using Luneraria.Core;
using UnityEngine;

namespace Luneraria.View
{
    /// <summary>
    /// Heights of the G1 world for placing figures and buildings (presentation only; the rules are
    /// flat). Baked from the Godot reference by tools/godot-golden/world_export.gd:
    /// the terrain walk height (1 m grid, lane decks instead of the river bed) and the height a
    /// figure stands on including plaza, dais steps and grotto terrace (0.5 m grid).
    /// </summary>
    public sealed class LuneGround : ScriptableObject
    {
        public float WalkExtent;
        public float WalkStep;
        public int WalkSize;
        public float[] Walk;
        public float StandExtent;
        public float StandStep;
        public int StandSize;
        public float[] Stand;

        /// <summary>LuneTerrain.walk_height: lane decks, ford and platform instead of the river bed.</summary>
        public float WalkHeight(Vec2 map)
        {
            return Bilinear(Walk, WalkSize, WalkExtent, WalkStep, map);
        }

        /// <summary>LuneWorld.height_at: walk height plus plaza, dais and grotto lifts.</summary>
        public float StandHeight(Vec2 map)
        {
            return Bilinear(Stand, StandSize, StandExtent, StandStep, map);
        }

        // Godot LuneTerrain._bilinear, in map coordinates.
        static float Bilinear(float[] field, int size, float extent, float step, Vec2 p)
        {
            if (field == null || field.Length == 0)
                return 0f;
            float fx = Mathf.Clamp((p.X + extent) / step, 0f, size - 1.001f);
            float fz = Mathf.Clamp((p.Y + extent) / step, 0f, size - 1.001f);
            int i = (int)fx;
            int j = (int)fz;
            float tx = fx - i;
            float tz = fz - j;
            float a = Mathf.Lerp(field[j * size + i], field[j * size + i + 1], tx);
            float b = Mathf.Lerp(field[(j + 1) * size + i], field[(j + 1) * size + i + 1], tx);
            return Mathf.Lerp(a, b, tz);
        }
    }
}