package service

import (
	"bytes"
	"cmp"
	"context"
	"crypto/sha256"
	"fmt"
	"image"
	"image/jpeg"
	"image/png"
	"io"
	"mime"
	"mime/multipart"
	"net/http"
	"path/filepath"
	"strings"

	"with_you/internal/model"
	"with_you/internal/pkg/s3"
	"with_you/internal/repository"

	"github.com/disintegration/imaging"
	"go.uber.org/zap"

	_ "golang.org/x/image/bmp"
	_ "golang.org/x/image/tiff"
)

// UploadFileResult 通用文件上传结果
type UploadFileResult struct {
	URL      string `json:"url"`
	Name     string `json:"name"`
	Size     int64  `json:"size"`
	MimeType string `json:"mime_type"`
}

// UploadService 上传服务接口
type UploadService interface {
	UploadImage(ctx context.Context, file *multipart.FileHeader) (string, string, string, error)
	UploadImageBytes(ctx context.Context, raw []byte, filename string) (url, previewURL, previewURLLarge string, err error)
	UploadAvatar(ctx context.Context, userID string, file *multipart.FileHeader) (string, error)
	UploadCover(ctx context.Context, userID string, file *multipart.FileHeader) (string, error)
	// UploadFile 上传聊天文件。
	// displayName 为前端显式传入的真实文件名（用于展示）；
	// 当为空时回退到 multipart header 中的 Filename。
	// 注意：原生端 expo-file-system 的 File.upload() 无法自定义 multipart filename，
	// 文件常被复制到缓存目录并以 UUID 命名，导致 Filename 丢失真实名，因此需要显式回传。
	UploadFile(ctx context.Context, file *multipart.FileHeader, folder string, uploaderID string, displayName string) (*UploadFileResult, error)
	GetURL(ctx context.Context, objectName string) (string, error)
	Delete(ctx context.Context, objectName string) error
	GeneratePreviewImages(ctx context.Context, originalData []byte, hash string) (previewURL, previewURLLarge string, err error)
	ValidateChatMessageImageSegments(segments model.MessageSegments) error
	// GetExpiredURLSet 返回所有已从 S3 清理的文件 URL 集合，供 DTO 层标记失效
	GetExpiredURLSet(ctx context.Context) (map[string]struct{}, error)
}

// uploadService 上传服务实现
type uploadService struct {
	s3Client     *s3.Client
	userService  UserService
	uploadedRepo repository.UploadedFileRepository
}

// 预览图配置
const (
	PreviewMaxWidth  = 300 // 列表/网格模式最大宽度
	PreviewMaxHeight = 800 // 详情页最大高度
	PreviewQuality   = 70  // WebP 质量
)

// NewUploadService 创建上传服务
func NewUploadService(s3Client *s3.Client, userService UserService, uploadedRepo repository.UploadedFileRepository) UploadService {
	return &uploadService{
		s3Client:     s3Client,
		userService:  userService,
		uploadedRepo: uploadedRepo,
	}
}

// UploadImage 上传图片（返回原图URL和预览图URL）
func (s *uploadService) UploadImage(ctx context.Context, file *multipart.FileHeader) (string, string, string, error) {
	processedData, contentType, ext, err := prepareImageForUpload(file)
	if err != nil {
		return "", "", "", err
	}

	// 压缩后再计算哈希，确保同一压缩结果映射同一对象名
	hash := sha256.Sum256(processedData)
	hashStr := fmt.Sprintf("%x", hash)

	// 上传原图
	objectName := fmt.Sprintf("images/%s%s", hashStr, ext)
	url, err := s.s3Client.UploadData(ctx, objectName, processedData, contentType)
	if err != nil {
		return "", "", "", fmt.Errorf("failed to upload to S3: %w", err)
	}

	// 生成预览图
	previewURL, previewURLLarge, err := s.GeneratePreviewImages(ctx, processedData, hashStr)
	if err != nil {
		zap.L().Warn("Failed to generate preview images",
			zap.Error(err),
		)
	}

	return url, previewURL, previewURLLarge, nil
}

const maxUploadImageBytesFromBuffer = 15 << 20 // 与聊天内联解码上限一致，略大于 upload.max_file_size 时可接受

// UploadImageBytes 从内存字节上传图片（与 multipart 上传走同一套压缩与存储逻辑）。
func (s *uploadService) UploadImageBytes(ctx context.Context, raw []byte, filename string) (url, previewURL, previewURLLarge string, err error) {
	if len(raw) == 0 {
		return "", "", "", fmt.Errorf("empty image data")
	}
	if len(raw) > maxUploadImageBytesFromBuffer {
		return "", "", "", fmt.Errorf("image data too large")
	}

	detectedType := normalizeImageContentType(http.DetectContentType(raw))
	compressedData, compressedType, cerr := compressImageData(raw, detectedType)
	if cerr != nil {
		compressedData = raw
		compressedType = detectedType
	}
	compressedType = cmp.Or(compressedType, http.DetectContentType(compressedData))
	ext := cmp.Or(getExtFromContentType(compressedType), strings.ToLower(filepath.Ext(filename)), ".jpg")

	hash := sha256.Sum256(compressedData)
	hashStr := fmt.Sprintf("%x", hash)
	objectName := fmt.Sprintf("images/%s%s", hashStr, ext)
	url, err = s.s3Client.UploadData(ctx, objectName, compressedData, compressedType)
	if err != nil {
		return "", "", "", fmt.Errorf("failed to upload to S3: %w", err)
	}

	previewURL, previewURLLarge, prevErr := s.GeneratePreviewImages(ctx, compressedData, hashStr)
	if prevErr != nil {
		zap.L().Warn("UploadImageBytes: preview generation failed", zap.Error(prevErr))
	}
	return url, previewURL, previewURLLarge, nil
}

// getExtFromContentType 根据Content-Type获取文件扩展名
func getExtFromContentType(contentType string) string {
	baseType, _, err := mime.ParseMediaType(contentType)
	if err == nil && baseType != "" {
		contentType = baseType
	}

	switch contentType {
	case "image/jpg", "image/jpeg":
		return ".jpg"
	case "image/png":
		return ".png"
	case "image/gif":
		return ".gif"
	case "image/webp":
		return ".webp"
	case "image/bmp", "image/x-ms-bmp":
		return ".bmp"
	case "image/tiff":
		return ".tiff"
	default:
		return ""
	}
}

// UploadAvatar 上传头像
func (s *uploadService) UploadAvatar(ctx context.Context, userID string, file *multipart.FileHeader) (string, error) {
	processedData, contentType, ext, err := prepareImageForUpload(file)
	if err != nil {
		return "", err
	}

	// 压缩后再计算哈希
	hash := sha256.Sum256(processedData)
	hashStr := fmt.Sprintf("%x", hash)

	objectName := fmt.Sprintf("avatars/%s%s", hashStr, ext)

	url, err := s.s3Client.UploadData(ctx, objectName, processedData, contentType)
	if err != nil {
		return "", fmt.Errorf("failed to upload to S3: %w", err)
	}

	// 更新用户头像
	if s.userService != nil {
		user, err := s.userService.GetUserByID(ctx, userID)
		if err == nil && user != nil {
			user.Avatar = url
			err = s.userService.UpdateUser(ctx, user)
			if err != nil {
				// 更新失败不影响上传结果，只记录日志
				fmt.Printf("[UploadAvatar] failed to update user avatar: %v\n", err)
			}
		}
	}

	return url, nil
}

// UploadCover 上传头图（个人主页封面）
func (s *uploadService) UploadCover(ctx context.Context, userID string, file *multipart.FileHeader) (string, error) {
	processedData, contentType, ext, err := prepareImageForUpload(file)
	if err != nil {
		return "", err
	}

	// 压缩后再计算哈希
	hash := sha256.Sum256(processedData)
	hashStr := fmt.Sprintf("%x", hash)

	objectName := fmt.Sprintf("covers/%s%s", hashStr, ext)

	url, err := s.s3Client.UploadData(ctx, objectName, processedData, contentType)
	if err != nil {
		return "", fmt.Errorf("failed to upload to S3: %w", err)
	}

	// 更新用户头图
	if s.userService != nil {
		user, err := s.userService.GetUserByID(ctx, userID)
		if err == nil && user != nil {
			user.CoverURL = url
			err = s.userService.UpdateUser(ctx, user)
			if err != nil {
				// 更新失败不影响上传结果，只记录日志
				fmt.Printf("[UploadCover] failed to update user cover: %v\n", err)
			}
		}
	}

	return url, nil
}

// 聊天文件上传限制
const (
	MaxChatFileSize     = 50 << 20 // 50MB
	chatFileFolderLimit = 32       // folder 名长度上限，避免路径注入
)

// chatFileAllowedMime 允许上传的文件 MIME 白名单（按类型前缀匹配）。
// 不在白名单内的类型一律拒绝，防止上传可执行脚本等高危文件。
var chatFileAllowedMime = map[string]bool{
	// 文档
	"application/pdf": true,
	"application/msword":                                               true,
	"application/vnd.openxmlformats-officedocument.wordprocessingml.document":   true,
	"application/vnd.ms-excel":                                          true,
	"application/vnd.openxmlformats-officedocument.spreadsheetml.sheet":        true,
	"application/vnd.ms-powerpoint":                                     true,
	"application/vnd.openxmlformats-officedocument.presentationml.presentation": true,
	"application/rtf":        true,
	"text/plain":             true,
	"text/csv":               true,
	"text/markdown":          true,
	"application/json":       true,
	"application/xml":        true,
	"text/xml":               true,
	"application/zip":        true,
	"application/x-zip-compressed": true,
	"application/x-rar-compressed": true,
	"application/x-7z-compressed":  true,
	"application/gzip":             true,
	"application/x-tar":            true,
	// 音视频/图片（聊天文件入口）
	"audio/mpeg":   true,
	"audio/mp3":    true,
	"audio/wav":    true,
	"audio/x-wav":  true,
	"audio/aac":    true,
	"audio/x-m4a":  true,
	"audio/flac":   true,
	"video/mp4":    true,
	"video/quicktime": true,
	"video/x-msvideo": true,
	"video/webm":   true,
	"image/jpeg":   true,
	"image/png":    true,
	"image/gif":    true,
	"image/webp":   true,
	"image/bmp":    true,
	// 其他常用类型
	"application/octet-stream": true, // 部分客户端（如 Windows）上传无明确类型，需结合扩展名二次校验
}

// chatFileExtFallback 当 MIME 为 octet-stream 时，按扩展名推断的真实类型
var chatFileExtFallback = map[string]string{
	".pdf":  "application/pdf",
	".doc":  "application/msword",
	".docx": "application/vnd.openxmlformats-officedocument.wordprocessingml.document",
	".xls":  "application/vnd.ms-excel",
	".xlsx": "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
	".ppt":  "application/vnd.ms-powerpoint",
	".pptx": "application/vnd.openxmlformats-officedocument.presentationml.presentation",
	".zip":  "application/zip",
	".rar":  "application/x-rar-compressed",
	".7z":   "application/x-7z-compressed",
	".gz":   "application/gzip",
	".tar":  "application/x-tar",
	".mp3":  "audio/mpeg",
	".mp4":  "video/mp4",
	".mov":  "video/quicktime",
	".avi":  "video/x-msvideo",
	".json": "application/json",
	".csv":  "text/csv",
	".md":   "text/markdown",
	".txt":  "text/plain",
}

// normalizeChatFileMime 校正文件 MIME 类型：
//  1. 解析 multipart header 的 Content-Type；
//  2. 若为通用 octet-stream，依据文件名扩展名回退到更具体的类型；
//  3. 全部兜底为 application/octet-stream。
func normalizeChatFileMime(headerType, filename string) string {
	baseType, _, err := mime.ParseMediaType(strings.TrimSpace(headerType))
	if err != nil || baseType == "" {
		baseType = "application/octet-stream"
	}
	baseType = strings.ToLower(baseType)

	if baseType == "application/octet-stream" {
		ext := strings.ToLower(filepath.Ext(filename))
		if real, ok := chatFileExtFallback[ext]; ok {
			return real
		}
	}
	return baseType
}

// validateChatFile 校验聊天文件大小与 MIME 白名单
func validateChatFile(size int64, mimeType string) error {
	if size <= 0 {
		return fmt.Errorf("文件为空")
	}
	if size > MaxChatFileSize {
		return fmt.Errorf("文件大小超过限制（最大 %d MB）", MaxChatFileSize>>20)
	}
	if !chatFileAllowedMime[mimeType] {
		return fmt.Errorf("不支持的文件类型: %s", mimeType)
	}
	return nil
}

// sanitizeFileName 清洗用于展示的文件名：
//   - 去除首尾空白与两侧的路径分隔符/点号，避免展示绝对路径或隐藏文件名；
//   - 去掉任何目录成分（防止 "a/b.pdf" 这类注入展示层）；
//   - 限制长度，避免超长名影响存储与列表展示。
//
// 注意：仅用于"展示名"，不影响 S3 对象名（对象名始终为内容哈希）。
func sanitizeFileName(name string) string {
	name = strings.TrimSpace(name)
	if name == "" {
		return ""
	}
	// 统一分隔符后只保留文件名部分（basename）
	name = filepath.Base(strings.ReplaceAll(name, "\\", "/"))
	// 去除开头多余的 "."（避免 ".file" 之外出现 "..file" 之类异常），但保留正常的隐藏文件名
	name = strings.TrimLeft(name, ".")
	name = strings.TrimSpace(name)
	if len(name) > 255 {
		// 过长时保留扩展名，截断主名
		ext := strings.ToLower(filepath.Ext(name))
		cut := 255 - len(ext)
		if cut < 1 {
			cut = 1
		}
		name = name[:cut] + ext
	}
	return name
}

// UploadFile 上传聊天文件（非图片，按文件类型原样存储到 S3）
// folder 用于隔离不同来源（如 chat/post），仅允许字母数字与下划线。
// uploaderID 为上传者用户 ID，用于审计。
// displayName 为前端显式传入的真实文件名（用于展示），
// 为空时回退到 multipart header 中的 Filename。
func (s *uploadService) UploadFile(ctx context.Context, file *multipart.FileHeader, folder string, uploaderID string, displayName string) (*UploadFileResult, error) {
	if file == nil {
		return nil, fmt.Errorf("文件为空")
	}
	if file.Size > MaxChatFileSize {
		return nil, fmt.Errorf("文件大小超过限制（最大 %d MB）", MaxChatFileSize>>20)
	}

	// 选择用于展示的真实文件名：优先用前端显式回传的 displayName，
	// 它最贴近用户原始文件名（multipart header 的 Filename 在原生端常被 UUID 覆盖）。
	displayName = sanitizeFileName(displayName)
	headerName := sanitizeFileName(file.Filename)
	fileName := cmp.Or(displayName, headerName)

	// 校验与规范化 folder，避免路径穿越
	folder = strings.Map(func(r rune) rune {
		if (r >= 'a' && r <= 'z') || (r >= 'A' && r <= 'Z') || (r >= '0' && r <= '9') || r == '_' {
			return r
		}
		return -1
	}, folder)
	if folder == "" || len(folder) > chatFileFolderLimit {
		folder = "chat"
	}

	// 校验 MIME 类型
	mimeType := normalizeChatFileMime(file.Header.Get("Content-Type"), file.Filename)
	if err := validateChatFile(file.Size, mimeType); err != nil {
		return nil, err
	}

	// 读取文件内容
	f, err := file.Open()
	if err != nil {
		return nil, fmt.Errorf("打开文件失败: %w", err)
	}
	defer f.Close()

	data, err := io.ReadAll(f)
	if err != nil {
		return nil, fmt.Errorf("读取文件失败: %w", err)
	}

	if err := validateChatFile(int64(len(data)), mimeType); err != nil {
		return nil, err
	}

	// 以内容哈希命名，避免重复存储；扩展名优先取真实文件名（便于浏览器识别）
	hash := sha256.Sum256(data)
	hashStr := fmt.Sprintf("%x", hash)
	// header Filename 在原生端常为 UUID，因此优先从真实展示名推导扩展名，
	// 两者都没有时再从 MIME 推断
	ext := strings.ToLower(filepath.Ext(fileName))
	if ext == "" {
		ext = strings.ToLower(filepath.Ext(file.Filename))
	}
	if ext == "" {
		// 从 MIME 推断扩展名（mime.ExtensionsByType 在新版本返回 (exts, err)）
		if es, _ := mime.ExtensionsByType(mimeType); len(es) > 0 {
			ext = es[0]
		} else {
			ext = ".bin"
		}
	}

	objectName := fmt.Sprintf("files/%s/%s%s", folder, hashStr, ext)
	url, err := s.s3Client.UploadData(ctx, objectName, data, mimeType)
	if err != nil {
		return nil, fmt.Errorf("上传到 S3 失败: %w", err)
	}

	// 写入上传记录，用于 7 天 TTL 过期清理（失败仅记日志，不影响上传）
	if s.uploadedRepo != nil {
		record := &model.UploadedFile{
			URL:        url,
			ObjectName: objectName,
			Name:       fileName,
			Size:       file.Size,
			MimeType:   mimeType,
			Folder:     folder,
			UploaderID: uploaderID,
		}
		if rerr := s.uploadedRepo.Create(ctx, record); rerr != nil {
			zap.L().Warn("写入文件上传记录失败", zap.String("url", url), zap.Error(rerr))
		}
	}

	return &UploadFileResult{
		URL:      url,
		Name:     fileName,
		Size:     file.Size,
		MimeType: mimeType,
	}, nil
}

// GetExpiredURLSet 返回所有已从 S3 清理的文件 URL 集合，供 DTO 层标记失效
func (s *uploadService) GetExpiredURLSet(ctx context.Context) (map[string]struct{}, error) {
	if s.uploadedRepo == nil {
		return nil, nil
	}
	return s.uploadedRepo.GetExpiredURLSet(ctx)
}

// GetURL 获取文件URL
func (s *uploadService) GetURL(ctx context.Context, objectName string) (string, error) {
	return s.s3Client.GetURL(ctx, objectName)
}

// Delete 删除文件
func (s *uploadService) Delete(ctx context.Context, objectName string) error {
	return s.s3Client.Delete(ctx, objectName)
}

func prepareImageForUpload(file *multipart.FileHeader) ([]byte, string, string, error) {
	f, err := file.Open()
	if err != nil {
		return nil, "", "", fmt.Errorf("failed to open file: %w", err)
	}
	defer f.Close()

	originalData, err := io.ReadAll(f)
	if err != nil {
		return nil, "", "", fmt.Errorf("failed to read file: %w", err)
	}

	// 优先从文件字节探测真实类型，避免前端压缩/转码后 header 与实际格式不一致
	detectedType := normalizeImageContentType(http.DetectContentType(originalData))
	headerType := normalizeImageContentType(file.Header.Get("Content-Type"))
	contentType := cmp.Or(detectedType, headerType, "application/octet-stream")

	compressedData, compressedType, err := compressImageData(originalData, contentType)
	if err != nil {
		// 压缩失败时回退到原图，保证上传可用性
		compressedData = originalData
		compressedType = contentType
	}

	compressedType = cmp.Or(compressedType, http.DetectContentType(compressedData))

	ext := cmp.Or(getExtFromContentType(compressedType), strings.ToLower(filepath.Ext(file.Filename)), ".jpg")

	return compressedData, compressedType, ext, nil
}

func compressImageData(data []byte, contentType string) ([]byte, string, error) {
	contentType = normalizeImageContentType(contentType)

	// GIF/WebP 等格式先保留原图，避免动画和透明通道丢失
	if contentType == "image/gif" || contentType == "image/webp" {
		return data, contentType, nil
	}

	if contentType != "image/jpeg" &&
		contentType != "image/png" &&
		contentType != "image/bmp" &&
		contentType != "image/x-ms-bmp" &&
		contentType != "image/tiff" {
		return data, contentType, nil
	}

	img, _, err := image.Decode(bytes.NewReader(data))
	if err != nil {
		return nil, "", fmt.Errorf("failed to decode image: %w", err)
	}

	var buf bytes.Buffer
	switch contentType {
	case "image/png":
		encoder := png.Encoder{CompressionLevel: png.BestCompression}
		if err := encoder.Encode(&buf, img); err != nil {
			return nil, "", fmt.Errorf("failed to encode png: %w", err)
		}
		return buf.Bytes(), "image/png", nil
	default:
		// BMP/TIFF 等无损大图统一压缩为 JPEG，控制体积
		if err := jpeg.Encode(&buf, img, &jpeg.Options{Quality: 82}); err != nil {
			return nil, "", fmt.Errorf("failed to encode jpeg: %w", err)
		}
		return buf.Bytes(), "image/jpeg", nil
	}
}

func normalizeImageContentType(contentType string) string {
	if contentType == "" {
		return ""
	}

	baseType, _, err := mime.ParseMediaType(contentType)
	if err == nil && baseType != "" {
		contentType = baseType
	}

	switch strings.ToLower(contentType) {
	case "image/jpg":
		return "image/jpeg"
	case "image/jpeg":
		return "image/jpeg"
	case "image/png":
		return "image/png"
	case "image/gif":
		return "image/gif"
	case "image/webp":
		return "image/webp"
	case "image/bmp", "image/x-ms-bmp":
		return "image/bmp"
	case "image/tiff":
		return "image/tiff"
	default:
		return contentType
	}
}

// GeneratePreviewImages 生成预览图
func (s *uploadService) GeneratePreviewImages(ctx context.Context, originalData []byte, hash string) (previewURL, previewURLLarge string, err error) {
	img, _, err := image.Decode(bytes.NewReader(originalData))
	if err != nil {
		return "", "", fmt.Errorf("failed to decode image: %w", err)
	}

	bounds := img.Bounds()
	originalWidth := bounds.Dx()
	originalHeight := bounds.Dy()

	// 生成普通预览图（列表/网格模式）
	previewURL, err = s.generatePreview(ctx, img, originalWidth, originalHeight, "preview", PreviewMaxWidth, hash)
	if err != nil {
		zap.L().Warn("Failed to generate preview",
			zap.Error(err),
		)
	}

	// 生成大预览图（详情页）
	previewURLLarge, err = s.generatePreview(ctx, img, originalWidth, originalHeight, "large", PreviewMaxHeight, hash)
	if err != nil {
		zap.L().Warn("Failed to generate large preview",
			zap.Error(err),
		)
	}

	return previewURL, previewURLLarge, nil
}

// generatePreview 生成单个预览图
func (s *uploadService) generatePreview(ctx context.Context, img image.Image, originalWidth, originalHeight int, mode string, maxDim int, hash string) (string, error) {
	var targetWidth, targetHeight int

	// 计算目标尺寸
	if originalWidth > originalHeight {
		// 宽图：按宽度缩放
		if originalWidth > maxDim {
			targetWidth = maxDim
			targetHeight = int(float64(originalHeight) * float64(maxDim) / float64(originalWidth))
		} else {
			return "", nil // 图片足够小，不需要生成预览图
		}
	} else {
		// 高图：按高度缩放
		if originalHeight > maxDim {
			targetHeight = maxDim
			targetWidth = int(float64(originalWidth) * float64(maxDim) / float64(originalHeight))
		} else {
			return "", nil // 图片足够小，不需要生成预览图
		}
	}

	// 缩放图片（使用高质量 Lanczos 算法）
	scaledImg := imaging.Resize(img, targetWidth, targetHeight, imaging.Lanczos)

	// 编码为 JPEG（WebP 在某些设备上可能不支持，使用 JPEG 保证兼容性）
	var buf bytes.Buffer
	if err := jpeg.Encode(&buf, scaledImg, &jpeg.Options{Quality: PreviewQuality}); err != nil {
		return "", fmt.Errorf("failed to encode jpeg: %w", err)
	}

	// 构建对象名：thumbnails/{hash}_{mode}.jpg
	objectName := fmt.Sprintf("thumbnails/%s_%s.jpg", hash, mode)

	// 上传到 S3
	url, err := s.s3Client.UploadData(ctx, objectName, buf.Bytes(), "image/jpeg")
	if err != nil {
		return "", fmt.Errorf("failed to upload preview: %w", err)
	}

	return url, nil
}