using System.Numerics;

namespace AcDream.App.World;

/// <summary>
/// Session-scoped owner of the landblock origin used to translate retail
/// full-cell coordinates into the current streamed world coordinate system.
/// A placeholder can exist before the first authoritative player position;
/// <see cref="IsKnown"/> distinguishes it from a server-confirmed origin.
/// </summary>
/// <remarks>
/// This owner is update/render-thread confined with the rest of live world
/// mutation. It intentionally exposes no cross-thread snapshot contract.
/// </remarks>
internal sealed class LiveWorldOriginState
{
    public int CenterX { get; private set; }
    public int CenterY { get; private set; }
    public bool IsKnown { get; private set; }

    public void SetPlaceholder(int centerX, int centerY)
    {
        CenterX = centerX;
        CenterY = centerY;
        IsKnown = false;
    }

    public bool TryInitialize(int centerX, int centerY)
    {
        if (IsKnown)
            return false;

        CenterX = centerX;
        CenterY = centerY;
        IsKnown = true;
        return true;
    }

    public void Recenter(int centerX, int centerY)
    {
        CenterX = centerX;
        CenterY = centerY;
    }

    public (int X, int Y) GetCenter() => (CenterX, CenterY);

    /// <summary>
    /// Converts the streamed render frame back into retail's landblock-local
    /// physics frame at the one placement seed boundary.
    /// </summary>
    public Vector3 CellLocalForSeed(Vector3 worldPosition, uint cellId)
    {
        int landblockX = (int)((cellId >> 24) & 0xFFu);
        int landblockY = (int)((cellId >> 16) & 0xFFu);
        var origin = new Vector3(
            (landblockX - CenterX) * 192f,
            (landblockY - CenterY) * 192f,
            0f);
        return worldPosition - origin;
    }

    /// <summary>
    /// Ends the accepted-origin lifetime while retaining the last coordinates
    /// as the next placeholder. Consumers must gate them on
    /// <see cref="IsKnown"/> until the next accepted player position.
    /// </summary>
    public void Reset() => IsKnown = false;
}