package business

import (
	"context"
	"fmt"
	"log/slog"
	"math/big"
	"strconv"
	"strings"
	"time"
)

type AlertTriggerChannel struct {
	ChannelKey
	Account                    string
	BusierID                   uint64
	LastLoginUnix, CreatedUnix int64
}

type AlertTriggerInput struct {
	Rules    []*AlertRule
	Accounts []*Account
	Bindings []*Binding
	Channels []*AlertTriggerChannel
}

type AlertComparison struct {
	FirstUnix         int64
	Current, Previous string
}

type AlertTriggerRepo interface {
	Input(context.Context) (*AlertTriggerInput, error)
	Comparison(context.Context, int, []ChannelKey, time.Time, int) (map[ChannelKey]AlertComparison, error)
	// 仓储在渠道/分类键锁及事务内读取未关闭记录，由领域决定是否刷新。
	StoreHit(context.Context, *AlertRecord, []int, func(*AlertRecord) bool) (bool, error)
}

type AlertTriggerResult struct{ Rules, Written, Skipped int }

type AlertTriggerUsecase struct{ repo AlertTriggerRepo }

func NewAlertTriggerUsecase(repo AlertTriggerRepo) *AlertTriggerUsecase {
	return &AlertTriggerUsecase{repo: repo}
}

func (uc *AlertTriggerUsecase) Run(ctx context.Context) error {
	_, err := uc.Detect(ctx, time.Now())
	return err
}

func validTriggerRule(rule *AlertRule) bool {
	if rule == nil || rule.CreatorID == 0 || strings.TrimSpace(rule.Type) == "" {
		return false
	}
	if rule.Metric == 3 {
		return rule.UnloginDays != nil && *rule.UnloginDays > 0
	}
	if rule.Metric != 1 && rule.Metric != 2 {
		return false
	}
	if rule.StatPeriodDays == nil || *rule.StatPeriodDays <= 0 || rule.MomDirection == nil || (*rule.MomDirection != 1 && *rule.MomDirection != 2) || rule.MomThreshold == nil {
		return false
	}
	threshold, ok := new(big.Rat).SetString(*rule.MomThreshold)
	// 历史规则检测允许零阈值，保持与旧任务一致；新增规则另有边界校验。
	return ok && threshold.Sign() >= 0
}

func triggerOwners(input *AlertTriggerInput) (map[ChannelKey]*Account, map[uint]*Account) {
	accounts := map[uint]*Account{}
	for _, account := range input.Accounts {
		if account != nil {
			accounts[account.ID] = account
		}
	}
	bindings := map[PlatformKey]uint{}
	conflicts := map[PlatformKey]bool{}
	for _, binding := range input.Bindings {
		if binding == nil || binding.Status != "0" || binding.UserID == 0 || binding.BusierID == 0 {
			continue
		}
		source, err := NormalizePlatform(binding.SourceDB)
		if err != nil {
			continue
		}
		key := PlatformKey{SourceDB: source, BusierID: binding.BusierID}
		if existing, ok := bindings[key]; ok && existing != binding.UserID {
			conflicts[key] = true
		}
		bindings[key] = binding.UserID
	}
	owners := map[ChannelKey]*Account{}
	for _, channel := range input.Channels {
		if channel == nil || channel.ID == 0 {
			continue
		}
		source, err := NormalizePlatform(channel.SourceDB)
		if err != nil {
			continue
		}
		channel.SourceDB = source
		key := PlatformKey{SourceDB: source, BusierID: channel.BusierID}
		account := accounts[bindings[key]]
		if conflicts[key] || account == nil || account.Level != 3 {
			continue
		}
		path := strings.Split(account.IDPath, ",")
		if len(path) < 2 {
			continue
		}
		id, err := strconv.ParseUint(path[1], 10, 64)
		owner := accounts[uint(id)]
		if err != nil || owner == nil || owner.Level != 1 {
			continue
		}
		owners[channel.ChannelKey] = owner
	}
	return owners, accounts
}

// 一次执行固定上海自然日，避免跨午夜时同一任务的各规则使用不同的比较窗口。
func (uc *AlertTriggerUsecase) Detect(ctx context.Context, now time.Time) (*AlertTriggerResult, error) {
	result := &AlertTriggerResult{}
	input, err := uc.repo.Input(ctx)
	if err != nil {
		return result, err
	}
	if input == nil {
		return result, ErrStorage
	}
	zone := time.FixedZone("Asia/Shanghai", 8*3600)
	now = now.In(zone)
	today := time.Date(now.Year(), now.Month(), now.Day(), 0, 0, 0, 0, zone)
	owners, accounts := triggerOwners(input)
	type snapshotKey struct {
		creator      uint
		metric, days int
	}
	snapshots := map[snapshotKey]map[ChannelKey]AlertComparison{}
	var failures []string
	for _, rule := range input.Rules {
		if err := ctx.Err(); err != nil {
			return result, err
		}
		if !validTriggerRule(rule) {
			result.Skipped++
			continue
		}
		creator := accounts[rule.CreatorID]
		if creator == nil || (creator.AuthorityID != 888 && creator.Level != 1) {
			result.Skipped++
			continue
		}
		channels := []*AlertTriggerChannel{}
		keys := []ChannelKey{}
		for _, channel := range input.Channels {
			if channel == nil {
				continue
			}
			owner := owners[channel.ChannelKey]
			if owner != nil && (creator.AuthorityID == 888 || owner.ID == creator.ID) {
				channels = append(channels, channel)
				keys = append(keys, channel.ChannelKey)
			}
		}
		if len(channels) == 0 {
			continue
		}
		result.Rules++
		var snapshot map[ChannelKey]AlertComparison
		if rule.Metric != 3 {
			key := snapshotKey{creator.ID, rule.Metric, *rule.StatPeriodDays}
			var exists bool
			snapshot, exists = snapshots[key]
			if !exists {
				snapshot, err = uc.repo.Comparison(ctx, rule.Metric, keys, today, key.days)
				if err != nil {
					failures = append(failures, fmt.Sprintf("规则 %d 读取指标失败: %v", rule.ID, err))
					continue
				}
				snapshots[key] = snapshot
			}
		}
		for _, channel := range channels {
			if err := ctx.Err(); err != nil {
				return result, err
			}
			content, hit, err := triggerContent(rule, channel, snapshot[channel.ChannelKey], today)
			if err != nil {
				failures = append(failures, fmt.Sprintf("规则 %d 渠道 %s/%d: %v", rule.ID, channel.SourceDB, channel.ID, err))
				continue
			}
			if !hit {
				continue
			}
			owner := owners[channel.ChannelKey]
			record := &AlertRecord{RuleID: rule.ID, RuleName: rule.Name, RuleType: strings.TrimSpace(rule.Type), MonitorMetric: &rule.Metric,
				PlatformCode: channel.SourceDB, PlatformName: PlatformName(channel.SourceDB), TargetPromoteID: channel.ID, TargetPromoteName: channel.Account,
				BusinessID: owner.ID, BusinessName: owner.Username, AlertContent: content, Status: AlertUnprocessed, CreatedAt: now, UpdatedAt: now}
			written, err := uc.repo.StoreHit(ctx, record, []int{AlertUnprocessed, AlertProcessing, AlertPendingAudit, AlertAuditRejected}, func(current *AlertRecord) bool { return current == nil || current.Status == AlertUnprocessed })
			if err != nil {
				failures = append(failures, fmt.Sprintf("规则 %d 渠道 %s/%d 写入失败: %v", rule.ID, channel.SourceDB, channel.ID, err))
				continue
			}
			if written {
				result.Written++
			}
		}
	}
	if len(failures) > 0 {
		for _, failure := range failures {
			slog.ErrorContext(ctx, "预警检测失败", "detail", failure)
		}
		return result, fmt.Errorf("预警规则检测存在 %d 项失败：%s", len(failures), strings.Join(failures[:min(5, len(failures))], "；"))
	}
	return result, nil
}

func triggerContent(rule *AlertRule, channel *AlertTriggerChannel, sample AlertComparison, today time.Time) (string, bool, error) {
	if rule.Metric == 3 {
		stamp := channel.LastLoginUnix
		if stamp <= 0 {
			stamp = channel.CreatedUnix
		}
		if stamp <= 0 {
			return "", false, nil
		}
		day := time.Unix(stamp, 0).In(today.Location())
		day = time.Date(day.Year(), day.Month(), day.Day(), 0, 0, 0, 0, today.Location())
		days := int(today.Sub(day) / (24 * time.Hour))
		if days < *rule.UnloginDays {
			return "", false, nil
		}
		return fmt.Sprintf("连续%d天未登录", days), true, nil
	}
	days := *rule.StatPeriodDays
	if sample.FirstUnix <= 0 || time.Unix(sample.FirstUnix, 0).In(today.Location()).Format("2006-01-02") > today.AddDate(0, 0, -2*days).Format("2006-01-02") {
		return "", false, nil
	}
	previous, err := portraitNumber(sample.Previous)
	if err != nil {
		return "", false, err
	}
	if previous.Sign() <= 0 {
		return "", false, nil
	}
	current, err := portraitNumber(sample.Current)
	if err != nil {
		return "", false, err
	}
	rate := new(big.Rat).Quo(new(big.Rat).Sub(current, previous), previous)
	// 先对比值保留四位再转百分比，与旧 BigDecimal HALF_UP 的阈值边界一致。
	rate, _ = new(big.Rat).SetString(portraitDecimal(rate, 4))
	rate.Mul(rate, big.NewRat(100, 1))
	threshold, _ := new(big.Rat).SetString(*rule.MomThreshold)
	if (*rule.MomDirection == 1 && rate.Cmp(threshold) < 0) || (*rule.MomDirection == 2 && rate.Cmp(new(big.Rat).Neg(threshold)) > 0) {
		return "", false, nil
	}
	direction := "上升"
	if rate.Sign() < 0 {
		direction = "下降"
	}
	percent := portraitDecimal(new(big.Rat).Abs(rate), 2)
	if rule.Metric == 1 {
		return fmt.Sprintf("截至昨日%d个完整自然日注册%s人，较此前%d个完整自然日（%s人）环比%s%s%%", days, portraitDecimal(current, 0), days, portraitDecimal(previous, 0), direction, percent), true, nil
	}
	yuan := big.NewRat(10000, 1)
	return fmt.Sprintf("截至昨日%d个完整自然日充值¥%s万，较此前%d个完整自然日（¥%s万）环比%s%s%%", days, portraitDecimal(new(big.Rat).Quo(current, yuan), 2), days, portraitDecimal(new(big.Rat).Quo(previous, yuan), 2), direction, percent), true, nil
}