using System.IO;

namespace SpdUp.Core;

/// <summary>
/// Application-wide logging service with live event for UI consumption.
/// </summary>
public static class Logger
{
    private static readonly object _lock = new();
    private static readonly string _logDir = Path.Combine(
        Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData), "SpdUp", "Logs");

    /// <summary>Fired on every log write – subscribers receive the formatted line.</summary>
    public static event Action<string>? LogWritten;

    static Logger()
    {
        Directory.CreateDirectory(_logDir);
    }

    private static string LogFile => Path.Combine(_logDir, $"SpdUp_{DateTime.Now:yyyy-MM-dd}.log");

    public static void Info(string message) => Write("INFO", message);
    public static void Warn(string message) => Write("WARN", message);
    public static void Error(string message, Exception? ex = null)
    {
        var msg = ex is null ? message : $"{message} | {ex.GetType().Name}: {ex.Message}\n{ex.StackTrace}";
        Write("ERROR", msg);
    }

    private static void Write(string level, string message)
    {
        var line = $"[{DateTime.Now:yyyy-MM-dd HH:mm:ss.fff}] [{level}] {message}";
        lock (_lock)
        {
            try
            {
                File.AppendAllText(LogFile, line + Environment.NewLine);
            }
            catch
            {
                // Swallow – logging must never crash the app.
            }
        }

        // Notify UI subscribers
        try { LogWritten?.Invoke(line); } catch { }

#if DEBUG
        System.Diagnostics.Debug.WriteLine(line);
#endif
    }

    /// <summary>
    /// Removes log files older than the specified number of days.
    /// </summary>
    public static void PurgeOldLogs(int keepDays = 14)
    {
        try
        {
            var cutoff = DateTime.Now.AddDays(-keepDays);
            foreach (var file in Directory.GetFiles(_logDir, "SpdUp_*.log"))
            {
                if (File.GetCreationTime(file) < cutoff)
                    File.Delete(file);
            }
        }
        catch { /* best-effort */ }
    }
}