package notification

import (
	"context"
	"fmt"
	"strconv"
	"time"

	"github.com/google/uuid"
	"go.uber.org/zap"
	"gorm.io/gorm"
	"gorm.io/gorm/clause"

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

// CleanupService 按通知类别的保留期限分批删除过期通知事实。
type CleanupService struct {
	db          *gorm.DB
	logger      *zap.Logger
	auditWriter *audit.Writer
	now         func() time.Time
}

// NewCleanupService 创建通知保留清理服务。
func NewCleanupService(db *gorm.DB, logger *zap.Logger, auditWriters ...*audit.Writer) *CleanupService {
	if logger == nil {
		logger = zap.NewNop()
	}
	service := &CleanupService{db: db, logger: logger, now: time.Now}
	if len(auditWriters) > 0 {
		service.auditWriter = auditWriters[0]
	}
	return service
}

// Run 按类别、创建时间和稳定主键执行有界分批清理。
func (s *CleanupService) Run(ctx context.Context) error {
	policies := []struct {
		category string
		days     int
	}{
		{constants.NotificationCategoryApproval, constants.NotificationApprovalRetentionDays},
		{constants.NotificationCategoryExpiry, constants.NotificationExpiryRetentionDays},
		{constants.NotificationCategorySync, constants.NotificationSyncRetentionDays},
		{constants.NotificationCategorySystem, constants.NotificationSystemRetentionDays},
	}
	for _, policy := range policies {
		deleted, err := s.cleanupCategory(ctx, policy.category, s.now().UTC().AddDate(0, 0, -policy.days))
		if err != nil {
			return err
		}
		s.logger.Info("站内通知保留清理完成",
			zap.String("category", policy.category), zap.Int64("deleted_count", deleted))
	}
	return nil
}

func (s *CleanupService) cleanupCategory(ctx context.Context, category string, cutoff time.Time) (int64, error) {
	if s.auditWriter == nil {
		return 0, errors.New(errors.CodeInvalidStatus, "通知清理统一审计接缝未配置")
	}
	var total int64
	for batch := 0; batch < constants.NotificationCleanupMaxBatches; batch++ {
		var deleted []*model.Notification
		if err := s.db.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
			if err := tx.WithContext(ctx).Clauses(clause.Locking{Strength: "UPDATE"}).
				Where("category = ? AND created_at < ?", category, cutoff).
				Order("created_at ASC, id ASC").Limit(constants.NotificationCleanupBatchSize).Find(&deleted).Error; err != nil {
				return errors.Wrap(errors.CodeDatabaseError, err, "查询待清理站内通知失败")
			}
			if len(deleted) == 0 {
				return nil
			}
			ids := make([]uint, 0, len(deleted))
			for _, notification := range deleted {
				ids = append(ids, notification.ID)
			}
			result := tx.WithContext(ctx).Where("id IN ?", ids).Delete(&model.Notification{})
			if result.Error != nil {
				return errors.Wrap(errors.CodeDatabaseError, result.Error, "清理站内通知失败")
			}
			if result.RowsAffected != int64(len(deleted)) {
				return errors.New(errors.CodeInvalidStatus, "通知清理数量发生并发变化")
			}
			return s.appendCleanupAudit(ctx, tx, category, cutoff, deleted)
		}); err != nil {
			return total, err
		}
		total += int64(len(deleted))
		if len(deleted) < constants.NotificationCleanupBatchSize {
			break
		}
	}
	return total, nil
}

func (s *CleanupService) appendCleanupAudit(ctx context.Context, tx *gorm.DB, category string, cutoff time.Time, notifications []*model.Notification) error {
	firstID, lastID := notifications[0].ID, notifications[len(notifications)-1].ID
	key := fmt.Sprintf("%s:%s:%d:%d", category, cutoff.UTC().Format(time.RFC3339), firstID, lastID)
	rootID := "evt_" + uuid.NewSHA1(uuid.NameSpaceOID, []byte("notification-cleanup:"+key)).String()
	children := make([]audit.AppendInput, 0, len(notifications))
	for _, notification := range notifications {
		children = append(children, audit.AppendInput{
			EventID:    audit.TaskEventID(constants.AuditResourceNotification, notification.ID, "cleanup"),
			ActionCode: constants.AuditActionNotificationCleanupItem, Summary: "清理单条过期通知",
			ScopeType: constants.AuditScopePlatform, Result: constants.AuditResultSuccess,
			Resources: []audit.ResourceInput{audit.NotificationResource(notification,
				constants.AuditResourceRelationPrimary, constants.AuditResourceRoleNotificationTarget,
				map[string]any{"exists": true}, map[string]any{"deleted": true})},
		})
	}
	return s.auditWriter.AppendBatch(ctx, tx, audit.BatchInput{
		Root: audit.AppendInput{
			EventID: rootID, ActionCode: constants.AuditActionNotificationCleanup, Summary: "清理过期通知",
			ScopeType: constants.AuditScopePlatform, Result: constants.AuditResultSuccess,
			BatchTotal: len(notifications), SuccessCount: len(notifications),
			Resources: []audit.ResourceInput{{
				Type: constants.AuditResourceNotificationCleanupBatch, Key: rootID, DisplayName: "通知清理批次",
				Relation: constants.AuditResourceRelationPrimary, Role: constants.AuditResourceRoleBatchTask,
				IdentitySnapshot: map[string]any{
					"category": category, "cutoff": cutoff.UTC(), "deleted_count": len(notifications),
					"first_id": firstID, "last_id": lastID,
				}, SubjectVisibility: constants.AuditSubjectInternalOnly,
			}},
			Metadata: map[string]any{"first_id": strconv.FormatUint(uint64(firstID), 10), "last_id": strconv.FormatUint(uint64(lastID), 10)},
		},
		Children: children,
	})
}