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

namespace Ips.Library.Basic
{
    public static class FileUtil
    {
        public static bool DeleteIfExists(string filePath)
        {
            if (!File.Exists(filePath))
            {
                return false;
            }

            File.Delete(filePath);
            return true;
        }

        public static string GetExtension(string fileNameWithExtension)
        {
            var lastDotIndex = fileNameWithExtension.LastIndexOf('.');
            if (lastDotIndex < 0)
            {
                return null;
            }

            return fileNameWithExtension.Substring(lastDotIndex + 1);
        }

        public static async Task<string> ReadAllTextAsync(string path)
        {
            using (var reader = File.OpenText(path))
            {
                return await reader.ReadToEndAsync();
            }
        }

        public static async Task<byte[]> ReadAllBytesAsync(string path)
        {
            using (var stream = File.Open(path, FileMode.Open))
            {
                var result = new byte[stream.Length];
                await stream.ReadAsync(result, 0, (int)stream.Length);
                return result;
            }
        }

        public static async Task<string[]> ReadAllLinesAsync(string path,
            Encoding encoding = null,
            FileMode fileMode = FileMode.Open,
            FileAccess fileAccess = FileAccess.Read,
            FileShare fileShare = FileShare.Read,
            int bufferSize = 4096,
            FileOptions fileOptions = FileOptions.Asynchronous | FileOptions.SequentialScan)
        {
            if (encoding == null)
            {
                encoding = Encoding.UTF8;
            }

            var lines = new List<string>();

            using (var stream = new FileStream(
                path,
                fileMode,
                fileAccess,
                fileShare,
                bufferSize,
                fileOptions))
            {
                using (var reader = new StreamReader(stream, encoding))
                {
                    string line;
                    while ((line = await reader.ReadLineAsync()) != null)
                    {
                        lines.Add(line);
                    }
                }
            }

            return lines.ToArray();
        }

        public static short[] ReadAllShorts(string file)
        {
            short[] result = null;
            using (var fs = new FileStream(file, FileMode.Open, FileAccess.Read, FileShare.Read))
            {
                result = new short[fs.Length / 2];
                using (var reader = new BinaryReader(fs))
                {
                    int i = 0;
                    while (i < result.Length)
                    {
                        result[i++] = reader.ReadInt16();
                    }
                }
            }
            return result;
        }

        public static void AppendToFileName(string val, ref string fileName)
        {
            if (fileName.IsNullOrWhitespace()) return;
            var dotIdx = fileName.LastIndexOf('.');
            var fileNameNoExt = fileName.Substring(0, dotIdx);
            var ext = fileName.Substring(dotIdx);
            fileName= fileNameNoExt + val + ext;
        }
    }
}