using Godot;

namespace IslaApocalypse.Tools
{
	/// <summary>
	/// Raw height-field I/O: little-endian float32, x-major (<c>index = x * MapSize + y</c>).
	///
	/// ⭐ THIS FILE IS WHY PRESENTATION AND GENERATION STAY SEPARATE. A relief render reads a dumped
	/// height field and re-colours it; it never re-runs the generator. So a look change provably
	/// cannot move the terrain — not by convention, but because the colours are computed from a
	/// file the renderer cannot write.
	///
	/// It also makes a byte-level port-fidelity oracle possible later: two generators agree, or
	/// their dumps differ. → `Design - Tooling - Iteration and Batching.md`, "build the oracle
	/// before the taste-iteration".
	/// </summary>
	public static class HeightField
	{
		public static void Save(float[,] height, int mapSize, string absolutePath)
		{
			using var f = Godot.FileAccess.Open(absolutePath, Godot.FileAccess.ModeFlags.Write);
			if (f == null)
			{
				GD.PrintErr($"[HeightField] cannot write {absolutePath}: {Godot.FileAccess.GetOpenError()}");
				return;
			}
			for (int x = 0; x < mapSize; x++)
				for (int y = 0; y < mapSize; y++)
					f.StoreFloat(height[x, y]);
		}

		/// <summary>Load a dump. Returns null if absent or the wrong size for <paramref name="mapSize"/>.</summary>
		public static float[,] Load(string absolutePath, int mapSize)
		{
			if (!Godot.FileAccess.FileExists(absolutePath)) return null;

			using var f = Godot.FileAccess.Open(absolutePath, Godot.FileAccess.ModeFlags.Read);
			if (f == null) return null;

			long expected = (long)mapSize * mapSize * 4;
			if ((long)f.GetLength() != expected)
			{
				GD.PrintErr($"[HeightField] {absolutePath} is {f.GetLength()} bytes, expected {expected} " +
							$"for MapSize {mapSize} — ignoring it rather than guessing.");
				return null;
			}

			var h = new float[mapSize, mapSize];
			for (int x = 0; x < mapSize; x++)
				for (int y = 0; y < mapSize; y++)
					h[x, y] = f.GetFloat();
			return h;
		}
	}
}