using System;
using System.Buffers.Binary;

namespace AcDream.Core.Net.Messages;

/// <summary>
/// Inbound <c>PrivateUpdatePropertyInt (0x02CD)</c> — the server updates one
/// <c>PropertyInt</c> on the player's OWN object. Unlike the sibling
/// <see cref="PublicUpdatePropertyInt"/> (0x02CE), this carries NO guid (it
/// implicitly targets the local player). Burden (<c>EncumbranceVal</c>, PropertyInt 5)
/// changes ride this opcode on every pick-up / drop.
///
/// <para>Wire layout (ACE <c>GameMessagePrivateUpdatePropertyInt</c>):</para>
/// <code>
///   u32 opcode = 0x02CD
///   u8  sequence    // single byte (ByteSequence) — not honored, latest-wins (DR-4)
///   u32 property    // PropertyInt enum
///   i32 value
/// </code>
/// </summary>
public static class PrivateUpdatePropertyInt
{
    public const uint Opcode = 0x02CDu;

    public readonly record struct Parsed(uint Property, int Value);

    /// <summary>Parse a raw 0x02CD body. Returns null on opcode mismatch / truncation.</summary>
    public static Parsed? TryParse(ReadOnlySpan<byte> body)
    {
        if (body.Length < 13) return null;          // 4 + 1 + 4 + 4
        if (BinaryPrimitives.ReadUInt32LittleEndian(body) != Opcode) return null;
        int pos = 4;
        pos += 1;                                   // sequence byte (not honored)
        uint prop = BinaryPrimitives.ReadUInt32LittleEndian(body[pos..]); pos += 4;
        int value = BinaryPrimitives.ReadInt32LittleEndian(body[pos..]);
        return new Parsed(prop, value);
    }
}