using System;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using HC_APTBS.Models;
using HC_APTBS.Services;

namespace HC_APTBS.ViewModels.Pages
{
    /// <summary>
    /// ViewModel for the Developer Tools navigation page — exposes a raw KWP/K-Line
    /// custom-command console for hardware development and debugging.
    ///
    /// <para>
    /// Compiled into <b>Debug builds only</b>. The project's
    /// <c>DEVELOPER_TOOLS</c> compile-time symbol gates every reference to this
    /// type, and the page files are <c>Compile Remove</c>'d from Release builds
    /// in <c>HC_APTBS.csproj</c>, so this page does not appear at all in
    /// consumer builds.
    /// </para>
    /// </summary>
    public sealed partial class DeveloperPageViewModel : ObservableObject
    {
        private const string LogId = nameof(DeveloperPageViewModel);

        private readonly IKwpService _kwp;
        private readonly IAppLogger _log;

        /// <summary>Root coordinator — exposes K-Line state for status binding.</summary>
        public MainViewModel Root { get; }

        // ── Input / output state ──────────────────────────────────────────────────

        /// <summary>
        /// Hex bytes typed by the developer. Whitespace, commas and dashes are
        /// accepted as separators; e.g. <c>"18 00 03 FF FF"</c> or <c>"18-00-03-FF-FF"</c>.
        /// </summary>
        [ObservableProperty] private string _hexInput = string.Empty;

        /// <summary>Single-line status message (parse error, send result, …).</summary>
        [ObservableProperty] private string _statusText = string.Empty;

        /// <summary>True while a send is in flight — disables the Send button.</summary>
        [ObservableProperty] private bool _isBusy;

        /// <summary>True when the underlying K-Line session is open.</summary>
        [ObservableProperty] private bool _isSessionOpen;

        /// <summary>Time-stamped record of every TX/RX packet exchanged on this page.</summary>
        public ObservableCollection<DeveloperLogEntry> Log { get; } = new();

        // ── Child VMs ─────────────────────────────────────────────────────────────

        /// <summary>Pump identification card VM, reused from the singleton on <see cref="MainViewModel"/>.</summary>
        public ViewModels.PumpIdentificationViewModel Identification => Root.PumpIdentification;

        /// <summary>ROM / EEPROM dump card.</summary>
        public DeveloperToolsDumpViewModel Dump { get; }

        /// <summary>Saved KWP custom commands library.</summary>
        public DeveloperToolsCommandsViewModel Commands { get; }

        /// <summary>EEPROM unlock password library.</summary>
        public DeveloperToolsPasswordsViewModel Passwords { get; }

        public DeveloperPageViewModel(
            MainViewModel root,
            IKwpService kwp,
            IConfigurationService config,
            IAppLogger log)
        {
            Root = root;
            _kwp = kwp;
            _log = log;

            IsSessionOpen = root.KLineState == KLineConnectionState.Connected;
            root.PropertyChanged += OnRootPropertyChanged;

            Dump      = new DeveloperToolsDumpViewModel(this, kwp, log);
            Commands  = new DeveloperToolsCommandsViewModel(this, kwp, config, log);
            Passwords = new DeveloperToolsPasswordsViewModel(this, kwp, config, log);
        }

        private void OnRootPropertyChanged(object? sender, PropertyChangedEventArgs e)
        {
            if (e.PropertyName == nameof(MainViewModel.KLineState))
            {
                IsSessionOpen = Root.KLineState == KLineConnectionState.Connected;
                SendCommand.NotifyCanExecuteChanged();
            }
        }

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

        /// <summary>Sends the hex payload as a raw KWP custom packet over the persistent session.</summary>
        [RelayCommand(CanExecute = nameof(CanSend))]
        private async Task SendAsync()
        {
            if (!TryParseHex(HexInput, out var bytes, out var error))
            {
                StatusText = $"Parse error: {error}";
                return;
            }

            IsBusy = true;
            try
            {
                var hex = FormatHex(bytes);
                StatusText = $"Sending {bytes.Length} byte(s)…";
                AppendLog(DeveloperLogDirection.Tx, hex);
                _log.Info(LogId, $"TX {hex}");

                var responses = await _kwp.SendRawCustomAsync(bytes, CancellationToken.None);

                if (responses.Count == 0)
                {
                    AppendLog(DeveloperLogDirection.Info, "(no response)");
                    StatusText = "No response packets.";
                    return;
                }

                foreach (var pkt in responses)
                {
                    var rxHex = FormatHex(pkt);
                    AppendLog(DeveloperLogDirection.Rx, rxHex);
                    _log.Info(LogId, $"RX {rxHex}");
                }
                StatusText = $"Received {responses.Count} packet(s).";
            }
            catch (Exception ex)
            {
                StatusText = $"Send failed: {ex.Message}";
                AppendLog(DeveloperLogDirection.Info, $"ERROR: {ex.Message}");
                _log.Warning(LogId, $"SendAsync failed: {ex.Message}");
            }
            finally
            {
                IsBusy = false;
            }
        }

        private bool CanSend() => !IsBusy && IsSessionOpen;

        /// <summary>Clears the on-screen log (does not affect AppLogger output).</summary>
        [RelayCommand]
        private void ClearLog()
        {
            Log.Clear();
            StatusText = string.Empty;
        }

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

        /// <summary>
        /// Appends a row to the shared transaction log. Exposed as <c>internal</c> so
        /// the page's child VMs (dump, command library, password library) can stream
        /// their own TX/RX rows into the same scrolling log.
        /// </summary>
        internal void AppendLog(DeveloperLogDirection dir, string text)
        {
            // Keep memory bounded — drop oldest entries when the list grows large.
            const int max = 500;
            if (Log.Count >= max) Log.RemoveAt(0);
            Log.Add(new DeveloperLogEntry(DateTime.Now, dir, text));
        }

        /// <summary>Internal accessor so child VMs can push status messages.</summary>
        internal void SetStatus(string text) => StatusText = text;

        /// <summary>
        /// Formats a byte array as a space-separated uppercase hex string. Internal so
        /// child VMs can produce log rows that match the parent's formatting.
        /// </summary>
        internal static string FormatHex(byte[] bytes) =>
            string.Join(" ", bytes.Select(b => b.ToString("X2")));

        /// <summary>
        /// Same formatter for any read-only sequence (e.g. <see cref="System.Collections.Generic.IReadOnlyList{T}"/>
        /// returned by KWP read primitives).
        /// </summary>
        internal static string FormatHex(System.Collections.Generic.IReadOnlyList<byte> bytes)
        {
            var sb = new System.Text.StringBuilder(bytes.Count * 3);
            for (int i = 0; i < bytes.Count; i++)
            {
                if (i > 0) sb.Append(' ');
                sb.Append(bytes[i].ToString("X2"));
            }
            return sb.ToString();
        }

        /// <summary>
        /// Parses a hex byte sequence. Accepts spaces, commas, dashes, and any
        /// combination as separators. Each token must be 1–2 hex digits.
        /// </summary>
        internal static bool TryParseHex(string input, out byte[] bytes, out string error)
        {
            bytes = Array.Empty<byte>();
            error = string.Empty;

            if (string.IsNullOrWhiteSpace(input))
            {
                error = "input is empty";
                return false;
            }

            var separators = new[] { ' ', ',', '-', '\t', '\r', '\n' };
            var tokens = input.Split(separators, StringSplitOptions.RemoveEmptyEntries);
            if (tokens.Length == 0)
            {
                error = "no hex bytes found";
                return false;
            }

            var result = new byte[tokens.Length];
            for (int i = 0; i < tokens.Length; i++)
            {
                var t = tokens[i];
                if (t.StartsWith("0x", StringComparison.OrdinalIgnoreCase)) t = t.Substring(2);
                if (t.Length is < 1 or > 2)
                {
                    error = $"token #{i + 1} '{tokens[i]}' must be 1–2 hex digits";
                    return false;
                }
                if (!byte.TryParse(t, System.Globalization.NumberStyles.HexNumber,
                                   System.Globalization.CultureInfo.InvariantCulture, out byte b))
                {
                    error = $"token #{i + 1} '{tokens[i]}' is not valid hex";
                    return false;
                }
                result[i] = b;
            }

            bytes = result;
            return true;
        }
    }

    /// <summary>Log entry direction — TX (sent), RX (received), or Info (status).</summary>
    public enum DeveloperLogDirection { Tx, Rx, Info }

    /// <summary>One row in the Developer Tools transaction log.</summary>
    public sealed record DeveloperLogEntry(DateTime Timestamp, DeveloperLogDirection Direction, string Hex)
    {
        /// <summary>Pre-formatted line text for binding into a single TextBlock.</summary>
        public string Display
        {
            get
            {
                var sb = new StringBuilder();
                sb.Append('[').Append(Timestamp.ToString("HH:mm:ss.fff")).Append(']').Append(' ');
                sb.Append(Direction switch
                {
                    DeveloperLogDirection.Tx => "TX",
                    DeveloperLogDirection.Rx => "RX",
                    _                        => "  "
                });
                sb.Append(' ').Append(Hex);
                return sb.ToString();
            }
        }
    }
}