using System;
using System.IO;
using System.Text;

namespace Siger.Middlelayer.Common.Helpers
{
    public  class FileHelper
    {
        public static void DeleteFile(string fileName)
        {
            try
            {
                if (System.IO.File.Exists(fileName))
                {
                    System.IO.File.Delete(fileName);
                }
            }
            catch 
            {
               //ignore
            }
        }

        public static bool IsExcelFile(string fileName)
        {
            fileName = fileName.ToLower();
            if (fileName.EndsWith(".xlsx"))
            {
                return true;
            }

            return false;
        }

        public static string GetExtension(string fileName)
        {
            return fileName.Substring(fileName.LastIndexOf('.'), fileName.Length - fileName.LastIndexOf('.'));
        }


        public static Encoding GetType(string fileName)
        {
            FileStream fs = new FileStream(fileName, FileMode.Open, FileAccess.Read);
            Encoding r = GetType(fs);
            fs.Close();
            return r;
        }

        /// <summary>
        /// 通过给定的文件流，判断文件的编码类型
        /// </summary>
        /// <param name="fs"></param>
        /// <returns>文件的编码类型</returns>
        public static Encoding GetType(FileStream fs)
        {
            Encoding reVal = Encoding.Default;

            BinaryReader r = new BinaryReader(fs, Encoding.Default);
            int i;
            int.TryParse(fs.Length.ToString(), out i);
            byte[] ss = r.ReadBytes(i);
            if (IsUTF8Bytes(ss) || (ss[0] == 0xEF && ss[1] == 0xBB && ss[2] == 0xBF))
            {
                reVal = Encoding.UTF8;
            }
            else if (ss[0] == 0xFE && ss[1] == 0xFF && ss[2] == 0x00)
            {
                reVal = Encoding.BigEndianUnicode;
            }
            else if (ss[0] == 0xFF && ss[1] == 0xFE && ss[2] == 0x41)
            {
                reVal = Encoding.Unicode;
            }
            r.Close();
            return reVal;
        }

        /// <summary>
        /// 判断是否是不带 BOM 的 UTF8 格式
        /// </summary>
        /// <param name="data"></param>
        /// <returns></returns>
        private static bool IsUTF8Bytes(byte[] data)
        {
            int charByteCounter = 1; //计算当前正分析的字符应还有的字节数
            byte curByte; //当前分析的字节.
            for (int i = 0; i < data.Length; i++)
            {
                curByte = data[i];
                if (charByteCounter == 1)
                {
                    if (curByte >= 0x80)
                    {
                        //判断当前
                        while (((curByte <<= 1) & 0x80) != 0)
                        {
                            charByteCounter++;
                        }
                        //标记位首位若为非0 则至少以2个1开始 如:110XXXXX...........1111110X
                        if (charByteCounter == 1 || charByteCounter > 6)
                        {
                            return false;
                        }
                    }
                }
                else
                {
                    //若是UTF-8 此时第一位必须为1
                    if ((curByte & 0xC0) != 0x80)
                    {
                        return false;
                    }
                    charByteCounter--;
                }
            }
            if (charByteCounter > 1)
            {
                throw new Exception("非预期的byte格式");
            }
            return true;
        }
        public static string ReadFile(string path)
        {
            try
            {
                var encoding = GetType(path);
                if (!Equals(encoding, Encoding.UTF8))
                {
                    Encoding.RegisterProvider(CodePagesEncodingProvider.Instance);
                    encoding = Encoding.GetEncoding("gb2312");
                }

                var fs = new FileStream(path, FileMode.Open, FileAccess.Read);
                var reader = new StreamReader(fs, encoding);
                var strhtml = reader.ReadToEnd();

                fs.Close();
                fs.Close();

                return strhtml;
            }
            catch
            {
                return string.Empty;
            }
        }
        public static void WriteFile(string content, string path)
        {
            StreamWriter writer = File.CreateText(path);
            writer.Write(content);
            writer.Close();
        }

        /// <summary>
        /// 读文件到byte[]
        /// </summary>
        /// <param name="fileName">硬盘文件路径</param>
        /// <returns></returns>
        public static byte[] ReadFileToByte(string fileName)
        {
            FileStream pFileStream = null;
            var pReadByte = new byte[0];
            try
            {
                pFileStream = new FileStream(fileName, FileMode.Open, FileAccess.Read);
                var r = new BinaryReader(pFileStream);
                r.BaseStream.Seek(0, SeekOrigin.Begin);
                pReadByte = r.ReadBytes((int)r.BaseStream.Length);
                return pReadByte;
            }
            catch
            {
                return pReadByte;
            }
            finally
            {
                pFileStream?.Close();
            }
        }
    }
}
