using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;

namespace FileServerApi.Common
{
    public class Common
    {
        /// <summary>  
        /// 获取文件的MD5码  
        /// </summary>  
        /// <param name="fileName">传入的文件名（含路径及后缀名）</param>  
        /// <returns></returns>  
        public static string GetMD5HashFromFile(string fileName)
        {
            try
            {
                FileStream file = new FileStream(fileName, System.IO.FileMode.Open);
                MD5 md5 = new MD5CryptoServiceProvider();
                byte[] retVal = md5.ComputeHash(file);
                file.Close();
                StringBuilder sb = new StringBuilder();
                for (int i = 0; i < retVal.Length; i++)
                {
                    sb.Append(retVal[i].ToString("x2"));
                }
                return sb.ToString();
            }
            catch (Exception ex)
            {
                throw new Exception("GetMD5HashFromFile() fail,error:" + ex.Message);
            }
        }

        /// <summary>
        /// 生成缩略图
        /// </summary>
        /// <param name="path"></param>
        /// <param name="fileName"></param>
        /// <returns></returns>
        public static string GetThumbImg(string path, string fileName,string fileExt)
        {
            string[] filetypes = new string[] { ".jpg", ".jpeg", ".gif", ".bmp", ".png" };

            if (filetypes.Contains(fileExt))
            {
                FileStream file = new FileStream(path + fileName, System.IO.FileMode.Open);
                //获取图片的高度和宽度
                System.Drawing.Image Img = System.Drawing.Image.FromStream(file);
                int _Width = Img.Width;
                int _Height = Img.Height;

                int _sHeight = 120;//设置生成缩略图的高度 
                int _sWidth = 120;//设置生成缩略图的宽度

                #region 缩略图大小只设置了最大范围，并不是实际大小
                float realbili = (float)_Width / (float)_Height;
                float wishbili = (float)_sWidth / (float)_sHeight;

                //实际图比缩略图最大尺寸更宽矮，以宽为准
                if (realbili > wishbili)
                {
                    _sHeight = (int)((float)_sWidth / realbili);
                }
                //实际图比缩略图最大尺寸更高长，以高为准
                else
                {
                    _sWidth = (int)((float)_sHeight * realbili);
                }
                #endregion

                string[] filenames = fileName.Split('.');
                string OutThumbFileName = filenames[0].ToString() + "_s." + filenames[1].ToString();
                string ImgFilePath = path + OutThumbFileName;

                System.Drawing.Image newImg = Img.GetThumbnailImage(_sWidth, _sHeight, null, System.IntPtr.Zero);
                newImg.Save(ImgFilePath);
                newImg.Dispose();

                Img.Dispose();

                return OutThumbFileName;
            }
            else
            {
                return "";
            }

        }
    }
}