using System;
using System.Collections.ObjectModel;
using System.Threading.Tasks;
using System.Windows;
using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using HC_APTBS.Services;

namespace HC_APTBS.ViewModels
{
    /// <summary>
    /// ViewModel for the Pump page §3.b DTC list (Diagnostic Trouble Codes).
    ///
    /// <para>Exposes a list of fault-code lines parsed from
    /// <see cref="IKwpService.ReadFaultCodesAsync"/>, with read/clear commands.
    /// Each line is surfaced as a structured <see cref="DtcEntry"/> so the UI
    /// can render them as rows rather than a raw blob.</para>
    /// </summary>
    public sealed partial class DtcListViewModel : ObservableObject
    {
        private readonly IKwpService _kwp;
        private readonly ILocalizationService _loc;
        private readonly IAppLogger _log;
        private const string LogId = "DtcListVM";

        /// <summary>Initialises the ViewModel with the required services.</summary>
        public DtcListViewModel(IKwpService kwp, ILocalizationService loc, IAppLogger log)
        {
            _kwp = kwp;
            _loc = loc;
            _log = log;
        }

        // ── State ─────────────────────────────────────────────────────────────────

        /// <summary>Parsed fault-code entries, one per line returned from K-Line.</summary>
        public ObservableCollection<DtcEntry> Codes { get; } = new();

        /// <summary>True while a read or clear operation is in progress.</summary>
        [ObservableProperty]
        [NotifyCanExecuteChangedFor(nameof(ReadCommand))]
        [NotifyCanExecuteChangedFor(nameof(ClearCommand))]
        private bool _isBusy;

        /// <summary>True when the last read returned no fault codes.</summary>
        [ObservableProperty] private bool _isClear;

        /// <summary>Status text shown above the list (empty, error, or "last read at …").</summary>
        [ObservableProperty] private string _statusText = string.Empty;

        // ── Commands ──────────────────────────────────────────────────────────────

        /// <summary>Reads the current DTCs from the ECU over K-Line.</summary>
        [RelayCommand(CanExecute = nameof(CanOperate))]
        private async Task ReadAsync()
        {
            var port = _kwp.DetectKLinePort();
            if (string.IsNullOrEmpty(port))
            {
                StatusText = _loc.GetString("Error.KLineNotFound");
                return;
            }

            IsBusy = true;
            try
            {
                string raw = await _kwp.ReadFaultCodesAsync(port);
                ApplyRawText(raw);
                StatusText = string.Format(_loc.GetString("Dtc.LastRead"), DateTime.Now);
            }
            catch (Exception ex)
            {
                _log.Error(LogId, $"ReadAsync: {ex.Message}");
                StatusText = ex.Message;
            }
            finally
            {
                IsBusy = false;
            }
        }

        /// <summary>Clears all DTCs on the ECU and refreshes the list.</summary>
        [RelayCommand(CanExecute = nameof(CanOperate))]
        private async Task ClearAsync()
        {
            var port = _kwp.DetectKLinePort();
            if (string.IsNullOrEmpty(port))
            {
                StatusText = _loc.GetString("Error.KLineNotFound");
                return;
            }

            IsBusy = true;
            try
            {
                string raw = await _kwp.ClearFaultCodesAsync(port);
                ApplyRawText(raw);
                StatusText = _loc.GetString("Dtc.Cleared");
            }
            catch (Exception ex)
            {
                _log.Error(LogId, $"ClearAsync: {ex.Message}");
                StatusText = ex.Message;
            }
            finally
            {
                IsBusy = false;
            }
        }

        private bool CanOperate() => !IsBusy;

        // ── Helpers ───────────────────────────────────────────────────────────────

        /// <summary>
        /// Populates <see cref="Codes"/> from the raw K-Line fault-code string.
        /// Handles the special "No fault codes" response by setting <see cref="IsClear"/>.
        /// </summary>
        private void ApplyRawText(string raw)
        {
            Application.Current.Dispatcher.Invoke(() =>
            {
                Codes.Clear();

                if (string.IsNullOrWhiteSpace(raw)
                 || raw.Contains("No fault", StringComparison.OrdinalIgnoreCase))
                {
                    IsClear = true;
                    return;
                }

                IsClear = false;
                foreach (var line in raw.Split('\n', StringSplitOptions.RemoveEmptyEntries))
                {
                    string trimmed = line.Trim();
                    if (trimmed.Length == 0) continue;
                    Codes.Add(DtcEntry.Parse(trimmed));
                }
            });
        }

        /// <summary>Clears any cached DTCs (used when the pump selection changes).</summary>
        public void Reset()
        {
            Application.Current.Dispatcher.Invoke(() =>
            {
                Codes.Clear();
                IsClear    = false;
                StatusText = string.Empty;
            });
        }
    }

    /// <summary>
    /// A single diagnostic trouble code row. Split into <see cref="Code"/> and
    /// <see cref="Description"/> when the raw line follows the usual "CODE — text"
    /// layout, otherwise the raw text is surfaced in <see cref="Description"/>.
    /// </summary>
    public sealed class DtcEntry
    {
        /// <summary>DTC code identifier (e.g. "P1688").</summary>
        public string Code { get; set; } = string.Empty;

        /// <summary>Human-readable description text.</summary>
        public string Description { get; set; } = string.Empty;

        /// <summary>Parses one line of K-Line fault-code output into a structured entry.</summary>
        public static DtcEntry Parse(string line)
        {
            // Common K-Line formats: "P1234 — Description", "P1234: Description",
            // "P1234 Description", or just raw text without a leading code.
            int split = -1;
            foreach (char sep in new[] { '—', '-', ':', '\t' })
            {
                split = line.IndexOf(sep);
                if (split > 0) break;
            }

            if (split <= 0 || split > 10)
                return new DtcEntry { Description = line };

            return new DtcEntry
            {
                Code = line[..split].Trim(),
                Description = line[(split + 1)..].Trim()
            };
        }
    }
}