using System.Collections.Generic;
using Godot;

namespace IslaApocalypse.Tools
{
	/// <summary>
	/// The offshore TAG / HEMISPHERE debug overlay (chat2/05): mainland one tint, offshore-island
	/// land tinted by hemisphere, seeded centres ringed, the midline drawn — so the island count,
	/// the N/S split and the tag's correctness are all visible at one glance.
	///
	/// ⚠ A DIAGNOSTIC, NOT A MAP. It draws the tag layer, which is DATA the shape pass set; it is
	/// the one artifact in the batch that shows what a downstream consumer of the tag would see.
	/// No hypsometry, no hillshade — three flat tints and some rings, on purpose.
	///
	/// Presentation only: it is handed arrays and returns a PNG. It cannot change them.
	/// </summary>
	public static class TagOverlayRenderer
	{
		private static readonly Color Sea       = new(0.055f, 0.110f, 0.235f);
		private static readonly Color Mainland  = new(0.310f, 0.360f, 0.300f);
		private static readonly Color IslandN   = new(0.250f, 0.850f, 0.950f);   // cool — north
		private static readonly Color IslandS   = new(0.980f, 0.600f, 0.200f);   // warm — south
		private static readonly Color Untagged  = new(0.950f, 0.150f, 0.800f);   // ⚠ land that is neither — must never appear
		private static readonly Color Midline   = new(0.700f, 0.720f, 0.760f);
		private static readonly Color Ring      = new(1.000f, 1.000f, 1.000f);
		private static readonly Color Ink       = new(0.941f, 0.949f, 0.961f);

		/// <param name="isMainlandLand">
		/// Per cell, land that is NOT offshore (from the offshore-OFF field, so a tag bug cannot hide
		/// by mis-tagging mainland). Null ⇒ derived as "land and not tagged", which is weaker.
		/// </param>
		public static void SavePng(float[,] height, bool[,] tag, byte[,] hemi, int mapSize, float sea,
			IReadOnlyList<(int x, int y, int r)> centres, int countN, int countS, string absolutePath)
		{
			var img = Image.CreateEmpty(mapSize, mapSize, false, Image.Format.Rgb8);

			for (int x = 0; x < mapSize; x++)
			{
				for (int y = 0; y < mapSize; y++)
				{
					Color c;
					bool land = height[x, y] >= sea;
					bool tagged = tag != null && tag[x, y];

					if (!land)            c = Sea;
					else if (!tagged)     c = Mainland;
					else if (hemi == null) c = Untagged;
					else c = hemi[x, y] switch
					{
						OffshoreAnalysis.HemiNorth => IslandN,
						OffshoreAnalysis.HemiSouth => IslandS,
						_ => Untagged,
					};
					img.SetPixel(x, y, c);
				}
			}

			// The hemisphere midline — the tag's convention, drawn where it bites.
			int mid = mapSize / 2;
			for (int x = 0; x < mapSize; x += 3) img.SetPixel(x, mid, Midline);

			// Seeded centres: a ring at the stamp radius, so the floor islands can be told from the
			// organic ones by eye.
			if (centres != null)
				foreach (var (cx, cy, r) in centres)
					DrawRing(img, cx, cy, r, mapSize);

			// A legend that cannot be separated from the picture.
			int s = mapSize >= 4096 ? 4 : 3;
			int lh = TinyFont.Height(s) + 6;
			TinyFont.Draw(img, "OFFSHORE TAG OVERLAY", 12, 12, s, Ink);
			TinyFont.Draw(img, "GREY: MAINLAND  CYAN: ISLAND N  ORANGE: ISLAND S", 12, 12 + lh, s, Ink);
			TinyFont.Draw(img, $"ISLANDS: {countN} NORTH  {countS} SOUTH  - RINGS: SEEDED FLOOR", 12, 12 + lh * 2, s, Ink);
			TinyFont.Draw(img, "N ABOVE THE LINE - S BELOW - Y RUNS SOUTH", 12, 12 + lh * 3, s, Ink);

			Error err = img.SavePng(absolutePath);
			if (err != Error.Ok) GD.PrintErr($"[TagOverlayRenderer] SavePng failed ({err}) for {absolutePath}");
		}

		private static void DrawRing(Image img, int cx, int cy, int r, int n)
		{
			int rr = r + 3;                                   // just outside the rim
			int steps = System.Math.Max(64, rr * 4);
			for (int i = 0; i < steps; i++)
			{
				double a = i * 2.0 * System.Math.PI / steps;
				for (int t = 0; t < 2; t++)                   // 2 px thick
				{
					int px = cx + (int)System.Math.Round((rr + t) * System.Math.Cos(a));
					int py = cy + (int)System.Math.Round((rr + t) * System.Math.Sin(a));
					if (px >= 0 && py >= 0 && px < n && py < n) img.SetPixel(px, py, Ring);
				}
			}
		}
	}
}