// Package janitor 后台清理循环（安全审计 M5）：
// 回收过期容量预留、超时未完成的上传会话（含其分片对象）与过期预签名会话
// （direct 模式残留对象一并删除）。此前这些资源仅在同 token 复用/显式取消时
// 释放，恶意 init 可长期占用容量预留或累积垃圾数据。
package janitor

import (
	"context"
	"errors"
	"log"
	"time"

	"gorm.io/gorm"

	"filecodebox/internal/model"
	"filecodebox/internal/storage"
)

// chunkSessionMaxAge 未完成分片会话的最大保留时长（预留 TTL 为 2h，
// 会话保留 24h 以支持断点续传；超时后由本循环清理）。
const chunkSessionMaxAge = 24 * time.Hour

// presignGrace 过期预签名会话的宽限时长（到点即删，避免与在途 confirm 竞争）。
const presignGrace = time.Hour

// Start 启动周期清理循环；ctx 取消时退出。
func Start(ctx context.Context, db *gorm.DB, store *storage.Manager, interval time.Duration) {
	go func() {
		ticker := time.NewTicker(interval)
		defer ticker.Stop()
		for {
			select {
			case <-ctx.Done():
				return
			case <-ticker.C:
				Run(ctx, db, store)
			}
		}
	}()
}

// Run 执行一轮清理；单项失败仅记日志，不影响其他项。
func Run(ctx context.Context, db *gorm.DB, store *storage.Manager) {
	now := time.Now()
	cleanExpiredReservations(ctx, db, now)
	cleanExpiredChunkSessions(ctx, db, store, now)
	cleanExpiredPresignSessions(ctx, db, store, now)
}

// cleanExpiredReservations 删除全部过期容量预留。
func cleanExpiredReservations(ctx context.Context, db *gorm.DB, now time.Time) {
	if err := db.WithContext(ctx).
		Where("expires_at <= ?", now).
		Delete(&model.StorageReservation{}).Error; err != nil {
		log.Printf("[janitor] 清理过期容量预留失败: %v", err)
	}
}

// engineFor 按归属引擎取回实例；空/未知引擎回落当前引擎（对齐 API 层 storeFor 语义）。
func engineFor(store *storage.Manager, name string) (storage.Storage, error) {
	if name != "" && storage.ValidEngine(name) {
		if s, err := store.EngineOf(name); err == nil {
			return s, nil
		}
	}
	return store.Current(), nil
}

// cleanExpiredChunkSessions 清理超时未完成的分片会话及其分片对象。
func cleanExpiredChunkSessions(ctx context.Context, db *gorm.DB, store *storage.Manager, now time.Time) {
	var sessions []model.UploadChunk
	if err := db.WithContext(ctx).
		Where("chunk_index = -1 AND created_at < ?", now.Add(-chunkSessionMaxAge)).
		Limit(200).
		Find(&sessions).Error; err != nil {
		log.Printf("[janitor] 查询过期分片会话失败: %v", err)
		return
	}
	for _, s := range sessions {
		engine, err := engineFor(store, s.Engine)
		if err == nil && s.SavePath != "" {
			if err := engine.CleanChunks(ctx, s.UploadID, s.SavePath); err != nil &&
				!errors.Is(err, storage.ErrNotFound) && !errors.Is(err, storage.ErrInvalidPath) {
				log.Printf("[janitor] 清理分片对象失败 upload_id=%s: %v", s.UploadID, err)
			}
		}
		if err := db.WithContext(ctx).
			Where("upload_id = ?", s.UploadID).
			Delete(&model.UploadChunk{}).Error; err != nil {
			log.Printf("[janitor] 删除过期分片会话失败 upload_id=%s: %v", s.UploadID, err)
			continue
		}
		log.Printf("[janitor] 已清理超时分片会话 upload_id=%s file=%s", s.UploadID, s.FileName)
	}
}

// cleanExpiredPresignSessions 清理过期预签名会话；direct 模式残留对象一并删除。
func cleanExpiredPresignSessions(ctx context.Context, db *gorm.DB, store *storage.Manager, now time.Time) {
	var sessions []model.PresignUploadSession
	if err := db.WithContext(ctx).
		Where("expires_at < ?", now.Add(-presignGrace)).
		Limit(200).
		Find(&sessions).Error; err != nil {
		log.Printf("[janitor] 查询过期预签名会话失败: %v", err)
		return
	}
	for _, s := range sessions {
		if s.Mode == "direct" && s.SavePath != "" {
			if engine, err := engineFor(store, s.Engine); err == nil {
				if err := engine.DeleteFile(ctx, s.SavePath); err != nil &&
					!errors.Is(err, storage.ErrNotFound) && !errors.Is(err, storage.ErrInvalidPath) {
					log.Printf("[janitor] 删除直传残留对象失败 upload_id=%s: %v", s.UploadID, err)
				}
			}
		}
		if err := db.WithContext(ctx).
			Where("upload_id = ?", s.UploadID).
			Delete(&model.PresignUploadSession{}).Error; err != nil {
			log.Printf("[janitor] 删除过期预签名会话失败 upload_id=%s: %v", s.UploadID, err)
			continue
		}
		log.Printf("[janitor] 已清理过期预签名会话 upload_id=%s mode=%s", s.UploadID, s.Mode)
	}
}