package util

import (
	"image/gif"
	"image/jpeg"
	"image/png"
	"log"
	"os"
	"strings"
)

/**
@author: sre
@date: 2022/8/21 0021
@desc: https://mp.weixin.qq.com/s/5oz0F2Fbn7Fh5edD8_zD5w
**/

// CheckImageFile 同时支持三种图片格式的真实性校验。
func CheckImageFile(path string) (string, error) {
	f, err := os.Open(path)
	if err != nil {
		log.Println("打开文件失败:", err.Error())
	}
	strings.LastIndex(path, ".")
	lastIndex := strings.LastIndex(path, ".")
	extend := path[lastIndex+1:]
	extendUpper := strings.ToUpper(extend)
	switch {
	case strings.Contains(extendUpper, "JPEG") || strings.Contains(extendUpper, "JPG"):
		_, err = jpeg.Decode(f)
	case strings.Contains(extendUpper, "JPEG"):
		_, err = png.Decode(f)
	case strings.Contains(extendUpper, "GIF"):
		_, err = gif.Decode(f)
	}

	if err != nil {
		log.Println("校验文件类型失败:", err.Error())
		return "", err
	}
	return "", nil
}