using System;
using System.Collections.Generic;
using System.IO;
using System.Numerics;
using System.Text;
using Microsoft.Extensions.Logging;
using SmartNav.Model.Navigation;

namespace SmartNav.Data;

public sealed class LgbZoneBoundarySource : IZoneBoundarySource
{
	private sealed record LgbData(List<ExitRangeEntry> ExitRanges, Dictionary<(ushort TerritoryId, uint InstanceId), PopRangeEntry> PopRangeIndex);

	private const uint BoundaryFileMagic = 1112425562u;

	private const int BoundaryFileFormatVersion = 1;

	private const string CacheFileName = "zone-boundary-cache.bin";

	private const int MaxPreallocatedEntries = 131072;

	private readonly ILogger<LgbZoneBoundarySource> _logger;

	private readonly string? _overrideDirectory;

	private readonly string? _gameVersion;

	private readonly object _buildLock = new object();

	private IReadOnlyList<ZoneBoundary>? _boundaries;

	public LgbZoneBoundarySource(ILogger<LgbZoneBoundarySource> logger, SmartNavDataOptions? dataOptions = null)
	{
		_logger = logger;
		_overrideDirectory = dataOptions?.UserOverrideDirectory?.FullName;
		_gameVersion = dataOptions?.GameVersion;
	}

	public IReadOnlyList<ZoneBoundary> GetBoundaries()
	{
		lock (_buildLock)
		{
			return _boundaries ?? (_boundaries = Build());
		}
	}

	public void Invalidate()
	{
		lock (_buildLock)
		{
			_boundaries = null;
		}
	}

	private IReadOnlyList<ZoneBoundary> Build()
	{
		try
		{
			var (lgbData, text) = LoadRawData();
			if (lgbData == null)
			{
				return Array.Empty<ZoneBoundary>();
			}
			List<ZoneBoundary> list = ZoneBoundaryDerivation.Derive(lgbData.ExitRanges, lgbData.PopRangeIndex, _logger);
			ZoneBoundaryDerivation.ApplyOverrides(list, ZoneBoundaryOverrides.FlyingPairs, ZoneBoundaryOverrides.PositionOverrides, _logger);
			_logger.LogDebug("Derived {Count} zone boundaries from {ExitCount} ExitRanges ({Source})", list.Count, lgbData.ExitRanges.Count, text);
			return list;
		}
		catch (Exception exception)
		{
			_logger.LogError(exception, "Zone boundary derivation failed - building graph without boundary edges");
			return Array.Empty<ZoneBoundary>();
		}
	}

	private (LgbData? Data, string Source) LoadRawData()
	{
		LgbData lgbData = TryLoadOverrideFile("override file");
		if (lgbData != null)
		{
			return (Data: lgbData, Source: "override file");
		}
		return (Data: TryLoadEmbedded("embedded resource"), Source: "embedded resource");
	}

	private LgbData? TryLoadOverrideFile(string source)
	{
		if (string.IsNullOrEmpty(_overrideDirectory))
		{
			return null;
		}
		string text = Path.Combine(_overrideDirectory, "zone-boundary-cache.bin");
		if (!File.Exists(text))
		{
			return null;
		}
		try
		{
			using Stream stream = File.OpenRead(text);
			LgbData lgbData = ReadCache(stream, source);
			if (lgbData.ExitRanges.Count == 0 && lgbData.PopRangeIndex.Count == 0)
			{
				_logger.LogWarning("Zone boundary {Source} {Path} holds no exits and no pops, ignoring it and using the embedded data", source, text);
				return null;
			}
			return lgbData;
		}
		catch (Exception exception)
		{
			_logger.LogWarning(exception, "Failed to read zone boundary {Source}, falling back to the embedded data", source);
			return null;
		}
	}

	private LgbData? TryLoadEmbedded(string source)
	{
		try
		{
			using Stream stream = AssemblyLgbCacheLoader.OpenZoneBoundaryCache();
			return ReadCache(stream, source);
		}
		catch (Exception exception)
		{
			_logger.LogError(exception, "Failed to read zone boundary {Source} - building graph without boundary edges", source);
			return null;
		}
	}

	private LgbData ReadCache(Stream stream, string source)
	{
		using BinaryReader binaryReader = new BinaryReader(stream, Encoding.UTF8, leaveOpen: true);
		if (binaryReader.ReadUInt32() != 1112425562 || binaryReader.ReadInt32() != 1)
		{
			throw new InvalidDataException("zone boundary " + source + " has an unknown header");
		}
		string text = binaryReader.ReadString();
		if (!string.IsNullOrEmpty(_gameVersion) && text != _gameVersion)
		{
			_logger.LogInformation("Zone boundary {Source} was built for game version {FileVersion}, running {GameVersion} - using it anyway", source, text, _gameVersion);
		}
		int num = binaryReader.ReadInt32();
		if (num < 0)
		{
			throw new InvalidDataException($"zone boundary {source} has a negative exit count ({num})");
		}
		List<ExitRangeEntry> list = new List<ExitRangeEntry>(Math.Min(num, 131072));
		for (int i = 0; i < num; i++)
		{
			list.Add(new ExitRangeEntry(binaryReader.ReadUInt16(), binaryReader.ReadUInt32(), new Vector3(binaryReader.ReadSingle(), binaryReader.ReadSingle(), binaryReader.ReadSingle()), binaryReader.ReadUInt16(), binaryReader.ReadUInt32(), binaryReader.ReadUInt32(), new Vector3(binaryReader.ReadSingle(), binaryReader.ReadSingle(), binaryReader.ReadSingle()), new Vector3(binaryReader.ReadSingle(), binaryReader.ReadSingle(), binaryReader.ReadSingle())));
		}
		int num2 = binaryReader.ReadInt32();
		if (num2 < 0)
		{
			throw new InvalidDataException($"zone boundary {source} has a negative pop count ({num2})");
		}
		Dictionary<(ushort, uint), PopRangeEntry> dictionary = new Dictionary<(ushort, uint), PopRangeEntry>(Math.Min(num2, 131072));
		for (int j = 0; j < num2; j++)
		{
			ushort num3 = binaryReader.ReadUInt16();
			uint num4 = binaryReader.ReadUInt32();
			Vector3 position = new Vector3(binaryReader.ReadSingle(), binaryReader.ReadSingle(), binaryReader.ReadSingle());
			dictionary[(num3, num4)] = new PopRangeEntry(num3, num4, position);
		}
		_logger.LogDebug("Zone boundary data loaded from {Source} ({ExitCount} exits, {PopCount} pops)", source, list.Count, dictionary.Count);
		return new LgbData(list, dictionary);
	}
}