package domain

import (
	"fmt"
	"sort"
	"time"
)

const (
	ScheduleTimezone = "Asia/Taipei"
	DefaultSweepHour = 6
	MaxSweepHours    = 6
	minSweepHour     = 0
	maxSweepHour     = 23
)

// RadarSchedule is the owner's automatic patrol timetable (Taipei local hours).
type RadarSchedule struct {
	OwnerUID  int64 `bson:"_id" json:"owner_uid"`
	Hours     []int `bson:"hours" json:"hours"`
	UpdatedAt int64 `bson:"updated_at" json:"updated_at"`
}

func TaipeiLocation() *time.Location {
	loc, err := time.LoadLocation(ScheduleTimezone)
	if err != nil {
		return time.FixedZone(ScheduleTimezone, 8*3600)
	}
	return loc
}

func DefaultSweepHours() []int {
	return []int{DefaultSweepHour}
}

func NormalizeSweepHours(hours []int) ([]int, error) {
	if len(hours) == 0 {
		return DefaultSweepHours(), nil
	}
	seen := map[int]bool{}
	out := make([]int, 0, len(hours))
	for _, h := range hours {
		if h < minSweepHour || h > maxSweepHour {
			return nil, fmt.Errorf("%w: hours must be 0–23 (got %d)", ErrValidation, h)
		}
		if seen[h] {
			continue
		}
		seen[h] = true
		out = append(out, h)
	}
	if len(out) == 0 {
		return DefaultSweepHours(), nil
	}
	if len(out) > MaxSweepHours {
		return nil, fmt.Errorf("%w: at most %d patrol hours", ErrValidation, MaxSweepHours)
	}
	sort.Ints(out)
	return out, nil
}

// SweepSlot is one due automatic patrol (Taipei calendar day + hour).
type SweepSlot struct {
	Date  string
	Hour  int
	RunAt int64
}

// DueSweepSlots returns selected hours that have already started today (Taipei)
// plus any earlier selected hours the same day, so a late worker still catches up.
func DueSweepSlots(now time.Time, hours []int) []SweepSlot {
	hours, err := NormalizeSweepHours(hours)
	if err != nil {
		hours = DefaultSweepHours()
	}
	loc := TaipeiLocation()
	local := now.In(loc)
	day := time.Date(local.Year(), local.Month(), local.Day(), 0, 0, 0, 0, loc)
	out := make([]SweepSlot, 0, len(hours))
	for _, h := range hours {
		slot := day.Add(time.Duration(h) * time.Hour)
		if local.Before(slot) {
			continue
		}
		out = append(out, SweepSlot{
			Date:  day.Format("2006-01-02"),
			Hour:  h,
			RunAt: slot.UnixNano(),
		})
	}
	return out
}