using System;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using HC_APTBS.Services;

namespace HC_APTBS.ViewModels.Pages
{
    /// <summary>Memory region selector for the dump card.</summary>
    public enum DumpRegion
    {
        /// <summary>ROM range 0x0000–0x9FFF, read via KWP <c>ReadRomEeprom</c> (0x03).</summary>
        Rom,
        /// <summary>EEPROM range 0x00–0xFF, read via KWP <c>ReadEeprom</c> (0x19).
        /// Note: only offsets 0x00–0xBF are valid per 256-byte block.</summary>
        Eeprom,
    }

    /// <summary>
    /// Developer Tools — ROM / EEPROM dump card. Iterates a user-supplied address
    /// range in 13-byte chunks aligned to 256-byte block boundaries (mirroring the
    /// legacy <c>DumpRom</c> / <c>DumpEeprom</c> routines in
    /// <c>docs/dump functions.txt</c>) and writes the result to
    /// <c>%UserProfile%\.HC_APTBS\dumps\{ident}_{swver1}_{start:X4}-{end:X4}.bin</c>.
    ///
    /// <para>Compiled into Debug builds only — see <c>HC_APTBS.csproj</c>.</para>
    /// </summary>
    public sealed partial class DeveloperToolsDumpViewModel : ObservableObject
    {
        private const int MaxChunk = 13;
        private const int BlockSize = 0x0100;
        // EEPROM has only 0x00–0xBF readable per 256-byte block via the unauth path;
        // the legacy DumpEeprom routine treats this as the "valid bytes per block" cap.
        private const int EepromValidBytesPerBlock = 0x00C0;

        private readonly DeveloperPageViewModel _parent;
        private readonly IKwpService _kwp;
        private readonly IAppLogger _log;
        private const string LogId = nameof(DeveloperToolsDumpViewModel);

        /// <summary>
        /// Threshold above which an in-flight dump shows the prominent overlay banner
        /// (instead of just the inline progress bar). 0x0A00 = 2560 bytes; below that,
        /// reads complete in a few seconds and don't need the bigger indicator.
        /// </summary>
        public const int LargeDumpByteThreshold = 0x0A00;

        public DeveloperToolsDumpViewModel(DeveloperPageViewModel parent, IKwpService kwp, IAppLogger log)
        {
            _parent = parent;
            _kwp    = kwp;
            _log    = log;

            // Sensible default: full ROM dump.
            StartAddressHex = "0000";
            EndAddressHex   = "9FFF";
        }

        // ── Inputs ────────────────────────────────────────────────────────────────

        /// <summary>Region radio: ROM or EEPROM. Updates address-range bounds + defaults.</summary>
        [ObservableProperty]
        [NotifyCanExecuteChangedFor(nameof(DumpCommand))]
        private DumpRegion _region = DumpRegion.Rom;

        /// <summary>Start address in hex (no <c>0x</c> prefix required).</summary>
        [ObservableProperty]
        [NotifyCanExecuteChangedFor(nameof(DumpCommand))]
        private string _startAddressHex = string.Empty;

        /// <summary>End address in hex (inclusive).</summary>
        [ObservableProperty]
        [NotifyCanExecuteChangedFor(nameof(DumpCommand))]
        private string _endAddressHex = string.Empty;

        /// <summary>Per-byte progress, 0..1, for the progress bar.</summary>
        [ObservableProperty] private double _progress;

        /// <summary>True while a dump is in flight — disables Dump button.</summary>
        [ObservableProperty]
        [NotifyCanExecuteChangedFor(nameof(DumpCommand))]
        private bool _isDumping;

        /// <summary>
        /// True while a dump is in flight AND the requested range is larger than
        /// <see cref="LargeDumpByteThreshold"/>. Drives the page-level banner overlay
        /// so the operator sees clearly that a long dump is running.
        /// </summary>
        [ObservableProperty] private bool _isLargeDumpInProgress;

        /// <summary>Total bytes the current dump intends to read.</summary>
        [ObservableProperty] private int _totalBytes;

        /// <summary>Bytes received so far for the current dump.</summary>
        [ObservableProperty] private int _bytesCollected;

        /// <summary>Address of the next byte to read (for the banner display).</summary>
        [ObservableProperty] private int _currentAddress;

        /// <summary>Status / hint text shown under the inputs.</summary>
        [ObservableProperty] private string _statusText = string.Empty;

        /// <summary>True when the ROM region is selected. Two-way bindable for radio buttons.</summary>
        public bool IsRomSelected
        {
            get => Region == DumpRegion.Rom;
            set { if (value) Region = DumpRegion.Rom; }
        }

        /// <summary>True when the EEPROM region is selected. Two-way bindable for radio buttons.</summary>
        public bool IsEepromSelected
        {
            get => Region == DumpRegion.Eeprom;
            set { if (value) Region = DumpRegion.Eeprom; }
        }

        partial void OnRegionChanged(DumpRegion value)
        {
            // Reset to typical full-range defaults so the user doesn't accidentally
            // dump a ROM-sized range out of EEPROM and get NAKs all the way.
            switch (value)
            {
                case DumpRegion.Rom:
                    StartAddressHex = "0000";
                    EndAddressHex   = "9FFF";
                    break;
                case DumpRegion.Eeprom:
                    StartAddressHex = "0000";
                    EndAddressHex   = "00BF";
                    break;
            }

            OnPropertyChanged(nameof(IsRomSelected));
            OnPropertyChanged(nameof(IsEepromSelected));
        }

        // ── Command ───────────────────────────────────────────────────────────────

        /// <summary>
        /// Iterates the selected range in 13-byte chunks aligned to 256-byte blocks
        /// and writes the bytes to disk. Filename built from the current pump
        /// identifier and SW ver 1 read by the K-Line session.
        /// </summary>
        [RelayCommand(CanExecute = nameof(CanDump))]
        private async Task DumpAsync()
        {
            if (!TryParseAddresses(out int startAddr, out int endAddr, out string parseError))
            {
                StatusText = parseError;
                return;
            }

            var ident   = (_parent.Root.PumpIdentification.KlinePumpId   ?? string.Empty).Trim();
            var swVer1  = (_parent.Root.PumpIdentification.KlineSwVersion1 ?? string.Empty).Trim();
            if (ident.Length == 0 || swVer1.Length == 0)
            {
                StatusText = "Read pump identification first — ident and SW ver 1 are required for the filename.";
                return;
            }

            var dir = Path.Combine(
                Environment.GetFolderPath(Environment.SpecialFolder.UserProfile),
                ".HC_APTBS", "dumps");
            try { Directory.CreateDirectory(dir); }
            catch (Exception ex)
            {
                StatusText = $"Could not create dump folder: {ex.Message}";
                return;
            }

            var fileName = $"{Sanitize(ident)}_{Sanitize(swVer1)}_{startAddr:X4}-{endAddr:X4}.bin";
            var fullPath = Path.Combine(dir, fileName);

            int totalBytes = endAddr - startAddr + 1;
            TotalBytes              = totalBytes;
            BytesCollected          = 0;
            CurrentAddress          = startAddr;
            IsDumping               = true;
            IsLargeDumpInProgress   = totalBytes > LargeDumpByteThreshold;
            Progress                = 0;

            var buffer = new List<byte>(totalBytes);
            int collected = 0;

            try
            {
                _parent.AppendLog(DeveloperLogDirection.Info,
                    $"DUMP {Region} 0x{startAddr:X4}-0x{endAddr:X4} ({totalBytes} bytes) → {fileName}");

                int addr = startAddr;
                while (addr <= endAddr)
                {
                    CurrentAddress = addr;
                    int blockBase = addr & 0xFF00;
                    int offsetInBlock = addr & 0x00FF;

                    int blockEndAbs;
                    if (Region == DumpRegion.Eeprom)
                    {
                        if (offsetInBlock >= EepromValidBytesPerBlock)
                        {
                            // Skip the unreadable tail of this block.
                            addr = blockBase + BlockSize;
                            continue;
                        }
                        blockEndAbs = blockBase + EepromValidBytesPerBlock - 1;
                    }
                    else
                    {
                        blockEndAbs = blockBase + BlockSize - 1;
                    }

                    int maxReadableAbs = Math.Min(endAddr, blockEndAbs);
                    while (addr <= maxReadableAbs)
                    {
                        int remaining = maxReadableAbs - addr + 1;
                        byte len = (byte)Math.Min(MaxChunk, remaining);

                        IReadOnlyList<byte> chunk = Region == DumpRegion.Rom
                            ? await _kwp.ReadRomEepromAsync((ushort)addr, len)
                            : await _kwp.ReadEepromAsync((ushort)addr, len);

                        if (chunk.Count == 0)
                        {
                            StatusText = $"Read failed at 0x{addr:X4} (NAK or no session). Saving partial dump.";
                            _parent.AppendLog(DeveloperLogDirection.Info,
                                $"DUMP aborted at 0x{addr:X4} — {collected}/{totalBytes} bytes captured.");
                            break;
                        }

                        buffer.AddRange(chunk);
                        addr += chunk.Count;
                        collected += chunk.Count;
                        BytesCollected = collected;
                        CurrentAddress = addr;
                        Progress = (double)collected / totalBytes;
                    }

                    if (addr <= endAddr && (addr & 0x00FF) == 0)
                    {
                        // Already advanced to the next block — keep going.
                        continue;
                    }
                    if (addr <= endAddr)
                    {
                        // We broke out of the inner loop early due to a read failure.
                        break;
                    }
                }

                if (buffer.Count > 0)
                {
                    File.WriteAllBytes(fullPath, buffer.ToArray());
                    _parent.AppendLog(DeveloperLogDirection.Info,
                        $"DUMP saved {buffer.Count} byte(s) → {fullPath}");
                    StatusText = buffer.Count == totalBytes
                        ? $"Dump complete: {buffer.Count} bytes saved."
                        : $"Partial dump: {buffer.Count}/{totalBytes} bytes saved.";
                }
                else
                {
                    StatusText = "Dump produced no bytes — nothing was written.";
                    _parent.AppendLog(DeveloperLogDirection.Info, "DUMP produced no bytes — skipped file write.");
                }
            }
            catch (Exception ex)
            {
                _log.Error(LogId, $"DumpAsync failed: {ex.Message}");
                StatusText = $"Dump failed: {ex.Message}";
                _parent.AppendLog(DeveloperLogDirection.Info, $"DUMP error: {ex.Message}");
            }
            finally
            {
                IsDumping             = false;
                IsLargeDumpInProgress = false;
            }

            // Modal confirmation so the operator can't miss completion of a long dump.
            var savedToText = buffer.Count > 0 ? $"\n\nFile: {fullPath}" : string.Empty;
            var summary     = $"{StatusText}{savedToText}";
            var image = buffer.Count == totalBytes
                ? System.Windows.MessageBoxImage.Information
                : System.Windows.MessageBoxImage.Warning;
            System.Windows.Application.Current?.Dispatcher.BeginInvoke(() =>
                System.Windows.MessageBox.Show(
                    summary,
                    "Dump finished",
                    System.Windows.MessageBoxButton.OK,
                    image));
        }

        private bool CanDump()
        {
            if (IsDumping) return false;
            if (string.IsNullOrWhiteSpace(StartAddressHex) || string.IsNullOrWhiteSpace(EndAddressHex)) return false;
            return TryParseAddresses(out _, out _, out _);
        }

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

        private bool TryParseAddresses(out int startAddr, out int endAddr, out string error)
        {
            startAddr = 0;
            endAddr   = 0;
            error     = string.Empty;

            if (!TryParseHexAddress(StartAddressHex, out startAddr))
            {
                error = $"Bad start address '{StartAddressHex}'.";
                return false;
            }
            if (!TryParseHexAddress(EndAddressHex, out endAddr))
            {
                error = $"Bad end address '{EndAddressHex}'.";
                return false;
            }
            if (startAddr > endAddr)
            {
                error = "Invalid range: start > end.";
                return false;
            }

            int min, max;
            switch (Region)
            {
                case DumpRegion.Rom:
                    min = 0x0000;
                    max = 0x9FFF;
                    break;
                case DumpRegion.Eeprom:
                    min = 0x0000;
                    max = 0x00FF;
                    break;
                default:
                    error = "Unknown region.";
                    return false;
            }
            if (startAddr < min || endAddr > max)
            {
                error = $"Range outside {Region} bounds (0x{min:X4}–0x{max:X4}).";
                return false;
            }
            return true;
        }

        private static bool TryParseHexAddress(string text, out int value)
        {
            value = 0;
            if (string.IsNullOrWhiteSpace(text)) return false;
            var t = text.Trim();
            if (t.StartsWith("0x", StringComparison.OrdinalIgnoreCase)) t = t.Substring(2);
            return int.TryParse(t, NumberStyles.HexNumber, CultureInfo.InvariantCulture, out value);
        }

        private static string Sanitize(string s)
        {
            var chars = s.Select(c => char.IsLetterOrDigit(c) || c == '.' || c == '_' || c == '-' ? c : '_').ToArray();
            return new string(chars);
        }
    }
}