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

namespace IslaApocalypse.Tools
{
	/// <summary>
	/// The Phase-1 generation entry point: runs a seed batch plus the ablation ladder, writes
	/// hypsometric PNGs and raw height dumps into the batch layout, and quits.
	///
	/// ═══ RUNNING IT ═══
	///
	///   Godot_v4.7.2-stable_mono_linux.x86_64 --headless \
	///     --path ~/celerNexus/islaApocalypse-v2 res://Tools/Scenes/TerrainGenTool.tscn
	///
	/// ⚠ `--headless` is correct HERE and will stay correct as long as the renderer writes a
	/// Godot.Image directly. It awaits no render frames. The moment anything composites a `_Draw`
	/// overlay through a SubViewport, this becomes an `xvfb-run` job — see Tools/README.md.
	///
	/// ═══ CONFIGURATION (all optional; every path is env-overridable per the tooling rails) ═══
	///
	///   ISLA_MAPSIZE     map side in columns          (default 2048 — iteration size)
	///   ISLA_SEEDS       comma-separated positive ints (default: the pinned batch below)
	///   ISLA_BATCH       batch folder name            (default 01_pass1_port)
	///   ISLA_OUTPUT_DIR  where batches/ lives         (Core/ToolingPaths)
	///   ISLA_SKIP_RAW    "1" to skip the .f32 dumps
	///   ISLA_LADDER      "0" to skip the ablation ladder (for a full-size confirmation pass)
	/// </summary>
	public partial class TerrainGenTool : Node
	{
		/// <summary>
		/// PINNED POSITIVE SEEDS. Pinned, not random, so a batch is reproducible and two batches are
		/// comparable — a standing convention. Positive only.
		/// </summary>
		private static readonly int[] DefaultSeeds = { 1063685222, 20260819, 777001, 424242 };

		private const int DefaultMapSize = 2048;

		public override void _Ready()
		{
			ToolingPaths.Configure(OS.GetUserDataDir());

			int mapSize   = EnvInt("ISLA_MAPSIZE", DefaultMapSize);
			int[] seeds   = EnvSeeds("ISLA_SEEDS", DefaultSeeds);
			string batch  = EnvStr("ISLA_BATCH", "01_pass1_port");
			bool skipRaw  = EnvStr("ISLA_SKIP_RAW", "0") == "1";
			bool ladder   = EnvStr("ISLA_LADDER", "1") == "1";

			var scale = new GenerationScale(mapSize);
			string batchRoot = Path.Combine(ToolingPaths.BatchesRoot, batch);
			string scratch   = ToolingPaths.BatchScratch(batchRoot);
			DirAccess.MakeDirRecursiveAbsolute(batchRoot);
			DirAccess.MakeDirRecursiveAbsolute(scratch);   // persistent; never cleaned

			GD.Print("==================================================================");
			GD.Print("  PASS-1 TERRAIN GENERATION — the crown-jewel port (Phase 1)");
			GD.Print("==================================================================");
			GD.Print($"MapSize      : {mapSize}   (scaleFactor {scale.ScaleFactor:F3})");
			GD.Print($"noise        : {TerrainNoise.Describe(0, scale).Replace(" · seed 0", "")}");
			GD.Print($"seeds        : {string.Join(", ", seeds)}");
			GD.Print($"batch        : {batchRoot}");
			GD.Print("------------------------------------------------------------------");
			GD.Print(ToolingPaths.Describe());
			GD.Print("==================================================================");

			var rows = new List<string>();

			// ═══ 1. THE ABLATION LADDER — first seed only, one element added per rung ═══
			//
			// This is the port-fidelity check: six simultaneous changes cannot be judged by their
			// sum, so each element is switched on in the reference's own order and looked at alone.
			if (ladder)
			{
				GD.Print("\n--- ABLATION LADDER (seed " + seeds[0] + ") ---");
				foreach (var (label, mutate) in Ladder())
				{
					var cfg = new TerrainGenConfig { MapSize = mapSize, Seed = seeds[0], VariantLabel = label };
					mutate(cfg);
					rows.Add(RunOne(cfg, batchRoot, skipRaw));
				}
			}
			else GD.Print("\n--- ablation ladder skipped (ISLA_LADDER=0) ---");

			// ═══ 2. THE SEED BATCH — the full six-element config across pinned seeds ═══
			GD.Print("\n--- SEED BATCH (full pass-1) ---");
			foreach (int seed in seeds)
			{
				var cfg = new TerrainGenConfig { MapSize = mapSize, Seed = seed, VariantLabel = "full" };
				rows.Add(RunOne(cfg, batchRoot, skipRaw));
			}

			WriteIndex(batchRoot, mapSize, scale, seeds, rows);

			GD.Print("\n==================================================================");
			GD.Print($"  DONE — {rows.Count} maps in {batchRoot}");
			GD.Print("==================================================================");
			GetTree().Quit(0);
		}

		/// <summary>
		/// The ablation rungs, in the reference's execution order. Each rung ADDS one element to the
		/// one before it, so a difference between adjacent images is attributable to exactly one
		/// ported element.
		/// </summary>
		private static List<(string, Action<TerrainGenConfig>)> Ladder() => new()
		{
			("ab1_base_only",   c => { c.IslandFalloff = false; c.EdgeNoise = false; c.SouthernSinker = false; c.Trench = false; c.MountainSpine = false; }),
			("ab2_falloff",     c => {                          c.EdgeNoise = false; c.SouthernSinker = false; c.Trench = false; c.MountainSpine = false; }),
			("ab3_edge",        c => {                                               c.SouthernSinker = false; c.Trench = false; c.MountainSpine = false; }),
			("ab4_sinker",      c => {                                                                         c.Trench = false; c.MountainSpine = false; }),
			("ab5_trench",      c => {                                                                                           c.MountainSpine = false; }),
			("ab6_spine_full",  c => { /* everything on — identical to the "full" variant */ }),
		};

		private static string RunOne(TerrainGenConfig cfg, string batchRoot, bool skipRaw)
		{
			Pass1Result r = Topography.Generate(cfg);

			// batches/NN_<name>/<seed>_<variant>/
			string dir = Path.Combine(batchRoot, $"{cfg.Seed}_{cfg.VariantLabel}");
			DirAccess.MakeDirRecursiveAbsolute(dir);

			string png = HeightMapRenderer.SavePng(r, cfg.SeaLevel, Path.Combine(dir, "height.png"));
			if (!skipRaw) HeightMapRenderer.SaveRaw(r, Path.Combine(dir, "height.f32"));

			float land = r.LandFraction(cfg.SeaLevel);
			GD.Print($"  {cfg.VariantLabel,-16} seed {cfg.Seed,-11} " +
					 $"h[{r.HMinSeed,7:F3} .. {r.HMaxSeed,6:F3}]  land {land * 100,5:F1}%  {r.ElapsedMs,5} ms");

			return $"| `{cfg.Seed}_{cfg.VariantLabel}` | {cfg.Seed} | {cfg.VariantLabel} | " +
				   $"{r.HMinSeed:F3} | {r.HMaxSeed:F3} | {land * 100:F1}% | {r.ElapsedMs} ms |";
		}

		private static void WriteIndex(string batchRoot, int mapSize, GenerationScale scale, int[] seeds, List<string> rows)
		{
			var sb = new StringBuilder();
			sb.AppendLine("# Batch — pass-1 port (Phase 1)");
			sb.AppendLine();
			sb.AppendLine("Raw pass-1 terrain from the ported crown-jewel noise. **No curve, no erosion, no");
			sb.AppendLine("rivers, no water, no crater, no biomes.** Each folder holds `height.png` (hypsometric)");
			sb.AppendLine("and `height.f32` (raw float32, x-major, for byte-level comparison).");
			sb.AppendLine();
			sb.AppendLine($"- **MapSize:** {mapSize} (scaleFactor {scale.ScaleFactor:F3})");
			sb.AppendLine($"- **Noise:** {TerrainNoise.Describe(0, scale).Replace(" · seed 0", "")}");
			sb.AppendLine($"- **Sea threshold (visualization only):** 0.15");
			sb.AppendLine($"- **Colour ramp anchors (FIXED across the batch):** sea {HeightMapRenderer.RampBottomHeight} .. 0.15, land 0.15 .. {HeightMapRenderer.RampTopHeight}");
			sb.AppendLine($"- **Seeds:** {string.Join(", ", seeds)}");
			sb.AppendLine();
			sb.AppendLine("## What to look at");
			sb.AppendLine();
			sb.AppendLine("**The ablation ladder** (`ab1`..`ab6`, all on seed " + seeds[0] + ") adds one ported element per");
			sb.AppendLine("rung, in the reference's execution order — so any difference between adjacent images is");
			sb.AppendLine("attributable to exactly one element:");
			sb.AppendLine();
			sb.AppendLine("| Rung | Adds | Expect to see |");
			sb.AppendLine("|---|---|---|");
			sb.AppendLine("| `ab1_base_only` | base noise | featureless fractal field, no island, no coast |");
			sb.AppendLine("| `ab2_falloff` | island mask + `Pow(·,2.5)` | an island appears, smooth-edged |");
			sb.AppendLine("| `ab3_edge` | edge roughness | the coastline goes jagged — **and only the coastline** |");
			sb.AppendLine("| `ab4_sinker` | southern sinker | the bottom 25% sinks; southern land bridges break up |");
			sb.AppendLine("| `ab5_trench` | the Trench | a hard ocean border on all four edges |");
			sb.AppendLine("| `ab6_spine_full` | mountain spine | a ridge up the centre, fading out toward the south |");
			sb.AppendLine();
			sb.AppendLine("**The seed batch** (`<seed>_full`) is the complete six-element pass-1 across pinned seeds.");
			sb.AppendLine();
			sb.AppendLine("> ⚠ **The seabed reads raw, and that is expected.** The submarine coast shelf and the");
			sb.AppendLine("> offshore islets are DEFERRED to Phase 2 — they act only below sea level and are judged");
			sb.AppendLine("> once water renders. Steep, plain bathymetry here is not a bug.");
			sb.AppendLine();
			sb.AppendLine("## Results");
			sb.AppendLine();
			sb.AppendLine("| Folder | Seed | Variant | h min | h max | land % | time |");
			sb.AppendLine("|---|---|---|---|---|---|---|");
			foreach (string row in rows) sb.AppendLine(row);
			sb.AppendLine();
			sb.AppendLine("`scratch/` is persistent and is never cleaned.");

			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 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;
		}
	}
}