package business

import (
	"encoding/json"
	"slices"
	"strconv"

	"gorm.io/gorm"
)

// 旧迁移 SQL 保留日志附件 JSON。只转换有原始备份且尚未变更的旧日志，避免误映射新文件 ID。
func migrateAlertAttachments(db *gorm.DB) error {
	tables, err := db.Migrator().GetTables()
	if err != nil {
		return err
	}
	for _, name := range []string{"sys_alert_operation_log", "sw_kra_id_map", "bak_sw2kra_20261103_sys_alert_operation_log"} {
		if !slices.Contains(tables, name) {
			return nil
		}
	}
	var lastID uint64
	for {
		var rows []struct {
			ID      uint64
			Current *string
			Legacy  *string
		}
		if err := db.Table("sys_alert_operation_log l").Select("l.id,l.attachment_ids AS current,b.attachment_ids AS legacy").Joins("JOIN bak_sw2kra_20261103_sys_alert_operation_log b ON b.id=l.id").Where("l.id > ?", lastID).Order("l.id").Limit(500).Scan(&rows).Error; err != nil {
			return err
		}
		if len(rows) == 0 {
			return nil
		}
		pending := map[uint64][]int64{}
		oldIDs := []string{}
		for _, row := range rows {
			lastID = row.ID
			current, ids := decodeAlertAttachments(row.Current)
			legacy, legacyIDs := decodeAlertAttachments(row.Legacy)
			if len(ids) == 0 || len(legacyIDs) == 0 || !slices.Equal(current, legacy) {
				continue
			}
			pending[row.ID] = ids
			for _, id := range ids {
				oldIDs = append(oldIDs, strconv.FormatInt(id, 10))
			}
		}
		if len(pending) == 0 {
			continue
		}
		mapped := map[int64]int64{}
		for start := 0; start < len(oldIDs); start += 500 {
			var mappings []struct {
				OldID string
				NewID int64
			}
			if err := db.Table("sw_kra_id_map").Select("old_id,new_id").Where("entity = ? AND old_id IN ?", "file", oldIDs[start:min(start+500, len(oldIDs))]).Scan(&mappings).Error; err != nil {
				return err
			}
			for _, m := range mappings {
				id, err := strconv.ParseInt(m.OldID, 10, 64)
				if err == nil {
					mapped[id] = m.NewID
				}
			}
		}
		if err := db.Transaction(func(tx *gorm.DB) error {
			for logID, ids := range pending {
				newIDs := []int64{}
				for _, id := range ids {
					// 缺失旧文件原本不展示，不能把旧 ID 当成同号的新文件；原始引用仍保留在备份中。
					if newID, ok := mapped[id]; ok {
						newIDs = append(newIDs, newID)
					}
				}
				raw, _ := json.Marshal(newIDs)
				if err := tx.Table("sys_alert_operation_log").Where("id = ?", logID).Update("attachment_ids", string(raw)).Error; err != nil {
					return err
				}
			}
			return nil
		}); err != nil {
			return err
		}
	}
}