using Lagerbestand.Models;
using Microsoft.Extensions.Logging;
using System.Text.Json;

namespace Lagerbestand.Services;

/// <summary>
/// File storage service for disk/NFS-based file operations
/// </summary>
public class FileStorageService : IFileStorageService
{
    private readonly ISiteSettingsService _siteSettingsService;
    private readonly ILogger<FileStorageService> _logger;
    private const string SettingsKey = "FileStorage";

    public FileStorageService(ISiteSettingsService siteSettingsService, ILogger<FileStorageService> logger)
    {
        _siteSettingsService = siteSettingsService;
        _logger = logger;
    }

    public async Task<FileStorageSettings> GetSettingsAsync()
    {
        try
        {
            var json = await _siteSettingsService.GetValueAsync(SettingsKey);
            if (string.IsNullOrEmpty(json))
            {
                return new FileStorageSettings();
            }

            return JsonSerializer.Deserialize<FileStorageSettings>(json) ?? new FileStorageSettings();
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Error loading file storage settings");
            return new FileStorageSettings();
        }
    }

    public async Task SaveSettingsAsync(FileStorageSettings settings)
    {
        var json = JsonSerializer.Serialize(settings);
        await _siteSettingsService.SetValueAsync(SettingsKey, json);
        _logger.LogInformation("File storage settings saved. Path: {BasePath}, Enabled: {IsEnabled}", 
            settings.BasePath, settings.IsEnabled);
    }

    public Task<(bool IsValid, string? ErrorMessage)> ValidateStoragePathAsync(string path)
    {
        if (string.IsNullOrWhiteSpace(path))
        {
            return Task.FromResult((false, (string?)"Der Pfad darf nicht leer sein."));
        }

        try
        {
            // Check if directory exists or can be created
            if (!Directory.Exists(path))
            {
                try
                {
                    Directory.CreateDirectory(path);
                    _logger.LogInformation("Created storage directory: {Path}", path);
                }
                catch (Exception ex)
                {
                    return Task.FromResult((false, (string?)$"Verzeichnis kann nicht erstellt werden: {ex.Message}"));
                }
            }

            // Test write access
            var testFile = Path.Combine(path, $".write_test_{Guid.NewGuid():N}");
            try
            {
                File.WriteAllText(testFile, "test");
                File.Delete(testFile);
            }
            catch (Exception ex)
            {
                return Task.FromResult((false, (string?)$"Keine Schreibrechte: {ex.Message}"));
            }

            return Task.FromResult((true, (string?)null));
        }
        catch (Exception ex)
        {
            return Task.FromResult((false, (string?)$"Fehler: {ex.Message}"));
        }
    }

    public async Task<string> SaveFileAsync(byte[] content, string fileName, string subDirectory = "attachments")
    {
        var settings = await GetSettingsAsync();
        
        if (!settings.IsEnabled || string.IsNullOrWhiteSpace(settings.BasePath))
        {
            throw new InvalidOperationException("Dateispeicher ist nicht konfiguriert.");
        }

        // Create unique filename to avoid collisions
        var timestamp = DateTime.UtcNow.ToString("yyyyMMdd_HHmmss");
        var uniqueId = Guid.NewGuid().ToString("N")[..8];
        var safeFileName = SanitizeFileName(fileName);
        var extension = Path.GetExtension(safeFileName);
        var nameWithoutExt = Path.GetFileNameWithoutExtension(safeFileName);
        var finalFileName = $"{nameWithoutExt}_{timestamp}_{uniqueId}{extension}";

        // Create subdirectory path with year/month structure
        var datePath = DateTime.UtcNow.ToString("yyyy/MM");
        var relativePath = Path.Combine(subDirectory, datePath, finalFileName);
        var fullPath = Path.Combine(settings.BasePath, relativePath);

        // Ensure directory exists
        var directory = Path.GetDirectoryName(fullPath);
        if (!string.IsNullOrEmpty(directory) && !Directory.Exists(directory))
        {
            Directory.CreateDirectory(directory);
        }

        await File.WriteAllBytesAsync(fullPath, content);
        _logger.LogInformation("File saved: {RelativePath} ({Size} bytes)", relativePath, content.Length);

        return relativePath;
    }

    public async Task<byte[]?> ReadFileAsync(string relativePath)
    {
        var settings = await GetSettingsAsync();
        
        if (!settings.IsEnabled || string.IsNullOrWhiteSpace(settings.BasePath))
        {
            return null;
        }

        var fullPath = ResolveSafePath(settings.BasePath, relativePath);

        if (fullPath == null || !File.Exists(fullPath))
        {
            _logger.LogWarning("File not found: {RelativePath}", relativePath);
            return null;
        }

        return await File.ReadAllBytesAsync(fullPath);
    }

    public async Task<bool> DeleteFileAsync(string relativePath)
    {
        var settings = await GetSettingsAsync();
        
        if (!settings.IsEnabled || string.IsNullOrWhiteSpace(settings.BasePath))
        {
            return false;
        }

        var fullPath = ResolveSafePath(settings.BasePath, relativePath);
        if (fullPath == null)
        {
            return false;
        }

        if (!File.Exists(fullPath))
        {
            return true; // Already deleted
        }

        try
        {
            File.Delete(fullPath);
            _logger.LogInformation("File deleted: {RelativePath}", relativePath);
            return true;
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Error deleting file: {RelativePath}", relativePath);
            return false;
        }
    }

    public async Task<bool> FileExistsAsync(string relativePath)
    {
        var settings = await GetSettingsAsync();
        
        if (!settings.IsEnabled || string.IsNullOrWhiteSpace(settings.BasePath))
        {
            return false;
        }

        var fullPath = ResolveSafePath(settings.BasePath, relativePath);
        return await Task.FromResult(fullPath != null && File.Exists(fullPath));
    }

    public async Task<long> GetFileSizeAsync(string relativePath)
    {
        var settings = await GetSettingsAsync();
        
        if (!settings.IsEnabled || string.IsNullOrWhiteSpace(settings.BasePath))
        {
            return 0;
        }

        var fullPath = ResolveSafePath(settings.BasePath, relativePath);

        if (fullPath == null || !File.Exists(fullPath))
        {
            return 0;
        }

        var fileInfo = new FileInfo(fullPath);
        return await Task.FromResult(fileInfo.Length);
    }

    /// <summary>
    /// Resolves a relative path against the base path and blocks path traversal attempts.
    /// Returns null if the resolved path escapes the base directory.
    /// </summary>
    private string? ResolveSafePath(string basePath, string relativePath)
    {
        try
        {
            var fullBasePath = Path.GetFullPath(basePath);
            var fullPath = Path.GetFullPath(Path.Combine(fullBasePath, relativePath));

            if (!fullPath.StartsWith(fullBasePath.TrimEnd(Path.DirectorySeparatorChar) + Path.DirectorySeparatorChar, StringComparison.OrdinalIgnoreCase))
            {
                _logger.LogWarning("Path traversal attempt blocked: {RelativePath}", relativePath);
                return null;
            }

            return fullPath;
        }
        catch (Exception ex)
        {
            _logger.LogWarning(ex, "Invalid path rejected: {RelativePath}", relativePath);
            return null;
        }
    }

    private static string SanitizeFileName(string fileName)
    {
        var invalidChars = Path.GetInvalidFileNameChars();
        var sanitized = string.Join("_", fileName.Split(invalidChars, StringSplitOptions.RemoveEmptyEntries));
        
        // Limit length
        if (sanitized.Length > 200)
        {
            var ext = Path.GetExtension(sanitized);
            var name = Path.GetFileNameWithoutExtension(sanitized);
            sanitized = name[..(200 - ext.Length)] + ext;
        }

        return sanitized;
    }
}