using System;
using System.IO;
using System.Runtime.CompilerServices;
using System.Text;
using HarmonyLib;
using UnityEngine;

namespace NecromancerTome
{
	/// <summary>
	/// Cross-restart persistence for the Spatial Bracelet's vault - the fix for the first bug
	/// report the mod ever got on Nexus (youkia96581, 11 Sep 2026: "Items stored in the space
	/// bracelet will disappear after leaving the game and going online again").
	///
	/// WHY IT LIVES IN THE PLAYER'S SAVE FILE - "почему не сделать принцип как у ящика?" (user,
	/// 13.09.2026). Right question, and it decided the design. A chest keeps its items because
	/// they live in a TileEntity, and a TileEntity belongs to a CHUNK: decompiled, `TileEntity`
	/// has chunkPos and chunk fields and its ONLY constructor is TileEntity(Chunk). The game saves
	/// and syncs the chunk; the container rides along. That is the whole trick - not a "storage
	/// system" one can call, but a home in something the engine already persists. The bracelet has
	/// no position and no chunk, so it got the closest equivalent for something personal: the
	/// player's own save data, written right after everything vanilla writes, in the same file and
	/// the same moment as the backpack.
	///
	/// THAT ALSO ANSWERS THE ID QUESTION ("у браслета, как и у ящика, наверняка есть id"). A
	/// chest's id IS its position. An item has no per-instance id by default - ItemValue.type is
	/// the item CLASS, identical on every bracelet - but ItemValue.Metadata would hold one and
	/// genuinely round-trips through saves (ItemValue.Write writes it, ItemValue.ReadData reads it
	/// back; both checked). Per-bracelet vaults are therefore buildable and deliberately not built:
	/// keying by the item means losing the bracelet locks the items away forever even though they
	/// are still in the save file, and it would let ten bracelets be ten warehouses. Keying by the
	/// player - which storing them IN the player's file does for free - has neither problem.
	///
	/// THE FOUR HOOKS:
	///   FromPlayer  - live player -> file object: attach that player's vault to the file.
	///   Write       - file object -> bytes (Save to disk, or WriteNetwork to the wire, which is
	///                 literally Write + PlayerMetaInfo): append the vault blob.
	///   Read        - bytes -> file object: pull the vault back off the stream.
	///   ToPlayer    - file object -> live player: hand the vault back.
	/// FromPlayer always reads the CURRENT vault, so there is no dirty flag and no save scheduling
	/// to get wrong: whenever the game saves the player, it saves the vault.
	///
	/// ================================================================================
	/// THE BUG THAT COST TWO TEST RUNS, AND WHY IT IS WORTH A BIG COMMENT
	/// ================================================================================
	/// Earlier versions cleared the session cache from a ModEvents.WorldShuttingDown handler, to
	/// stop one save's vault leaking into the next. The user reported the vault kept losing its
	/// contents, and the diagnostics printed the murder weapon in order:
	///
	///     INF SaveAndCleanupWorld
	///     [NecromancerTome] world shutting down, dropped 1 in-memory vault(s)
	///     [NecromancerTome] FromPlayer entity 171 - vault NONE
	///     [NecromancerTome] Write - no vault attached (writes an EMPTY marker)
	///
	/// **WorldShuttingDown fires BEFORE the final player save, not after.** Confirmed in
	/// GameManager.SaveAndCleanupWorld by decompilation rather than inferred from the log: the
	/// event is invoked at IL_0026 and SaveLocalPlayerData() is called at IL_00c4, a hundred-odd
	/// instructions later. So the handler emptied the cache, and the save that followed
	/// faithfully recorded "this player has no vault" over the real one. Every clean exit wiped
	/// the vault - which is exactly the symptom the Nexus report described, reintroduced by the
	/// fix for it.
	///
	/// There is no documentation to have checked first: the community consensus is that the
	/// official ModAPI is barebones and has no reference for event ordering, so the decompiler is
	/// the only authority. Treat every ModEvent's position in the shutdown sequence as unknown
	/// until read out of the method that invokes it.
	///
	/// TWO RULES CAME OUT OF IT, and both are load-bearing here:
	///
	///   1. A RESTORE PATH MAY FAIL; IT MAY NEVER DELETE. An empty session cache is not evidence
	///      that the player has no vault - it is the absence of evidence. LastLoadedVault below is
	///      the safety net, so a broken restore chain costs a restore, not the data.
	///   2. FRESHNESS IS DECIDED BY WHAT WAS READ, NOT BY A TIMER. Cross-save leaking is now
	///      prevented by ToPlayer being authoritative: a player file that was read and explicitly
	///      carried no vault CLEARS the cache. Nothing has to be cleared "at the right moment"
	///      any more, which is what made the old approach fragile in the first place.
	/// </summary>
	public static class SpatialVaultPersistence
	{
		/// <summary>Payload layout version, independent of the blob framing in
		/// SpatialVaultBlobIO. An unknown version is skipped, not guessed at - the framing's
		/// explicit length means we can always step over a payload we do not understand.</summary>
		public const byte PayloadVersion = 1;

		/// <summary>What a PlayerDataFile carries. A class rather than a bare Bag because its mere
		/// PRESENCE is information: "this file has been read/filled, and the answer - including a
		/// null Bag - is authoritative". ConditionalWeakTable cannot store null, so a null Bag
		/// needs a wrapper to be expressible at all.</summary>
		public class VaultSlot
		{
			public Bag Bag;
		}

		/// <summary>Vault attached to a PlayerDataFile while it is being written, read or
		/// converted. Weak, because PlayerDataFile objects are created fresh for every save and
		/// every network packet and nothing here should keep one alive.</summary>
		public static readonly ConditionalWeakTable<PlayerDataFile, VaultSlot> AttachedVaults =
			new ConditionalWeakTable<PlayerDataFile, VaultSlot>();

		/// <summary>
		/// Last vault seen this session, kept outside the weak table. This is rule 1 above made
		/// concrete: if the Read -> ToPlayer -> PlayerVaults chain ever fails to complete, the bag
		/// is still here, so the next save writes the real contents instead of an empty marker.
		///
		/// SINGLE LOCAL PLAYER ONLY. There is one of these per process, so on a dedicated server
		/// it would be one player's vault handed to whoever asked next. Every use is gated on the
		/// player being an EntityPlayerLocal - which a dedicated server does not have, and a host
		/// or single-player game has exactly one of.
		/// </summary>
		public static Bag LastLoadedVault;

		/// <summary>Last line printed by the save path, so an unchanged vault saved over and over
		/// does not repeat itself in the log. Kept 2026-09-13 when the fix was confirmed: the
		/// save pair fires on every autosave, and a player's log should not carry two lines of
		/// inventory listing every few minutes - but the moment anything CHANGES it still says so,
		/// which is the part that had diagnostic value.</summary>
		public static string lastSaveLogged;

		/// <summary>Builds the opaque payload SpatialVaultBlobIO wraps. Uses netstandard's own
		/// BinaryWriter over a MemoryStream, which is why Bag serialization can stay in this
		/// project instead of the satellite assembly.</summary>
		public static byte[] BuildPayload(Bag _bag)
		{
			using (MemoryStream ms = new MemoryStream())
			using (BinaryWriter bw = new BinaryWriter(ms))
			{
				bw.Write(PayloadVersion);
				bool hasBag = _bag != null;
				bw.Write(hasBag);
				if (hasBag)
				{
					// Plain BinaryWriter is enough: Bag.Write only demands a PooledBinaryWriter
					// when bag.preferences != null, and vault bags come from `new Bag(int)`, whose
					// constructor sets nothing but the item array.
					_bag.Write(bw);
				}
				bw.Flush();
				return ms.ToArray();
			}
		}

		/// <summary>Null when the payload holds no vault or is a version we do not know.</summary>
		public static Bag ParsePayload(byte[] _payload)
		{
			if (_payload == null || _payload.Length == 0)
			{
				return null;
			}
			using (MemoryStream ms = new MemoryStream(_payload, false))
			using (BinaryReader br = new BinaryReader(ms))
			{
				byte version = br.ReadByte();
				if (version != PayloadVersion)
				{
					Debug.LogWarning("[NecromancerTome] SpatialVaultPersistence: vault payload version " + version + ", expected " + PayloadVersion + " - skipped");
					return null;
				}
				if (!br.ReadBoolean())
				{
					return null;
				}
				// Bag.Read is the STATIC one and returns a new Bag; ReadInto is the instance
				// version. Symmetric with BuildPayload: preferences were written as absent, so no
				// PooledBinaryReader is needed here either.
				return Bag.Read(br);
			}
		}

		public static void Attach(PlayerDataFile _file, Bag _bag)
		{
			AttachedVaults.Remove(_file);
			AttachedVaults.Add(_file, new VaultSlot { Bag = _bag });
		}

		/// <summary>Contents of a bag, for the log. Item names rather than just a count, because
		/// "2 slots, 0 used" was true and useless three test runs in a row - what was needed was
		/// whether the items the user put in had actually reached this object.</summary>
		public static string Describe(Bag _bag)
		{
			if (_bag == null)
			{
				return "NONE";
			}
			ItemStack[] slots = _bag.GetSlots();
			StringBuilder sb = new StringBuilder();
			sb.Append(_bag.SlotCount).Append(" slots, ").Append(_bag.GetUsedSlotCount()).Append(" used");
			if (slots != null)
			{
				for (int i = 0; i < slots.Length; i++)
				{
					ItemStack stack = slots[i];
					if (stack == null || stack.IsEmpty())
					{
						continue;
					}
					string name = stack.itemValue != null && stack.itemValue.ItemClass != null
						? stack.itemValue.ItemClass.GetItemName()
						: "?";
					sb.Append(" [").Append(i).Append("]=").Append(name).Append("x").Append(stack.count);
				}
			}
			return sb.ToString();
		}
	}

	/// <summary>Live player -> save file: take the vault along.</summary>
	[HarmonyPatch(typeof(PlayerDataFile), "FromPlayer")]
	public static class Patch_PlayerDataFile_FromPlayer_SpatialVault
	{
		public static void Postfix(PlayerDataFile __instance, EntityPlayer _player)
		{
			try
			{
				if (_player == null)
				{
					return;
				}
				Patch_ItemActionEat_ExecuteAction_SpatialVault.PlayerVaults.TryGetValue(_player.entityId, out Bag bag);
				string source = bag != null ? "session cache" : null;
				if (bag == null && _player is EntityPlayerLocal && SpatialVaultPersistence.LastLoadedVault != null)
				{
					// Rule 1: never write "no vault" over a vault we know exists.
					bag = SpatialVaultPersistence.LastLoadedVault;
					source = "last loaded (session cache was empty)";
				}
				SpatialVaultPersistence.Attach(__instance, bag);
				string line = "FromPlayer entity " + _player.entityId + " - " + SpatialVaultPersistence.Describe(bag) +
				              (source != null ? ", from " + source : "");
				if (line != SpatialVaultPersistence.lastSaveLogged)
				{
					SpatialVaultPersistence.lastSaveLogged = line;
					Debug.Log("[NecromancerTome] SpatialVaultPersistence: " + line);
				}
			}
			catch (Exception e)
			{
				Debug.LogError("[NecromancerTome] SpatialVaultPersistence: FromPlayer postfix failed: " + e);
			}
		}
	}

	/// <summary>
	/// Save file -> live player: hand the vault back. This is also where freshness is decided
	/// (rule 2): a file that WAS read and explicitly carried no vault clears the cache, so loading
	/// a different save cannot inherit the previous world's vault. Only a file that was never read
	/// at all falls back to LastLoadedVault, which is the broken-chain safety net.
	/// </summary>
	[HarmonyPatch(typeof(PlayerDataFile), "ToPlayer")]
	public static class Patch_PlayerDataFile_ToPlayer_SpatialVault
	{
		public static void Postfix(PlayerDataFile __instance, EntityPlayer _player)
		{
			try
			{
				if (_player == null)
				{
					return;
				}
				bool isLocal = _player is EntityPlayerLocal;
				string note;
				Bag bag;

				if (SpatialVaultPersistence.AttachedVaults.TryGetValue(__instance, out SpatialVaultPersistence.VaultSlot slot))
				{
					bag = slot.Bag;
					note = bag != null ? "from this player file" : "this player file says there is no vault";
				}
				else if (isLocal && SpatialVaultPersistence.LastLoadedVault != null)
				{
					bag = SpatialVaultPersistence.LastLoadedVault;
					note = "nothing attached to this file - fell back to the last loaded vault";
				}
				else
				{
					bag = null;
					note = "nothing attached and nothing loaded";
				}

				if (bag != null)
				{
					Patch_ItemActionEat_ExecuteAction_SpatialVault.PlayerVaults[_player.entityId] = bag;
				}
				else
				{
					Patch_ItemActionEat_ExecuteAction_SpatialVault.PlayerVaults.Remove(_player.entityId);
				}
				if (isLocal)
				{
					SpatialVaultPersistence.LastLoadedVault = bag;
				}

				Debug.Log("[NecromancerTome] SpatialVaultPersistence: ToPlayer entity " + _player.entityId +
				          " - " + SpatialVaultPersistence.Describe(bag) + " (" + note + ")");
			}
			catch (Exception e)
			{
				Debug.LogError("[NecromancerTome] SpatialVaultPersistence: ToPlayer postfix failed: " + e);
			}
		}
	}

	/// <summary>Appends the vault after everything vanilla wrote - to disk via Save, or to the
	/// wire via WriteNetwork.</summary>
	[HarmonyPatch(typeof(PlayerDataFile), "Write")]
	public static class Patch_PlayerDataFile_Write_SpatialVault
	{
		public static void Postfix(PlayerDataFile __instance, PooledBinaryWriter _bw)
		{
			try
			{
				SpatialVaultPersistence.AttachedVaults.TryGetValue(__instance, out SpatialVaultPersistence.VaultSlot slot);
				Bag bag = slot != null ? slot.Bag : null;
				SpatialVaultBlobIO.Write(_bw, SpatialVaultPersistence.BuildPayload(bag));
				if (bag == null)
				{
					// Always shouted: writing an empty marker is how the vault got destroyed twice,
					// so it must never again scroll past unnoticed.
					Debug.LogWarning("[NecromancerTome] SpatialVaultPersistence: Write - no vault attached (writes an EMPTY marker)");
				}
			}
			catch (Exception e)
			{
				Debug.LogError("[NecromancerTome] SpatialVaultPersistence: Write postfix failed: " + e);
			}
		}
	}

	/// <summary>Reads the vault back off the stream. Must never throw: PlayerDataFile.Load treats
	/// any exception out of Read as "this save is broken, fall back to the .bak".</summary>
	[HarmonyPatch(typeof(PlayerDataFile), "Read")]
	public static class Patch_PlayerDataFile_Read_SpatialVault
	{
		public static void Postfix(PlayerDataFile __instance, PooledBinaryReader _br)
		{
			try
			{
				byte[] payload = SpatialVaultBlobIO.TryRead(_br);
				if (payload == null)
				{
					// No vault block: a save from before this feature existed, or player data from
					// somebody without the mod. Deliberately NOT recorded as an authoritative
					// "no vault" - an absent block is silence, not a denial, and ToPlayer's
					// fallback is what should handle it. SpatialVaultBlobIO has already put the
					// stream position back.
					Debug.Log("[NecromancerTome] SpatialVaultPersistence: Read - no vault block on this stream");
					return;
				}

				Bag bag = SpatialVaultPersistence.ParsePayload(payload);
				// Attached even when null: a blob that says "no vault" IS an answer, and ToPlayer
				// uses it to clear a stale cache when a different save is loaded.
				SpatialVaultPersistence.Attach(__instance, bag);
				if (bag != null)
				{
					SpatialVaultPersistence.LastLoadedVault = bag;
				}
				Debug.Log("[NecromancerTome] SpatialVaultPersistence: Read - blob of " + payload.Length +
				          " byte(s), " + SpatialVaultPersistence.Describe(bag));
			}
			catch (Exception e)
			{
				Debug.LogError("[NecromancerTome] SpatialVaultPersistence: Read postfix failed: " + e);
			}
		}
	}
}