using System.Collections.ObjectModel;
using System.IO;
using System.Text;
using System.Windows;
using System.Windows.Threading;
using EmbyToolbox.ViewModels;

namespace EmbyToolbox.Services;

public sealed class LoggingService
{
    private const int UiLogLimit = 1000;
    private readonly string _logsDirectory;

    public LoggingService()
    {
        _logsDirectory = Path.Combine(
            Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData),
            "EmbyToolbox",
            "Logs");
        Directory.CreateDirectory(_logsDirectory);
    }

    public ObservableCollection<LogEntryViewModel> UiEntries { get; } = new();

    public LogLevel MinimumFileLogLevel { get; set; } = LogLevel.Info;

    public string LogsDirectory => _logsDirectory;

    public void Debug(string message, string module = "app", Exception? exception = null, string? command = null, string? stdout = null, string? stderr = null)
    {
        Write(LogLevel.Debug, message, module, exception, command, stdout, stderr);
    }

    public void Info(string message, string module = "app", Exception? exception = null, string? command = null, string? stdout = null, string? stderr = null)
    {
        Write(LogLevel.Info, message, module, exception, command, stdout, stderr);
    }

    public void Warning(string message, string module = "app", Exception? exception = null, string? command = null, string? stdout = null, string? stderr = null)
    {
        Write(LogLevel.Warning, message, module, exception, command, stdout, stderr);
    }

    public void Error(string message, string module = "app", Exception? exception = null, string? command = null, string? stdout = null, string? stderr = null)
    {
        Write(LogLevel.Error, message, module, exception, command, stdout, stderr);
    }

    public void ClearUi()
    {
        UiEntries.Clear();
    }

    private void Write(LogLevel level, string message, string module, Exception? exception, string? command, string? stdout, string? stderr)
    {
        var now = DateTime.Now;
        var entry = new LogEntryViewModel
        {
            Timestamp = now,
            Level = level,
            LevelText = level.ToString(),
            Module = module,
            Message = message
        };

        AddUiEntryThreadSafe(entry);

        if (level < MinimumFileLogLevel)
        {
            return;
        }

        WriteToFile(now, level, module, message, exception, command, stdout, stderr);
    }

    private void AddUiEntryThreadSafe(LogEntryViewModel entry)
    {
        var dispatcher = Application.Current?.Dispatcher;
        if (dispatcher is null || dispatcher.CheckAccess())
        {
            UiEntries.Add(entry);
            while (UiEntries.Count > UiLogLimit)
            {
                UiEntries.RemoveAt(0);
            }

            return;
        }

        dispatcher.BeginInvoke(
            DispatcherPriority.DataBind,
            new Action(
                () =>
                {
                    UiEntries.Add(entry);
                    while (UiEntries.Count > UiLogLimit)
                    {
                        UiEntries.RemoveAt(0);
                    }
                }));
    }

    private void WriteToFile(DateTime timestamp, LogLevel level, string module, string message, Exception? exception, string? command, string? stdout, string? stderr)
    {
        var path = Path.Combine(_logsDirectory, $"app-{timestamp:yyyy-MM-dd}.log");
        var sb = new StringBuilder();

        sb.Append('[').Append(timestamp.ToString("yyyy-MM-dd HH:mm:ss")).Append("] ");
        sb.Append(level.ToString().ToUpperInvariant()).Append(" ");
        sb.Append("module=").Append(module).Append(" ");
        sb.Append("message=").Append(message);
        sb.AppendLine();

        if (exception is not null)
        {
            sb.AppendLine("exception:");
            sb.AppendLine(exception.ToString());
        }

        if (!string.IsNullOrWhiteSpace(command))
        {
            sb.Append("command: ").AppendLine(command);
        }

        if (!string.IsNullOrWhiteSpace(stdout))
        {
            sb.AppendLine("stdout:");
            sb.AppendLine(stdout);
        }

        if (!string.IsNullOrWhiteSpace(stderr))
        {
            sb.AppendLine("stderr:");
            sb.AppendLine(stderr);
        }

        sb.AppendLine(new string('-', 80));
        File.AppendAllText(path, sb.ToString(), Encoding.UTF8);
    }
}