using System.Collections.Concurrent;
using System.Diagnostics;
using System.Security.Cryptography;
using System.Text;
using System.Text.RegularExpressions;
using Cleanuparr.Domain.Enums;
using Cleanuparr.Infrastructure.Helpers;
using Cleanuparr.Persistence;
using Cleanuparr.Persistence.Models.Configuration.MalwareBlocker;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Caching.Memory;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;

namespace Cleanuparr.Infrastructure.Features.MalwareBlocker;

public sealed class BlocklistProvider : IBlocklistProvider
{
    private readonly ILogger<BlocklistProvider> _logger;
    private readonly IServiceScopeFactory _scopeFactory;
    private readonly IMemoryCache _cache;
    private readonly Dictionary<InstanceType, string> _configHashes = new();
    private readonly Dictionary<string, DateTime> _lastLoadTimes = new();
    private const int DefaultLoadIntervalHours = 4;
    private const int FastLoadIntervalMinutes = 5;
    private const string MalwareListUrl = "https://cleanuparr.pages.dev/static/known_malware_file_name_patterns";
    private const string MalwareListKey = "MALWARE_PATTERNS";

    public BlocklistProvider(
        ILogger<BlocklistProvider> logger,
        IServiceScopeFactory scopeFactory,
        IMemoryCache cache
    )
    {
        _logger = logger;
        _scopeFactory = scopeFactory;
        _cache = cache;
    }

    public async Task LoadBlocklistsAsync()
    {
        try
        {
            await using var scope = _scopeFactory.CreateAsyncScope();
            await using var dataContext = scope.ServiceProvider.GetRequiredService<DataContext>();
            var fileReader = scope.ServiceProvider.GetRequiredService<FileReader>();
            
            int changedCount = 0;
            var malwareBlockerConfig = await dataContext.ContentBlockerConfigs
                .AsNoTracking()
                .FirstAsync();
            
            if (!malwareBlockerConfig.Enabled)
            {
                _logger.LogDebug("Malware Blocker is disabled, skipping blocklist loading");
                return;
            }
            
            var instances = new Dictionary<InstanceType, BlocklistSettings>
            {
                { InstanceType.Sonarr, malwareBlockerConfig.Sonarr },
                { InstanceType.Radarr, malwareBlockerConfig.Radarr },
                { InstanceType.Lidarr, malwareBlockerConfig.Lidarr },
                { InstanceType.Readarr, malwareBlockerConfig.Readarr },
                { InstanceType.Whisparr, malwareBlockerConfig.Whisparr }
            };

            foreach (var kv in instances)
            {
                if (await EnsureInstanceLoadedAsync(kv.Value, kv.Key, fileReader))
                {
                    changedCount++;
                }
            }
            
            // Always check and update malware patterns
            await LoadMalwarePatternsAsync(fileReader);
            
            if (changedCount > 0)
            {
                _logger.LogInformation("Successfully loaded {count} blocklists", changedCount);
            }
            else
            {
                _logger.LogTrace("All blocklists are already up to date");
            }
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Failed to load blocklists");
            throw;
        }
    }

    public BlocklistType GetBlocklistType(InstanceType instanceType)
    {
        _cache.TryGetValue(CacheKeys.BlocklistType(instanceType), out BlocklistType? blocklistType);

        return blocklistType ?? BlocklistType.Blacklist;
    }
    
    public ConcurrentBag<string> GetPatterns(InstanceType instanceType)
    {
        _cache.TryGetValue(CacheKeys.BlocklistPatterns(instanceType), out ConcurrentBag<string>? patterns);

        return patterns ?? [];
    }

    public ConcurrentBag<Regex> GetRegexes(InstanceType instanceType)
    {
        _cache.TryGetValue(CacheKeys.BlocklistRegexes(instanceType), out ConcurrentBag<Regex>? regexes);
        
        return regexes ?? [];
    }
    
    public ConcurrentBag<string> GetMalwarePatterns()
    {
        _cache.TryGetValue(CacheKeys.KnownMalwarePatterns(), out ConcurrentBag<string>? patterns);
        
        return patterns ?? [];
    }
    
    private async Task<bool> EnsureInstanceLoadedAsync(BlocklistSettings settings, InstanceType instanceType, FileReader fileReader)
    {
        if (!settings.Enabled || string.IsNullOrEmpty(settings.BlocklistPath))
        {
            return false;
        }

        string hash = GenerateSettingsHash(settings);
        var interval = GetLoadInterval(settings.BlocklistPath);
        var identifier = $"{instanceType}_{settings.BlocklistPath}";

        if (ShouldReloadBlocklist(identifier, interval) || !_configHashes.TryGetValue(instanceType, out string? oldHash) || hash != oldHash)
        {
            _logger.LogDebug("Loading {instance} blocklist", instanceType);
            await LoadPatternsAndRegexesAsync(settings, instanceType, fileReader);
            _configHashes[instanceType] = hash;
            _lastLoadTimes[identifier] = DateTime.UtcNow;
            return true;
        }

        return false;
    }
    
    private TimeSpan GetLoadInterval(string? path)
    {
        if (!string.IsNullOrEmpty(path) && Uri.TryCreate(path, UriKind.Absolute, out var uri))
        {
            if (uri.Host.Equals("cleanuparr.pages.dev", StringComparison.OrdinalIgnoreCase))
            {
                return TimeSpan.FromMinutes(FastLoadIntervalMinutes);
            }

            return TimeSpan.FromHours(DefaultLoadIntervalHours);
        }
        
        // If fast load interval for local files
        return TimeSpan.FromMinutes(FastLoadIntervalMinutes);
    }
    
    private bool ShouldReloadBlocklist(string identifier, TimeSpan interval)
    {
        if (!_lastLoadTimes.TryGetValue(identifier, out DateTime lastLoad))
        {
            return true;
        }
        
        return DateTime.UtcNow - lastLoad >= interval;
    }
    
    private async Task LoadMalwarePatternsAsync(FileReader fileReader)
    {
        var malwareInterval = TimeSpan.FromMinutes(FastLoadIntervalMinutes);
        
        if (!ShouldReloadBlocklist(MalwareListKey, malwareInterval))
        {
            return;
        }
        
        try
        {
            _logger.LogDebug("Loading malware patterns");
            
            string[] filePatterns = await fileReader.ReadContentAsync(MalwareListUrl);
            
            long startTime = Stopwatch.GetTimestamp();
            ParallelOptions options = new() { MaxDegreeOfParallelism = 5 };
            ConcurrentBag<string> patterns = [];
            
            Parallel.ForEach(filePatterns, options, pattern =>
            {
                patterns.Add(pattern);
            });

            TimeSpan elapsed = Stopwatch.GetElapsedTime(startTime);

            _cache.Set(CacheKeys.KnownMalwarePatterns(), patterns);
            _lastLoadTimes[MalwareListKey] = DateTime.UtcNow;
            
            _logger.LogDebug("loaded {count} known malware patterns", patterns.Count);
            _logger.LogDebug("malware patterns loaded in {elapsed} ms", elapsed.TotalMilliseconds);
        }
        catch (Exception ex)
        {
            _logger.LogWarning(ex, "Failed to load malware patterns from {url}", MalwareListUrl);
        }
    }

    private async Task LoadPatternsAndRegexesAsync(BlocklistSettings blocklistSettings, InstanceType instanceType, FileReader fileReader)
    {
        if (string.IsNullOrEmpty(blocklistSettings.BlocklistPath))
        {
            return;
        }
        
        string[] filePatterns = await fileReader.ReadContentAsync(blocklistSettings.BlocklistPath);
        
        long startTime = Stopwatch.GetTimestamp();
        ParallelOptions options = new() { MaxDegreeOfParallelism = 5 };
        const string regexId = "regex:";
        ConcurrentBag<string> patterns = [];
        ConcurrentBag<Regex> regexes = [];
        
        Parallel.ForEach(filePatterns, options, pattern =>
        {
            if (!pattern.StartsWith(regexId))
            {
                patterns.Add(pattern);
                return;
            }
            
            pattern = pattern[regexId.Length..];
            
            try
            {
                Regex regex = new(pattern, RegexOptions.Compiled);
                regexes.Add(regex);
            }
            catch (ArgumentException)
            {
                _logger.LogWarning("invalid regex | {pattern}", pattern);
            }
        });

        TimeSpan elapsed = Stopwatch.GetElapsedTime(startTime);

        _cache.Set(CacheKeys.BlocklistType(instanceType), blocklistSettings.BlocklistType);
        _cache.Set(CacheKeys.BlocklistPatterns(instanceType), patterns);
        _cache.Set(CacheKeys.BlocklistRegexes(instanceType), regexes);
        
        _logger.LogDebug("loaded {count} patterns", patterns.Count);
        _logger.LogDebug("loaded {count} regexes", regexes.Count);
        _logger.LogDebug("blocklist loaded in {elapsed} ms | {path}", elapsed.TotalMilliseconds, blocklistSettings.BlocklistPath);
    }
    
    private string GenerateSettingsHash(BlocklistSettings blocklistSettings)
    {
        // Create a string that represents the relevant blocklist configuration
        var configStr = $"{blocklistSettings.Enabled}|{blocklistSettings.BlocklistPath ?? string.Empty}|{blocklistSettings.BlocklistType}";
        
        // Create SHA256 hash of the configuration string
        using var sha = SHA256.Create();
        var bytes = Encoding.UTF8.GetBytes(configStr);
        var hashBytes = sha.ComputeHash(bytes);
        
        return Convert.ToHexString(hashBytes).ToLowerInvariant();
    }
}