fix: calendar day-of-week offset off by one, nav double-jump, race conditions

- Fix Jalali/Gregorian/Hijri day-of-week startOffset formulas
  (dow returns 0=Sat, not 0=Sun as the old comment claimed)
- Fix calendar and export month picker navigation jumping 2 months
  (navMonth buttons already have pre-computed values; handlers
  were decrementing/incrementing them again)
- Fix GetOrCreateUser/GetOrCreateDay race condition with INSERT OR IGNORE
- Add month/day bounds validation in handleEditMsg to prevent panic

internal/bot/dateutil.go

@@ -180,7 +180,7 @@ func gregorianToHijri(gy, gm, gd int) (int, int, int) {
 }
 
 func dayOfWeekGregorian(gy, gm, gd int) int {
-	// Zeller-like: returns 0=Sun,1=Mon,...,6=Sat
+	// Zeller-like: returns 0=Sat,1=Sun,2=Mon,3=Tue,4=Wed,5=Thu,6=Fri
 	if gm < 3 {
 		gm += 12
 		gy--
@@ -211,7 +211,7 @@ func buildCalendarMonth(cal string, year, month int) calMonth {
 
 		gy, gm, gd := jalaliToGregorian(year, month, 1)
 		dow := dayOfWeekGregorian(gy, gm, gd)
-		startOffset := (dow + 1) % 7
+		startOffset := dow
 
 		var days []calDay
 		for i := 0; i < startOffset; i++ {
@@ -234,7 +234,7 @@ func buildCalendarMonth(cal string, year, month int) calMonth {
 
 		gy, gm, gd := hijriToGregorian(year, month, 1)
 		dow := dayOfWeekGregorian(gy, gm, gd)
-		startOffset := (dow + 6) % 7
+		startOffset := (dow + 5) % 7
 
 		var days []calDay
 		for i := 0; i < startOffset; i++ {
@@ -255,7 +255,7 @@ func buildCalendarMonth(cal string, year, month int) calMonth {
 	totalDays = monthLenGreg(year, month)
 
 	dow := dayOfWeekGregorian(year, month, 1)
-	startOffset := (dow + 6) % 7
+	startOffset := (dow + 5) % 7
 
 	var days []calDay
 	for i := 0; i < startOffset; i++ {
@@ -290,6 +290,33 @@ func formatDateForCalendar(date, calType string) string {
 	}
 }
 
+// userDateToGregorian converts a YYYY-MM-DD string in the user's calendar
+// to the corresponding Gregorian YYYY-MM-DD string.
+func userDateToGregorian(dateStr, cal string) string {
+	y, m, d := parseGregorianDateKey(dateStr)
+	switch cal {
+	case "jalali":
+		y, m, d = jalaliToGregorian(y, m, d)
+	case "hijri":
+		y, m, d = hijriToGregorian(y, m, d)
+	}
+	return fmt.Sprintf("%04d-%02d-%02d", y, m, d)
+}
+
+// userYearMonthToGregorian converts a (year, month) in the user's calendar
+// to the corresponding Gregorian (year, month). The day is assumed to be 1.
+func userYearMonthToGregorian(year, month int, cal string) (int, int) {
+	switch cal {
+	case "jalali":
+		gy, gm, _ := jalaliToGregorian(year, month, 1)
+		return gy, gm
+	case "hijri":
+		gy, gm, _ := hijriToGregorian(year, month, 1)
+		return gy, gm
+	}
+	return year, month
+}
+
 // monthGregorianRange returns the Gregorian start and end date strings
 // for a given calendar month (cal=gregorian|jalali|hijri).
 func monthGregorianRange(cal string, year, month int) (start, end string) {

internal/bot/handlers.go

@@ -403,7 +403,7 @@ func (h *Handler) handleHelp(msg *tgbotapi.Message) {
 /worktype - Select work type
 /dayoff - Toggle day off
 /report - Show today report
-/export - Export monthly report (Excel)
+/export [YYYY-MM] - Export monthly report (current month if omitted)
 /history - View calendar history
 /edit YYYY-MM-DD - Edit a specific day
 /reporttoggle - Enable/disable auto report
@@ -411,6 +411,7 @@ func (h *Handler) handleHelp(msg *tgbotapi.Message) {
 /setaccent - Select accent color
 /settimezone <name> - Set your timezone (e.g. Asia/Tehran)
 
+Dates use your calendar type (Gregorian/Jalali/Hijri).
 Buttons on the main menu also work.`
 	h.sendText(msg.Chat.ID, text)
 }
@@ -708,11 +709,16 @@ func (h *Handler) historyCallback(chatID int64, msgID int, callbackID string) {
 func (h *Handler) handleEditMsg(msg *tgbotapi.Message) {
 	date := msg.CommandArguments()
 	if date == "" {
-		h.sendText(msg.Chat.ID, "Usage: /edit YYYY-MM-DD")
+		h.sendText(msg.Chat.ID, "Usage: /edit YYYY-MM-DD (your calendar type)")
 		return
 	}
 	if len(date) != 10 || date[4] != '-' || date[7] != '-' {
-		h.sendText(msg.Chat.ID, "Invalid date. Use: /edit YYYY-MM-DD")
+		h.sendText(msg.Chat.ID, "Invalid date. Use: /edit YYYY-MM-DD (your calendar type)")
+		return
+	}
+	_, m, d := parseGregorianDateKey(date)
+	if m < 1 || m > 12 || d < 1 || d > 31 {
+		h.sendText(msg.Chat.ID, "Invalid date.")
 		return
 	}
 	user, err := h.getOrCreateUser(msg.Chat.ID)
@@ -721,6 +727,7 @@ func (h *Handler) handleEditMsg(msg *tgbotapi.Message) {
 		return
 	}
 	loc, _ := time.LoadLocation(user.Timezone)
+	date = userDateToGregorian(date, user.Calendar)
 	h.sendDayView(msg.Chat.ID, 0, user, date, loc, true)
 }
 
@@ -743,21 +750,11 @@ func (h *Handler) handleHistoryCallback(chatID int64, msgID int, callbackID, dat
 
 	// cal_prev_YYYY_M
 	if n, _ := fmt.Sscanf(data, "cal_prev_%d_%d", &y, &m); n == 2 {
-		m--
-		if m < 1 {
-			m = 12
-			y--
-		}
 		h.editCalendar(chatID, msgID, y, m)
 		return
 	}
 	// cal_next_YYYY_M
 	if n, _ := fmt.Sscanf(data, "cal_next_%d_%d", &y, &m); n == 2 {
-		m++
-		if m > 12 {
-			m = 1
-			y++
-		}
 		h.editCalendar(chatID, msgID, y, m)
 		return
 	}
@@ -1189,14 +1186,45 @@ func (h *Handler) handleExport(msg *tgbotapi.Message) {
 	}
 	loc, _ := time.LoadLocation(user.Timezone)
 	now := time.Now().In(loc)
-	cy, cm := now.Year(), int(now.Month())
-	switch user.Calendar {
-	case "jalali":
-		cy, cm, _ = gregorianToJalali(cy, cm, now.Day())
-	case "hijri":
-		cy, cm, _ = gregorianToHijri(cy, cm, now.Day())
+
+	// Parse optional YYYY-MM argument (in user's calendar)
+	gy, gm := now.Year(), int(now.Month())
+	if len(msg.Text) > 7 {
+		if n, _ := fmt.Sscanf(msg.Text[7:], "%d-%d", &gy, &gm); n == 2 {
+			if gy < 0 || gm < 1 || gm > 12 {
+				h.sendText(msg.Chat.ID, "Invalid date. Use: /export YYYY-MM")
+				return
+			}
+			gy, gm = userYearMonthToGregorian(gy, gm, user.Calendar)
+		}
+	}
+
+	h.sendExportDirect(msg.Chat.ID, user, gy, gm)
+}
+
+func (h *Handler) sendExportDirect(chatID int64, user *db.User, gy, gm int) {
+	// Check if clocked in
+	last, err := h.DB.GetLastEvent(user.ID)
+	if err == nil && last != nil && last.EventType == "in" {
+		h.sendText(chatID, "You are currently clocked in. Please clock out first, then try again.")
+		return
+	}
+
+	slog.Info("export", "user_id", user.ID, "year", gy, "month", gm)
+	data, err := GenerateMonthlyReport(h.DB, user.ID, user.Timezone, user.ExportAccent, user.Calendar, gy, time.Month(gm))
+	if err != nil {
+		slog.Error("generate report", "error", err)
+		h.sendText(chatID, "Error generating report")
+		return
+	}
+	slog.Info("report generated", "bytes", len(data))
+	doc := tgbotapi.NewDocument(chatID, tgbotapi.FileBytes{
+		Name:  fmt.Sprintf("worktime_%s.xlsx", fmt.Sprintf("%04d_%02d", gy, gm)),
+		Bytes: data,
+	})
+	if _, err := h.Bot.Send(doc); err != nil {
+		slog.Error("send document", "error", err)
 	}
-	h.sendExportMonthPicker(msg.Chat.ID, 0, cy, cm, user)
 }
 
 func (h *Handler) exportCallback(chatID int64, msgID int, callbackID string) {
@@ -1262,20 +1290,10 @@ func (h *Handler) handleExportCallback(chatID int64, msgID int, callbackID, data
 	var y, m int
 
 	if n, _ := fmt.Sscanf(data, "exp_prev_%d_%d", &y, &m); n == 2 {
-		m--
-		if m < 1 {
-			m = 12
-			y--
-		}
 		h.editExportMonthPicker(chatID, msgID, y, m, user)
 		return
 	}
 	if n, _ := fmt.Sscanf(data, "exp_next_%d_%d", &y, &m); n == 2 {
-		m++
-		if m > 12 {
-			m = 1
-			y++
-		}
 		h.editExportMonthPicker(chatID, msgID, y, m, user)
 		return
 	}

internal/db/store.go

@@ -289,15 +289,8 @@ func migrateSettings(db *sql.DB) {
 }
 
 func (s *Store) GetOrCreateUser(chatID int64) (*User, error) {
-	user, err := s.GetUserByChatID(chatID)
-	if err == nil {
-		return user, nil
-	}
-	if err != sql.ErrNoRows {
-		return nil, err
-	}
-	_, err = s.db.Exec(
-		"INSERT INTO users (chat_id) VALUES (?)",
+	_, err := s.db.Exec(
+		"INSERT OR IGNORE INTO users (chat_id) VALUES (?)",
 		chatID,
 	)
 	if err != nil {
@@ -399,15 +392,8 @@ func (s *Store) GetWorkType(id int64) (*WorkType, error) {
 }
 
 func (s *Store) GetOrCreateDay(userID int64, date string) (*Day, error) {
-	day, err := s.GetDay(userID, date)
-	if err == nil {
-		return day, nil
-	}
-	if err != sql.ErrNoRows {
-		return nil, err
-	}
-	_, err = s.db.Exec(
-		"INSERT INTO days (user_id, date) VALUES (?, ?)",
+	_, err := s.db.Exec(
+		"INSERT OR IGNORE INTO days (user_id, date) VALUES (?, ?)",
 		userID, date,
 	)
 	if err != nil {