using System.IO;
using System.Text.Json;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Logging.Abstractions;
using NeoSmart.SecureStore;

namespace JdeScoping.SecureStoreManager.Services;

/// <summary>
/// Manages SecureStore encrypted secret stores for the Avalonia application.
/// </summary>
public class SecureStoreManager : ISecureStoreManager, IDisposable
{
    private readonly ILogger<SecureStoreManager> _logger;
    private SecretsManager? _secretsManager;
    private string? _currentStorePath;
    private readonly HashSet<string> _keys = new();
    private bool _hasUnsavedChanges;
    private bool _disposed;

    private const string KeysMetadataKey = "__keys__";

    private static readonly HashSet<string> ReservedKeys = new(StringComparer.OrdinalIgnoreCase)
    {
        KeysMetadataKey
    };

    /// <summary>
    /// Creates a new SecureStoreManager with no logging.
    /// </summary>
    public SecureStoreManager() : this(NullLogger<SecureStoreManager>.Instance)
    {
    }

    /// <summary>
    /// Creates a new SecureStoreManager with the specified logger.
    /// </summary>
    /// <param name="logger">Logger instance for diagnostic output.</param>
    public SecureStoreManager(ILogger<SecureStoreManager> logger)
    {
        _logger = logger ?? NullLogger<SecureStoreManager>.Instance;
    }

    /// <inheritdoc />
    public bool IsStoreOpen => _secretsManager != null;

    /// <inheritdoc />
    public string? CurrentStorePath => _currentStorePath;

    /// <inheritdoc />
    public bool HasUnsavedChanges => _hasUnsavedChanges;

    /// <inheritdoc />
    public void CreateStore(string storePath, string keyFilePath)
    {
        ThrowIfDisposed();
        _logger.LogInformation("Creating new store at {StorePath}", storePath);
        CloseStoreInternal();

        EnsureDirectory(storePath);
        EnsureDirectory(keyFilePath);

        _secretsManager = SecretsManager.CreateStore();
        _secretsManager.GenerateKey();
        _secretsManager.ExportKey(keyFilePath);

        _currentStorePath = storePath;
        _keys.Clear();
        _hasUnsavedChanges = true;

        Save();
        _logger.LogInformation("Store created with key file: {KeyFilePath}", keyFilePath);
    }

    /// <inheritdoc />
    public void OpenStore(string storePath, string keyFilePath)
    {
        ThrowIfDisposed();
        _logger.LogInformation("Opening store at {StorePath}", storePath);
        CloseStoreInternal();

        if (!File.Exists(storePath))
            throw new FileNotFoundException("Store file not found.", storePath);

        if (!File.Exists(keyFilePath))
            throw new FileNotFoundException("Key file not found.", keyFilePath);

        _secretsManager = SecretsManager.LoadStore(storePath);
        _secretsManager.LoadKeyFromFile(keyFilePath);

        _currentStorePath = storePath;
        LoadKeysMetadata();
        _hasUnsavedChanges = false;
        _logger.LogDebug("Store opened with key file, contains {KeyCount} keys", _keys.Count);
    }

    /// <inheritdoc />
    public void CloseStore()
    {
        ThrowIfDisposed();
        _logger.LogInformation("Closing store");
        CloseStoreInternal();
    }

    /// <inheritdoc />
    public void Save()
    {
        ThrowIfDisposed();

        if (_secretsManager == null || _currentStorePath == null)
            throw new InvalidOperationException("No store is currently open.");

        _logger.LogInformation("Saving store changes");
        SaveKeysMetadata();
        _secretsManager.SaveStore(_currentStorePath);
        _hasUnsavedChanges = false;
    }

    /// <inheritdoc />
    public IReadOnlyList<string> GetKeys()
    {
        ThrowIfDisposed();

        if (_secretsManager == null)
            throw new InvalidOperationException("No store is currently open.");

        return _keys.Where(k => k != KeysMetadataKey).ToList().AsReadOnly();
    }

    /// <inheritdoc />
    public string GetSecret(string key)
    {
        ThrowIfDisposed();

        if (_secretsManager == null)
            throw new InvalidOperationException("No store is currently open.");

        if (string.IsNullOrEmpty(key))
            throw new ArgumentException("Key cannot be empty.", nameof(key));

        if (!_keys.Contains(key))
            throw new KeyNotFoundException($"Secret '{key}' not found.");

        return _secretsManager.Get(key);
    }

    /// <inheritdoc />
    public void SetSecret(string key, string value)
    {
        ThrowIfDisposed();

        if (_secretsManager == null)
            throw new InvalidOperationException("No store is currently open.");

        if (string.IsNullOrWhiteSpace(key))
            throw new ArgumentException("Key cannot be null or whitespace.", nameof(key));

        if (ReservedKeys.Contains(key))
        {
            _logger.LogWarning("Attempted to access reserved key {Key}", key);
            throw new ArgumentException($"The key '{key}' is reserved for internal use.", nameof(key));
        }

        _logger.LogDebug("Setting secret for key {Key}", key);
        _secretsManager.Set(key, value ?? string.Empty);
        _keys.Add(key);
        _hasUnsavedChanges = true;
    }

    /// <inheritdoc />
    public void RemoveSecret(string key)
    {
        ThrowIfDisposed();

        if (_secretsManager == null)
            throw new InvalidOperationException("No store is currently open.");

        if (string.IsNullOrWhiteSpace(key))
            throw new ArgumentException("Key cannot be null or whitespace.", nameof(key));

        if (ReservedKeys.Contains(key))
        {
            _logger.LogWarning("Attempted to access reserved key {Key}", key);
            throw new ArgumentException($"The key '{key}' is reserved for internal use.", nameof(key));
        }

        if (!_keys.Remove(key))
            throw new KeyNotFoundException($"Secret '{key}' not found.");

        _logger.LogInformation("Removing secret for key {Key}", key);
        _secretsManager.Delete(key);
        _hasUnsavedChanges = true;
    }

    /// <inheritdoc />
    public void GenerateKeyFile(string path)
    {
        ThrowIfDisposed();

        if (string.IsNullOrEmpty(path))
            throw new ArgumentException("Path cannot be empty.", nameof(path));

        EnsureDirectory(path);

        using var tempManager = SecretsManager.CreateStore();
        tempManager.GenerateKey();
        tempManager.ExportKey(path);
    }

    /// <inheritdoc />
    public void ExportKey(string path)
    {
        ThrowIfDisposed();

        if (_secretsManager == null)
            throw new InvalidOperationException("No store is currently open.");

        if (string.IsNullOrEmpty(path))
            throw new ArgumentException("Path cannot be empty.", nameof(path));

        EnsureDirectory(path);
        _secretsManager.ExportKey(path);
    }

    private void LoadKeysMetadata()
    {
        _keys.Clear();

        try
        {
            var keysJson = _secretsManager!.Get(KeysMetadataKey);
            if (!string.IsNullOrEmpty(keysJson))
            {
                var keys = JsonSerializer.Deserialize<string[]>(keysJson);
                if (keys != null)
                {
                    foreach (var key in keys)
                        _keys.Add(key);
                }
            }
        }
        catch (KeyNotFoundException)
        {
            // No keys metadata yet
        }
    }

    private void SaveKeysMetadata()
    {
        var keys = _keys.Where(k => k != KeysMetadataKey).ToArray();
        var keysJson = JsonSerializer.Serialize(keys);
        _secretsManager!.Set(KeysMetadataKey, keysJson);
        _keys.Add(KeysMetadataKey);
    }

    private void CloseStoreInternal()
    {
        _secretsManager?.Dispose();
        _secretsManager = null;
        _currentStorePath = null;
        _keys.Clear();
        _hasUnsavedChanges = false;
    }

    private static void EnsureDirectory(string filePath)
    {
        var directory = Path.GetDirectoryName(filePath);
        if (!string.IsNullOrEmpty(directory) && !Directory.Exists(directory))
        {
            Directory.CreateDirectory(directory);
        }
    }

    private void ThrowIfDisposed()
    {
        ObjectDisposedException.ThrowIf(_disposed, this);
    }

    /// <summary>
    /// Releases the resources used by the <see cref="SecureStoreManager"/>.
    /// </summary>
    public void Dispose()
    {
        if (_disposed) return;

        _secretsManager?.Dispose();
        _secretsManager = null;
        _disposed = true;
        GC.SuppressFinalize(this);
    }
}