using System.IO;
using System.Text;

namespace UtopiaCanteenSystem.Services.Logging;

/// <summary>
/// Thread-safe daily file logger. Never throws to callers.
/// </summary>
public static class FileLogger
{
    private static readonly object Lock = new();
    private static FileLogTarget? _target;

    public static bool IsConfigured => _target.HasValue;

    public static void ConfigureBackend() => Configure(FileLogTarget.Backend);

    public static void ConfigureClient() => Configure(FileLogTarget.Client);

    public static void Configure(FileLogTarget target)
    {
        _target = target;
        var dir = GetLogsDirectory();
        try
        {
            Directory.CreateDirectory(dir);
        }
        catch
        {
            // Ignore
        }

        Info("FileLogger", $"Logging initialized. Directory={dir}");
    }

    public static string GetLogsDirectory() =>
        _target == FileLogTarget.Client
            ? LogPaths.ClientLogsDirectory
            : LogPaths.BackendLogsDirectory;

    public static void Debug(string component, string message) => Write("DEBUG", component, message, null);

    public static void Info(string component, string message) => Write("INFO", component, message, null);

    public static void Warn(string component, string message, Exception? ex = null) =>
        Write("WARN", component, message, ex);

    public static void Error(string component, string message, Exception? ex = null) =>
        Write("ERROR", component, message, ex);

    private static void Write(string level, string component, string message, Exception? ex)
    {
        if (!_target.HasValue)
            return;

        try
        {
            var dir = GetLogsDirectory();
            var prefix = _target == FileLogTarget.Client ? "client" : "backend";
            var file = Path.Combine(dir, $"{prefix}-{DateTime.Now:yyyy-MM-dd}.log");
            var line = FormatLine(level, component, message, ex);

            lock (Lock)
            {
                Directory.CreateDirectory(dir);
                File.AppendAllText(file, line, Encoding.UTF8);
            }
        }
        catch
        {
            // Never crash the app because logging failed.
        }
    }

    private static string FormatLine(string level, string component, string message, Exception? ex)
    {
        var sb = new StringBuilder();
        sb.Append($"{DateTime.Now:yyyy-MM-dd HH:mm:ss.fff} [{level}] [{component}] {message}");
        if (ex != null)
        {
            sb.AppendLine();
            sb.Append($"Exception: {ex.GetType().Name}: {ex.Message}");
            if (!string.IsNullOrWhiteSpace(ex.StackTrace))
            {
                sb.AppendLine();
                sb.Append(ex.StackTrace);
            }

            if (ex.InnerException != null)
            {
                sb.AppendLine();
                sb.Append($"InnerException: {ex.InnerException.GetType().Name}: {ex.InnerException.Message}");
            }
        }

        sb.AppendLine();
        return sb.ToString();
    }
}