package service

import (
	"crypto/md5"
	"encoding/hex"
	"fmt"
	"io"
	"mime"
	"mime/multipart"
	"os"
	"path/filepath"
	"strings"
	"time"

	"github.com/gin-gonic/gin"

	"filestoragesystem/internal/config"
	"filestoragesystem/internal/model"
	"filestoragesystem/internal/repository"
	"filestoragesystem/internal/utils"
	"filestoragesystem/pkg/apperr"
)

// FileService 文件服务
type FileService struct {
	cfg          *config.Config
	fileRepo     *repository.FileRepo
	projectRepo  *repository.ProjectRepo
	userRepo     *repository.UserRepo
	tempLinkRepo *repository.TempLinkRepo
	trafficRepo  *repository.TrafficRepo
	settingRepo  *repository.SettingRepo
	opLogRepo    *repository.OpLogRepo
	webhookSvc   *WebhookService
}

// settingInt 读取数字型设置
func (s *FileService) settingInt(key string, def int64) int64 {
	if v, err := s.settingRepo.GetValue(key); err == nil {
		var n int64
		if _, e := fmt.Sscanf(v, "%d", &n); e == nil && n > 0 {
			return n
		}
	}
	return def
}

// settingBool 读取布尔型设置
func (s *FileService) settingBool(key string, def bool) bool {
	if v, err := s.settingRepo.GetValue(key); err == nil {
		return v == "true" || v == "1"
	}
	return def
}

// Upload 上传文件：校验配额/类型/大小，MD5去重，落盘，记录统计
func (s *FileService) Upload(c *gin.Context, userID uint, fh *multipart.FileHeader) (*model.File, error) {
	projectID, _ := strconvUint(c.PostForm("project_id"))
	if projectID == 0 {
		return nil, fmt.Errorf("缺少项目ID")
	}

	project, err := s.projectRepo.FindByID(projectID)
	if err != nil || project.UserID != userID {
		return nil, apperr.ErrForbidden
	}
	if project.Status != 1 {
		return nil, fmt.Errorf("项目已被禁用")
	}

	src, err := fh.Open()
	if err != nil {
		return nil, err
	}
	defer src.Close()

	size := fh.Size
	// 大小限制
	maxSize := s.settingInt("max_file_size", 104857600)
	if size > maxSize {
		return nil, apperr.ErrFileTooLarge
	}
	// 类型限制
	allowed := "*"
	if v, err := s.settingRepo.GetValue("allowed_file_types"); err == nil {
		allowed = v
	}
	if !s.checkTypeAllowed(fh.Filename, allowed) {
		return nil, apperr.ErrFileTypeDenied
	}
	// 配额
	if project.StorageUsed+size > project.StorageLimit {
		return nil, apperr.ErrQuotaExceeded
	}
	user, err := s.userRepo.FindByID(userID)
	if err != nil {
		return nil, apperr.ErrNotFound
	}
	if user.StorageUsed+size > user.StorageLimit {
		return nil, apperr.ErrQuotaExceeded
	}

	// 虚拟路径 + 文件名
	virtualPath := utils.SanitizePath(c.PostForm("path"))
	baseName := filepath.Base(utils.SanitizePath(fh.Filename))
	if baseName == "" || baseName == "." || baseName == "/" {
		baseName = "unnamed"
	}
	filename := baseName
	if virtualPath != "" {
		filename = virtualPath + "/" + baseName
	}
	visibility := int8(1)
	if c.PostForm("visibility") == "2" || c.PostForm("visibility") == "public" {
		visibility = 2
	}

	// 写入临时文件并计算MD5
	tmpFile, err := os.CreateTemp("", "fss-upload-*")
	if err != nil {
		return nil, err
	}
	tmpPath := tmpFile.Name()
	defer os.Remove(tmpPath)

	hasher := md5.New()
	if _, err := io.Copy(io.MultiWriter(tmpFile, hasher), src); err != nil {
		tmpFile.Close()
		return nil, err
	}
	tmpFile.Close()
	md5sum := hex.EncodeToString(hasher.Sum(nil))

	// 去重：相同MD5复用已有物理文件
	storedRel := ""
	if exist, err := s.fileRepo.FindByMD5AndPath(md5sum); err == nil && exist.StoredPath != "" {
		if _, serr := os.Stat(filepath.Join(s.cfg.Storage.Root, exist.StoredPath)); serr == nil {
			storedRel = exist.StoredPath
		}
	}

	// 无可复用文件则保存到 blob/<md5前2位>/<md5>
	if storedRel == "" {
		blobRel := filepath.ToSlash(filepath.Join("blobs", md5sum[:2], md5sum))
		blobAbs := filepath.Join(s.cfg.Storage.Root, blobRel)
		if err := os.MkdirAll(filepath.Dir(blobAbs), 0o755); err != nil {
			return nil, err
		}
		if err := os.Rename(tmpPath, blobAbs); err != nil {
			// 跨盘时回退为复制
			if cerr := copyFile(tmpPath, blobAbs); cerr != nil {
				return nil, cerr
			}
		}
		storedRel = blobRel
	}

	mimeType := fh.Header.Get("Content-Type")
	if mimeType == "" || mimeType == "application/octet-stream" {
		if t := mime.TypeByExtension(strings.ToLower(filepath.Ext(baseName))); t != "" {
			mimeType = t
		}
	}

	f := &model.File{
		ProjectID:  projectID,
		UserID:     userID,
		Filename:   filename,
		StoredPath: storedRel,
		Size:       size,
		MimeType:   mimeType,
		MD5:        md5sum,
		Visibility: visibility,
		Status:     1,
	}
	if err := s.fileRepo.Create(f); err != nil {
		return nil, err
	}

	// 更新配额、流量、webhook
	_ = s.projectRepo.UpdateStorageUsed(projectID, size)
	_ = s.userRepo.UpdateStorageUsed(userID, size)
	_ = s.trafficRepo.Create(&model.TrafficLog{
		UserID: userID, ProjectID: projectID, FileID: f.ID,
		Type: 1, Size: size, IP: utils.ClientIP(c), CreatedAt: time.Now(),
	})
	s.webhookSvc.Dispatch(userID, projectID, "file.upload", map[string]interface{}{
		"file_id": f.ID, "filename": f.Filename, "size": f.Size, "md5": f.MD5, "project_id": projectID,
	})
	utils.Info("storage", "用户#%d 上传文件 %s (%d字节)", userID, f.Filename, f.Size)
	return f, nil
}

func (s *FileService) checkTypeAllowed(filename, allowed string) bool {
	allowed = strings.TrimSpace(allowed)
	if allowed == "" || allowed == "*" {
		return true
	}
	ext := strings.ToLower(strings.TrimPrefix(filepath.Ext(filename), "."))
	if ext == "" {
		return true // 无扩展名不限制
	}
	for _, t := range strings.Split(allowed, ",") {
		t = strings.ToLower(strings.TrimSpace(strings.TrimPrefix(t, ".")))
		if t == "*" || t == ext {
			return true
		}
	}
	return false
}

// GetInfo 获取文件信息(所有者或管理员)
func (s *FileService) GetInfo(userID uint, id uint, isAdmin bool) (*model.File, error) {
	f, err := s.fileRepo.FindByID(id)
	if err != nil {
		return nil, apperr.ErrNotFound
	}
	if !isAdmin && f.UserID != userID {
		return nil, apperr.ErrForbidden
	}
	return f, nil
}

// List 文件列表
func (s *FileService) List(userID uint, isAdmin bool, filter repository.FileListFilter) ([]model.File, int64, error) {
	if !isAdmin {
		filter.UserID = userID
	}
	if filter.Page <= 0 {
		filter.Page = 1
	}
	if filter.PageSize <= 0 {
		filter.PageSize = 20
	}
	return s.fileRepo.List(filter)
}

// Open 打开文件物理句柄并校验访问权，记录流量
func (s *FileService) Open(c *gin.Context, userID uint, id uint, isAdmin bool) (*model.File, *os.File, error) {
	f, err := s.GetInfo(userID, id, isAdmin)
	if err != nil {
		return nil, nil, err
	}
	if f.Status != 1 {
		return nil, nil, apperr.ErrFileDeleted
	}
	abs := filepath.Join(s.cfg.Storage.Root, f.StoredPath)
	fp, err := os.Open(abs)
	if err != nil {
		utils.Error("storage", "打开文件失败 path=%s err=%v", abs, err)
		return nil, nil, fmt.Errorf("文件读取失败")
	}
	return f, fp, nil
}

// RecordDownload 记录下载行为
func (s *FileService) RecordDownload(c *gin.Context, f *model.File) {
	_ = s.fileRepo.IncrDownloadCount(f.ID)
	_ = s.trafficRepo.Create(&model.TrafficLog{
		UserID: f.UserID, ProjectID: f.ProjectID, FileID: f.ID,
		Type: 2, Size: f.Size, IP: utils.ClientIP(c), CreatedAt: time.Now(),
	})
}

// Delete 删除文件；permanent=true时硬删除
func (s *FileService) Delete(userID uint, id uint, isAdmin bool, permanent bool) error {
	f, err := s.GetInfo(userID, id, isAdmin)
	if err != nil {
		return err
	}

	if !permanent {
		if f.Status == 0 {
			return apperr.ErrFileDeleted
		}
		if err := s.fileRepo.SoftDelete(id); err != nil {
			return err
		}
		// 回收站不占配额
		_ = s.projectRepo.UpdateStorageUsed(f.ProjectID, -f.Size)
		_ = s.userRepo.UpdateStorageUsed(f.UserID, -f.Size)
		return nil
	}

	// 硬删除
	if err := s.fileRepo.Delete(id); err != nil {
		return err
	}
	_ = s.tempLinkRepo.DeleteByFile(id)
	// 若处于回收站，配额已扣减过
	if f.Status == 1 {
		_ = s.projectRepo.UpdateStorageUsed(f.ProjectID, -f.Size)
		_ = s.userRepo.UpdateStorageUsed(f.UserID, -f.Size)
	}
	// 物理文件无其他引用时删除
	if n, err := s.fileRepo.CountByStoredPath(f.StoredPath); err == nil && n == 0 {
		_ = os.Remove(filepath.Join(s.cfg.Storage.Root, f.StoredPath))
	}
	s.webhookSvc.Dispatch(f.UserID, f.ProjectID, "file.delete", map[string]interface{}{
		"file_id": f.ID, "filename": f.Filename, "permanent": permanent,
	})
	return nil
}

// Restore 从回收站恢复文件
func (s *FileService) Restore(userID uint, id uint, isAdmin bool) error {
	f, err := s.GetInfo(userID, id, isAdmin)
	if err != nil {
		return err
	}
	if f.Status != 0 {
		return fmt.Errorf("文件不在回收站中")
	}
	// 恢复前检查配额
	project, err := s.projectRepo.FindByID(f.ProjectID)
	if err == nil {
		if project.StorageUsed+f.Size > project.StorageLimit {
			return apperr.ErrQuotaExceeded
		}
	}
	user, err := s.userRepo.FindByID(f.UserID)
	if err == nil && user.StorageUsed+f.Size > user.StorageLimit {
		return apperr.ErrQuotaExceeded
	}
	if err := s.fileRepo.Restore(id); err != nil {
		return err
	}
	_ = s.projectRepo.UpdateStorageUsed(f.ProjectID, f.Size)
	_ = s.userRepo.UpdateStorageUsed(f.UserID, f.Size)
	return nil
}

// CreateTempLink 生成临时访问链接
func (s *FileService) CreateTempLink(userID uint, id uint, isAdmin bool, password string, maxCount int, expiresInSeconds int64) (*model.TempLink, error) {
	f, err := s.GetInfo(userID, id, isAdmin)
	if err != nil {
		return nil, err
	}
	if f.Status != 1 {
		return nil, apperr.ErrFileDeleted
	}
	if expiresInSeconds <= 0 {
		expiresInSeconds = s.settingInt("temp_link_max_age", 3600)
	}
	if expiresInSeconds > 7*24*3600 {
		expiresInSeconds = 7 * 24 * 3600
	}
	link := &model.TempLink{
		FileID:    f.ID,
		UserID:    userID,
		Token:     utils.RandomKey(48),
		MaxCount:  maxCount,
		ExpiresAt: time.Now().Add(time.Duration(expiresInSeconds) * time.Second),
	}
	if password != "" {
		link.Password = password
	}
	if err := s.tempLinkRepo.Create(link); err != nil {
		return nil, err
	}
	link.HasPwd = link.Password != ""
	return link, nil
}

// ResolveTempLink 通过token解析临时链接(校验有效期/次数/密码)，返回文件与物理句柄
func (s *FileService) ResolveTempLink(token, password string) (*model.File, *os.File, error) {
	link, err := s.tempLinkRepo.FindByToken(token)
	if err != nil {
		return nil, nil, apperr.ErrLinkExpired
	}
	if time.Now().After(link.ExpiresAt) {
		return nil, nil, apperr.ErrLinkExpired
	}
	if link.MaxCount > 0 && link.UsedCount >= link.MaxCount {
		return nil, nil, apperr.ErrLinkExpired
	}
	if link.Password != "" && link.Password != password {
		return nil, nil, apperr.ErrLinkPassword
	}
	f, err := s.fileRepo.FindByID(link.FileID)
	if err != nil || f.Status != 1 {
		return nil, nil, apperr.ErrNotFound
	}
	fp, err := os.Open(filepath.Join(s.cfg.Storage.Root, f.StoredPath))
	if err != nil {
		return nil, nil, fmt.Errorf("文件读取失败")
	}
	_ = s.tempLinkRepo.IncrUsed(link.ID)
	return f, fp, nil
}

// ---- 辅助函数 ----

func copyFile(src, dst string) error {
	in, err := os.Open(src)
	if err != nil {
		return err
	}
	defer in.Close()
	out, err := os.Create(dst)
	if err != nil {
		return err
	}
	defer out.Close()
	if _, err := io.Copy(out, in); err != nil {
		return err
	}
	return out.Sync()
}

func strconvUint(s string) (uint, error) {
	var n uint
	if s == "" {
		return 0, fmt.Errorf("empty")
	}
	for _, ch := range s {
		if ch < '0' || ch > '9' {
			return 0, fmt.Errorf("invalid")
		}
		n = n*10 + uint(ch-'0')
	}
	return n, nil
}