using Unity.Mathematics;

namespace ProjectM.Simulation
{
    /// <summary>
    /// Deterministic, side-effect-free math for the home-base build grid. Pure (no RNG, no wall-clock)
    /// so server and predicting client agree on cell occupancy. Convention: <see cref="BaseAnchor.GridOrigin"/>
    /// is the min-XZ CORNER of cell (0,0); <see cref="CellToWorld"/> returns cell CENTERS; cell bounds are
    /// half-open so a point on a cell's lower edge belongs to that cell and the far plot edge is out of plot.
    /// World-&gt;cell uses math.floor (not truncation) so negative coordinates snap correctly. Unit-tested in
    /// EditMode (no netcode world required); M6's server placement handler calls these directly.
    /// </summary>
    public static class BaseGridMath
    {
        /// <summary>Planar (XZ) world position -&gt; integer grid cell. Uses floor, so values below GridOrigin go negative (out of plot).</summary>
        public static int2 WorldToCell(in BaseAnchor a, float3 worldPos)
        {
            float2 local = (worldPos.xz - a.GridOrigin.xz) / a.CellSize;
            return (int2)math.floor(local);
        }

        /// <summary>Grid cell -&gt; world position of the cell CENTER, on the base plane (Y = GridOrigin.y).</summary>
        public static float3 CellToWorld(in BaseAnchor a, int2 cell)
        {
            float2 centerXZ = a.GridOrigin.xz + ((float2)cell + 0.5f) * a.CellSize;
            return new float3(centerXZ.x, a.GridOrigin.y, centerXZ.y);
        }

        /// <summary>True when the cell is inside the plot. Half-open: [0, GridDims), so the far edge is out.</summary>
        public static bool IsCellInPlot(in BaseAnchor a, int2 cell)
        {
            return math.all(cell >= 0) && math.all(cell < a.GridDims);
        }

        /// <summary>True when the world point falls inside the plot (its cell is in-plot).</summary>
        public static bool IsPointInPlot(in BaseAnchor a, float3 worldPos)
        {
            return IsCellInPlot(a, WorldToCell(a, worldPos));
        }

        /// <summary>Clamp a cell into the valid [0, GridDims-1] range.</summary>
        public static int2 ClampCell(in BaseAnchor a, int2 cell)
        {
            return math.clamp(cell, new int2(0, 0), a.GridDims - 1);
        }

        /// <summary>World-space center of the whole plot (== AnchorPos when baked correctly).</summary>
        public static float3 PlotCenter(in BaseAnchor a)
        {
            float2 centerXZ = a.GridOrigin.xz + (float2)a.GridDims * a.CellSize * 0.5f;
            return new float3(centerXZ.x, a.GridOrigin.y, centerXZ.y);
        }
    }
}