using System.Buffers.Binary;

namespace MoShiro.Measurement.Tests;

public sealed class IcmpReplyTests
{
    [Theory]
    [InlineData((byte)0)]
    [InlineData((byte)129)]
    public void ReplyMustMatchTypeCodeSequenceAndPayload(byte replyType)
    {
        byte[] request = new byte[44];
        request[8] = 71;
        byte[] reply = (byte[])request.Clone();
        reply[0] = replyType;
        BinaryPrimitives.WriteUInt16BigEndian(reply.AsSpan(6), 123);
        // Linux changes the identifier; it is not the request's zero identifier.
        reply[4] = 42;
        Assert.True(LinuxIcmpEcho.IsReply(reply, request, replyType, 123));
        Assert.False(LinuxIcmpEcho.IsReply(reply, request, replyType, 124));
        Assert.False(LinuxIcmpEcho.IsReply(reply.AsSpan(0, 7), request, replyType, 123));
        reply[1] = 1;
        Assert.False(LinuxIcmpEcho.IsReply(reply, request, replyType, 123));
        reply[1] = 0;
        reply[0]++;
        Assert.False(LinuxIcmpEcho.IsReply(reply, request, replyType, 123));
        reply[0] = replyType;
        reply[8]++;
        Assert.False(LinuxIcmpEcho.IsReply(reply, request, replyType, 123));
    }
}