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

namespace System.IO
{
	/// <summary>
	/// Provides extension methods for the <see cref="Stream"/>.
	/// </summary>
	public static class StreamExtensions
	{
		/// <summary>
		/// Reads a line from a <see cref="Stream"/>.
		/// </summary>
		/// <param name="stream">The stream to read from.</param>
		/// <param name="encoding">The encoding to use.</param>
		/// <param name="eol">The character determinating a line end.</param>
		/// <returns></returns>
		public static string ReadLine(this Stream stream, Encoding encoding = null, char? eol = null)
		{
			encoding ??= Encoding.Default;
			eol ??= Environment.NewLine.Last();

			if (!stream.CanRead)
				return null;

			var bytes = new List<byte>();
			char ch;
			do
			{
				int result = stream.ReadByte();
				if (result == -1)
					break;

				byte b = (byte)result;
				bytes.Add(b);
				ch = (char)result;
			}
			while (ch != eol);

			return encoding.GetString(bytes.ToArray()).Trim();
		}

		/// <summary>
		/// Reads a line from a <see cref="Stream"/> asynchronous.
		/// </summary>
		/// <param name="stream">The stream to read from.</param>
		/// <param name="encoding">The encoding to use.</param>
		/// <param name="eol">The character determinating a line end.</param>
		/// <param name="cancellationToken">The token to monitor for cancellation requests. The default value is <see cref="CancellationToken.None"/>.</param>
		/// <returns></returns>
		public static async Task<string> ReadLineAsync(this Stream stream, Encoding encoding = null, char? eol = null, CancellationToken cancellationToken = default)
		{
			encoding ??= Encoding.Default;
			eol ??= Environment.NewLine.Last();

			if (!stream.CanRead)
				return null;

			var bytes = new List<byte>();
			char ch;
			do
			{
				byte[] buffer = new byte[1];
				int count = await stream.ReadAsync(buffer, 0, buffer.Length, cancellationToken);
				if (count == 0)
					break;

				bytes.Add(buffer[0]);
				ch = (char)buffer[0];
			}
			while (ch != eol);

			return encoding.GetString(bytes.ToArray()).Trim();
		}
	}
}