using System.Buffers.Binary;
using SuiteLink.Client.Protocol;

namespace SuiteLink.Client.Tests.Protocol;

public sealed class SuiteLinkHandshakeCodecTests
{
    [Fact]
    public void EncodeNormalQueryHandshake_WritesLengthMagicsAndIdentityStrings()
    {
        var bytes = SuiteLinkHandshakeCodec.EncodeNormalQueryHandshake(
            targetApplication: "Intouch",
            sourceNode: "NodeA",
            sourceUser: "UserA");

        Assert.Equal(bytes.Length - 1, bytes[0]);
        Assert.Equal(SuiteLinkHandshakeCodec.QueryMagic.ToArray(), bytes.AsSpan(1, 16).ToArray());
        Assert.Equal(SuiteLinkHandshakeCodec.UnknownQueryMagic.ToArray(), bytes.AsSpan(17, 16).ToArray());
        Assert.Equal(1u, BinaryPrimitives.ReadUInt32LittleEndian(bytes.AsSpan(33, 4)));

        var expectedApp = SuiteLinkEncoding.EncodeNullTerminatedUtf16("Intouch");
        var expectedNode = SuiteLinkEncoding.EncodeNullTerminatedUtf16("NodeA");
        var expectedUser = SuiteLinkEncoding.EncodeNullTerminatedUtf16("UserA");
        var payload = bytes.AsSpan(37);

        Assert.True(payload.StartsWith(expectedApp));
        payload = payload[expectedApp.Length..];
        Assert.True(payload.StartsWith(expectedNode));
        payload = payload[expectedNode.Length..];
        Assert.True(payload.StartsWith(expectedUser));
    }

    [Fact]
    public void ParseNormalHandshakeAck_WithNormalAckFrame_ReturnsAckData()
    {
        // Fixed vector for normal ACK assumption:
        // remaining=0x0006, type=0x0001, payload=0xA1B2C3, marker=0xA5.
        byte[] frame = [0x06, 0x00, 0x01, 0x00, 0xA1, 0xB2, 0xC3, 0xA5];

        var ack = SuiteLinkHandshakeCodec.ParseNormalHandshakeAck(frame);

        Assert.Equal(0x0001, ack.MessageType);
        Assert.Equal(new byte[] { 0xA1, 0xB2, 0xC3 }, ack.Data.ToArray());
    }

    [Fact]
    public void EncodeNormalQueryHandshake_WhenPayloadExceedsOneByteLength_ThrowsWithPayloadContext()
    {
        var ex = Assert.Throws<ArgumentOutOfRangeException>(() =>
            SuiteLinkHandshakeCodec.EncodeNormalQueryHandshake(
                targetApplication: "App",
                sourceNode: new string('N', 80),
                sourceUser: new string('U', 80)));

        Assert.Equal("payloadLength", ex.ParamName);
        Assert.Contains("Total handshake payload", ex.Message, StringComparison.OrdinalIgnoreCase);
    }
}