using System;
using System.Buffers.Binary;

namespace AcDream.Core.Net.Messages;

/// <summary>
/// Inbound <c>0x01E0 EmoteText</c> top-level GameMessage.
/// Server-driven third-person emote announcement (e.g.
/// "The Olthoi growls at you.").
///
/// <para>
/// This is a standalone GameMessage — NOT wrapped in the 0xF7B0
/// GameEvent envelope. Dispatched directly from the opcode switch in
/// <see cref="WorldSession.ProcessDatagram"/>.
/// </para>
///
/// <para>
/// Wire layout (port from holtburger
/// <c>references/holtburger/.../messages/chat/types.rs::EmoteTextData</c>,
/// see also opcodes.rs:155):
/// <code>
///   u32 opcode               // 0x01E0
///   u32 senderGuid
///   string16L senderName
///   string16L text
/// </code>
/// </para>
/// </summary>
public static class EmoteText
{
    public const uint Opcode = 0x01E0u;

    public readonly record struct Parsed(
        uint SenderGuid,
        string SenderName,
        string Text);

    public static Parsed? TryParse(ReadOnlySpan<byte> body)
    {
        if (body.Length < 8) return null;
        uint opcode = BinaryPrimitives.ReadUInt32LittleEndian(body);
        if (opcode != Opcode) return null;

        try
        {
            int pos = 4;
            uint senderGuid = BinaryPrimitives.ReadUInt32LittleEndian(body.Slice(pos));
            pos += 4;
            string senderName = StringReader.ReadString16L(body, ref pos);
            string text       = StringReader.ReadString16L(body, ref pos);
            return new Parsed(senderGuid, senderName, text);
        }
        catch { return null; }
    }
}