using System;
using System.Collections.Generic;
using System.IO;
using System.Reflection;
using HarmonyLib;
using UnityEngine;

namespace NecromancerTome
{
	/// <summary>
	/// Adds the mod's own paint to the game's opaque block texture atlas, so the Pyramid of
	/// Spirits can ship with a surface that does not exist in vanilla.
	///
	/// WHY A PATCH IS THE ONLY WAY. A block's Texture property is an INDEX into a prebuilt
	/// atlas; a paint entry in painting.xml carries TextureId/PaintCost/Group/SortIndex and
	/// never a path to an image, and the atlas itself is compiled into
	/// blocktextureatlases_assets_all.bundle. Nothing in the XML layer can introduce new image
	/// data, so the array has to be extended at runtime.
	///
	/// WHY THIS HOOK. CreateBlockTextures is the coroutine that reads painting.xml. Hooking its
	/// completion is deliberate and was learned the hard way: an earlier probe ran from
	/// MeshDescription.ReloadTextureArrays and found BlockTextureData.list still null, because
	/// the texture arrays load BEFORE painting.xml. By the time this coroutine finishes, both the
	/// arrays and the paint table exist.
	///
	/// THE NUMBERS THIS RELIES ON were measured in-game rather than assumed (BlockAtlasProbe,
	/// 2026-09-10): the opaque atlas holds 407 slices of 512x512 with a full 10-level mip chain,
	/// diffuse as DXT1 and normal/specular as DXT5, and all three arrays are non-readable. Two
	/// consequences drive the code below - our textures must match those numbers exactly, and
	/// every copy must go through the GPU, since a non-readable array cannot be read back.
	///
	/// SAFETY. Everything is wrapped: this runs inside the game's own XML loading, and an
	/// escaping exception aborts that step - which is exactly how a careless earlier version
	/// produced "XML loader: Executing post load step on 'materials.xml' failed". If anything
	/// here fails, the mod logs it and leaves the game exactly as it was.
	/// </summary>
	public static class CustomBlockPaintPatch
	{
		/// <summary>Bundle we ship the paint textures in, relative to the mod folder.</summary>
		const string BundlePath = "Resources/necroatlas";

		const string DiffuseAsset = "Assets/NecroAtlas/atlas_necroPyramid_d.png";
		const string NormalAsset = "Assets/NecroAtlas/atlas_necroPyramid_n.png";
		const string SpecularAsset = "Assets/NecroAtlas/atlas_necroPyramid_m.png";

		/// <summary>Name the paint is registered under; blocks.xml refers to the resulting id.</summary>
		public const string PaintName = "txName_NecroAsh";

		/// <summary>Paint id handed out by the game once registration succeeds, -1 while unset.
		/// Logged on success so it can be written into blocks.xml.</summary>
		public static int AssignedPaintId = -1;

		static bool alreadyRan;

		/// <summary>
		/// Patch the coroutine's MoveNext. A coroutine compiles into a hidden state-machine
		/// class, so the method that actually runs is MoveNext, not CreateBlockTextures itself -
		/// AccessTools.EnumeratorMoveNext resolves it for us.
		/// </summary>
		[HarmonyPatch]
		static class CreateBlockTexturesHook
		{
			static IEnumerable<MethodBase> TargetMethods()
			{
				MethodBase coroutine = AccessTools.Method(
					typeof(BlockTexturesFromXML), "CreateBlockTextures");
				if (coroutine == null)
				{
					Debug.LogWarning("[NecromancerTome] CustomBlockPaint: " +
						"BlockTexturesFromXML.CreateBlockTextures not found - paint not added");
					yield break;
				}
				MethodBase moveNext = AccessTools.EnumeratorMoveNext(coroutine);
				if (moveNext == null)
				{
					Debug.LogWarning("[NecromancerTome] CustomBlockPaint: " +
						"could not resolve the coroutine's MoveNext - paint not added");
					yield break;
				}
				yield return moveNext;
			}

			// __result == false means the enumerator is done: the XML has been read in full.
			static void Postfix(bool __result)
			{
				if (__result || alreadyRan) return;
				alreadyRan = true;
				try
				{
					AddPaint();
				}
				catch (Exception e)
				{
					Debug.LogWarning("[NecromancerTome] CustomBlockPaint: failed, game left " +
						"untouched: " + e);
				}
			}
		}

		static void AddPaint()
		{
			if (GameManager.IsDedicatedServer)
			{
				Debug.Log("[NecromancerTome] CustomBlockPaint: dedicated server, textures skipped");
				return;
			}

			MeshDescription mesh = MeshDescription.meshes[MeshDescription.MESH_OPAQUE];
			var atlas = mesh == null ? null : mesh.textureAtlas as TextureAtlasBlocks;
			if (atlas == null)
			{
				Debug.LogWarning("[NecromancerTome] CustomBlockPaint: opaque atlas unavailable");
				return;
			}

			AssetBundle bundle = LoadBundle();
			if (bundle == null) return;

			try
			{
				var diffuse = bundle.LoadAsset<Texture2D>(DiffuseAsset);
				var normal = bundle.LoadAsset<Texture2D>(NormalAsset);
				var specular = bundle.LoadAsset<Texture2D>(SpecularAsset);
				if (diffuse == null || normal == null || specular == null)
				{
					Debug.LogWarning("[NecromancerTome] CustomBlockPaint: bundle is missing one " +
						"of the three textures - nothing added");
					return;
				}

				Describe("our diffuse ", diffuse);
				Describe("our normal  ", normal);
				Describe("our specular", specular);

				int slice = Append(ref atlas.diffuseTexture, diffuse, "diffuse");
				Append(ref atlas.normalTexture, normal, "normal");
				Append(ref atlas.specularTexture, specular, "specular");
				if (slice < 0) return;

				mesh.TexDiffuse = atlas.diffuseTexture;
				mesh.TexNormal = atlas.normalTexture;
				mesh.TexSpecular = atlas.specularTexture;
				mesh.ReloadTextureArrays(false);

				int textureId = RegisterUvMapping(atlas, slice);
				RegisterPaint(textureId);
			}
			finally
			{
				// Keep the loaded textures alive: only the bundle wrapper is released.
				bundle.Unload(false);
			}
		}

		/// <summary>
		/// Give the new slice an entry in uvMapping and return its index - that index is what a
		/// block's Texture property in blocks.xml actually refers to.
		///
		/// The entry is CLONED from an existing plain opaque paint rather than built field by
		/// field. UVRectTiling carries more than a slice number (tiling, block size, material
		/// flags), and copying a known-good neighbour keeps every one of those correct without
		/// guessing at fields we have never inspected. Only the slice index is changed.
		/// </summary>
		static int RegisterUvMapping(TextureAtlasBlocks atlas, int slice)
		{
			// 356 is txName_Steel_wall - an ordinary full-block opaque paint, which is exactly
			// the shape of entry we want.
			const int TemplateTextureId = 356;
			if (atlas.uvMapping == null || atlas.uvMapping.Length <= TemplateTextureId)
			{
				Debug.LogWarning("[NecromancerTome] CustomBlockPaint: uvMapping too small to " +
					"clone a template from - paint not registered");
				return -1;
			}

			int textureId = atlas.uvMapping.Length;
			Array.Resize(ref atlas.uvMapping, textureId + 1);
			UVRectTiling tile = atlas.uvMapping[TemplateTextureId];
			// Только индекс слоя: имени у UVRectTiling нет, оно живёт в BlockTextureData.
			tile.index = slice;
			atlas.uvMapping[textureId] = tile;

			Debug.Log("[NecromancerTome] CustomBlockPaint: uvMapping entry " + textureId +
				" points at slice " + slice + " (cloned from " + TemplateTextureId + ")");
			return textureId;
		}

		/// <summary>
		/// Register the paint itself, so it has a name, shows up in the paint brush, and can be
		/// referred to by name. The block only needs the texture id, but a nameless texture with
		/// no paint entry would be invisible to the rest of the game.
		/// </summary>
		static void RegisterPaint(int textureId)
		{
			if (textureId < 0) return;
			if (BlockTextureData.list == null)
			{
				Debug.LogWarning("[NecromancerTome] CustomBlockPaint: paint table missing - " +
					"texture added but not named");
				return;
			}

			int free = -1;
			for (int i = 0; i < BlockTextureData.list.Length; i++)
			{
				if (BlockTextureData.list[i] == null) { free = i; break; }
			}
			if (free < 0)
			{
				Debug.LogWarning("[NecromancerTome] CustomBlockPaint: no free paint slot - " +
					"texture added but not named");
				return;
			}

			var data = new BlockTextureData
			{
				ID = free,
				Name = PaintName,
				LocalizedName = Localization.Get(PaintName),
				TextureID = (ushort)textureId,
				Group = "txGroupMasonry",
				PaintCost = 1,
				SortIndex = 0,
				Hidden = false,
			};
			data.Init();

			AssignedPaintId = free;
			Debug.Log("[NecromancerTome] CustomBlockPaint: paint registered, slot " + free +
				", texture id " + textureId + " -> put Texture=\"" + textureId +
				"\" on the block in blocks.xml");
		}

		static AssetBundle LoadBundle()
		{
			if (ModEntry.Instance == null)
			{
				Debug.LogWarning("[NecromancerTome] CustomBlockPaint: mod path unknown");
				return null;
			}

			string path = Path.Combine(ModEntry.Instance.Path, BundlePath);
			if (!File.Exists(path))
			{
				Debug.LogWarning("[NecromancerTome] CustomBlockPaint: bundle not found at " + path);
				return null;
			}

			AssetBundle bundle = AssetBundle.LoadFromFile(path);
			if (bundle == null)
			{
				Debug.LogWarning("[NecromancerTome] CustomBlockPaint: bundle failed to load: " + path);
			}
			return bundle;
		}

		/// <summary>
		/// Rebuild a texture array one slice larger and put our texture in the new last slot.
		/// Returns the new slice index, or -1 if the arrays disagree on anything that makes a
		/// copy impossible.
		/// </summary>
		static int Append(ref Texture target, Texture2D ours, string label)
		{
			var src = target as Texture2DArray;
			if (src == null)
			{
				Debug.LogWarning("[NecromancerTome] CustomBlockPaint: " + label +
					" is not a Texture2DArray - skipped");
				return -1;
			}

			if (ours.width != src.width || ours.height != src.height)
			{
				Debug.LogWarning("[NecromancerTome] CustomBlockPaint: " + label + " size mismatch, " +
					"atlas is " + src.width + "x" + src.height + " but ours is " +
					ours.width + "x" + ours.height + " - skipped");
				return -1;
			}
			if (ours.graphicsFormat != src.graphicsFormat)
			{
				Debug.LogWarning("[NecromancerTome] CustomBlockPaint: " + label + " format mismatch, " +
					"atlas is " + src.graphicsFormat + " but ours is " + ours.graphicsFormat +
					" - skipped");
				return -1;
			}
			if (ours.mipmapCount != src.mipmapCount)
			{
				Debug.LogWarning("[NecromancerTome] CustomBlockPaint: " + label + " mip mismatch, " +
					"atlas has " + src.mipmapCount + " but ours has " + ours.mipmapCount +
					" - skipped");
				return -1;
			}

			int slice = src.depth;
			var grown = new Texture2DArray(src.width, src.height, slice + 1,
				src.graphicsFormat, UnityEngine.Experimental.Rendering.TextureCreationFlags.MipChain,
				src.mipmapCount);
			grown.name = src.name + "+necro";
			grown.wrapMode = src.wrapMode;
			grown.filterMode = src.filterMode;
			grown.anisoLevel = src.anisoLevel;

			// GPU-side copy: the game's arrays are non-readable, so nothing can be pulled back
			// to the CPU. CopyTexture moves whole slices with their mip chains.
			for (int i = 0; i < slice; i++) Graphics.CopyTexture(src, i, grown, i);
			Graphics.CopyTexture(ours, 0, grown, slice);

			target = grown;
			Debug.Log("[NecromancerTome] CustomBlockPaint: " + label + " grown from " + slice +
				" to " + (slice + 1) + " slices");
			return slice;
		}

		static void Describe(string label, Texture2D tex)
		{
			Debug.Log("[NecromancerTome] CustomBlockPaint: " + label + " " +
				tex.width + "x" + tex.height + " format=" + tex.format +
				" graphicsFormat=" + tex.graphicsFormat + " mips=" + tex.mipmapCount);
		}
	}
}