package service

import (
	"context"
	"errors"
	"fmt"
	"time"

	"gorm.io/gorm"

	smokemodel "wx_service/internal/smoke/model"
)

type SmokeNextService struct {
	db *gorm.DB
}

func NewSmokeNextService(db *gorm.DB) *SmokeNextService {
	return &SmokeNextService{db: db}
}

type NextSmokeSuggestion struct {
	LastSmokeAt         *time.Time `json:"last_smoke_at,omitempty"`
	NextSmokeAt         *time.Time `json:"next_smoke_at,omitempty"`
	BaseIntervalMinutes int        `json:"base_interval_minutes"`
	IntervalMinutes     int        `json:"interval_minutes"`
	Stage               int        `json:"stage"`
	Resisted7d          int        `json:"resisted_7d"`
	SleepAdjusted       bool       `json:"sleep_adjusted"`
	Algorithm           string     `json:"algorithm"`
	AsOf                string     `json:"as_of"`
}

// GetDefaultSuggestion 返回“未使用 AI 时”的默认下次抽烟时间建议（阶梯式延时算法）。
func (s *SmokeNextService) GetDefaultSuggestion(ctx context.Context, uid int, asOf time.Time, planDate time.Time, profileView SmokeProfileView) (NextSmokeSuggestion, error) {
	now := asOf.In(time.Local)
	planDay := dateOnly(planDate)
	today := dateOnly(now)

	base := profileView.BaselineIntervalMinute
	if base <= 0 {
		base = 60
	}

	lastSmokeAt, ok, err := s.loadLastActualSmokeAt(ctx, uid)
	if err != nil {
		return NextSmokeSuggestion{}, err
	}
	if !ok {
		lastCopy := now
		lastSmokeAt = &lastCopy
	} else if lastSmokeAt.After(now) {
		clamped := now
		lastSmokeAt = &clamped
	}

	resisted, err := s.countResistedLastDays(ctx, uid, 7)
	if err != nil {
		return NextSmokeSuggestion{}, err
	}

	stage := resisted / 5
	if stage > 12 {
		stage = 12
	}

	interval := base + stage*5
	if interval < 5 {
		interval = 5
	}
	if interval > 240 {
		interval = 240
	}

	intervalDuration := time.Duration(interval) * time.Minute
	next := lastSmokeAt.Add(intervalDuration)

	if !planDay.After(today) && next.Before(now) {
		if intervalDuration <= 0 {
			next = now
		} else {
			elapsed := now.Sub(*lastSmokeAt)
			missed := int(elapsed / intervalDuration)
			if missed < 0 {
				missed = 0
			}
			next = lastSmokeAt.Add(time.Duration(missed+1) * intervalDuration)
		}
	}

	sleepAdjusted := false

	var wakeUp, sleep string
	if profileView.Profile != nil {
		wakeUp = profileView.Profile.WakeUpTime
		sleep = profileView.Profile.SleepTime
	}

	// 如果是“生成某一天的计划”（例如明天），默认不早于该日的起床时间（若未配置则使用 07:00）。
	if planDay.After(today) {
		minNotBefore := time.Date(planDay.Year(), planDay.Month(), planDay.Day(), 7, 0, 0, 0, time.Local)
		if wakeUp != "" {
			if m, err := parseHHMMToMinutes(wakeUp); err == nil {
				minNotBefore = time.Date(planDay.Year(), planDay.Month(), planDay.Day(), m/60, m%60, 0, 0, time.Local)
			}
		}
		if next.Before(minNotBefore) {
			next = minNotBefore
		}
	}

	if wakeUp != "" && sleep != "" {
		adjusted, ok, err := adjustToWakeIfInSleep(next, wakeUp, sleep)
		if err != nil && !errors.Is(err, ErrSmokeProfileInvalidTime) {
			return NextSmokeSuggestion{}, err
		}
		if ok {
			next = adjusted
			sleepAdjusted = true
		}
	}

	out := NextSmokeSuggestion{
		BaseIntervalMinutes: base,
		IntervalMinutes:     interval,
		Stage:               stage,
		Resisted7d:          resisted,
		SleepAdjusted:       sleepAdjusted,
		Algorithm:           "staircase_delay_v1",
		AsOf:                now.Format(time.RFC3339),
	}
	out.LastSmokeAt = lastSmokeAt
	if !next.IsZero() {
		t := next
		out.NextSmokeAt = &t
	}
	return out, nil
}

func (s *SmokeNextService) loadLastActualSmokeAt(ctx context.Context, uid int) (*time.Time, bool, error) {
	var last smokemodel.SmokeLog
	err := s.db.WithContext(ctx).
		Where("uid = ? AND (deletetime IS NULL OR deletetime = 0)", uid).
		Where("num > 0").
		Order("COALESCE(smoke_at, FROM_UNIXTIME(createtime), smoke_time) DESC").
		Order("id DESC").
		Limit(1).
		Take(&last).Error
	if err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			return nil, false, nil
		}
		return nil, false, fmt.Errorf("load last smoke log: %w", err)
	}
	t, ok := lastEventTime(last)
	if !ok {
		return nil, false, nil
	}
	return &t, true, nil
}

func (s *SmokeNextService) countResistedLastDays(ctx context.Context, uid int, days int) (int, error) {
	if days <= 0 {
		days = 7
	}
	end := dateOnly(time.Now().In(time.Local))
	start := end.AddDate(0, 0, -(days - 1))

	var count int64
	if err := s.db.WithContext(ctx).
		Model(&smokemodel.SmokeLog{}).
		Where("uid = ? AND (deletetime IS NULL OR deletetime = 0)", uid).
		Where("num = 0").
		Where("smoke_time BETWEEN ? AND ?", start.Format("2006-01-02"), end.Format("2006-01-02")).
		Count(&count).Error; err != nil {
		return 0, fmt.Errorf("count resisted logs: %w", err)
	}
	return int(count), nil
}

func adjustToWakeIfInSleep(t time.Time, wakeUpHHMM, sleepHHMM string) (time.Time, bool, error) {
	wakeMin, err := parseHHMMToMinutes(wakeUpHHMM)
	if err != nil {
		return time.Time{}, false, ErrSmokeProfileInvalidTime
	}
	sleepMin, err := parseHHMMToMinutes(sleepHHMM)
	if err != nil {
		return time.Time{}, false, ErrSmokeProfileInvalidTime
	}
	if wakeMin == sleepMin {
		return t, false, nil
	}

	minutes := t.Hour()*60 + t.Minute()
	inSleep := isInSleepWindow(minutes, wakeMin, sleepMin)
	if !inSleep {
		return t, false, nil
	}

	wakeToday := time.Date(t.Year(), t.Month(), t.Day(), wakeMin/60, wakeMin%60, 0, 0, t.Location())
	if !wakeToday.After(t) {
		wakeToday = wakeToday.Add(24 * time.Hour)
	}
	return wakeToday, true, nil
}

func isInSleepWindow(minuteOfDay int, wakeMin int, sleepMin int) bool {
	if minuteOfDay < 0 {
		minuteOfDay = 0
	}
	if minuteOfDay >= 24*60 {
		minuteOfDay = 24*60 - 1
	}
	// wake < sleep: awake=[wake,sleep), sleep=else
	if wakeMin < sleepMin {
		return minuteOfDay < wakeMin || minuteOfDay >= sleepMin
	}
	// wake > sleep: awake 跨午夜，sleep=[sleep,wake)
	return minuteOfDay >= sleepMin && minuteOfDay < wakeMin
}