using System;
using System.Collections.Generic;
using System.IO;
using System.Text;
using Godot;
using IslaApocalypse.Core;

namespace IslaApocalypse.Tools
{
	/// <summary>
	/// ⭐ THE CONTINUOUS-GRADE EXPLORATION BATCH (chat2/02, rev 3) — smooth the upper staircase,
	/// preserve the lowlands, and prove both claims before anyone looks at a render.
	///
	/// ═══ THE TARGET SILHOUETTE (judge every shaped histogram against THIS) ═══
	///
	/// The bottom shoulder stays exactly where it is — the broad low pile, ~75 % of land below
	/// 30 m, UNLIFTED. Above it, the bench and plateau spikes dissolve and the empty valleys fill
	/// in: one smooth continuous falloff out to a thin dramatic peak at 420 m. Only the top ~25 %
	/// of land moves.
	///
	/// ═══ THE VARIANTS — tight, one axis each ═══
	///
	///   staircase                 the faithful M3 control (task 01, bit-identical — oracle a2)
	///   continuous_default        lowland to 30 m, feather 0.40, drama 2.5 — the centerpiece
	///   continuous_hold_higher    lowland ceiling raised to 50 m — the primary axis explored up
	///   continuous_dramatic_peak  drama 4.5 — how pointy the peak gets
	///   continuous_lifted_WRONG   ⚠ the even whole-island lift — DELIBERATELY the wrong direction,
	///                             a contrast bookend. Its oracle-(d) failure is EXPECTED and is
	///                             reported as confirmation of why the direction is wrong.
	///
	/// ═══ ⚠ WHY THIS TOOL RE-MEASURES THE KNOTS INSTEAD OF USING CurveKnots.V2Baseline ═══
	///
	/// Task 01's batch was generated with the knots MEASURED IN THAT RUN, at full float precision.
	/// The baked V2Baseline constants are those values quoted to six decimals — off by &lt;1e-7 raw,
	/// which is invisible to every consumer EXCEPT a bit-identity oracle. Oracle (a2) demands the
	/// staircase reproduce task 01's `.f32` byte-for-byte, so this tool re-runs the identical
	/// 6-seed calibration (same seeds, same size, same instrument) and uses the measured knots.
	/// It prints the measured-vs-baked deltas so the equivalence is evidence, not assumption.
	///
	/// ═══ RUNNING IT ═══
	///
	///   xvfb-run -a Godot_v4.7.2-stable_mono_linux.x86_64 \
	///     --path ~/celerNexus/islaApocalypse-v2 res://Tools/Scenes/CurveContinuousTool.tscn
	///
	///   ISLA_TASK            authoring task number           (default 2)
	///   ISLA_BATCH           descriptor, NO prefix           (default "curve_continuous")
	///   ISLA_MAPSIZE         variant profile                 (default 2048)
	///   ISLA_SEEDS           variant seeds, comma-separated  (default: the 2 pinned below)
	///   ISLA_SHOWPIECE_SIZE  the big confirmation render     (default 8192)
	///   ISLA_SHOWPIECE       "0" to skip it
	///   ISLA_PHASE1_SOURCE   batch holding Phase-1 .f32      (default "chat1/02_pass1_port")
	///   ISLA_SKIP_RAW        "1" to skip the .f32 dumps
	///   ISLA_CEILING_M       probe override: lowland ceiling, metres  (default 30)
	///   ISLA_FEATHER         probe override: climb feather, 0..1      (default 0.4)
	///   ISLA_DRAMA           probe override: summit drama, >= 1       (default 2.5)
	///
	/// ⚠ The three knob overrides move the BASE config only. Each batch variant sets its own axis
	/// explicitly in its mutator, so a probe env can shift `continuous_default` but can never
	/// silently move `hold_higher`'s ceiling or `dramatic_peak`'s drama out from under their names.
	/// </summary>
	public partial class CurveContinuousTool : Node
	{
		/// <summary>Two representative variant seeds — the primary Phase-1 seed and the tallest one.</summary>
		private static readonly int[] DefaultSeeds = { 1063685222, 777001 };

		/// <summary>
		/// ⚠ THE TASK-01 CALIBRATION POOL, VERBATIM — same six seeds, so the measured knots (and
		/// with them the staircase control) reproduce task 01 bit-for-bit. Do not "simplify" this
		/// to the variant seeds; the pool is part of the knots' identity.
		/// </summary>
		private static readonly int[] CalibrationSeeds = { 1063685222, 20260819, 777001, 424242, 90210, 31337 };

		private const int DefaultMapSize = 2048;
		private const int DefaultShowpieceSize = 8192;

		public override void _Ready()
		{
			// ⚠ An exception out of _Ready does not stop Godot — it logs and the process HANGS with
			// no main loop to end it. Catch, say what was refused, exit 2. (The standing rule.)
			try { Run(); }
			catch (Exception e)
			{
				GD.PrintErr("==================================================================");
				GD.PrintErr($"  REFUSED: {e.Message}");
				GD.PrintErr("==================================================================");
				GetTree().Quit(2);
			}
		}

		private void Run()
		{
			ToolingPaths.Configure(OS.GetUserDataDir());
			// ⭐ rivers/01: batches are namespaced by chat. The default is this tool's AUTHORING chat,
			// so re-running it reproduces its own batch in place; ISLA_CHAT redirects a run to another
			// chat's namespace — which is what keeps an acceptance run from overwriting its own anchor.
			ToolingPaths.ConfigureChat(EnvStr(ToolingPaths.ChatVar, "chat2"));

			int task        = EnvInt("ISLA_TASK", 2);
			string descr    = EnvStr("ISLA_BATCH", "curve_continuous");
			int mapSize     = EnvInt("ISLA_MAPSIZE", DefaultMapSize);
			int[] seeds     = EnvSeeds("ISLA_SEEDS", DefaultSeeds);
			int showSize    = EnvInt("ISLA_SHOWPIECE_SIZE", DefaultShowpieceSize);
			bool showpiece  = EnvStr("ISLA_SHOWPIECE", "1") == "1";
			string p1Source = EnvStr("ISLA_PHASE1_SOURCE", "chat1/02_pass1_port");
			bool skipRaw    = EnvStr("ISLA_SKIP_RAW", "0") == "1";

			string batchRoot = ToolingPaths.BatchRoot(task, descr);   // composed, never free-form
			DirAccess.MakeDirRecursiveAbsolute(batchRoot);
			DirAccess.MakeDirRecursiveAbsolute(ToolingPaths.BatchScratch(batchRoot));

			var anchors = CurveAnchors.Default;
			float sea = 0.15f;
			int primary = seeds[0];

			GD.Print("==================================================================");
			GD.Print("  CURVE CONTINUOUS (rev 3) — smooth the upper staircase,");
			GD.Print("  preserve the lowlands. The staircase rides along as the control.");
			GD.Print("==================================================================");
			GD.Print($"MapSize   : {mapSize}   showpiece {(showpiece ? showSize.ToString() : "off")}");
			GD.Print($"yardstick : {WorldScale.Describe()}");
			GD.Print($"seeds     : {string.Join(", ", seeds)}   (calibration pool: {string.Join(", ", CalibrationSeeds)})");
			GD.Print($"batch     : {batchRoot}");
			GD.Print("------------------------------------------------------------------");
			GD.Print(ToolingPaths.Describe());
			GD.Print("==================================================================");

			// ═══ 0. RE-MEASURE THE KNOTS — task 01's calibration, verbatim (see the type header) ═══
			GD.Print("\n--- 0. CALIBRATION (the task-01 pool, re-run for bit-identity) ---");
			var rawPool = new LandHistogram(sea);
			var pass1 = new Dictionary<int, Pass1Result>();
			foreach (int seed in CalibrationSeeds)
			{
				var p1 = Topography.Generate(TerrainGenConfig.CalibrationPool(mapSize, seed));
				pass1[seed] = p1;
				rawPool.Accumulate(p1.Height, mapSize);
				GD.Print($"  pooled seed {seed,-11} h[{p1.HMinSeed,7:F3} .. {p1.HMaxSeed,6:F3}]  {p1.ElapsedMs,5} ms");
			}
			var knots = new CurveKnots(2, "v2_balanced",
				rawPool.Quantile(CurveKnots.Percentiles[0]), rawPool.Quantile(CurveKnots.Percentiles[1]),
				rawPool.Quantile(CurveKnots.Percentiles[2]), rawPool.Quantile(CurveKnots.Percentiles[3]),
				rawPool.Quantile(CurveKnots.Percentiles[4]), rawPool.Quantile(CurveKnots.Percentiles[5]));

			GD.Print("  measured vs baked V2Baseline (6-decimal roundings — expect <1e-6):");
			for (int i = 0; i < 6; i++)
				GD.Print($"    K{i + 1}: measured {knots[i]:G9}  baked {CurveKnots.V2Baseline[i]:G9}  " +
						 $"delta {knots[i] - CurveKnots.V2Baseline[i]:E2}");

			// ═══ 1. THE VARIANTS ═══
			var variants = new List<(string label, Action<TerrainGenConfig> mutate)>
			{
				("staircase",                c => { c.CurveMode = CurveModeKind.Staircase; c.ShelfDetail = true; }),
				("continuous_default",       c => { c.CurveMode = CurveModeKind.Continuous; }),
				("continuous_hold_higher",   c => { c.CurveMode = CurveModeKind.Continuous; c.LowlandCeilingM = 50f; }),
				("continuous_dramatic_peak", c => { c.CurveMode = CurveModeKind.Continuous; c.SummitDrama = 4.5f; }),
				("continuous_lifted_WRONG",  c => { c.CurveMode = CurveModeKind.LiftedWrong; }),
			};

			GD.Print("\n--- 1. VARIANTS ---");
			var results = new Dictionary<(int seed, string label), Pass2Result>();
			var offs = new Dictionary<int, Pass2Result>();
			var rows = new List<string>();
			bool notesPrinted = false;

			foreach (int seed in seeds)
			{
				Pass1Result p1 = pass1[seed];
				offs[seed] = Shaping.Shape(p1, BaseConfig(mapSize, seed, knots, anchors, "curve_off", off: true));

				foreach (var (label, mutate) in variants)
				{
					var cfg = BaseConfig(mapSize, seed, knots, anchors, label, off: false);
					mutate(cfg);
					Pass2Result p2 = Shaping.Shape(p1, cfg);
					results[(seed, label)] = p2;

					if (!notesPrinted) foreach (string n in p2.Notes) GD.Print("  " + n);

					rows.Add(WriteVariant(batchRoot, p2, sea, anchors, skipRaw));
				}
				notesPrinted = true;
			}

			// ═══ 2. THE ORACLE — before anything is looked at ═══
			GD.Print("\n--- 2. ORACLE ---");
			var hard = new List<ShapingOracle.Check>();
			var soft = new List<ShapingOracle.Check>();
			ShapingOracle.Check bookend;

			{
				Pass1Result pp1 = pass1[primary];

				// (a1) curve off == Phase 1's own dump. ⭐ KEPT at rivers/01: the family-off pass-1 guard,
				// the last link between today's generator and the Phase-1 port. The config is pinned
				// family-off so it still means what it says. ⚠ A missing dump now THROWS.
				string p1Dump = Path.Combine(ToolingPaths.BatchesRoot, p1Source, $"{primary}_full", "height.f32");
				hard.Add(ShapingOracle.DumpRegression("a1", "curve OFF == Phase-1 .f32 dump",
					offs[primary].Height, ShapingOracle.LoadAnchor("a1", "ISLA_PHASE1_SOURCE", p1Dump, mapSize), mapSize, p1Dump));

				// ⚑ RETIRED at rivers/01 — a2, the staircase == `01_curve_baseline` control.
				//   The staircase curve is SUPERSEDED by the continuous grade (→ D-062). A control that
				//   reproduces a curve nothing ships is scaffolding, and holding it green cost a
				//   4-variant batch run to prove a mode no design doc describes any more.
				// The dump is NOT deleted (file-safety; it is regenerable and it is the record of what
				// was judged); its `INDEX.md` is marked superseded. The check is gone so nothing can
				// pass against a superseded baseline. → XX_Human/output/rivers/01_*.report.md §A4.

				// (b) classify == raw, every seed × every variant.
				long bFail = 0;
				foreach (int seed in seeds)
					foreach (var (label, _) in variants)
					{
						var c = ShapingOracle.ClassifyFidelity(pass1[seed], results[(seed, label)]);
						if (!c.Passed) { bFail++; GD.PrintErr($"  classify drift: seed {seed} {label}: {c.Detail}"); }
					}
				hard.Add(new ShapingOracle.Check
				{
					Id = "b", Name = "classify == raw, all seeds × all variants",
					Passed = bFail == 0,
					Detail = bFail == 0
						? $"bit-identical on {seeds.Length} seeds × {variants.Count} variants"
						: $"{bFail} (seed, variant) pairs drifted",
				});

				// (c) monotone — the staircase's sweep and the continuous strict-increase sample
				// both throw on violation, so reaching here means they passed; state it explicitly.
				bool cStair = results[(primary, "staircase")].Notes.Exists(n => n.Contains("Monotonicity assertion passed"));
				bool cCont = results[(primary, "continuous_default")].Notes.Exists(n => n.Contains("strict-increase sample passed"));
				hard.Add(new ShapingOracle.Check
				{
					Id = "c", Name = "monotone — staircase sweep + continuous strict-increase sample",
					Passed = cStair && cCont,
					Detail = $"staircase sweep {(cStair ? "confirmed" : "MISSING")}, " +
							 $"continuous sample {(cCont ? "confirmed" : "MISSING")} (both throw-and-refuse on violation)",
				});

				// (d) ⭐ lowlands preserved — every continuous variant, both seeds. HARD.
				foreach (int seed in seeds)
					foreach (string label in new[] { "continuous_default", "continuous_hold_higher", "continuous_dramatic_peak" })
					{
						var c = ShapingOracle.LowlandsPreserved(pass1[seed], results[(seed, "staircase")], results[(seed, label)]);
						c.Name += $" [seed {seed}]";
						hard.Add(c);
					}

				// (d, bookend) the WRONG lift is EXPECTED to fail this — its failure is the point.
				bookend = ShapingOracle.LowlandsPreserved(pp1, results[(primary, "staircase")],
					results[(primary, "continuous_lifted_WRONG")]);

				// (e) upper climb profile — SOFT (exploration): warn loudly, do not gate the exit.
				foreach (int seed in seeds)
					foreach (string label in new[] { "continuous_default", "continuous_hold_higher", "continuous_dramatic_peak" })
					{
						var c = ShapingOracle.UpperClimbProfile(results[(seed, label)]);
						c.Name += $" [seed {seed}]";
						soft.Add(c);
					}

				// (f) sea identity — every variant, both seeds, per cell. HARD.
				foreach (int seed in seeds)
					foreach (var (label, _) in variants)
					{
						var c = ShapingOracle.SeaIdentity(offs[seed], results[(seed, label)], sea);
						c.Name += $" [seed {seed}]";
						hard.Add(c);
					}
			}

			foreach (var c in hard) GD.Print("  " + c);
			foreach (var c in soft)
			{
				if (c.Passed) GD.Print("  " + c);
				else GD.PrintErr("  ⚠ SLOPE PROFILE: " + c);
			}
			GD.Print($"  bookend (expected FAIL): {bookend}");
			if (bookend.Passed)
				GD.PrintErr("  ⚠⚠ the lifted_WRONG bookend PRESERVED the lowlands — it is not doing its job as a contrast.");

			bool hardOk = hard.TrueForAll(c => c.Passed) && !bookend.Passed;
			GD.Print($"  ORACLE: {(hardOk ? "ALL HARD CHECKS PASS" : "*** HARD FAILURES ***")}" +
					 $"{(soft.TrueForAll(c => c.Passed) ? "" : "  (soft slope warnings present — see above)")}");

			// ═══ 3. HISTOGRAMS — the contrast, adjacent by filename ═══
			GD.Print("\n--- 3. HISTOGRAMS ---");
			foreach (int seed in seeds)
			{
				var rawSeed = new LandHistogram(sea);
				rawSeed.Accumulate(pass1[seed].Height, mapSize);
				DrawRawHist(rawSeed, knots, seed, mapSize, batchRoot);

				int order = 1;
				foreach (var (label, _) in variants)
				{
					DrawShapedHist(results[(seed, label)], rawSeed, anchors, seed, mapSize, batchRoot, order++);
				}
			}

			// ═══ 4. SHOWPIECE — continuous_default at the big profile ═══
			string showNote = "skipped (ISLA_SHOWPIECE=0)";
			if (showpiece)
			{
				GD.Print($"\n--- 4. SHOWPIECE at {showSize} (continuous_default, seed {primary}) ---");
				var cfg = BaseConfig(showSize, primary, knots, anchors, "continuous_default_showpiece", off: false);
				cfg.CurveMode = CurveModeKind.Continuous;

				Pass1Result p1 = Topography.Generate(cfg);
				GD.Print($"  pass1 {showSize}: h[{p1.HMinSeed:F3} .. {p1.HMaxSeed:F3}]  {p1.ElapsedMs} ms");

				Pass2Result big = Shaping.Shape(p1, cfg);
				foreach (string n in big.Notes) GD.Print("  " + n);

				// The cheap checks that transfer to the big profile: classify fidelity + sea identity.
				var cb = ShapingOracle.ClassifyFidelity(p1, big);
				var offBig = Shaping.Shape(p1, BaseConfig(showSize, primary, knots, anchors, "off", off: true));
				var cf = ShapingOracle.SeaIdentity(offBig, big, sea);
				GD.Print($"  {cb}");
				GD.Print($"  {cf}");
				if (!cb.Passed || !cf.Passed) hardOk = false;

				rows.Add(WriteVariant(batchRoot, big, sea, anchors, skipRaw));
				showNote = $"seed {primary} at {showSize} — classify + sea identity re-verified there";
			}

			WriteIndex(batchRoot, mapSize, showSize, seeds, primary, knots, anchors,
				results, hard, soft, bookend, rows, hardOk, showNote);

			GD.Print("\n==================================================================");
			GD.Print($"  DONE — {batchRoot}");
			GD.Print($"  ORACLE {(hardOk ? "HARD CHECKS ALL PASS" : "*** HARD FAILURES — see the table ***")}");
			GD.Print("==================================================================");
			GetTree().Quit(hardOk ? 0 : 3);
		}

		// ---- configs ----------------------------------------------------------

		private static TerrainGenConfig BaseConfig(int mapSize, int seed, CurveKnots k, CurveAnchors a,
			string label, bool off) => new TerrainGenConfig
		{
			MapSize = mapSize, Seed = seed, VariantLabel = label,
			Curve = !off, ShelfDetail = false, Knots = k, Anchors = a,
			// Continuous knob defaults; variant mutators override per axis.
			//
			// ⚠ ENV-OVERRIDABLE so the knobs can be probed WITHOUT editing source and rebuilding —
			// they are "eye-iteration knobs" per the task, and a knob you have to recompile to turn
			// is not one. A probe run redirects ISLA_OUTPUT_DIR to scratch and sweeps these; the
			// BATCH variants set them explicitly in their mutators, so a probe env cannot silently
			// move the batch of record.
			LowlandCeilingM = EnvFloat("ISLA_CEILING_M", 30f),
			ClimbFeather    = EnvFloat("ISLA_FEATHER", 0.4f),
			SummitDrama     = EnvFloat("ISLA_DRAMA", 2.5f),
		}
		// ⭐ rivers/01 — FAMILY-OFF PINNED, not defaulted. chat2/02 is CURVE development, measured on
		// the family-off distribution the knots are percentiles of; the re-baseline flipped the bare
		// defaults family-ON. → TerrainGenConfig.WithFamilyOff().
		.WithFamilyOff();

		// ---- output -----------------------------------------------------------

		private static string WriteVariant(string batchRoot, Pass2Result p2, float sea,
			CurveAnchors anchors, bool skipRaw)
		{
			string dir = Path.Combine(batchRoot, $"{p2.Seed}_{LabelOf(p2)}");
			DirAccess.MakeDirRecursiveAbsolute(dir);

			// Plain data beside the pretty render, always.
			var (gMin, gMax) = GrayscaleRenderer.SavePng(p2.Height, p2.MapSize, Path.Combine(dir, "grayscale.png"));
			if (!skipRaw) HeightField.Save(p2.Height, p2.MapSize, Path.Combine(dir, "height.f32"));

			// ⚠ HILLSHADED, deliberately — the continuous grade is the first terrain with coherent
			// shape worth lighting (Phase 1's rule was "flat is the hero" BECAUSE raw noise fuzzes;
			// that reasoning inverts once the climb is smooth). Subtle settings, and the palette is
			// the PROVISIONAL even ramp — flagged as such in the palette, the INDEX and the report.
			var look = new LookConfig
			{
				Name = "hillshade_even", Palette = ReliefPalette.Kind.ProvisionalEven,
				ZExaggeration = 18f, LightAzimuth = 315f, LightAltitude = 45f,
				HillshadeStrength = 0.30f, SeaLevel = sea,
			};
			Image map = ReliefRenderer.Render(p2.Height, p2.MapSize, look);
			Image withLegend = LegendRenderer.WithLegend(map, look.Palette, sea, anchors.PeakCap,
				LabelOf(p2).ToUpperInvariant());
			withLegend.SavePng(Path.Combine(dir, "relief.png"));

			float land = p2.LandFraction(sea);
			GD.Print($"  {LabelOf(p2),-26} seed {p2.Seed,-11} h[{p2.HMin,7:F3} .. {p2.HMax,6:F3}] " +
					 $" land {land * 100,5:F1}%  {p2.ElapsedMs,5} ms");

			return $"| `{p2.Seed}_{LabelOf(p2)}` | {p2.Seed} | {LabelOf(p2)} | {p2.HMin:F3} | {p2.HMax:F3} | " +
				   $"{land * 100:F1}% | {gMin:F3}..{gMax:F3} | {p2.ElapsedMs} ms |";
		}

		/// <summary>The variant folder name — read off the result, never re-derived.</summary>
		private static string LabelOf(Pass2Result p2) => p2.VariantLabel;

		private static void DrawRawHist(LandHistogram raw, CurveKnots k, int seed, int mapSize, string batchRoot)
		{
			float top = MathF.Ceiling(raw.MaxLand * 20f) / 20f;
			var display = raw.Rebin((top - raw.SeaLevel) / 360f);

			var o = new HistogramRenderer.Options
			{
				Title = $"RAW LAND HEIGHTS - SEED {seed}",
				Subtitle = "PRE-CURVE. K2 IS THE LOWLAND CEILING - EVERYTHING LEFT OF IT IS PRESERVED.",
				XAxisLabel = "RAW HEIGHT (PRE-CURVE)",
				XTop = top,
				Footer = $"{raw.TotalLand} LAND COLUMNS AT MAPSIZE {mapSize}",
			};
			o.Markers.Add(new HistogramRenderer.Marker { Value = k.K2, Label = "K2 LOWLAND CEIL" });
			o.Bands.Add(new HistogramRenderer.Band
			{
				Lo = raw.SeaLevel, Hi = k.K2, Label = "preserved lowland",
				SharePercent = raw.FractionBelow(k.K2) * 100.0,
			});
			o.Bands.Add(new HistogramRenderer.Band
			{
				Lo = k.K2, Hi = top, Label = "the climb's input",
				SharePercent = (1.0 - raw.FractionBelow(k.K2)) * 100.0,
			});

			HistogramRenderer.SavePng(display, o, Path.Combine(batchRoot, $"hist_{seed}_0_raw.png"));
			GD.Print($"  hist_{seed}_0_raw.png");
		}

		private static void DrawShapedHist(Pass2Result p2, LandHistogram rawSeed, CurveAnchors a,
			int seed, int mapSize, string batchRoot, int order)
		{
			var shaped = new LandHistogram(rawSeed.SeaLevel);
			shaped.Accumulate(p2.Height, mapSize);

			float top = MathF.Ceiling(shaped.MaxLand * 20f) / 20f;
			var display = shaped.Rebin((top - shaped.SeaLevel) / 360f);
			string label = LabelOf(p2);

			var o = new HistogramRenderer.Options
			{
				Title = $"SHAPED - {label.ToUpperInvariant()} - SEED {seed}",
				XAxisLabel = "RAW HEIGHT (POST-CURVE)",
				XTop = top,
				Footer = $"{shaped.TotalLand} LAND COLUMNS AT MAPSIZE {mapSize}",
			};

			if (p2.Continuous != null)
			{
				var c = p2.Continuous;
				var (onsetRaw, onsetOut) = c.SummitOnsetPoint();
				o.Subtitle = "TARGET: BOTTOM PILE UNMOVED - ABOVE IT ONE SMOOTH FALLOFF TO A THIN PEAK.";
				o.Markers.Add(new HistogramRenderer.Marker { Value = c.CeilingOut, Label = $"LOWLAND {c.LowlandCeilingM:F0}M" });
				o.Markers.Add(new HistogramRenderer.Marker { Value = onsetOut, Label = "SUMMIT ONSET", Strong = false });
				o.Markers.Add(new HistogramRenderer.Marker { Value = a.PeakCap, Label = "CAP 420M" });
				o.Bands.Add(new HistogramRenderer.Band
				{
					Lo = rawSeed.SeaLevel, Hi = c.CeilingOut, Label = "preserved lowland",
					SharePercent = rawSeed.FractionBelow(c.CeilingRaw) * 100.0,
				});
				o.Bands.Add(new HistogramRenderer.Band
				{
					Lo = c.CeilingOut, Hi = onsetOut, Label = "the climb",
					SharePercent = rawSeed.FractionBetween(c.CeilingRaw, onsetRaw) * 100.0,
				});
				o.Bands.Add(new HistogramRenderer.Band
				{
					Lo = onsetOut, Hi = top, Label = "summit",
					SharePercent = (1.0 - rawSeed.FractionBelow(onsetRaw)) * 100.0,
				});
			}
			else if (p2.CurveModeLabel == "staircase")
			{
				o.Subtitle = "THE CONTROL: THE M3 STAIRCASE - BENCH AND PLATEAU SPIKES BY DESIGN.";
				o.Markers.Add(new HistogramRenderer.Marker { Value = a.OrangeCeil, Label = "ORANGE", Strong = false });
				o.Markers.Add(new HistogramRenderer.Marker { Value = a.RedCeil, Label = "RED", Strong = false });
				o.Markers.Add(new HistogramRenderer.Marker { Value = a.BenchBase, Label = "BENCH" });
				o.Markers.Add(new HistogramRenderer.Marker { Value = a.PlateauBase, Label = "PLATEAU" });
				o.Markers.Add(new HistogramRenderer.Marker { Value = a.PeakCap, Label = "CAP 420M" });
			}
			else
			{
				o.Subtitle = "THE WRONG DIRECTION: THE WHOLE ISLAND LIFTED OFF ITS SHORELINE. A BOOKEND.";
				o.Markers.Add(new HistogramRenderer.Marker { Value = a.RedCeil, Label = "OLD 30M LINE", Strong = false });
				o.Markers.Add(new HistogramRenderer.Marker { Value = a.PeakCap, Label = "CAP 420M" });
			}

			string file = $"hist_{seed}_{order}_{label}.png";
			HistogramRenderer.SavePng(display, o, Path.Combine(batchRoot, file));
			GD.Print($"  {file}");
		}

		// ---- the index ----------------------------------------------------------

		private static void WriteIndex(string batchRoot, int mapSize, int showSize, int[] seeds,
			int primary, CurveKnots knots, CurveAnchors a,
			Dictionary<(int, string), Pass2Result> results,
			List<ShapingOracle.Check> hard, List<ShapingOracle.Check> soft,
			ShapingOracle.Check bookend, List<string> rows, bool hardOk, string showNote)
		{
			var sb = new StringBuilder();
			sb.AppendLine("# Batch 02 — continuous grade: smooth the upper staircase, preserve the lowlands");
			sb.AppendLine();
			sb.AppendLine("**rev 3.** The lowlands are GOOD and are preserved bit-for-bit (oracle d). Everything");
			sb.AppendLine("above the 30 m flood line is replaced by one smooth monotone climb to the 420 m cap.");
			sb.AppendLine("The staircase rides along as the control; the WRONG-direction whole-island lift rides");
			sb.AppendLine("along as a contrast bookend. **Exploration, not convergence** — a tuning pass follows");
			sb.AppendLine("once a direction is picked.");
			sb.AppendLine();
			sb.AppendLine("## ⭐ Open this first");
			sb.AppendLine();
			sb.AppendLine($"1. **`{primary}_continuous_default_showpiece/relief.png`** — the centerpiece ({showNote}).");
			sb.AppendLine($"2. **`hist_{primary}_1_staircase.png` → `hist_{primary}_2_continuous_default.png`** — the");
			sb.AppendLine("   contrast, adjacent by filename: bottom pile unchanged, the bench/plateau spikes above");
			sb.AppendLine("   it dissolved into a smooth falloff.");
			sb.AppendLine($"3. **`hist_{primary}_5_continuous_lifted_WRONG.png`** — the bookend: the whole pile shoved");
			sb.AppendLine("   up off the shoreline. This is what \"make the island stand up\" would have done.");
			sb.AppendLine($"4. `{primary}_staircase/relief.png` vs `{primary}_continuous_default/relief.png` — the A/B.");
			sb.AppendLine();
			sb.AppendLine("## The variants and their knobs");
			sb.AppendLine();
			sb.AppendLine("| Variant | Mode | Knobs | Control points |");
			sb.AppendLine("|---|---|---|---|");
			sb.AppendLine("| `staircase` | staircase | task-01 defaults (ShelfDetail on) | the v5 bands |");
			foreach (string label in new[] { "continuous_default", "continuous_hold_higher", "continuous_dramatic_peak" })
			{
				var c = results[(primary, label)].Continuous;
				sb.AppendLine($"| `{label}` | continuous | ceiling {c.LowlandCeilingM:F0} m · feather {c.ClimbFeather:F2} · " +
							  $"drama {c.SummitDrama:F2} | {c.DescribeControlPoints()} |");
			}
			sb.AppendLine("| `continuous_lifted_WRONG` | lifted | none — an even ×~1.47 lift of all land | n/a |");
			sb.AppendLine();
			sb.AppendLine("## ⚠ The palette is PROVISIONAL");
			sb.AppendLine();
			sb.AppendLine("`ProvisionalEven` — the CostaRica colours re-spaced **evenly** SEA → 420 m, so equal");
			sb.AppendLine("colour = equal height and nothing is emphasized. Final palette calibration waits for the");
			sb.AppendLine("chosen curve profile. **Grayscale + the histograms are the honest instruments.**");
			sb.AppendLine();
			sb.AppendLine("## The oracle");
			sb.AppendLine();
			sb.AppendLine(ShapingOracle.ToMarkdownTable(hard));
			sb.AppendLine($"**{(hardOk ? "ALL HARD CHECKS PASS" : "⚠⚠ HARD FAILURES — do not judge this batch")}**");
			sb.AppendLine();
			sb.AppendLine("Soft slope profile (e) — warn-and-report, exploration:");
			sb.AppendLine();
			sb.AppendLine(ShapingOracle.ToMarkdownTable(soft));
			sb.AppendLine($"**The bookend, expected to FAIL (d):** {bookend.Detail}");
			sb.AppendLine();
			sb.AppendLine("## Disposability");
			sb.AppendLine();
			sb.AppendLine("| Artifact | Keep? |");
			sb.AppendLine("|---|---|");
			sb.AppendLine("| `relief.png`, `hist_*.png`, `INDEX.md` | **keep** — the judging plates and the finding |");
			sb.AppendLine("| `grayscale.png` | ♻ regenerable from the `.f32` |");
			sb.AppendLine("| `height.f32` | ♻ regenerable from seed + code (it is the byte-level oracle) |");
			sb.AppendLine("| `scratch/` | persistent by rule; never cleaned |");
			sb.AppendLine();
			sb.AppendLine("## Results");
			sb.AppendLine();
			sb.AppendLine("| Folder | Seed | Variant | h min | h max | land % | grayscale range | time |");
			sb.AppendLine("|---|---|---|---|---|---|---|---|");
			foreach (string row in rows) sb.AppendLine(row);
			sb.AppendLine();
			sb.AppendLine($"Setup: MapSize {mapSize}, showpiece {showSize}, seeds {string.Join(", ", seeds)}, " +
						  $"knots re-measured on the task-01 pool. {WorldScale.Describe()}.");

			string index = Path.Combine(batchRoot, "INDEX.md");
			using var f = Godot.FileAccess.Open(index, Godot.FileAccess.ModeFlags.Write);
			if (f == null) { GD.PrintErr($"could not write {index}"); return; }
			f.StoreString(sb.ToString());
		}

		// ---- env helpers --------------------------------------------------------

		private static string EnvStr(string k, string fallback)
		{
			string v = System.Environment.GetEnvironmentVariable(k);
			return string.IsNullOrWhiteSpace(v) ? fallback : v;
		}

		private static int EnvInt(string k, int fallback)
			=> int.TryParse(EnvStr(k, null) ?? "", out int v) ? v : fallback;

		private static float EnvFloat(string k, float fallback)
			=> float.TryParse(EnvStr(k, null) ?? "", System.Globalization.NumberStyles.Float,
				System.Globalization.CultureInfo.InvariantCulture, out float v) ? v : fallback;

		private static int[] EnvSeeds(string k, int[] fallback)
		{
			string v = EnvStr(k, null);
			if (v == null) return fallback;
			var outp = new List<int>();
			foreach (string part in v.Split(',', StringSplitOptions.RemoveEmptyEntries))
				if (int.TryParse(part.Trim(), out int s) && s > 0) outp.Add(s);
			return outp.Count > 0 ? outp.ToArray() : fallback;
		}
	}
}