using System.Numerics;
using AcDream.Core.Net.Packets;

namespace AcDream.Core.Net.Messages;

/// <summary>
/// Outbound <c>GameAction(AutonomousPosition)</c> message — opcode
/// <c>0xF753</c>. Sent roughly every 200ms while the player is moving to
/// give the server a periodic ground-truth position heartbeat. Simpler than
/// <see cref="MoveToState"/>: no RawMotionState, just the GameAction
/// envelope, a WorldPosition, sequence numbers, a contact byte, and 4-byte
/// alignment padding.
///
/// <para>
/// Wire layout (ported from
/// <c>references/holtburger/crates/holtburger-protocol/src/messages/movement/actions.rs</c>
/// <c>AutonomousPositionActionData::pack</c>):
/// </para>
/// <list type="bullet">
///   <item><b>GameAction envelope</b>: u32 0xF7B1, u32 sequence, u32 0xF753</item>
///   <item><b>WorldPosition</b>: u32 cellId, f32 x, f32 y, f32 z,
///         f32 rotW, f32 rotX, f32 rotY, f32 rotZ</item>
///   <item><b>Sequences</b>: u16 instance, u16 serverControl,
///         u16 teleport, u16 forcePosition</item>
///   <item><b>Contact byte</b>: u8 (1 = on ground, 0 = airborne)</item>
///   <item><b>Align to 4 bytes</b></item>
/// </list>
/// </summary>
public static class AutonomousPosition
{
    public const uint GameActionOpcode         = 0xF7B1u;
    public const uint AutonomousPositionAction = 0xF753u;

    /// <summary>
    /// Build an AutonomousPosition GameAction body.
    /// </summary>
    /// <param name="gameActionSequence">Monotonically increasing counter from
    ///   <see cref="WorldSession.NextGameActionSequence"/>.</param>
    /// <param name="cellId">Landblock cell ID (u32).</param>
    /// <param name="position">World-space position relative to the landblock.</param>
    /// <param name="rotation">Rotation quaternion. AC wire order is W, X, Y, Z.</param>
    /// <param name="instanceSequence">Instance sequence number from the server.</param>
    /// <param name="serverControlSequence">Server-control sequence number.</param>
    /// <param name="teleportSequence">Teleport sequence number.</param>
    /// <param name="forcePositionSequence">Force-position sequence number.</param>
    /// <param name="lastContact">1 if the character was last on the ground, 0 if airborne.</param>
    public static byte[] Build(
        uint       gameActionSequence,
        uint       cellId,
        Vector3    position,
        Quaternion rotation,
        ushort     instanceSequence,
        ushort     serverControlSequence,
        ushort     teleportSequence,
        ushort     forcePositionSequence,
        byte       lastContact = 1)
    {
        var w = new PacketWriter(64);

        // --- GameAction envelope ---
        w.WriteUInt32(GameActionOpcode);
        w.WriteUInt32(gameActionSequence);
        w.WriteUInt32(AutonomousPositionAction);

        // --- WorldPosition (32 bytes) ---
        w.WriteUInt32(cellId);
        w.WriteFloat(position.X);
        w.WriteFloat(position.Y);
        w.WriteFloat(position.Z);
        // Quaternion wire order: W, X, Y, Z
        w.WriteFloat(rotation.W);
        w.WriteFloat(rotation.X);
        w.WriteFloat(rotation.Y);
        w.WriteFloat(rotation.Z);

        // --- Sequence numbers ---
        w.WriteUInt16(instanceSequence);
        w.WriteUInt16(serverControlSequence);
        w.WriteUInt16(teleportSequence);
        w.WriteUInt16(forcePositionSequence);

        // --- Contact byte + 4-byte align ---
        w.WriteByte(lastContact);
        w.AlignTo4();

        return w.ToArray();
    }
}