// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

using System;
using System.Buffers;
using System.IO;
using System.Text;
using Microsoft.AspNetCore.SignalR.Internal;
using Xunit;

namespace Microsoft.AspNetCore.SignalR.Common.Tests.Internal.Protocol
{
    public class Utf8BufferTextReaderTests
    {
        [Fact]
        public void ReadingWhenCharBufferBigEnough()
        {
            var buffer = new ReadOnlySequence<byte>(Encoding.UTF8.GetBytes("Hello World"));
            var reader = new Utf8BufferTextReader();
            reader.SetBuffer(buffer);

            var chars = new char[1024];
            var read = reader.Read(chars, 0, chars.Length);

            Assert.Equal("Hello World", new string(chars, 0, read));
        }

        [Fact]
        public void ReadingUnicodeWhenCharBufferBigEnough()
        {
            var buffer = new ReadOnlySequence<byte>(Encoding.UTF8.GetBytes("a\u00E4\u00E4\u00a9o"));
            var reader = new Utf8BufferTextReader();
            reader.SetBuffer(buffer);

            var chars = new char[1024];
            var read = reader.Read(chars, 0, chars.Length);

            Assert.Equal(5, read);
            Assert.Equal("a\u00E4\u00E4\u00a9o", new string(chars, 0, read));

            read = reader.Read(chars, 0, chars.Length);

            Assert.Equal(0, read);
        }

        [Fact]
        public void ReadingWhenCharBufferBigEnoughAndNotStartingFromZero()
        {
            var buffer = new ReadOnlySequence<byte>(Encoding.UTF8.GetBytes("Hello World"));
            var reader = new Utf8BufferTextReader();
            reader.SetBuffer(buffer);

            var chars = new char[1024];
            var read = reader.Read(chars, 10, chars.Length - 10);

            Assert.Equal(11, read);
            Assert.Equal("Hello World", new string(chars, 10, read));
        }

        [Fact]
        public void ReadingWhenBufferTooSmall()
        {
            var buffer = new ReadOnlySequence<byte>(Encoding.UTF8.GetBytes("Hello World"));
            var reader = new Utf8BufferTextReader();
            reader.SetBuffer(buffer);

            var chars = new char[5];
            var read = reader.Read(chars, 0, chars.Length);

            Assert.Equal(5, read);
            Assert.Equal("Hello", new string(chars, 0, read));

            read = reader.Read(chars, 0, chars.Length);

            Assert.Equal(5, read);
            Assert.Equal(" Worl", new string(chars, 0, read));

            read = reader.Read(chars, 0, chars.Length);

            Assert.Equal(1, read);
            Assert.Equal("d", new string(chars, 0, read));

            read = reader.Read(chars, 0, chars.Length);

            Assert.Equal(0, read);

            read = reader.Read(chars, 0, 1);

            Assert.Equal(0, read);
        }

        [Fact]
        public void ReadingUnicodeWhenBufferTooSmall()
        {
            var buffer = new ReadOnlySequence<byte>(Encoding.UTF8.GetBytes("\u00E4\u00E4\u00E5"));
            var reader = new Utf8BufferTextReader();
            reader.SetBuffer(buffer);

            var chars = new char[2];
            var read = reader.Read(chars, 0, chars.Length);

            Assert.Equal(2, read);
            Assert.Equal("\u00E4\u00E4", new string(chars, 0, read));

            read = reader.Read(chars, 0, chars.Length);

            Assert.Equal(1, read);
            Assert.Equal("\u00E5", new string(chars, 0, read));

            read = reader.Read(chars, 0, chars.Length);

            Assert.Equal(0, read);

            read = reader.Read(chars, 0, 1);

            Assert.Equal(0, read);
        }
    }
}