package business

import (
	"context"
	"gorm.io/gorm"
	"kra/internal/biz/business"
	"math/big"
	"strings"
	"time"
)

func alertTree(db *gorm.DB, roots []business.ChannelKey) *gorm.DB {
	base := func() *gorm.DB {
		return db.Table("tab_promote r").Where("(r.source_db,r.id) IN ?", channelPairs(roots))
	}
	self := base().Select("r.source_db,r.id,r.id AS leaf_id")
	children := base().Joins("JOIN tab_promote child ON child.source_db=r.source_db AND child.parent_id=r.id").Select("r.source_db,r.id,child.id AS leaf_id")
	descendants := base().Joins("JOIN tab_promote child ON child.source_db=r.source_db AND child.top_promote_id=r.id").Select("r.source_db,r.id,child.id AS leaf_id")
	// Each branch can use its own equality index. UNION removes channels reached
	// through both parent and top-level relationships without an OR join scan.
	return db.Table("(? UNION ? UNION ?) root", self, children, descendants).
		Joins("JOIN tab_promote p ON p.source_db=root.source_db AND p.id=root.leaf_id")
}
func alertMetricSpec(db *gorm.DB, metric int) (table, stamp, condition, amount string) {
	if metric == 2 {
		return "tab_spend", "m.pay_time", "m.pay_status=1", "m.pay_amount"
	}
	stamp = "CAST(m.register_time AS INTEGER)"
	if db.Dialector.Name() == "mysql" {
		stamp = "m.sw_register_time_unix"
	}
	return "tab_user", stamp, "(m.puid=0 OR m.puid IS NULL)", "1"
}

func (r *alertTriggerRepo) Comparison(ctx context.Context, metric int, channels []business.ChannelKey, today time.Time, days int) (map[business.ChannelKey]business.AlertComparison, error) {
	db := r.data.DB().WithContext(ctx)
	if metric != 1 && metric != 2 {
		return nil, business.ErrAlertRuleInput
	}
	table, stamp, condition, amount := alertMetricSpec(db, metric)
	available, err := businessTablesAvailable(db, table, "tab_promote")
	if err != nil {
		return nil, err
	}
	if !available {
		return nil, business.ErrReportBuildUnavailable
	}
	result := map[business.ChannelKey]business.AlertComparison{}
	current, previous := today.AddDate(0, 0, -days).Unix(), today.AddDate(0, 0, -2*days).Unix()
	// 先取小规模渠道映射，再按固定平台及渠道 ID 批量聚合；避免 MySQL 5.7
	// 将动态 JOIN 的时间范围退化为 ref 扫描，读取每个渠道的全部历史明细。
	owners := map[business.ChannelKey][]business.ChannelKey{}
	bySource := map[string][]uint64{}
	for start := 0; start < len(channels); start += 100 {
		var pairs []struct {
			SourceDB          string
			RootID, PromoteID uint64
		}
		if err := alertTree(db, channels[start:min(start+100, len(channels))]).Select("root.source_db,root.id AS root_id,p.id AS promote_id").Scan(&pairs).Error; err != nil {
			return nil, business.ErrStorage
		}
		for _, p := range pairs {
			leaf := business.ChannelKey{SourceDB: p.SourceDB, ID: p.PromoteID}
			root := business.ChannelKey{SourceDB: p.SourceDB, ID: p.RootID}
			if len(owners[leaf]) == 0 {
				bySource[p.SourceDB] = append(bySource[p.SourceDB], p.PromoteID)
			}
			owners[leaf] = append(owners[leaf], root)
			result[root] = business.AlertComparison{Current: "0", Previous: "0"}
		}
	}
	for source, ids := range bySource {
		for start := 0; start < len(ids); start += 300 {
			batch := ids[start:min(start+300, len(ids))]
			firstQueries := []string{}
			args := []any{}
			for _, id := range batch {
				// MIN 的三个等值前缀命中覆盖索引，MySQL 可直接读取首个索引项。
				firstQueries = append(firstQueries, "SELECT ? AS promote_id,(SELECT MIN("+stamp+") FROM "+table+" m WHERE m.source_db=? AND m.promote_id=? AND "+condition+" AND "+stamp+">0) AS first_unix")
				args = append(args, id, source, id)
			}
			var first []struct {
				PromoteID uint64
				FirstUnix *int64
			}
			if err := db.Raw(strings.Join(firstQueries, " UNION ALL "), args...).Scan(&first).Error; err != nil {
				return nil, business.ErrStorage
			}
			for _, row := range first {
				if row.FirstUnix == nil {
					continue
				}
				for _, root := range owners[business.ChannelKey{SourceDB: source, ID: row.PromoteID}] {
					v := result[root]
					if v.FirstUnix == 0 || *row.FirstUnix < v.FirstUnix {
						v.FirstUnix = *row.FirstUnix
					}
					result[root] = v
				}
			}
			var rows []struct {
				PromoteID                   uint64
				CurrentValue, PreviousValue string
			}
			selection := "m.promote_id,COALESCE(SUM(CASE WHEN " + stamp + ">=? THEN " + amount + " ELSE 0 END),0) AS current_value,COALESCE(SUM(CASE WHEN " + stamp + "<? THEN " + amount + " ELSE 0 END),0) AS previous_value"
			q := db.Table(table+" m").Where("m.source_db=? AND m.promote_id IN ?", source, batch).Where(condition).Where(stamp+">=? AND "+stamp+"<?", previous, today.Unix())
			if err := q.Select(selection, current, current).Group("m.promote_id").Scan(&rows).Error; err != nil {
				return nil, business.ErrStorage
			}
			scale := 0
			if metric == 2 {
				scale = 2
			}
			for _, row := range rows {
				for _, root := range owners[business.ChannelKey{SourceDB: source, ID: row.PromoteID}] {
					v := result[root]
					var err error
					v.Current, err = addAlertMetric(v.Current, row.CurrentValue, scale)
					if err != nil {
						return nil, err
					}
					v.Previous, err = addAlertMetric(v.Previous, row.PreviousValue, scale)
					if err != nil {
						return nil, err
					}
					result[root] = v
				}
			}
		}
	}
	return result, nil
}

func addAlertMetric(a, b string, scale int) (string, error) {
	left, ok := new(big.Rat).SetString(a)
	if !ok {
		return "", business.ErrStorage
	}
	right, ok := new(big.Rat).SetString(b)
	if !ok {
		return "", business.ErrStorage
	}
	return left.Add(left, right).FloatString(scale), nil
}

func (r *alertTriggerRepo) Snapshots(ctx context.Context, channels []business.ChannelKey, now time.Time, dedup bool) (map[business.ChannelKey]business.AlertSnapshot, error) {
	db := r.data.DB().WithContext(ctx)
	available, err := businessTablesAvailable(db, "tab_user", "tab_spend", "tab_promote")
	if err != nil {
		return nil, err
	}
	if !available {
		return nil, business.ErrReportBuildUnavailable
	}
	result := map[business.ChannelKey]business.AlertSnapshot{}
	for _, key := range channels {
		result[key] = business.AlertSnapshot{Pay: "0.00"}
	}
	for start := 0; start < len(channels); start += 100 {
		batch := channels[start:min(start+100, len(channels))]
		var players []struct {
			SourceDB  string
			PromoteID uint64
			Players   int64
		}
		_, stamp, condition, _ := alertMetricSpec(db, 1)
		identity := "CAST(m.id AS TEXT)"
		if db.Dialector.Name() == "mysql" {
			identity = "CAST(m.id AS CHAR)"
		}
		if dedup {
			identity = "CASE WHEN TRIM(COALESCE(m.idcard,''))<>'' THEN 'card:' || TRIM(m.idcard) ELSE 'user:' || " + identity + " END"
			if db.Dialector.Name() == "mysql" {
				identity = "CASE WHEN TRIM(COALESCE(m.idcard,''))<>'' THEN CONCAT('card:',TRIM(m.idcard)) ELSE CONCAT('user:',m.id) END"
			}
		}
		q := alertTree(db, batch).Joins("JOIN tab_user m ON m.source_db=p.source_db AND m.promote_id=p.id").Where(condition).Where(stamp+"<=?", now.Unix())
		if err := q.Select("root.source_db,root.id AS promote_id,COUNT(DISTINCT " + identity + ") AS players").Group("root.source_db,root.id").Scan(&players).Error; err != nil {
			return nil, business.ErrStorage
		}
		for _, row := range players {
			key := business.ChannelKey{SourceDB: row.SourceDB, ID: row.PromoteID}
			v := result[key]
			v.Players = row.Players
			result[key] = v
		}
		var payments []struct {
			SourceDB  string
			PromoteID uint64
			Amount    string
		}
		if err := alertTree(db, batch).Joins("JOIN tab_spend m ON m.source_db=p.source_db AND m.promote_id=p.id").Where("m.pay_status=1 AND m.pay_time<=?", now.Unix()).Select("root.source_db,root.id AS promote_id,COALESCE(SUM(m.pay_amount),0) AS amount").Group("root.source_db,root.id").Scan(&payments).Error; err != nil {
			return nil, business.ErrStorage
		}
		for _, row := range payments {
			key := business.ChannelKey{SourceDB: row.SourceDB, ID: row.PromoteID}
			v := result[key]
			v.Pay = row.Amount
			result[key] = v
		}
	}
	return result, nil
}