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.Heidenhain
{
    public sealed class HeidenhainMachine : ICncMachine
    {
        private static readonly Logger _log = LogManager.GetCurrentClassLogger();

        private readonly HeidenhainConnectionConfig _config;
        private readonly INcProgramValidator _validator;
        private readonly List<CncError> _errors = new List<CncError>();
        private readonly SemaphoreSlim _gate = new SemaphoreSlim(1, 1);
        private ILsv2Client _client;
        private ConnectionState _state = ConnectionState.Disconnected;

        public HeidenhainMachine(HeidenhainConnectionConfig config)
        {
            if (config == null) throw new ArgumentNullException("config");
            _config = config;
            _validator = new NcProgramValidator(CncManufacturer.Heidenhain);
        }

        internal HeidenhainMachine(HeidenhainConnectionConfig config, ILsv2Client client,
            INcProgramValidator validator = null)
        {
            _config = config ?? throw new ArgumentNullException("config");
            _client = client ?? throw new ArgumentNullException("client");
            _validator = validator ?? new NcProgramValidator(CncManufacturer.Heidenhain);
            _state = ConnectionState.Connected;
        }

        public string Name => _config.Name;
        public ConnectionState State => _state;

        public event EventHandler<ConnectionState> StateChanged;

        public Task<CncResult<bool>> ConnectAsync(CancellationToken ct = default(CancellationToken))
        {
            return RunGuardedAsync(() =>
            {
                SetState(ConnectionState.Connecting);
                _client = new Lsv2Client(_config);
                if (!_client.Connect())
                {
                    SetState(ConnectionState.Faulted);
                    _errors.Add(new CncError(0, "Connect", "LSV2 connection or login failed"));
                    return false;
                }
                SetState(ConnectionState.Connected);
                return true;
            }, ct);
        }

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

        public Task<CncResult<string>> ReadProgramAsync(string path, CancellationToken ct = default(CancellationToken))
        {
            return RunGuardedAsync(() =>
            {
                EnsureConnected();
                string content = _client.ReceiveFile(path);
                if (content == null)
                    _errors.Add(new CncError(0, "ReadProgram", "ReceiveFile returned null for: " + path));
                return content;
            }, 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", "Program 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;
                }
                string ncPath = BuildNcPath(path, program.Name);
                bool ok = _client.SendFile(ncPath, program.Content);
                if (!ok) _errors.Add(new CncError(0, "WriteProgram", "SendFile failed for: " + ncPath));
                return ok;
            }, 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)) =>
            Task.FromResult(CncResult<string>.Fail("ReadActiveProgram", "Not supported via basic LSV2"));

        public Task<CncResult<bool>> SelectMainProgramAsync(string path, CancellationToken ct = default(CancellationToken)) =>
            Task.FromResult(CncResult<bool>.Fail("SelectMainProgram", "Not supported via basic LSV2"));

        public Task<CncResult<bool>> DeleteProgramAsync(string path, CancellationToken ct = default(CancellationToken)) =>
            Task.FromResult(CncResult<bool>.Fail("DeleteProgram", "Not supported via basic LSV2"));

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

        // ── private ──────────────────────────────────────────────────────────

        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, "HeidenhainMachine", ex.Message));
                        return CncResult<T>.Fail(_errors.ToArray());
                    }
                }, ct).ConfigureAwait(false);
            }
            finally
            {
                _gate.Release();
            }
        }

        private void EnsureConnected()
        {
            if (_state != ConnectionState.Connected || _client == null)
                throw new InvalidOperationException("HeidenhainMachine 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"); }
            }
        }

        private static string BuildNcPath(string folder, string name)
        {
            if (string.IsNullOrEmpty(name)) return folder;
            string sep = (folder.EndsWith("\\") || folder.EndsWith("/")) ? "" : "\\";
            string ext = name.Contains(".") ? "" : ".H";
            return folder + sep + name + ext;
        }
    }
}