package packageexpiry

import (
	"context"
	"time"

	"github.com/redis/go-redis/v9"
	"go.uber.org/zap"

	"github.com/break/junhong_cmp_fiber/internal/model/dto"
	packageexpiryquery "github.com/break/junhong_cmp_fiber/internal/query/packageexpiry"
	"github.com/break/junhong_cmp_fiber/pkg/constants"
)

// entryReminderWindowDays 临期提醒窗口：剩余 0～15 个上海自然日。
const entryReminderWindowDays = 15

var entryReminderLocation = time.FixedZone("Asia/Shanghai", 8*60*60)

// PersonalReminderPublisher 为单个个人客户幂等写一条临期通知。
type PersonalReminderPublisher interface {
	PublishPersonal(ctx context.Context, candidate dto.ExpiringAssetItem, customerID uint) error
}

// EntryReminder 在 H5 进入资产时判定并发出套餐临期提醒，同一客户、同一资产、同一上海自然日至多一次。
type EntryReminder struct {
	redis     *redis.Client
	publisher PersonalReminderPublisher
	logger    *zap.Logger
	now       func() time.Time
}

// NewEntryReminder 创建进入资产时的临期提醒用例。
func NewEntryReminder(redisClient *redis.Client, publisher PersonalReminderPublisher, logger *zap.Logger) *EntryReminder {
	return &EntryReminder{redis: redisClient, publisher: publisher, logger: logger, now: time.Now}
}

// Remind 返回本次应展示的临期提醒；不在窗口、当天已提醒或通知写入失败时返回 nil，不让资产信息接口失败。
// 顺序：检查去重键 → 写通知 → SET NX → 抢到键才返回；Redis 不可用按未提醒处理，通知由事件号幂等。
func (r *EntryReminder) Remind(ctx context.Context, customerID uint, candidate dto.ExpiringAssetItem) *dto.AssetExpiryReminder {
	if r == nil || r.publisher == nil || customerID == 0 || !inEntryReminderWindow(candidate.PackageExpiryEstimate) {
		return nil
	}
	now := r.now().In(entryReminderLocation)
	key := constants.RedisPackageExpiryEntryReminderKey(customerID, candidate.AssetType, candidate.Identifier, now.Format("20060102"))
	redisOK := r.redis != nil
	if redisOK {
		exists, err := r.redis.Exists(ctx, key).Result()
		if err != nil {
			redisOK = false
			r.warn("检查临期提醒去重键失败，按未提醒处理", err)
		} else if exists > 0 {
			return nil
		}
	}
	if err := r.publisher.PublishPersonal(ctx, candidate, customerID); err != nil {
		// 写通知失败不占键、不返回字段，下次进入重试。
		r.warn("写入进入资产临期通知失败", err)
		return nil
	}
	if redisOK {
		ttl := endOfShanghaiDay(now).Sub(now) + constants.PackageExpiryEntryReminderTTLBuffer
		acquired, err := r.redis.SetNX(ctx, key, "1", ttl).Result()
		if err != nil {
			r.warn("占用临期提醒去重键失败，按未提醒处理", err)
		} else if !acquired {
			return nil
		}
	}
	days := *candidate.DaysUntilFinalExpiry
	level, levelName := packageexpiryquery.ExpiryLevel(days)
	return &dto.AssetExpiryReminder{
		RemainingDays: days, ExpiresAt: *candidate.EstimatedFinalExpiresAt,
		Level: level, LevelName: levelName,
	}
}

// inEntryReminderWindow 判断最终到期可精确推算且剩余 0～15 个上海自然日。
func inEntryReminderWindow(estimate dto.PackageExpiryEstimate) bool {
	if estimate.ExpiryEstimateStatus != constants.PackageExpiryEstimateStatusExact ||
		estimate.DaysUntilFinalExpiry == nil || estimate.EstimatedFinalExpiresAt == nil {
		return false
	}
	days := *estimate.DaysUntilFinalExpiry
	return days >= 0 && days <= entryReminderWindowDays
}

// endOfShanghaiDay 返回上海时间当天结束时刻（次日零点）。
func endOfShanghaiDay(now time.Time) time.Time {
	year, month, day := now.In(entryReminderLocation).Date()
	return time.Date(year, month, day+1, 0, 0, 0, 0, entryReminderLocation)
}

func (r *EntryReminder) warn(message string, err error) {
	if r.logger != nil {
		r.logger.Warn(message, zap.Error(err))
	}
}