package domain

// DayKind represents the kind of a closed day.
type DayKind string

const (
	DayKindWork     DayKind = "work"
	DayKindHoliday  DayKind = "holiday"
	DayKindVacation DayKind = "vacation"
	DayKindSick     DayKind = "sick"
)

func (k DayKind) Valid() bool {
	switch k {
	case DayKindWork, DayKindHoliday, DayKindVacation, DayKindSick:
		return true
	}
	return false
}

// Entry is a tracked time range within a single day.
type Entry struct {
	ID          string  `json:"id"`
	StartTime   int64   `json:"start_time"` // unix ms UTC
	EndTime     *int64  `json:"end_time"`   // nil while running
	AutoStopped bool    `json:"auto_stopped"`
	Note        string  `json:"note"`
	DayKey      string  `json:"day_key"` // YYYY-MM-DD in configured tz
	UpdatedAt   int64   `json:"updated_at"`
	DeletedAt   *int64  `json:"deleted_at,omitempty"`
}

// IsRunning returns true if the entry has no end time.
func (e *Entry) IsRunning() bool {
	return e.EndTime == nil
}

// DurationMs returns the duration in milliseconds. Returns 0 for running entries.
func (e *Entry) DurationMs() int64 {
	if e.EndTime == nil {
		return 0
	}
	return *e.EndTime - e.StartTime
}

// ClosedDay is the merged result of closing a day.
type ClosedDay struct {
	DayKey    string  `json:"day_key"`
	StartTime *int64  `json:"start_time"` // nil for non-work kinds
	EndTime   *int64  `json:"end_time"`   // nil for non-work kinds
	WorkedMs  int64   `json:"worked_ms"`
	Kind      DayKind `json:"kind"`
	ClosedAt  int64   `json:"closed_at"`
	UpdatedAt int64   `json:"updated_at"`
}

// ClosedWeek is the overtime/undertime snapshot for a week.
type ClosedWeek struct {
	WeekKey    string `json:"week_key"` // YYYY-Www ISO week
	ExpectedMs int64  `json:"expected_ms"`
	WorkedMs   int64  `json:"worked_ms"`
	DeltaMs    int64  `json:"delta_ms"` // worked - expected (signed)
	ClosedAt   int64  `json:"closed_at"`
	UpdatedAt  int64  `json:"updated_at"`
}

// Settings holds the effective configuration for a period.
type Settings struct {
	ID            int64   `json:"id"`
	EffectiveFrom string  `json:"effective_from"` // YYYY-MM-DD
	HoursPerWeek  float64 `json:"hours_per_week"`
	WorkdaysMask  int     `json:"workdays_mask"` // bits Mon=1..Sun=64
	Timezone      string  `json:"timezone"`
	CreatedAt     int64   `json:"created_at"`
}

// DailyExpectedMs returns the expected milliseconds for a single workday.
func (s *Settings) DailyExpectedMs() int64 {
	days := popcount(s.WorkdaysMask)
	if days == 0 {
		return 0
	}
	totalMs := int64(s.HoursPerWeek * 3_600_000)
	return totalMs / int64(days)
}

// IsWorkday returns true if the given weekday (0=Sunday..6=Saturday, time.Weekday) is a workday.
// We use Mon=bit0 .. Sun=bit6 internally.
func (s *Settings) IsWorkday(wd int) bool {
	// time.Weekday: Sunday=0, Monday=1, ..., Saturday=6
	// our mask:     Monday=bit0(1), Tuesday=bit1(2), ... Sunday=bit6(64)
	var bit int
	switch wd {
	case 0: // Sunday
		bit = 64
	case 1: // Monday
		bit = 1
	case 2:
		bit = 2
	case 3:
		bit = 4
	case 4:
		bit = 8
	case 5:
		bit = 16
	case 6: // Saturday
		bit = 32
	}
	return s.WorkdaysMask&bit != 0
}

func popcount(n int) int {
	count := 0
	for n != 0 {
		count += n & 1
		n >>= 1
	}
	return count
}