/*
Copyright 2025-2026 linux.do
Modified by Arctel.net, 2026

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package upload

import (
	"context"
	"fmt"
	"time"

	"github.com/Rain-kl/Wavelet/internal/db"
	"github.com/Rain-kl/Wavelet/internal/model"
	"github.com/Rain-kl/Wavelet/internal/storage"
	"github.com/Rain-kl/Wavelet/internal/task"
	"gorm.io/gorm"
)

// CleanupUnusedUploadsHandler 清理未使用上传文件的异步任务处理器
type CleanupUnusedUploadsHandler struct{}

// Execute 执行清理未使用上传文件的业务逻辑
func (h *CleanupUnusedUploadsHandler) Execute(ctx context.Context, payload []byte) (*task.TaskResult, error) {
	const batchSize = 100 // 每批处理100个文件
	var lastID uint64 = 0
	var totalProcessed int
	var totalDeleted int

	// 计算1小时前的时间
	oneHourAgo := time.Now().Add(-1 * time.Hour)

	task.AppendLog(ctx, "开始扫描未使用上传文件，阈值: %s", oneHourAgo.Format(time.RFC3339))

	for {
		// 使用游标分页查询未使用且超过1小时的上传记录
		var unusedUploads []model.Upload
		if err := db.DB(ctx).
			Where("id > ? AND status = ? AND created_at < ?", lastID, model.UploadStatusPending, oneHourAgo).
			Order("id ASC").
			Limit(batchSize).
			Find(&unusedUploads).Error; err != nil {
			task.AppendLog(ctx, "查询未使用的上传文件失败: %v", err)
			return nil, fmt.Errorf(ErrQueryUnusedUploadsFailed, err)
		}

		// 没有更多数据，退出循环
		if len(unusedUploads) == 0 {
			break
		}

		task.AppendLog(ctx, "本批次找到 %d 个需要清理的上传文件", len(unusedUploads))

		// 处理每个未使用的上传文件
		for _, upload := range unusedUploads {
			totalProcessed++

			if err := db.DB(ctx).Transaction(func(tx *gorm.DB) error {
				// 更新上传记录状态
				if err := tx.Model(&model.Upload{}).
					Where("id = ? AND status = ?", upload.ID, model.UploadStatusPending).
					Update("status", model.UploadStatusDeleted).Error; err != nil {
					return err
				}

				// Delete from S3
				if err := storage.DeleteObject(ctx, upload.FilePath); err != nil {
					return err
				}

				return nil
			}); err != nil {
				task.AppendLog(ctx, "清理上传文件失败 [ID:%d]: %v", upload.ID, err)
				lastID = upload.ID
				continue
			}

			totalDeleted++
			lastID = upload.ID
		}
	}

	msg := fmt.Sprintf("共处理 %d 个文件，成功删除 %d 个", totalProcessed, totalDeleted)
	task.AppendLog(ctx, "%s", msg)
	return &task.TaskResult{Message: msg}, nil
}