paliad/internal/services/holidays.go

// Package services holds the Paliad domain services backed by paliad.* tables.
package services

import (
	"context"
	"fmt"
	"sync"
	"time"

	"github.com/jmoiron/sqlx"
)

// Holiday is a non-working day. Mirrors paliad.holidays + the German federal
// hardcoded set used as a fallback when the DB lookup misses.
type Holiday struct {
	Date       time.Time
	Name       string
	IsVacation bool // part of court vacation period
	IsClosure  bool // single-day closure (public holiday)
}

// HolidayService loads and caches per-year holidays from paliad.holidays,
// merging with German federal holidays as a safety net.
//
// Concurrency: cache is guarded by a sync.Map of *sync.Once per year, which
// fixes audit §1.6 (the original KanzlAI version had an unprotected map).
// Each year is loaded at most once across all concurrent callers.
type HolidayService struct {
	db    *sqlx.DB
	cache sync.Map // year (int) → *yearEntry
}

type yearEntry struct {
	once     sync.Once
	holidays []Holiday
	err      error
}

// NewHolidayService creates a new holiday service.
func NewHolidayService(db *sqlx.DB) *HolidayService {
	return &HolidayService{db: db}
}

type dbHoliday struct {
	ID          int       `db:"id"`
	Date        time.Time `db:"date"`
	Name        string    `db:"name"`
	Country     string    `db:"country"`
	State       *string   `db:"state"`
	HolidayType string    `db:"holiday_type"`
}

// LoadHolidaysForYear loads holidays for a year (cached, race-safe).
func (s *HolidayService) LoadHolidaysForYear(year int) ([]Holiday, error) {
	v, _ := s.cache.LoadOrStore(year, &yearEntry{})
	entry := v.(*yearEntry)
	entry.once.Do(func() {
		entry.holidays, entry.err = s.loadYear(year)
	})
	return entry.holidays, entry.err
}

func (s *HolidayService) loadYear(year int) ([]Holiday, error) {
	holidays := make([]Holiday, 0, 30)

	if s.db != nil {
		var rows []dbHoliday
		err := s.db.SelectContext(context.Background(), &rows,
			`SELECT id, date, name, country, state, holiday_type
			   FROM paliad.holidays
			  WHERE EXTRACT(YEAR FROM date) = $1
			  ORDER BY date`, year)
		if err != nil {
			return nil, fmt.Errorf("load holidays for %d: %w", year, err)
		}
		for _, h := range rows {
			holidays = append(holidays, Holiday{
				Date:       h.Date,
				Name:       h.Name,
				IsClosure:  h.HolidayType == "public_holiday" || h.HolidayType == "closure",
				IsVacation: h.HolidayType == "vacation",
			})
		}
	}

	// Merge with German federal holidays so a misconfigured DB never silently
	// returns a working day for, say, Christmas.
	seen := make(map[string]bool, len(holidays))
	for _, h := range holidays {
		seen[h.Date.Format("2006-01-02")] = true
	}
	for _, h := range germanFederalHolidays(year) {
		key := h.Date.Format("2006-01-02")
		if !seen[key] {
			holidays = append(holidays, h)
		}
	}
	return holidays, nil
}

// IsHoliday returns the matching Holiday entry if the date is a holiday, else nil.
func (s *HolidayService) IsHoliday(date time.Time) *Holiday {
	holidays, err := s.LoadHolidaysForYear(date.Year())
	if err != nil {
		return nil
	}
	key := date.Format("2006-01-02")
	for i := range holidays {
		if holidays[i].Date.Format("2006-01-02") == key {
			return &holidays[i]
		}
	}
	return nil
}

// IsNonWorkingDay returns true on weekends or holidays.
func (s *HolidayService) IsNonWorkingDay(date time.Time) bool {
	if wd := date.Weekday(); wd == time.Saturday || wd == time.Sunday {
		return true
	}
	return s.IsHoliday(date) != nil
}

// AdjustForNonWorkingDays moves the date forward to the next working day.
// Returns adjusted date, the original (unmodified) date, and whether any
// adjustment was made. Capped at 30 forward iterations as a safety bound.
func (s *HolidayService) AdjustForNonWorkingDays(date time.Time) (adjusted time.Time, original time.Time, wasAdjusted bool) {
	original = date
	adjusted = date
	for i := 0; i < 30 && s.IsNonWorkingDay(adjusted); i++ {
		adjusted = adjusted.AddDate(0, 0, 1)
		wasAdjusted = true
	}
	return adjusted, original, wasAdjusted
}

// germanFederalHolidays returns the 11 holidays observed in all 16 German Länder.
func germanFederalHolidays(year int) []Holiday {
	em, ed := CalculateEasterSunday(year)
	easter := time.Date(year, time.Month(em), ed, 0, 0, 0, 0, time.UTC)
	return []Holiday{
		{Date: time.Date(year, time.January, 1, 0, 0, 0, 0, time.UTC), Name: "Neujahr", IsClosure: true},
		{Date: easter.AddDate(0, 0, -2), Name: "Karfreitag", IsClosure: true},
		{Date: easter, Name: "Ostersonntag", IsClosure: true},
		{Date: easter.AddDate(0, 0, 1), Name: "Ostermontag", IsClosure: true},
		{Date: time.Date(year, time.May, 1, 0, 0, 0, 0, time.UTC), Name: "Tag der Arbeit", IsClosure: true},
		{Date: easter.AddDate(0, 0, 39), Name: "Christi Himmelfahrt", IsClosure: true},
		{Date: easter.AddDate(0, 0, 49), Name: "Pfingstsonntag", IsClosure: true},
		{Date: easter.AddDate(0, 0, 50), Name: "Pfingstmontag", IsClosure: true},
		{Date: time.Date(year, time.October, 3, 0, 0, 0, 0, time.UTC), Name: "Tag der Deutschen Einheit", IsClosure: true},
		{Date: time.Date(year, time.December, 25, 0, 0, 0, 0, time.UTC), Name: "1. Weihnachtstag", IsClosure: true},
		{Date: time.Date(year, time.December, 26, 0, 0, 0, 0, time.UTC), Name: "2. Weihnachtstag", IsClosure: true},
	}
}

// CalculateEasterSunday computes Easter Sunday for the given year using the
// Anonymous Gregorian algorithm. Returns (month 1-12, day 1-31).
func CalculateEasterSunday(year int) (int, int) {
	a := year % 19
	b := year / 100
	c := year % 100
	d := b / 4
	e := b % 4
	f := (b + 8) / 25
	g := (b - f + 1) / 3
	h := (19*a + b - d - g + 15) % 30
	i := c / 4
	k := c % 4
	l := (32 + 2*e + 2*i - h - k) % 7
	m := (a + 11*h + 22*l) / 451
	month := (h + l - 7*m + 114) / 31
	day := ((h + l - 7*m + 114) % 31) + 1
	return month, day
}