':
		if y == 1 {
			// first year of a given era is called "Gannen"
			return era + "元年"
		} else {
			return fmt.Sprintf("%s%d年", era, y)
		}
	}
	return fmt.Sprintf("%%E%c", r)
}

var jpDigits = [...]string{"〇", "一", "二", "三", "四", "五", "六", "七", "八", "九"}
var jpUnits = [...]struct {
	U string
	V uint
}{
	//{"兆", 1000000000000},
	{"億", 100000000},
	{"万", 10000},
	{"千", 1000},
	{"百", 100},
	{"十", 10},
}

// strftimeJapaneseDigit converts value v into string representation using unicode japanese characters.
// this will usually never receive a value over 100
func strftimeJapaneseDigit(b []byte, v int) []byte {
	if v < 0 {
		// generally, shouldn't happen
		v = -v
		b = append(b, '-')
	}
	u := uint(v)

	appd := false

	for _, unit := range jpUnits {
		if u >= unit.V {
			n := u / unit.V
			if n >= 10 {
				b = strftimeJapaneseDigit(b, int(n))
			} else if n > 1 {
				b = append(b, []byte(jpDigits[n])...)
			}
			b = append(b, []byte(unit.U)...)
			u = u - (n * unit.V)
			appd = true
		}
	}

	if u > 0 || !appd {
		b = append(b, []byte(jpDigits[u])...)
	}

	return b
}