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

namespace IslaApocalypse.Server
{
	public partial class ServerChunkManager : Node
	{
		private WorldBlueprint _blueprint;
		private Dictionary<Vector2I, ChunkData> _activeChunks = new Dictionary<Vector2I, ChunkData>();
		public int chunkSize = 24;

		public override void _Ready()
		{

			// 1. LOAD CONFIGURATION and the seed-based blueprint data from the MapDataParser!
			ConfigManager.LoadConfig();
			chunkSize = ConfigManager.ChunkRadius; // Update chunk radius from config file
			_blueprint = MapDataParser.LoadMapData(ConfigManager.WorldSeed.ToString());

			if (_blueprint != null)
			{
				GD.Print("[Server] Blueprint loaded. Locating Capitol City...");

				// 2. Find the Capitol in the parsed data
				
				Vector2 capitolPos = new Vector2(2048, 2048); // Safe fallback center
				foreach (var town in _blueprint.Towns) {
					if (town.Tier == TownTier.Capitol) {
						capitolPos = town.Position;
						break;
					}
				}

				// Old original png map coords
				// Vector2 capitolPos = new Vector2(2405, 3296); // hardcoded for now since we know exactly where it is in this seed, which is the "paradise" biome hub


				GD.Print($"[Server] Capitol found at {capitolPos}. Generating chunks...");

				// 3. Convert pixel coordinates to Chunk coordinates
				int capitolChunkX = (int)(capitolPos.X / Constants.CHUNK_SIZE_X);
				int capitolChunkZ = (int)(capitolPos.Y / Constants.CHUNK_SIZE_Z);

				int radius = ConfigManager.ChunkRadius;

				for (int x = capitolChunkX - radius; x < capitolChunkX + radius; x++)
				{
					for (int z = capitolChunkZ - radius; z < capitolChunkZ + radius; z++)
					{
						GenerateChunk(new Vector2I(x, z));
					}
				}

				// 5. Teleport the Camera to look down at our creation!
				Camera3D cam = GetNodeOrNull<Camera3D>("Camera3D");
				if (cam != null)
				{
					// Put the camera 120 meters in the air above the Capitol
					cam.GlobalPosition = new Vector3(capitolPos.X, 120f, capitolPos.Y);
					// Point it straight down at the ground
					cam.LookAt(new Vector3(capitolPos.X, 0, capitolPos.Y)); 
				}
			}
		}

		public void GenerateChunk(Vector2I chunkCoord)
		{
			if (_activeChunks.ContainsKey(chunkCoord)) return; 

			ChunkData newChunk = new ChunkData(chunkCoord);

			int startX = chunkCoord.X * Constants.CHUNK_SIZE_X;
			int startZ = chunkCoord.Y * Constants.CHUNK_SIZE_Z; 

// --- NEW: SPATIAL CULLING FOR ROADS ---
			// Create a bounding box for this chunk, plus a 15-meter padding to account for the road's dirt shoulders
			Rect2 chunkBounds = new Rect2(startX - 15, startZ - 15, Constants.CHUNK_SIZE_X + 30, Constants.CHUNK_SIZE_Z + 30);
			List<Vector2[]> localRoadSegments = new List<Vector2[]>();

			// Filter Highways: Only save the segments that actually cross this specific chunk!
			foreach (var highway in _blueprint.Highways) {
				for (int i = 0; i < highway.Length - 1; i++) {
					Vector2 a = highway[i];
					Vector2 b = highway[i+1];
					Rect2 segBounds = new Rect2(Mathf.Min(a.X, b.X), Mathf.Min(a.Y, b.Y), Mathf.Abs(b.X - a.X), Mathf.Abs(b.Y - a.Y));
					if (chunkBounds.Intersects(segBounds.Grow(1.0f))) {
						localRoadSegments.Add(new Vector2[] { a, b });
					}
				}
			}
			// Filter Branch Roads
			foreach (var branch in _blueprint.BranchRoads) {
				for (int i = 0; i < branch.Length - 1; i++) {
					Vector2 a = branch[i];
					Vector2 b = branch[i+1];
					Rect2 segBounds = new Rect2(Mathf.Min(a.X, b.X), Mathf.Min(a.Y, b.Y), Mathf.Abs(b.X - a.X), Mathf.Abs(b.Y - a.Y));
					if (chunkBounds.Intersects(segBounds.Grow(1.0f))) {
						localRoadSegments.Add(new Vector2[] { a, b });
					}
				}
			}
			// ---------------------------------------

			for (int x = 0; x <= Constants.CHUNK_SIZE_X; x++)
			{
				for (int z = 0; z <= Constants.CHUNK_SIZE_Z; z++)
				{
					int globalX = startX + x;
					int globalZ = startZ + z;

					if (globalX >= _blueprint.MapSize || globalZ >= _blueprint.MapSize || globalX < 0 || globalZ < 0)
						continue;

					float GetExactSurface(int gX, int gZ, out bool isRoad) 
					{
						isRoad = false;
						if (gX >= _blueprint.MapSize) gX = _blueprint.MapSize - 1;
						if (gZ >= _blueprint.MapSize) gZ = _blueprint.MapSize - 1;
						
						float raw = _blueprint.HeightMap[gX, gZ];
						float baseHeight = Mathf.Clamp(raw * (Constants.CHUNK_HEIGHT - 5), 2.0f, Constants.CHUNK_HEIGHT - 2.0f);
						
						// If no roads are in this chunk, skip the heavy math entirely!
						if (localRoadSegments.Count == 0) return baseHeight;

						float finalHeight = baseHeight;
						float minDist = 9999f;
						Vector2 currentPos = new Vector2(gX, gZ);
						
						float roadRadius = 4.0f;    // The flat asphalt part (8 meters total width)
						float shoulderRadius = 12.0f; // The sloped dirt/rock carving into the mountain

						float closestRoadElevation = baseHeight;

						foreach (var seg in localRoadSegments)
						{
							// 'alongT' tells us HOW FAR ALONG this segment the nearest point is
							// (0 = at the start point, 1 = at the end point).
							float dist = DistanceToLineSegment(currentPos, seg[0], seg[1], out float alongT);
							if (dist < minDist)
							{
								minDist = dist;
								if (dist <= shoulderRadius)
								{
									// F2 FIX — the road elevation is now taken at the point on the
									// segment CLOSEST TO US, not at the segment's midpoint.
									//
									// The old code gave every column near a segment that segment's
									// single midpoint height, so each stretch of road was one flat
									// plank and consecutive planks stepped up/down like a staircase.
									//
									// Two honest ways to read the height at our closest point:
									//   rampElevation - a straight line between this segment's two
									//                   end points. Holds a grade; cuts and fills.
									//   landElevation - the actual terrain under that point.
									//                   Hugs the land; inherits its bumps.
									// ROAD_GRADE_SMOOTHING dials between them (see D-021).
									//
									// Either way it varies CONTINUOUSLY as we move along the road,
									// which is what kills the steps. And because neighbouring
									// segments share an end point, the height matches exactly where
									// one segment hands over to the next — no seam at the joins.
									float rampElevation = Mathf.Lerp(HeightAtPixel(seg[0]), HeightAtPixel(seg[1]), alongT);
									float landElevation = HeightAtPixel(seg[0].Lerp(seg[1], alongT));

									closestRoadElevation = Mathf.Lerp(landElevation, rampElevation, Constants.ROAD_GRADE_SMOOTHING);
								}
							}
						}

						// THE BULLDOZER: Carve the terrain
						if (minDist <= roadRadius) {
							finalHeight = closestRoadElevation; // Flatten it completely!
							isRoad = true;
						} else if (minDist <= shoulderRadius) {
							// Smoothly interpolate from the flat road up/down to the natural mountain height
							float t = (minDist - roadRadius) / (shoulderRadius - roadRadius);
							t = t * t * (3f - 2f * t); // SmoothStep equation for a beautiful curved slope
							finalHeight = Mathf.Lerp(closestRoadElevation, baseHeight, t);
						}

						return finalHeight;
					}

					// Pass the boolean out for the main voxel so we can paint it!
					bool isMainRoad = false;
					float exactSurfaceY = GetExactSurface(globalX, globalZ, out isMainRoad);
					
					// We discard the 'out' variable for the normals using an underscore '_'
					float surfaceRight = GetExactSurface(globalX + 1, globalZ, out _);
					float surfaceFwd = GetExactSurface(globalX, globalZ + 1, out _);

					Biome columnBiome = _blueprint.BiomeMap[globalX, globalZ];

					// Hand the renderer the TRUE surface height for this column, plus the
					// biome and road flag that go with it. The BlockIDs below still use the
					// rounded height (unchanged) — but the colour no longer has to.
					newChunk.SurfaceHeights[x, z] = exactSurfaceY;
					newChunk.ColumnBiomes[x, z] = columnBiome;
					newChunk.ColumnIsRoad[x, z] = isMainRoad;

					float hRight = surfaceRight - exactSurfaceY;
					float hFwd = surfaceFwd - exactSurfaceY;
					float slopeX = hRight / Constants.VOXEL_SCALE;
					float slopeZ = hFwd / Constants.VOXEL_SCALE;

					float len = Mathf.Sqrt(slopeX * slopeX + 1.0f + slopeZ * slopeZ);

					for (int y = 0; y <= Constants.CHUNK_HEIGHT; y++)
					{
						float verticalDist = y - exactSurfaceY; 
						float density = verticalDist / len;
						
						newChunk.Densities[x, y, z] = density;

						int blockY = Mathf.RoundToInt(exactSurfaceY);
						
						// THE PAINT: Pass isMainRoad into the Biome Palette!
						newChunk.BlockIDs[x, y, z] = BiomePalette.GetVoxelID(columnBiome, blockY, y, isMainRoad);
					}
				} // End of Z loop
			} // End of X loop

			_activeChunks.Add(chunkCoord, newChunk);

			var renderer = new IslaApocalypse.Client.ChunkRenderer();
			AddChild(renderer);
			renderer.RenderChunk(newChunk);
		}

		/// <summary>
		/// Turns a map-pixel position into a world surface height, with bounds clamping.
		/// Same mapping used everywhere else: raw 0-1 heightmap value scaled into the
		/// usable vertical band of the chunk.
		///
		/// The position handed in is usually FRACTIONAL (road path points land between
		/// heightmap cells), so we read the four cells around it and blend — bilinear
		/// interpolation — rather than snapping to whichever cell we happen to land in.
		///
		/// Why that matters: snapping made the height jump by a whole cell's worth the
		/// instant a point crossed a cell boundary, and hold perfectly flat until it did.
		/// Along a road whose points sit less than a metre apart, that produced a fine
		/// metre-scale staircase — the "washboard". Blending makes the height vary
		/// continuously as the position moves, so the staircase has nothing to stand on.
		/// </summary>
		private float HeightAtPixel(Vector2 pixel)
		{
			int max = _blueprint.MapSize - 1;

			// The four heightmap cells surrounding this position.
			// At the very edge of the map x1/y1 clamp back onto x0/y0, which makes the
			// blend a harmless no-op instead of reading out of bounds.
			int x0 = Mathf.Clamp(Mathf.FloorToInt(pixel.X), 0, max);
			int y0 = Mathf.Clamp(Mathf.FloorToInt(pixel.Y), 0, max);
			int x1 = Mathf.Clamp(x0 + 1, 0, max);
			int y1 = Mathf.Clamp(y0 + 1, 0, max);

			// How far between those cells we actually are, 0 to 1 on each axis.
			// Clamped so a position outside the map can't push the blend past its corners.
			float fx = Mathf.Clamp(pixel.X - x0, 0.0f, 1.0f);
			float fy = Mathf.Clamp(pixel.Y - y0, 0.0f, 1.0f);

			// Blend across X on the near row and the far row, then blend those two down Y.
			float nearRow = Mathf.Lerp(_blueprint.HeightMap[x0, y0], _blueprint.HeightMap[x1, y0], fx);
			float farRow  = Mathf.Lerp(_blueprint.HeightMap[x0, y1], _blueprint.HeightMap[x1, y1], fx);
			float raw     = Mathf.Lerp(nearRow, farRow, fy);

			return Mathf.Clamp(raw * (Constants.CHUNK_HEIGHT - 5), 2.0f, Constants.CHUNK_HEIGHT - 2.0f);
		}

		/// <summary>
		/// Calculates the shortest distance from a point to a line segment defined by v and w.
		/// </summary>
		private float DistanceToLineSegment(Vector2 point, Vector2 v, Vector2 w)
		{
			return DistanceToLineSegment(point, v, w, out _);
		}

		/// <summary>
		/// Same as above, but also reports WHERE along the segment the nearest point falls:
		/// <paramref name="t"/> is 0 at v, 1 at w. The road carving needs this so it can read
		/// the height at the spot next to us instead of at the segment's midpoint.
		/// </summary>
		private float DistanceToLineSegment(Vector2 point, Vector2 v, Vector2 w, out float t)
		{
			float l2 = v.DistanceSquaredTo(w);
			if (l2 == 0) // v == w case
			{
				t = 0f;
				return point.DistanceTo(v);
			}

			// Consider the line extending the segment, parameterized as v + t (w - v).
			// We find projection of point p onto the line.
			// It falls where t = [(p-v) . (w-v)] / |w-v|^2
			t = Mathf.Max(0, Mathf.Min(1, (point - v).Dot(w - v) / l2));

			// Projection falls on the segment
			Vector2 projection = v + t * (w - v);
			return point.DistanceTo(projection);
		}

	}
}