using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using NLog;
using NcProgramManager.Cnc;
using NcProgramManager.Cnc.Models;

namespace NcProgramManager.Cnc.Mazak
{
    /// <summary>
    /// Mazak CNC machine - EIA/ISO program transfer over FTP.
    /// Targets Mazak Smooth/Matrix controls exposing an FTP server for the
    /// NC program directory. EIA/ISO files are dropped/read by their exact
    /// filename: there is no active-program channel over FTP.
    /// </summary>
    public sealed class MazakMachine : ICncMachine
    {
        private static readonly Logger _log = LogManager.GetCurrentClassLogger();

        private readonly MazakConnectionConfig _config;
        private readonly IMazakFtpClient _ftp;
        private readonly INcProgramValidator _validator;
        private readonly List<CncError> _errors = new List<CncError>();
        private readonly SemaphoreSlim _gate = new SemaphoreSlim(1, 1);
        private ConnectionState _state = ConnectionState.Disconnected;

        public MazakMachine(MazakConnectionConfig config)
        {
            _config = config ?? throw new ArgumentNullException("config");
            _ftp = new MazakFtpClient(config);
            _validator = new NcProgramValidator(CncManufacturer.Mazak);
        }

        internal MazakMachine(MazakConnectionConfig config, IMazakFtpClient ftpClient,
            INcProgramValidator validator = null)
        {
            _config = config ?? throw new ArgumentNullException("config");
            _ftp = ftpClient ?? throw new ArgumentNullException("ftpClient");
            _validator = validator ?? new NcProgramValidator(CncManufacturer.Mazak);
        }

        public string Name { get { return _config.Name; } }
        public ConnectionState State { get { return _state; } }
        public event EventHandler<ConnectionState> StateChanged;

        public Task<CncResult<bool>> ConnectAsync(CancellationToken ct = default(CancellationToken))
        {
            return RunGuardedAsync(() =>
            {
                SetState(ConnectionState.Connecting);
                if (!_ftp.Ping())
                {
                    SetState(ConnectionState.Faulted);
                    _errors.Add(new CncError(0, "Connect",
                        string.Format("FTP server unreachable at {0}:{1}", _config.IpAddress, _config.Port)));
                    return false;
                }
                SetState(ConnectionState.Connected);
                return true;
            }, ct);
        }

        public Task DisconnectAsync()
        {
            return RunGuardedAsync<bool>(() =>
            {
                SetState(ConnectionState.Disconnected);
                return true;
            }, CancellationToken.None);
        }

        public Task<CncResult<string>> ReadProgramAsync(string path, CancellationToken ct = default(CancellationToken))
        {
            return RunGuardedAsync(() =>
            {
                EnsureConnected();
                string ncPath = ResolvePath(path);
                try { return _ftp.DownloadFile(ncPath); }
                catch (Exception ex)
                {
                    _errors.Add(new CncError(0, "ReadProgram", ex.Message));
                    return null;
                }
            }, ct);
        }

        public Task<CncResult<bool>> WriteProgramAsync(string path, CncProgram program, CancellationToken ct = default(CancellationToken))
        {
            return RunGuardedAsync(() =>
            {
                EnsureConnected();
                if (program == null || string.IsNullOrEmpty(program.Content))
                {
                    _errors.Add(new CncError(0, "WriteProgram", "Content is empty"));
                    return false;
                }
                var vr = _validator.Validate(program.Name ?? path, program.Content);
                if (!vr.Success)
                {
                    string msg = string.Join("; ", vr.Errors
                        .Where(e => e.Severity == ValidationSeverity.Error)
                        .Select(e => e.Message));
                    _errors.Add(new CncError(0, "Validator", msg));
                    return false;
                }
                // ISS-020: resolve the write path the same way ReadProgramAsync does.
                // `path` is the EIA/ISO filename verbatim (e.g. "O1234" -> /PRG/O1234)
                // or a full FTP path, NOT a directory to combine with program.Name.
                // Mazak addresses files by their exact filename; program.Name is used
                // for validation only, not for path construction.
                string ncPath = ResolvePath(path);
                try { _ftp.UploadFile(ncPath, program.Content); return true; }
                catch (Exception ex)
                {
                    _errors.Add(new CncError(0, "WriteProgram", ex.Message));
                    return false;
                }
            }, ct);
        }

        public Task<CncResult<bool>> DeleteProgramAsync(string path, CancellationToken ct = default(CancellationToken))
        {
            return RunGuardedAsync(() =>
            {
                EnsureConnected();
                string ncPath = ResolvePath(path);
                try { _ftp.DeleteFile(ncPath); return true; }
                catch (Exception ex)
                {
                    _errors.Add(new CncError(0, "DeleteProgram", ex.Message));
                    return false;
                }
            }, ct);
        }

        /// <summary>
        /// Lista una directory FTP del Mazak (un solo livello). Utile per sondare
        /// la connessione e verificare che <see cref="MazakConnectionConfig.ProgramDirectory"/>
        /// sia vista correttamente e quali file EIA/ISO siano disponibili.
        /// Path vuoto = ProgramDirectory configurata.
        /// </summary>
        public Task<CncResult<IReadOnlyList<FtpEntry>>> ListDirectoryAsync(string path = null, CancellationToken ct = default(CancellationToken))
        {
            return RunGuardedAsync(() =>
            {
                EnsureConnected();
                string dir = string.IsNullOrEmpty(path) ? _config.ProgramDirectory : path;
                try { return _ftp.ListDirectory(dir); }
                catch (Exception ex)
                {
                    _errors.Add(new CncError(0, "ListDirectory", ex.Message));
                    return null;
                }
            }, ct);
        }

        /// <summary>
        /// Costruisce un albero testuale (tree) della directory FTP a partire da
        /// <paramref name="path"/>, scendendo ricorsivamente fino a
        /// <paramref name="maxDepth"/> livelli. Diagnostica: mostra come il server
        /// FTP del Mazak espone la cartella programmi e quali file contiene.
        /// Errori per singola sottocartella sono annotati inline e non interrompono
        /// l'intero albero.
        /// </summary>
        public Task<CncResult<string>> BuildTreeAsync(string path = null, int maxDepth = 2, CancellationToken ct = default(CancellationToken))
        {
            return RunGuardedAsync(() =>
            {
                EnsureConnected();
                string root = string.IsNullOrEmpty(path) ? _config.ProgramDirectory : path;
                var sb = new System.Text.StringBuilder();
                sb.AppendLine(string.IsNullOrEmpty(root) ? "/" : root);
                // Root-level list failure MUST propagate -> RunGuardedAsync -> Fail.
                // A diagnostic probe that can't even list its root must not exit 0.
                var rootEntries = _ftp.ListDirectory(root);
                AppendEntries(sb, rootEntries, "", maxDepth - 1, ct);
                return sb.ToString();
            }, ct);
        }

        /// <summary>
        /// Rende gli entry di una directory e ricorre nelle sottocartelle finche'
        /// <paramref name="depthLeft"/> &gt; 0. Best-effort per i figli: gli errori
        /// di lista delle sottocartelle sono annotati inline e non interrompono
        /// l'intero albero (la root e' gestita a monte e propaga).
        /// </summary>
        private void AppendEntries(System.Text.StringBuilder sb, IReadOnlyList<FtpEntry> entries, string prefix, int depthLeft, CancellationToken ct)
        {
            ct.ThrowIfCancellationRequested();

            for (int i = 0; i < entries.Count; i++)
            {
                var e = entries[i];
                bool last = i == entries.Count - 1;
                string connector = last ? "└─ " : "├─ "; // "└─ " / "├─ "
                sb.AppendLine(string.Format("{0}{1}{2}{3}",
                    prefix, connector, e.Name,
                    e.IsDirectory ? "/" : (e.Size >= 0 ? string.Format("  ({0} B)", e.Size) : "")));

                if (e.IsDirectory && depthLeft > 0)
                {
                    string childPrefix = prefix + (last ? "   " : "│  "); // "│  "
                    IReadOnlyList<FtpEntry> childEntries;
                    try { childEntries = _ftp.ListDirectory(e.FullPath); }
                    catch (Exception ex)
                    {
                        sb.AppendLine(string.Format("{0}!! <errore lista: {1}>", childPrefix, ex.Message));
                        continue;
                    }
                    AppendEntries(sb, childEntries, childPrefix, depthLeft - 1, ct);
                }
            }
        }

        public Task<CncResult<MachineSnapshot>> ReadAsync(CancellationToken ct = default(CancellationToken))
        {
            return RunGuardedAsync(() =>
            {
                EnsureConnected();
                return new MachineSnapshot
                {
                    CapturedAt = DateTime.Now,
                    Mode = MachineMode.Unknown,
                    Run = RunState.Unknown,
                    Motion = MotionState.Unknown,
                    Alarms = new List<string>(),
                    OperatorMessages = new List<string>()
                };
            }, ct);
        }

        public Task<CncResult<string>> ReadActiveProgramAsync(CancellationToken ct = default(CancellationToken))
        {
            return Task.FromResult(CncResult<string>.Fail("ReadActiveProgram", "Not supported via FTP"));
        }

        public Task<CncResult<bool>> SelectMainProgramAsync(string path, CancellationToken ct = default(CancellationToken))
        {
            return Task.FromResult(CncResult<bool>.Fail("SelectMainProgram", "Not supported via FTP"));
        }

        public void Dispose()
        {
            try { DisconnectAsync().GetAwaiter().GetResult(); } catch { /* cleanup - intentionally swallowed */ }
            try { _gate.Dispose(); } catch { /* cleanup - intentionally swallowed */ }
        }

        private async Task<CncResult<T>> RunGuardedAsync<T>(Func<T> body, CancellationToken ct)
        {
            await _gate.WaitAsync(ct).ConfigureAwait(false);
            try
            {
                return await Task.Run(() =>
                {
                    _errors.Clear();
                    try
                    {
                        T value = body();
                        return _errors.Count > 0
                            ? CncResult<T>.Fail(_errors.ToArray())
                            : CncResult<T>.Ok(value);
                    }
                    catch (OperationCanceledException) { return CncResult<T>.Cancelled(); }
                    catch (Exception ex)
                    {
                        _errors.Add(new CncError(0, "MazakMachine", ex.Message));
                        return CncResult<T>.Fail(_errors.ToArray());
                    }
                }, ct).ConfigureAwait(false);
            }
            finally { _gate.Release(); }
        }

        private void EnsureConnected()
        {
            if (_state != ConnectionState.Connected)
                throw new InvalidOperationException("MazakMachine is not connected.");
        }

        private void SetState(ConnectionState next)
        {
            if (_state == next) return;
            _state = next;
            var h = StateChanged;
            if (h != null)
            {
                try { h(this, next); } catch (Exception ex) { _log.Warn(ex, "StateChanged handler threw"); }
            }
        }

        /// <summary>
        /// Build full FTP path. Mazak EIA/ISO files are addressed by their exact
        /// filename verbatim - there is NO extension append (the operator supplies
        /// the filename as it lives on the control). A bare identifier ("O1234") is
        /// combined with <see cref="MazakConnectionConfig.ProgramDirectory"/>; an
        /// explicit path containing '/' is used as-is. Read and write resolve
        /// identically (ISS-020 symmetric path).
        /// </summary>
        private string ResolvePath(string path)
        {
            if (string.IsNullOrEmpty(path)) return _config.ProgramDirectory;
            if (path.Contains("/")) return path;
            string dir = _config.ProgramDirectory ?? "/";
            if (!dir.EndsWith("/")) dir += "/";
            return dir + path;
        }
    }
}