using K4os.Compression.LZ4.Streams;
using MareSynchronos.Interop;
using MareSynchronos.MareConfiguration;
using MareSynchronos.Services.Mediator;
using MareSynchronos.Utils;
using Microsoft.Extensions.Logging;
using System.Collections.Concurrent;
using System.Globalization;
using System.Text;

namespace MareSynchronos.FileCache;

public sealed class FileCacheManager : IDisposable
{
    public const string CachePrefix = "{cache}";
    public const string CsvSplit = "|";
    public const string PenumbraPrefix = "{penumbra}";
    private readonly MareConfigService _configService;
    private readonly MareMediator _mareMediator;
    private readonly string _csvPath;
    private readonly ConcurrentDictionary<string, List<FileCacheEntity>> _fileCaches = new(StringComparer.Ordinal);
    private readonly object _fileWriteLock = new();
    private readonly IpcManager _ipcManager;
    private readonly ILogger<FileCacheManager> _logger;

    public FileCacheManager(ILogger<FileCacheManager> logger, IpcManager ipcManager, MareConfigService configService, MareMediator mareMediator)
    {
        _logger = logger;
        _ipcManager = ipcManager;
        _configService = configService;
        _mareMediator = mareMediator;
        _csvPath = Path.Combine(configService.ConfigurationDirectory, "FileCache.csv");

        lock (_fileWriteLock)
        {
            try
            {
                if (File.Exists(CsvBakPath))
                {
                    File.Move(CsvBakPath, _csvPath, overwrite: true);
                }
            }
            catch (Exception ex)
            {
                _logger.LogWarning(ex, "Failed to move BAK to ORG, deleting BAK");
                try
                {
                    if (File.Exists(CsvBakPath))
                        File.Delete(CsvBakPath);
                }
                catch (Exception ex1)
                {
                    _logger.LogWarning(ex1, "Could not delete bak file");
                }
            }
        }

        if (File.Exists(_csvPath))
        {
            bool success = false;
            string[] entries = [];
            int attempts = 0;
            while (!success && attempts < 10)
            {
                try
                {
                    entries = File.ReadAllLines(_csvPath);
                    success = true;
                }
                catch (Exception ex)
                {
                    attempts++;
                    _logger.LogWarning(ex, "Could not open {file}, trying again", _csvPath);
                    Thread.Sleep(100);
                }
            }

            if (!entries.Any())
            {
                _logger.LogWarning("Could not load entries from {path}, continuing with empty file cache", _csvPath);
            }

            Dictionary<string, bool> processedFiles = new(StringComparer.OrdinalIgnoreCase);
            foreach (var entry in entries)
            {
                var splittedEntry = entry.Split(CsvSplit, StringSplitOptions.None);
                try
                {
                    var hash = splittedEntry[0];
                    if (hash.Length != 40) throw new InvalidOperationException("Expected Hash length of 40, received " + hash.Length);
                    var path = splittedEntry[1];
                    var time = splittedEntry[2];

                    if (processedFiles.ContainsKey(path))
                    {
                        _logger.LogWarning("Already processed {file}, ignoring", path);
                        continue;
                    }

                    processedFiles.Add(path, value: true);

                    long size = -1;
                    long compressed = -1;
                    if (splittedEntry.Length > 3)
                    {
                        if (long.TryParse(splittedEntry[3], CultureInfo.InvariantCulture, out long result))
                        {
                            size = result;
                        }
                        if (long.TryParse(splittedEntry[4], CultureInfo.InvariantCulture, out long resultCompressed))
                        {
                            compressed = resultCompressed;
                        }
                    }
                    AddHashedFile(ReplacePathPrefixes(new FileCacheEntity(hash, path, time, size, compressed)));
                }
                catch (Exception ex)
                {
                    _logger.LogWarning(ex, "Failed to initialize entry {entry}, ignoring", entry);
                }
            }

            if (processedFiles.Count != entries.Length)
            {
                WriteOutFullCsv();
            }
        }
    }

    private string CsvBakPath => _csvPath + ".bak";

    public FileCacheEntity? CreateCacheEntry(string path)
    {
        _logger.LogTrace("Creating cache entry for {path}", path);
        FileInfo fi = new(path);
        if (!fi.Exists) return null;
        var fullName = fi.FullName.ToLowerInvariant();
        if (!fullName.Contains(_configService.Current.CacheFolder.ToLowerInvariant(), StringComparison.Ordinal)) return null;
        string prefixedPath = fullName.Replace(_configService.Current.CacheFolder.ToLowerInvariant(), CachePrefix + "\\", StringComparison.Ordinal).Replace("\\\\", "\\", StringComparison.Ordinal);
        return CreateFileCacheEntity(fi, prefixedPath);
    }

    public FileCacheEntity? CreateFileEntry(string path)
    {
        _logger.LogTrace("Creating file entry for {path}", path);
        FileInfo fi = new(path);
        if (!fi.Exists) return null;
        var fullName = fi.FullName.ToLowerInvariant();
        if (!fullName.Contains(_ipcManager.PenumbraModDirectory!.ToLowerInvariant(), StringComparison.Ordinal)) return null;
        string prefixedPath = fullName.Replace(_ipcManager.PenumbraModDirectory!.ToLowerInvariant(), PenumbraPrefix + "\\", StringComparison.Ordinal).Replace("\\\\", "\\", StringComparison.Ordinal);
        return CreateFileCacheEntity(fi, prefixedPath);
    }

    public void Dispose()
    {
        _logger.LogTrace("Disposing {type}", GetType());
        WriteOutFullCsv();
        GC.SuppressFinalize(this);
    }

    public List<FileCacheEntity> GetAllFileCaches() => _fileCaches.Values.SelectMany(v => v).ToList();

    public List<FileCacheEntity> GetAllFileCachesByHash(string hash)
    {
        List<FileCacheEntity> output = [];
        if (_fileCaches.TryGetValue(hash, out var fileCacheEntities))
        {
            foreach (var filecache in fileCacheEntities.ToList())
            {
                var validated = GetValidatedFileCache(filecache);
                if (validated != null) output.Add(validated);
            }
        }

        return output;
    }

    public Task<List<FileCacheEntity>> ValidateLocalIntegrity(IProgress<(int, int, FileCacheEntity)> progress, CancellationToken cancellationToken)
    {
        _mareMediator.Publish(new HaltScanMessage(nameof(ValidateLocalIntegrity)));
        _logger.LogInformation("Validating local storage");
        var cacheEntries = _fileCaches.SelectMany(v => v.Value).Where(v => v.IsCacheEntry).ToList();
        List<FileCacheEntity> brokenEntities = new();
        int i = 0;
        foreach (var fileCache in cacheEntries)
        {
            _logger.LogInformation("Validating {file}", fileCache.ResolvedFilepath);

            progress.Report((i, cacheEntries.Count, fileCache));
            i++;
            var computedHash = Crypto.GetFileHash(fileCache.ResolvedFilepath);
            if (!string.Equals(computedHash, fileCache.Hash, StringComparison.Ordinal))
            {
                _logger.LogInformation("Failed to validate {file}, got hash {hash}, expected hash {hash}", fileCache.ResolvedFilepath, computedHash, fileCache.Hash);
                brokenEntities.Add(fileCache);
            }

            if (cancellationToken.IsCancellationRequested) break;
        }

        foreach (var brokenEntity in brokenEntities)
        {
            RemoveHashedFile(brokenEntity.Hash, brokenEntity.PrefixedFilePath);

            try
            {
                File.Delete(brokenEntity.ResolvedFilepath);
            }
            catch (Exception ex)
            {
                _logger.LogWarning(ex, "Could not delete {file}", brokenEntity.ResolvedFilepath);
            }
        }

        _mareMediator.Publish(new ResumeScanMessage(nameof(ValidateLocalIntegrity)));
        return Task.FromResult(brokenEntities);
    }

    public string GetCacheFilePath(string hash, string extension)
    {
        return Path.Combine(_configService.Current.CacheFolder, hash + "." + extension);
    }

    public async Task<long> GetCompressedFileLength(string fileHash, CancellationToken uploadToken)
    {
        var fileCache = GetFileCacheByHash(fileHash)!.ResolvedFilepath;
        using var fs = File.OpenRead(fileCache);
        var cs = new CountedStream(Stream.Null);
        using var encstream = LZ4Stream.Encode(cs, new LZ4EncoderSettings(){CompressionLevel=K4os.Compression.LZ4.LZ4Level.L09_HC});
        await fs.CopyToAsync(encstream, uploadToken).ConfigureAwait(false);
        encstream.Close();
        return uploadToken.IsCancellationRequested ? 0 : cs.BytesWritten;
    }

    public async Task<byte[]> GetCompressedFileData(string fileHash, CancellationToken uploadToken)
    {
        var fileCache = GetFileCacheByHash(fileHash)!.ResolvedFilepath;
        using var fs = File.OpenRead(fileCache);
        var ms = new MemoryStream(64 * 1024);
        using var encstream = LZ4Stream.Encode(ms, new LZ4EncoderSettings(){CompressionLevel=K4os.Compression.LZ4.LZ4Level.L09_HC});
        await fs.CopyToAsync(encstream, uploadToken).ConfigureAwait(false);
        encstream.Close();
        return ms.ToArray();
    }

    public FileCacheEntity? GetFileCacheByHash(string hash)
    {
        if (_fileCaches.TryGetValue(hash, out var hashes))
        {
            var item = hashes.FirstOrDefault();
            if (item != null) return GetValidatedFileCache(item);
        }
        return null;
    }

    public FileCacheEntity? GetFileCacheByPath(string path)
    {
        var cleanedPath = path.Replace("/", "\\", StringComparison.OrdinalIgnoreCase).ToLowerInvariant().Replace(_ipcManager.PenumbraModDirectory!.ToLowerInvariant(), "", StringComparison.OrdinalIgnoreCase);
        var entry = _fileCaches.SelectMany(v => v.Value).FirstOrDefault(f => f.ResolvedFilepath.EndsWith(cleanedPath, StringComparison.OrdinalIgnoreCase));

        if (entry == null)
        {
            _logger.LogDebug("Found no entries for {path}", cleanedPath);
            return CreateFileEntry(path);
        }

        var validatedCacheEntry = GetValidatedFileCache(entry);

        return validatedCacheEntry;
    }

    public Dictionary<string, FileCacheEntity?> GetFileCachesByPaths(string[] paths)
    {
        var cleanedPaths = paths.Distinct(StringComparer.OrdinalIgnoreCase).ToDictionary(p => p,
            p => p.Replace("/", "\\", StringComparison.OrdinalIgnoreCase)
            .Replace(_ipcManager.PenumbraModDirectory!,
                _ipcManager.PenumbraModDirectory!.EndsWith('\\') ? (PenumbraPrefix + "\\") : PenumbraPrefix,
                StringComparison.OrdinalIgnoreCase),
            StringComparer.OrdinalIgnoreCase);

        Dictionary<string, FileCacheEntity?> result = new(StringComparer.OrdinalIgnoreCase);

        var dict = _fileCaches.SelectMany(f => f.Value).Where(f => f.PrefixedFilePath.StartsWith(PenumbraPrefix, StringComparison.Ordinal))
            .ToDictionary(d => d.PrefixedFilePath, d => d, StringComparer.Ordinal);

        foreach (var entry in cleanedPaths)
        {
            if (dict.TryGetValue(entry.Value, out var entity))
            {
                var validatedCache = GetValidatedFileCache(entity);
                result.Add(entry.Key, validatedCache);
            }
            else
            {
                result.Add(entry.Key, CreateFileEntry(entry.Key));
            }
        }

        return result;
    }

    public void RemoveHashedFile(string hash, string prefixedFilePath)
    {
        if (_fileCaches.TryGetValue(hash, out var caches))
        {
            caches?.RemoveAll(c => string.Equals(c.PrefixedFilePath, prefixedFilePath, StringComparison.Ordinal));
            if (caches?.Count == 0)
            {
                _fileCaches.Remove(hash, out _);
            }
        }
    }

    public void UpdateHashedFile(FileCacheEntity fileCache, bool computeProperties = true)
    {
        _logger.LogTrace("Updating hash for {path}", fileCache.ResolvedFilepath);
        var oldHash = fileCache.Hash;
        var prefixedPath = fileCache.PrefixedFilePath;
        if (computeProperties)
        {
            var fi = new FileInfo(fileCache.ResolvedFilepath);
            fileCache.Size = fi.Length;
            fileCache.CompressedSize = null;
            fileCache.Hash = Crypto.GetFileHash(fileCache.ResolvedFilepath);
            fileCache.LastModifiedDateTicks = fi.LastWriteTimeUtc.Ticks.ToString(CultureInfo.InvariantCulture);
        }
        RemoveHashedFile(oldHash, prefixedPath);
        AddHashedFile(fileCache);
    }

    public (FileState State, FileCacheEntity FileCache) ValidateFileCacheEntity(FileCacheEntity fileCache)
    {
        fileCache = ReplacePathPrefixes(fileCache);
        FileInfo fi = new(fileCache.ResolvedFilepath);
        if (!fi.Exists)
        {
            return (FileState.RequireDeletion, fileCache);
        }
        if (!string.Equals(fi.LastWriteTimeUtc.Ticks.ToString(CultureInfo.InvariantCulture), fileCache.LastModifiedDateTicks, StringComparison.Ordinal))
        {
            return (FileState.RequireUpdate, fileCache);
        }

        return (FileState.Valid, fileCache);
    }

    public void WriteOutFullCsv()
    {
        StringBuilder sb = new();
        foreach (var entry in _fileCaches.SelectMany(k => k.Value).OrderBy(f => f.PrefixedFilePath, StringComparer.OrdinalIgnoreCase))
        {
            sb.AppendLine(entry.CsvEntry);
        }
        lock (_fileWriteLock)
        {
            if (File.Exists(_csvPath))
            {
                File.Copy(_csvPath, CsvBakPath, overwrite: true);
            }

            try
            {
                File.WriteAllText(_csvPath, sb.ToString());
                File.Delete(CsvBakPath);
            }
            catch
            {
                File.WriteAllText(CsvBakPath, sb.ToString());
            }
        }
    }

    internal FileCacheEntity MigrateFileHashToExtension(FileCacheEntity fileCache, string ext)
    {
        try
        {
            RemoveHashedFile(fileCache.Hash, fileCache.PrefixedFilePath);
            FileInfo fileInfo = new(fileCache.ResolvedFilepath);
            FileInfo oldCache = fileInfo;
            var extensionPath = fileCache.ResolvedFilepath.ToUpper(CultureInfo.InvariantCulture) + "." + ext;
            File.Move(fileCache.ResolvedFilepath, extensionPath, overwrite: true);
            var newHashedEntity = new FileCacheEntity(fileCache.Hash, fileCache.PrefixedFilePath + "." + ext, DateTime.UtcNow.Ticks.ToString(CultureInfo.InvariantCulture));
            newHashedEntity.SetResolvedFilePath(extensionPath);
            AddHashedFile(newHashedEntity);
            _logger.LogDebug("Migrated from {oldPath} to {newPath}", fileCache.ResolvedFilepath, newHashedEntity.ResolvedFilepath);
            return newHashedEntity;
        }
        catch (Exception ex)
        {
            AddHashedFile(fileCache);
            _logger.LogWarning(ex, "Failed to migrate entity {entity}", fileCache.PrefixedFilePath);
            return fileCache;
        }
    }

    private void AddHashedFile(FileCacheEntity fileCache)
    {
        if (!_fileCaches.TryGetValue(fileCache.Hash, out var entries) || entries is null)
        {
            _fileCaches[fileCache.Hash] = entries = [];
        }

        if (!entries.Exists(u => string.Equals(u.PrefixedFilePath, fileCache.PrefixedFilePath, StringComparison.OrdinalIgnoreCase)))
        {
            entries.Add(fileCache);
        }
    }

    private FileCacheEntity? CreateFileCacheEntity(FileInfo fileInfo, string prefixedPath, string? hash = null)
    {
        hash ??= Crypto.GetFileHash(fileInfo.FullName);
        var entity = new FileCacheEntity(hash, prefixedPath, fileInfo.LastWriteTimeUtc.Ticks.ToString(CultureInfo.InvariantCulture), fileInfo.Length);
        entity = ReplacePathPrefixes(entity);
        AddHashedFile(entity);
        lock (_fileWriteLock)
        {
            File.AppendAllLines(_csvPath, new[] { entity.CsvEntry });
        }
        var result = GetFileCacheByPath(fileInfo.FullName);
        _logger.LogDebug("Creating file cache for {name} success: {success}", fileInfo.FullName, (result != null));
        return result;
    }

    private FileCacheEntity? GetValidatedFileCache(FileCacheEntity fileCache)
    {
        var resulingFileCache = ReplacePathPrefixes(fileCache);
        resulingFileCache = Validate(resulingFileCache);
        return resulingFileCache;
    }

    private FileCacheEntity ReplacePathPrefixes(FileCacheEntity fileCache)
    {
        if (fileCache.PrefixedFilePath.StartsWith(PenumbraPrefix, StringComparison.OrdinalIgnoreCase))
        {
            fileCache.SetResolvedFilePath(fileCache.PrefixedFilePath.Replace(PenumbraPrefix, _ipcManager.PenumbraModDirectory, StringComparison.Ordinal));
        }
        else if (fileCache.PrefixedFilePath.StartsWith(CachePrefix, StringComparison.OrdinalIgnoreCase))
        {
            fileCache.SetResolvedFilePath(fileCache.PrefixedFilePath.Replace(CachePrefix, _configService.Current.CacheFolder, StringComparison.Ordinal));
        }

        return fileCache;
    }

    private FileCacheEntity? Validate(FileCacheEntity fileCache)
    {
        var file = new FileInfo(fileCache.ResolvedFilepath);
        if (!file.Exists)
        {
            RemoveHashedFile(fileCache.Hash, fileCache.PrefixedFilePath);
            return null;
        }

        if (!string.Equals(file.LastWriteTimeUtc.Ticks.ToString(CultureInfo.InvariantCulture), fileCache.LastModifiedDateTicks, StringComparison.Ordinal))
        {
            UpdateHashedFile(fileCache);
        }

        return fileCache;
    }
}