using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Threading.Tasks;
using Avalonia;
using Avalonia.Controls.ApplicationLifetimes;
using Avalonia.Input.Platform;
using ClaudeDo.Data.Models;
using ClaudeDo.Ui.Localization;
using ClaudeDo.Ui.Services;
using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;

namespace ClaudeDo.Ui.ViewModels.Modals;

/// <summary>
/// Log Visualizer overlay — shows the worker's last 30 min of log records (all levels),
/// fetched once on open via <see cref="IWorkerClient.GetRecentLogsAsync"/> with a manual
/// Refresh and a "warnings &amp; errors only" filter.
/// </summary>
public sealed partial class LogVisualizerViewModel : ViewModelBase
{
    private const int CopyLastCount = 40;

    private readonly IWorkerClient _worker;
    private readonly Func<string, Task<bool>> _copyToClipboard;
    private IReadOnlyList<WorkerLogEntry> _all = Array.Empty<WorkerLogEntry>();

    public ObservableCollection<LogVisualizerRow> Rows { get; } = new();

    [ObservableProperty] private bool _warnErrorOnly;
    [ObservableProperty] private string _statusText = "";

    public Action? CloseAction { get; set; }

    public LogVisualizerViewModel(IWorkerClient worker) : this(worker, CopyToClipboardAsync) { }

    internal LogVisualizerViewModel(IWorkerClient worker, Func<string, Task<bool>> copyToClipboard)
    {
        _worker = worker;
        _copyToClipboard = copyToClipboard;
        Rows.CollectionChanged += (_, _) => CopyLastCommand.NotifyCanExecuteChanged();
        // Phase 3 reconcile tick: this overlay is long-lived (stays open while the user reads
        // through the log), so refresh it on the same cadence as TasksIslandViewModel's tick
        // instead of leaving it frozen at the moment it was opened.
        _reconcileTimer.Elapsed += (_, _) =>
            Avalonia.Threading.Dispatcher.UIThread.Post(() => _ = RefreshAsync());
        _reconcileTimer.Start();
    }

    private readonly System.Timers.Timer _reconcileTimer = new(4_000);

    [RelayCommand]
    public async Task RefreshAsync()
    {
        var latest = await _worker.GetRecentLogsAsync();
        Reconcile(latest);
    }

    partial void OnWarnErrorOnlyChanged(bool value) => Apply();

    private void Apply()
    {
        Rows.Clear();
        IEnumerable<WorkerLogEntry> items = WarnErrorOnly
            ? _all.Where(e => e.Level is WorkerLogLevel.Warn or WorkerLogLevel.Error)
            : _all;
        foreach (var e in items.Reverse())
            Rows.Add(new LogVisualizerRow(e.TimestampUtc.ToLocalTime().ToString("HH:mm:ss"), e.Message, e.Level));
        UpdateStatusText();
    }

    // `_all` (oldest-first) mirrors the worker's LogRingBuffer: append-mostly, with the oldest
    // entries falling off the front once they age past the 30-min window. A full Rows.Clear()
    // on every 4s tick would reset the user's scroll position/selection while they're mid-read,
    // so patch just the delta instead: entries still present keep their row, aged-out entries
    // are trimmed off the (oldest) tail of Rows, new entries are inserted at the (newest) head.
    private void Reconcile(IReadOnlyList<WorkerLogEntry> latest)
    {
        var previous = _all;
        _all = latest;

        if (previous.Count == 0)
        {
            Apply();
            return;
        }

        var overlap = FindOverlap(previous, latest);
        var evictedCount = previous.Count - overlap;
        var added = latest.Skip(overlap).ToList();
        if (evictedCount == 0 && added.Count == 0)
            return; // nothing aged out, nothing new — leave Rows (and scroll/selection) untouched

        if (evictedCount > 0)
        {
            var removeCount = WarnErrorOnly
                ? previous.Take(evictedCount).Count(e => e.Level is WorkerLogLevel.Warn or WorkerLogLevel.Error)
                : evictedCount;
            for (var i = 0; i < removeCount; i++)
                Rows.RemoveAt(Rows.Count - 1);
        }

        foreach (var e in added)
        {
            if (WarnErrorOnly && e.Level is not (WorkerLogLevel.Warn or WorkerLogLevel.Error))
                continue;
            Rows.Insert(0, new LogVisualizerRow(e.TimestampUtc.ToLocalTime().ToString("HH:mm:ss"), e.Message, e.Level));
        }

        UpdateStatusText();
    }

    // The longest run of `previous`'s tail that reappears as `latest`'s head — i.e. how much of
    // the old snapshot survived unevicted. 0 when nothing overlaps (e.g. right after opening).
    private static int FindOverlap(IReadOnlyList<WorkerLogEntry> previous, IReadOnlyList<WorkerLogEntry> latest)
    {
        for (var k = Math.Min(previous.Count, latest.Count); k > 0; k--)
        {
            var matches = true;
            for (var i = 0; i < k; i++)
            {
                if (!previous[previous.Count - k + i].Equals(latest[i])) { matches = false; break; }
            }
            if (matches) return k;
        }
        return 0;
    }

    private void UpdateStatusText() =>
        StatusText = Rows.Count == 0
            ? Loc.T("modals.logVisualizer.empty")
            : Loc.T("modals.logVisualizer.count", Rows.Count);

    [RelayCommand]
    private void Close()
    {
        StopReconcileTick();
        CloseAction?.Invoke();
    }

    /// <summary>Stops the reconcile tick. Also called from the dialog's native-close fallback
    /// (WindowDialogService), which bypasses <see cref="CloseCommand"/> — otherwise an Alt+F4
    /// leaves the timer polling the worker on an orphaned VM. Idempotent.</summary>
    internal void StopReconcileTick()
    {
        _reconcileTimer.Stop();
        _reconcileTimer.Dispose();
    }

    private bool CanCopyLast() => Rows.Count > 0;

    [RelayCommand(CanExecute = nameof(CanCopyLast))]
    private async Task CopyLastAsync()
    {
        var count = Math.Min(Rows.Count, CopyLastCount);
        var ok = await _copyToClipboard(BuildCopyText());
        StatusText = ok
            ? Loc.T("modals.logVisualizer.copied", count)
            : Loc.T("modals.logVisualizer.copyFailed");
    }

    internal string BuildCopyText() =>
        string.Join('\n', Rows.Take(CopyLastCount).Reverse()
            .Select(r => $"{r.Time}  {r.Level.ToString().ToUpperInvariant()}  {r.Message}"));

    private static async Task<bool> CopyToClipboardAsync(string text)
    {
        if (Application.Current?.ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop &&
            desktop.MainWindow?.Clipboard is { } clipboard)
        {
            try { await clipboard.SetTextAsync(text); return true; }
            catch { return false; }
        }
        return false;
    }
}

public sealed record LogVisualizerRow(string Time, string Message, WorkerLogLevel Level);