namespace AcDream.Core.Physics.Motion;

/// <summary>
/// R5 — port of retail's <c>TargettedVoyeurInfo</c> (acclient.h:52807,
/// struct #5801). One entry in a <see cref="TargetManager"/>'s voyeur table:
/// a subscriber watching THIS object, the send-on-move <see cref="Radius"/>
/// threshold it registered, its dead-reckoning <see cref="Quantum"/>, and the
/// <see cref="LastSentPosition"/> already delivered to it (the delta baseline
/// <c>CheckAndUpdateVoyeur</c> compares against). Mutable class (retail heap
/// record updated in place by <c>AddVoyeur</c>/<c>SendVoyeurUpdate</c>).
/// </summary>
public sealed class TargettedVoyeurInfo
{
    /// <summary>
    /// Exact watcher incarnation captured when this subscription is created.
    /// Retail object IDs are process-lifetime object-table identities; the App
    /// preserves that pointer-like identity explicitly while an old
    /// INSTANCE_TS teardown may overlap a newer record with the same GUID.
    /// </summary>
    internal IPhysicsObjHost WatcherHost { get; }

    /// <summary>+0x00 retail <c>object_id</c> — the subscriber's guid.</summary>
    public uint ObjectId { get; }

    /// <summary>+0x04 retail <c>quantum</c> — the subscriber's dead-reckoning
    /// lookahead horizon (seconds).</summary>
    public double Quantum { get; set; }

    /// <summary>+0x10 retail <c>radius</c> — the send-on-move threshold: an
    /// update is pushed only when the tracked object drifts more than this from
    /// <see cref="LastSentPosition"/>.</summary>
    public float Radius { get; set; }

    /// <summary>+0x14 retail <c>last_sent_position</c> — the position last
    /// delivered to this subscriber (updated by <c>SendVoyeurUpdate</c>).</summary>
    public Position LastSentPosition { get; set; }

    public TargettedVoyeurInfo(
        uint objectId,
        float radius,
        double quantum,
        IPhysicsObjHost watcherHost)
    {
        ArgumentNullException.ThrowIfNull(watcherHost);
        if (watcherHost.Id != objectId)
        {
            throw new ArgumentException(
                "Watcher identity must match the voyeur object ID.",
                nameof(watcherHost));
        }

        ObjectId = objectId;
        Radius = radius;
        Quantum = quantum;
        WatcherHost = watcherHost;
    }
}