package constants

import (
	"github.com/gabriel-vasile/mimetype"
	"io"
	"strings"
)

type FileType string

const (
	FileTypeUnknown FileType = "unknown"
	FileTypeImage   FileType = "image"
	//FileTypeVideo FileType = "video"
	FileTypeExcel FileType = "excel"
	FileTypeWord  FileType = "word"
	FileTypeTxt   FileType = "txt"
	FileTypePDF   FileType = "pdf"
)

var FileTypeMappings = map[FileType][]string{
	FileTypeImage: {
		"image/jpeg", "image/png", "image/gif", "image/webp", "image/svg+xml",
		".jpg", ".jpeg", ".png", ".gif", ".webp", ".svg",
	},
	FileTypeExcel: {
		"application/vnd.ms-excel",
		"application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
		".xls", ".xlsx",
	},
	FileTypeWord: {
		"application/msword",
		"application/vnd.openxmlformats-officedocument.wordprocessingml.document",
		".doc", ".docx",
	},
	FileTypePDF: {
		"application/pdf",
		".pdf",
	},
	FileTypeTxt: {
		"text/plain",
		".txt",
	},
}

func DetectFileType(file io.ReadSeeker) (FileType, error) {
	// 读取文件头（512字节足够检测大多数类型）
	buffer := make([]byte, 512)
	n, err := file.Read(buffer)
	if err != nil && err != io.EOF {
		return FileTypeUnknown, err
	}

	// 重置读取位置
	if _, err := file.Seek(0, io.SeekStart); err != nil {
		return FileTypeUnknown, err
	}

	// 检测 MIME 类型
	detectedMIME := mimetype.Detect(buffer[:n]).String()

	// 遍历映射表，匹配 MIME 或扩展名
	for fileType, mimesOrExts := range FileTypeMappings {
		for _, item := range mimesOrExts {
			if strings.HasPrefix(item, ".") {
				continue // 跳过扩展名（仅 MIME 检测）
			}
			if item == detectedMIME {
				return fileType, nil
			}
		}
	}

	return FileTypeUnknown, nil
}