using Godot;

namespace IslaApocalypse.Tools
{
	/// <summary>
	/// A print-and-quit diagnostic: reports this engine build's <see cref="FastNoiseLite"/>
	/// CONSTRUCTOR DEFAULTS, and checks them against the values the ported terrain expects.
	///
	/// ═══ WHY THIS EXISTS ═══
	///
	/// The reference prototype set only three noise properties — NoiseType, Seed, Frequency — and
	/// left fractal type, octaves, gain, lacunarity and weighted-strength untouched. So the island's
	/// entire fractal character was Godot 4.7.1's CONSTRUCTOR DEFAULTS, not code. Nothing in that
	/// repo recorded what they were. (chat1/00 §4.1.)
	///
	/// <see cref="TerrainNoise"/> now pins every one of them explicitly, so the terrain no longer
	/// depends on an engine default. This probe is the other half of that guarantee: it makes a
	/// silent default change VISIBLE on an engine upgrade instead of quietly reshaping the island.
	///
	/// Run it after any Godot version bump:
	///
	///   Godot_v4.7.2-stable_mono_linux.x86_64 --headless \
	///     --path ~/celerNexus/islaApocalypse-v2 res://Tools/Scenes/NoiseDefaultsProbe.tscn
	///
	/// Exits non-zero if this engine's defaults have drifted from the recorded baseline — so it
	/// works as a pre-flight check, not just by eye. A non-zero exit is NOT "the terrain is broken":
	/// the terrain is pinned and fine. It means the baseline note below needs updating, and that
	/// anyone reading old code which relied on defaults should be warned.
	/// </summary>
	public partial class NoiseDefaultsProbe : Node
	{
		// The defaults measured on Godot 4.7.2.stable.mono (this project's pinned engine), which
		// match the Godot 4 documented defaults the reference implicitly rode on 4.7.1.
		private const FastNoiseLite.FractalTypeEnum BaselineFractalType = FastNoiseLite.FractalTypeEnum.Fbm;
		private const int   BaselineOctaves         = 5;
		private const float BaselineGain            = 0.5f;
		private const float BaselineLacunarity      = 2.0f;
		private const float BaselineWeightedStrength = 0.0f;

		public override void _Ready()
		{
			var n = new FastNoiseLite();

			GD.Print("==================================================================");
			GD.Print("  FastNoiseLite CONSTRUCTOR DEFAULTS — this engine build");
			GD.Print("==================================================================");
			GD.Print($"engine                  : {Engine.GetVersionInfo()["string"]}");
			GD.Print("------------------------------------------------------------------");
			GD.Print($"NoiseType               : {n.NoiseType}");
			GD.Print($"Frequency               : {n.Frequency}");
			GD.Print($"FractalType             : {n.FractalType}");
			GD.Print($"FractalOctaves          : {n.FractalOctaves}");
			GD.Print($"FractalGain             : {n.FractalGain}");
			GD.Print($"FractalLacunarity       : {n.FractalLacunarity}");
			GD.Print($"FractalWeightedStrength : {n.FractalWeightedStrength}");
			GD.Print($"Seed                    : {n.Seed}");
			GD.Print("------------------------------------------------------------------");
			GD.Print("  DRIFT CHECK vs the recorded 4.7.2 baseline");
			GD.Print("------------------------------------------------------------------");

			bool drift = false;
			drift |= Check("FractalType",             n.FractalType.ToString(),     BaselineFractalType.ToString());
			drift |= Check("FractalOctaves",          n.FractalOctaves.ToString(),  BaselineOctaves.ToString());
			drift |= Check("FractalGain",             n.FractalGain.ToString(),     BaselineGain.ToString());
			drift |= Check("FractalLacunarity",       n.FractalLacunarity.ToString(), BaselineLacunarity.ToString());
			drift |= Check("FractalWeightedStrength", n.FractalWeightedStrength.ToString(), BaselineWeightedStrength.ToString());

			GD.Print("------------------------------------------------------------------");
			GD.Print(drift
				? "  ⚠ DRIFT — this engine's defaults differ from the recorded baseline.\n" +
				  "    The PORTED TERRAIN IS UNAFFECTED: TerrainNoise pins every value explicitly.\n" +
				  "    Update the baseline constants in this probe, and note the delta."
				: "  ✓ NO DRIFT — defaults match the recorded baseline.");
			GD.Print("==================================================================");

			GetTree().Quit(drift ? 1 : 0);
		}

		private static bool Check(string name, string actual, string expected)
		{
			bool differs = actual != expected;
			GD.Print($"  {(differs ? "✗" : "✓")} {name,-24} actual={actual,-12} baseline={expected}");
			return differs;
		}
	}
}