using System.Buffers.Binary;
using AcDream.Core.Net.Packets;

namespace AcDream.Core.Net.Messages;

/// <summary>
/// Retail character-logoff request and server confirmation (opcode
/// <c>0xF653</c>).
/// </summary>
/// <remarks>
/// Retail <c>Proto_UI::LogOffCharacter</c> at <c>0x00546A20</c> sends the
/// opcode followed by the active character id. The server confirmation uses
/// the same opcode with no trailing payload. <c>CPlayerSystem::RequestLogOff</c>
/// at <c>0x00562DD0</c> waits for that confirmation; its inbound dispatch calls
/// <c>CPlayerSystem::ExecuteLogOff</c> at <c>0x0055D780</c>, which only then
/// disconnects the world connection.
/// </remarks>
public static class CharacterLogOff
{
    public const uint Opcode = 0xF653u;

    /// <summary>Builds retail's eight-byte client request.</summary>
    public static byte[] BuildRequestBody(uint characterId)
    {
        var writer = new PacketWriter(8);
        writer.WriteUInt32(Opcode);
        writer.WriteUInt32(characterId);
        return writer.ToArray();
    }

    /// <summary>
    /// Returns whether a complete game-message body is the server's logoff
    /// confirmation. ACE emits the canonical four-byte opcode-only form.
    /// </summary>
    public static bool IsConfirmation(ReadOnlySpan<byte> body) =>
        body.Length == sizeof(uint) &&
        BinaryPrimitives.ReadUInt32LittleEndian(body) == Opcode;
}