using LightlessSync.FileCache;
using Microsoft.Extensions.Logging;
using System.Diagnostics;
using System.IO.Pipes;
using System.Text.Json;

internal sealed class WorkerCompactorContext : ICompactorContext
{
    public WorkerCompactorContext(string cacheFolder, bool isWine)
    {
        CacheFolder = cacheFolder;
        IsWine = isWine;
    }

    public bool UseCompactor => true;
    public string CacheFolder { get; }
    public bool IsWine { get; }
}

internal sealed class WorkerOptions
{
    public string? FilePath { get; init; }
    public bool IsWine { get; init; }
    public string CacheFolder { get; init; } = string.Empty;
    public LogLevel LogLevel { get; init; } = LogLevel.Information;
    public string PipeName { get; init; } = "LightlessCompactor";
    public int? ParentProcessId { get; init; }
}

internal static class Program
{
    public static async Task<int> Main(string[] args)
    {
        var options = ParseOptions(args, out var error);
        if (options is null)
        {
            Console.Error.WriteLine(error ?? "Invalid arguments.");
            Console.Error.WriteLine("Usage: LightlessCompactorWorker --file <path> [--wine] [--cache-folder <path>] [--verbose]");
            Console.Error.WriteLine("   or: LightlessCompactorWorker --pipe <name> [--wine] [--parent <pid>] [--verbose]");
            return 2;
        }

        TrySetLowPriority();

        using var loggerFactory = LoggerFactory.Create(builder =>
        {
            builder.SetMinimumLevel(options.LogLevel);
            builder.AddSimpleConsole(o =>
            {
                o.SingleLine = true;
                o.TimestampFormat = "HH:mm:ss.fff ";
            });
        });

        var logger = loggerFactory.CreateLogger<FileCompactor>();
        var context = new WorkerCompactorContext(options.CacheFolder, options.IsWine);

        using var compactor = new FileCompactor(logger, context, new NoopCompactionExecutor());

        if (!string.IsNullOrWhiteSpace(options.FilePath))
        {
            var success = compactor.TryCompactFile(options.FilePath!);
            return success ? 0 : 1;
        }

        var serverLogger = loggerFactory.CreateLogger("CompactorWorker");
        return await RunServerAsync(compactor, options, serverLogger).ConfigureAwait(false);
    }

    private static async Task<int> RunServerAsync(FileCompactor compactor, WorkerOptions options, ILogger serverLogger)
    {
        using var cts = new CancellationTokenSource();
        var token = cts.Token;

        if (options.ParentProcessId.HasValue)
        {
            _ = Task.Run(() => MonitorParent(options.ParentProcessId.Value, cts));
        }

        serverLogger.LogInformation("Compactor worker listening on pipe {pipe}", options.PipeName);

        try
        {
            while (!token.IsCancellationRequested)
            {
                var server = new NamedPipeServerStream(
                    options.PipeName,
                    PipeDirection.InOut,
                    NamedPipeServerStream.MaxAllowedServerInstances,
                    PipeTransmissionMode.Byte,
                    PipeOptions.Asynchronous);

                try
                {
                    await server.WaitForConnectionAsync(token).ConfigureAwait(false);
                }
                catch
                {
                    server.Dispose();
                    throw;
                }

                _ = Task.Run(() => HandleClientAsync(server, compactor, cts));
            }
        }
        catch (OperationCanceledException)
        {
            // shutdown requested
        }
        catch (Exception ex)
        {
            serverLogger.LogWarning(ex, "Compactor worker terminated unexpectedly.");
            return 1;
        }

        return 0;
    }

    private static async Task HandleClientAsync(NamedPipeServerStream pipe, FileCompactor compactor, CancellationTokenSource shutdownCts)
    {
        await using var _ = pipe;
        using var reader = new StreamReader(pipe);
        using var writer = new StreamWriter(pipe) { AutoFlush = true };

        var line = await reader.ReadLineAsync().ConfigureAwait(false);
        if (string.IsNullOrWhiteSpace(line))
            return;

        CompactorRequest? request = null;
        try
        {
            request = JsonSerializer.Deserialize<CompactorRequest>(line);
        }
        catch
        {
            // ignore
        }

        CompactorResponse response;
        if (request is null)
        {
            response = new CompactorResponse { Success = false, Error = "Invalid request." };
        }
        else if (string.Equals(request.Type, "shutdown", StringComparison.OrdinalIgnoreCase))
        {
            shutdownCts.Cancel();
            response = new CompactorResponse { Success = true };
        }
        else if (string.Equals(request.Type, "compact", StringComparison.OrdinalIgnoreCase))
        {
            var success = compactor.TryCompactFile(request.Path ?? string.Empty);
            response = new CompactorResponse { Success = success };
        }
        else
        {
            response = new CompactorResponse { Success = false, Error = "Unknown request type." };
        }

        await writer.WriteLineAsync(JsonSerializer.Serialize(response)).ConfigureAwait(false);
    }

    private static void MonitorParent(int parentPid, CancellationTokenSource shutdownCts)
    {
        try
        {
            var parent = Process.GetProcessById(parentPid);
            parent.WaitForExit();
        }
        catch
        {
            // parent missing
        }
        finally
        {
            shutdownCts.Cancel();
        }
    }

    private static WorkerOptions? ParseOptions(string[] args, out string? error)
    {
        string? filePath = null;
        bool isWine = false;
        string cacheFolder = string.Empty;
        var logLevel = LogLevel.Information;
        string pipeName = "LightlessCompactor";
        int? parentPid = null;

        for (int i = 0; i < args.Length; i++)
        {
            var arg = args[i];
            switch (arg)
            {
                case "--file":
                    if (i + 1 >= args.Length)
                    {
                        error = "Missing value for --file.";
                        return null;
                    }
                    filePath = args[++i];
                    break;
                case "--cache-folder":
                    if (i + 1 >= args.Length)
                    {
                        error = "Missing value for --cache-folder.";
                        return null;
                    }
                    cacheFolder = args[++i];
                    break;
                case "--pipe":
                    if (i + 1 >= args.Length)
                    {
                        error = "Missing value for --pipe.";
                        return null;
                    }
                    pipeName = args[++i];
                    break;
                case "--parent":
                    if (i + 1 >= args.Length || !int.TryParse(args[++i], out var pid))
                    {
                        error = "Invalid value for --parent.";
                        return null;
                    }
                    parentPid = pid;
                    break;
                case "--wine":
                    isWine = true;
                    break;
                case "--verbose":
                    logLevel = LogLevel.Trace;
                    break;
            }
        }

        error = null;
        return new WorkerOptions
        {
            FilePath = filePath,
            IsWine = isWine,
            CacheFolder = cacheFolder,
            LogLevel = logLevel,
            PipeName = pipeName,
            ParentProcessId = parentPid
        };
    }

    private static void TrySetLowPriority()
    {
        try
        {
            if (OperatingSystem.IsWindows())
                Process.GetCurrentProcess().PriorityClass = ProcessPriorityClass.BelowNormal;
        }
        catch
        {
            // ignore
        }
    }

    private sealed class CompactorRequest
    {
        public string Type { get; init; } = "compact";
        public string? Path { get; init; }
    }

    private sealed class CompactorResponse
    {
        public bool Success { get; init; }
        public string? Error { get; init; }
    }
}