package polling

import (
	"context"
	"strconv"
	"time"

	"github.com/break/junhong_cmp_fiber/internal/model"
	"github.com/break/junhong_cmp_fiber/pkg/constants"
)

// shanghaiLocation 返回业务时区（上海）。
func shanghaiLocation() *time.Location {
	location, err := time.LoadLocation("Asia/Shanghai")
	if err != nil {
		return time.FixedZone("CST", 8*3600)
	}
	return location
}

// nextResetAt 返回 now 之后最近一次流量重置时刻：重置日当天 0 点（上海时区）。
func nextResetAt(now time.Time, resetDay int) time.Time {
	if resetDay < 1 || resetDay > 28 {
		resetDay = 1
	}
	local := now.In(shanghaiLocation())
	candidate := time.Date(local.Year(), local.Month(), resetDay, 0, 0, 0, 0, shanghaiLocation())
	if !candidate.After(local) {
		candidate = candidate.AddDate(0, 1, 0)
	}
	return candidate
}

// PreResetNextDue 计算重置日前加密后的流量检查下次到期时间。
//   - 当前在窗口 [reset-window, reset) 内：下次 = now + 窗口间隔；越过重置时刻则改为 reset - 收尾提前量，已过则按正常间隔；
//   - 当前在窗口前、按正常间隔算出的下次越过窗口起点：截断到窗口起点，保证按时进入窗口；
//   - 其余按正常间隔。
func PreResetNextDue(now time.Time, normalInterval, window, windowInterval time.Duration, reset time.Time, tail time.Duration) time.Time {
	normal := now.Add(normalInterval)
	windowStart := reset.Add(-window)
	if !now.Before(windowStart) && now.Before(reset) {
		next := now.Add(windowInterval)
		if next.Before(reset) {
			return next
		}
		last := reset.Add(-tail)
		if last.After(now) {
			return last
		}
		return normal
	}
	if now.Before(windowStart) && normal.After(windowStart) {
		return windowStart
	}
	return normal
}

// NextCheckAt 返回卡某检查类型的下次到期时间：流量检查在来源配置开启重置日前加密时按窗口规则计算，其余为 now + 间隔。
func (m *PollingConfigManager) NextCheckAt(ctx context.Context, card *model.IotCard, taskType string, info TaskTypeInterval, now time.Time) time.Time {
	normal := now.Add(time.Duration(info.Interval) * time.Second)
	if taskType != constants.TaskTypePollingCarddata || card == nil || info.ConfigID == 0 {
		return normal
	}
	cfg := m.configByID(info.ConfigID)
	if cfg == nil || cfg.PreResetWindow == nil || cfg.PreResetCarddataInterval == nil {
		return normal
	}
	resetDay := 1
	if m.tier != nil {
		resetDay = m.tier.ResetDay(ctx, card.CarrierID)
	}
	return PreResetNextDue(now, time.Duration(info.Interval)*time.Second,
		time.Duration(*cfg.PreResetWindow)*time.Second, time.Duration(*cfg.PreResetCarddataInterval)*time.Second,
		nextResetAt(now, resetDay), constants.PollingPreResetTailMinutes*time.Minute)
}

func (m *PollingConfigManager) configByID(id uint) *model.PollingConfig {
	m.mu.RLock()
	defer m.mu.RUnlock()
	for _, cfg := range m.configs {
		if cfg.ID == id {
			return cfg
		}
	}
	return nil
}

// RecordPreResetCheck 在流量查询成功后记录重置日前加密效果：处于该卡来源配置的加密窗口内时，
// 把卡记入窗口已查集合，并记下本次查询距重置时刻的分钟数（同卡取最后一次）。统计失败不影响轮询。
func (m *PollingConfigManager) RecordPreResetCheck(ctx context.Context, card *model.IotCard, now time.Time) {
	if m == nil || m.redis == nil || card == nil {
		return
	}
	info, ok := m.MergedTaskIntervals(card)[constants.TaskTypePollingCarddata]
	if !ok {
		return
	}
	cfg := m.configByID(info.ConfigID)
	if cfg == nil || cfg.PreResetWindow == nil || cfg.PreResetCarddataInterval == nil {
		return
	}
	resetDay := 1
	if m.tier != nil {
		resetDay = m.tier.ResetDay(ctx, card.CarrierID)
	}
	reset := nextResetAt(now, resetDay)
	if now.Before(reset.Add(-time.Duration(*cfg.PreResetWindow) * time.Second)) {
		return
	}
	// 只统计有生效套餐的卡，与统计接口"有生效套餐但窗口内未查到"的口径一致。
	if facts := m.TierFactsOf(card); !facts.Known || facts.PackageState != constants.PollingPackageStateActive {
		return
	}
	date := reset.Format("20060102")
	member := strconv.FormatUint(uint64(card.ID), 10)
	minutes := int(reset.Sub(now).Minutes())
	ttl := constants.PollingPreResetStatTTLSeconds * time.Second
	pipe := m.redis.Pipeline()
	pipe.PFAdd(ctx, constants.RedisPollingPreResetCheckedKey(card.CarrierID, date), member)
	pipe.Expire(ctx, constants.RedisPollingPreResetCheckedKey(card.CarrierID, date), ttl)
	pipe.HSet(ctx, constants.RedisPollingPreResetOffsetKey(card.CarrierID, date), member, minutes)
	pipe.Expire(ctx, constants.RedisPollingPreResetOffsetKey(card.CarrierID, date), ttl)
	_, _ = pipe.Exec(ctx)
}

// ResetMoments 返回某运营商账户最近一次已过去的重置时刻与下一次重置时刻。
func (m *PollingConfigManager) ResetMoments(ctx context.Context, carrierID uint, now time.Time) (time.Time, time.Time) {
	resetDay := 1
	if m.tier != nil {
		resetDay = m.tier.ResetDay(ctx, carrierID)
	}
	next := nextResetAt(now, resetDay)
	return next.AddDate(0, -1, 0), next
}