init

internal/jalali/jalali.go

@@ -0,0 +1,109 @@
+package jalali
+
+import (
+	"fmt"
+	"time"
+)
+
+var MonthNames = [...]string{
+	"", "Farvardin", "Ordibehesht", "Khordad", "Tir", "Mordad", "Shahrivar",
+	"Mehr", "Aban", "Azar", "Dey", "Bahman", "Esfand",
+}
+
+var MonthNamesFA = [...]string{
+	"", "فروردین", "اردیبهشت", "خرداد", "تیر", "مرداد", "شهریور",
+	"مهر", "آبان", "آذر", "دی", "بهمن", "اسفند",
+}
+
+type Date struct {
+	Year  int
+	Month int
+	Day   int
+}
+
+func (d Date) String() string { return fmt.Sprintf("%04d-%02d-%02d", d.Year, d.Month, d.Day) }
+
+func IsLeap(year int) bool {
+	return ToGregorian(year+1, 1, 1).Sub(ToGregorian(year, 1, 1)) == 366*24*time.Hour
+}
+
+func DaysInMonth(year, month int) int {
+	if month <= 6 {
+		return 31
+	}
+	if month <= 11 {
+		return 30
+	}
+	if IsLeap(year) {
+		return 30
+	}
+	return 29
+}
+
+func FromTime(t time.Time) Date {
+	gy, gm, gd := t.Date()
+	jy, jm, jd := gregorianToJalali(gy, int(gm), gd)
+	return Date{jy, jm, jd}
+}
+
+func ToGregorian(jy, jm, jd int) time.Time {
+	gy, gm, gd := jalaliToGregorian(jy, jm, jd)
+	return time.Date(gy, time.Month(gm), gd, 0, 0, 0, 0, time.Local)
+}
+
+func gregorianToJalali(gy, gm, gd int) (int, int, int) {
+	gdm := [...]int{0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334}
+	gy2 := gy
+	if gm > 2 {
+		gy2++
+	}
+	days := 355666 + 365*gy + (gy2+3)/4 - (gy2+99)/100 + (gy2+399)/400 + gd + gdm[gm-1]
+	jy := -1595 + 33*(days/12053)
+	days %= 12053
+	jy += 4 * (days / 1461)
+	days %= 1461
+	if days > 365 {
+		jy += (days - 1) / 365
+		days = (days - 1) % 365
+	}
+	if days < 186 {
+		return jy, 1 + days/31, 1 + days%31
+	}
+	return jy, 7 + (days-186)/30, 1 + (days-186)%30
+}
+
+func jalaliToGregorian(jy, jm, jd int) (int, int, int) {
+	jy += 1595
+	days := -355668 + 365*jy + (jy/33)*8 + (jy%33+3)/4 + jd
+	if jm < 7 {
+		days += (jm - 1) * 31
+	} else {
+		days += (jm-7)*30 + 186
+	}
+	gy := 400 * (days / 146097)
+	days %= 146097
+	if days > 36524 {
+		gy += 100 * ((days - 1) / 36524)
+		days = (days - 1) % 36524
+		if days >= 365 {
+			days++
+		}
+	}
+	gy += 4 * (days / 1461)
+	days %= 1461
+	if days > 365 {
+		gy += (days - 1) / 365
+		days = (days - 1) % 365
+	}
+	gd := days + 1
+	sal := [...]int{0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}
+	if (gy%4 == 0 && gy%100 != 0) || gy%400 == 0 {
+		sal[2] = 29
+	}
+	gm := 1
+	for gm <= 12 && gd > sal[gm] {
+		gd -= sal[gm]
+		gm++
+	}
+	return gy, gm, gd
+}

internal/jalali/jalali_test.go

@@ -0,0 +1,36 @@
+package jalali
+
+import (
+	"testing"
+	"time"
+)
+
+func TestKnownDates(t *testing.T) {
+	tests := []struct {
+		gregorian string
+		jalali    Date
+	}{
+		{"2024-03-20", Date{1403, 1, 1}},
+		{"2025-03-21", Date{1404, 1, 1}},
+		{"2026-07-28", Date{1405, 5, 6}},
+	}
+	for _, tt := range tests {
+		g, _ := time.Parse("2006-01-02", tt.gregorian)
+		if got := FromTime(g); got != tt.jalali {
+			t.Errorf("%s: got %v, want %v", tt.gregorian, got, tt.jalali)
+		}
+		back := ToGregorian(tt.jalali.Year, tt.jalali.Month, tt.jalali.Day)
+		if got := back.Format("2006-01-02"); got != tt.gregorian {
+			t.Errorf("%v: got %s, want %s", tt.jalali, got, tt.gregorian)
+		}
+	}
+}
+
+func TestMonthLength(t *testing.T) {
+	if got := DaysInMonth(1399, 12); got != 30 {
+		t.Fatalf("leap Esfand: got %d, want 30", got)
+	}
+	if got := DaysInMonth(1400, 12); got != 29 {
+		t.Fatalf("regular Esfand: got %d, want 29", got)
+	}
+}