using Microsoft.Extensions.Logging;

namespace JdeScoping.ConfigManager.Services;

/// <summary>
/// Service for auto-discovering configuration file locations.
/// Searches in prioritized order:
/// 1. JDESCOPING_CONFIG_PATH environment variable
/// 2. Same directory as executable
/// 3. ../JdeScoping.Host/ relative to executable
/// 4. User config directory (~/.jdescoping on Unix, %LOCALAPPDATA%\JdeScoping on Windows)
/// </summary>
public class AutoDiscoveryService : IAutoDiscoveryService
{
    private readonly IFileSystem _fileSystem;
    private readonly ILogger<AutoDiscoveryService>? _logger;
    private const string EnvVarName = "JDESCOPING_CONFIG_PATH";
    private const string AppSettingsFileName = "appsettings.json";

    /// <summary>
    /// Initializes a new instance of the <see cref="AutoDiscoveryService"/> class.
    /// </summary>
    /// <param name="fileSystem">The file system abstraction to use for directory and file checks.</param>
    /// <param name="logger">Optional logger for recording discovery process information.</param>
    public AutoDiscoveryService(IFileSystem fileSystem, ILogger<AutoDiscoveryService>? logger = null)
    {
        _fileSystem = fileSystem;
        _logger = logger;
    }

    /// <summary>
    /// Finds the configuration folder using a prioritized search strategy.
    /// </summary>
    /// <param name="ct">Cancellation token for the async operation.</param>
    /// <returns>The path to a valid configuration folder, or null if none is found.</returns>
    public Task<string?> FindConfigFolderAsync(CancellationToken ct = default)
    {
        // 1. Check environment variable
        var envPath = Environment.GetEnvironmentVariable(EnvVarName);
        if (!string.IsNullOrEmpty(envPath) && IsValidConfigFolder(envPath))
        {
            _logger?.LogInformation("Found config folder from environment variable: {Path}", envPath);
            return Task.FromResult<string?>(envPath);
        }

        // 2. Check same directory as executable
        var exeDir = AppContext.BaseDirectory;
        if (IsValidConfigFolder(exeDir))
        {
            _logger?.LogInformation("Found config folder in executable directory: {Path}", exeDir);
            return Task.FromResult<string?>(exeDir);
        }

        // 3. Check ../JdeScoping.Host/ relative to executable
        var hostDir = _fileSystem.Combine(exeDir, "..", "JdeScoping.Host");
        if (IsValidConfigFolder(hostDir))
        {
            _logger?.LogInformation("Found config folder in host directory: {Path}", hostDir);
            return Task.FromResult<string?>(hostDir);
        }

        // 4. Check project structure paths (for development)
        // When running from bin/Debug/net10.0, go up to find src/JdeScoping.Host
        var projectHostPaths = new[]
        {
            // From bin/Debug/net10.0 -> src/JdeScoping.Host
            _fileSystem.Combine(exeDir, "..", "..", "..", "..", "..", "JdeScoping.Host"),
            // Absolute fallback for development
            "/Users/dohertj2/Desktop/JdeScopingTool/NEW/src/JdeScoping.Host"
        };

        foreach (var projectPath in projectHostPaths)
        {
            if (IsValidConfigFolder(projectPath))
            {
                _logger?.LogInformation("Found config folder in project directory: {Path}", projectPath);
                return Task.FromResult<string?>(Path.GetFullPath(projectPath));
            }
        }

        // 5. Check user config directory
        var userConfigDir = GetUserConfigDirectory();
        if (userConfigDir != null && IsValidConfigFolder(userConfigDir))
        {
            _logger?.LogInformation("Found config folder in user directory: {Path}", userConfigDir);
            return Task.FromResult<string?>(userConfigDir);
        }

        _logger?.LogWarning("Could not find config folder in any standard location");
        return Task.FromResult<string?>(null);
    }

    private bool IsValidConfigFolder(string path)
    {
        if (!_fileSystem.DirectoryExists(path))
            return false;

        var appSettingsPath = _fileSystem.Combine(path, AppSettingsFileName);
        return _fileSystem.FileExists(appSettingsPath);
    }

    private string? GetUserConfigDirectory()
    {
        if (OperatingSystem.IsWindows())
        {
            var localAppData = Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData);
            return _fileSystem.Combine(localAppData, "JdeScoping");
        }
        else
        {
            var home = Environment.GetFolderPath(Environment.SpecialFolder.UserProfile);
            return _fileSystem.Combine(home, ".jdescoping");
        }
    }
}