using System;
using System.IO;
using FluentAssertions;
using NUnit.Framework;

namespace Unplugged.IbmBits.Tests
{
    public class BinaryWriterExtensionMethodsTest
    {
        [Test]
        public void WriteEbcdicShouldWriteConvertedBytes()
        {
            var value = "Nope";
            var expected = new byte[] { 0xD5, 0x96, 0x97, 0x85 };
            VerifyBytesWritten(w => w.WriteEbcdic(value), expected);
        }

        [Test]
        public void WriteInt16ShouldReverseBytes()
        {
            Int16 value = 100 + 7 * 256;
            var expected = new byte[] { 7, 100 };
            VerifyBytesWritten(w => w.WriteBigEndian(value), expected);
        }

        [Test]
        public void WriteInt32ShouldReverseBytes()
        {
            Int32 value = 13 + (11 + (29 + 17 * 256) * 256) * 256;
            var expected = new byte[] { 17, 29, 11, 13 };
            VerifyBytesWritten(w => w.WriteBigEndian(value), expected);
        }

        [Test]
        public void WriteSingleShouldConvertToIbmFormat()
        {
            Single value = 64.125488f;
            var expected = new byte[] { 66, 64, 32, 32 };
            VerifyBytesWritten(w => w.WriteIbmSingle(value), expected);
        }

        public static void VerifyBytesWritten(Action<BinaryWriter> act, byte[] expected)
        {
            var bytes = new byte[expected.Length];
            using (var stream = new MemoryStream(bytes))
            using (var writer = new BinaryWriter(stream))
            {
                // Act
                act(writer);

                // Assert
                stream.Position.Should().Be(expected.Length, "Wrong number of bytes were written.");
            }
            bytes.Should().Equal(expected);
        }
    }
}