using System.Collections.ObjectModel;
using System.Globalization;
using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using ClaudeDo.Data;
using ClaudeDo.Data.Models;
using Microsoft.EntityFrameworkCore;
using TaskStatus = ClaudeDo.Data.Models.TaskStatus;

namespace ClaudeDo.Ui.ViewModels.Islands;

public sealed partial class TasksIslandViewModel : ViewModelBase
{
    private readonly IDbContextFactory<ClaudeDoDbContext> _dbFactory;
    private ListNavItemViewModel? _currentList;
    private CancellationTokenSource? _loadCts;

    public event EventHandler? SelectionChanged;
    public event EventHandler? FocusAddTaskRequested;
    public void RequestFocusAddTask() => FocusAddTaskRequested?.Invoke(this, EventArgs.Empty);

    public ObservableCollection<TaskRowViewModel> Items { get; } = new();
    public ObservableCollection<TaskRowViewModel> OverdueItems { get; } = new();
    public ObservableCollection<TaskRowViewModel> OpenItems { get; } = new();
    public ObservableCollection<TaskRowViewModel> CompletedItems { get; } = new();

    [ObservableProperty] private string _newTaskTitle = "";
    [ObservableProperty] private TaskRowViewModel? _selectedTask;
    [ObservableProperty] private string _headerTitle = "";
    [ObservableProperty] private string _headerEyebrow = "";
    [ObservableProperty] private string _subtitle = "";
    [ObservableProperty] private string _statusPill = "";
    [ObservableProperty] private bool _hasStatusPill;
    [ObservableProperty] private bool _isShowingCompleted = true;
    [ObservableProperty] private bool _hasOverdue;
    [ObservableProperty] private bool _hasOpen;
    [ObservableProperty] private bool _hasCompleted;
    [ObservableProperty] private bool _showOpenLabel;
    [ObservableProperty] private string _completedHeader = "COMPLETED";

    public TasksIslandViewModel(IDbContextFactory<ClaudeDoDbContext> dbFactory)
    {
        _dbFactory = dbFactory;
    }

    public void LoadForList(ListNavItemViewModel? list)
    {
        _loadCts?.Cancel();
        _loadCts?.Dispose();
        _loadCts = new CancellationTokenSource();
        var ct = _loadCts.Token;

        _currentList = list;
        Items.Clear();
        OverdueItems.Clear();
        OpenItems.Clear();
        CompletedItems.Clear();
        HasOverdue    = false;
        HasOpen       = false;
        HasCompleted  = false;
        ShowOpenLabel = false;
        if (list is null) return;

        HeaderTitle = list.Name;
        HeaderEyebrow = DateTime.Now.ToString("dddd · MMM dd", CultureInfo.InvariantCulture).ToUpperInvariant();

        _ = LoadForListAsync(list, ct);
    }

    private async Task LoadForListAsync(ListNavItemViewModel list, CancellationToken ct)
    {
        try
        {
            await using var db = await _dbFactory.CreateDbContextAsync(ct);
            var all = await db.Tasks
                .Include(t => t.List)
                .Include(t => t.Worktree)
                .ToListAsync(ct);

            ct.ThrowIfCancellationRequested();

            IEnumerable<TaskEntity> filtered = list.Kind switch
            {
                ListKind.Smart when list.Id == "smart:my-day"      => all.Where(t => t.IsMyDay),
                ListKind.Smart when list.Id == "smart:important"   => all.Where(t => t.IsStarred),
                ListKind.Smart when list.Id == "smart:planned"     => all.Where(t => t.ScheduledFor != null),
                ListKind.Virtual when list.Id == "virtual:running" => all.Where(t => t.Status == TaskStatus.Running),
                ListKind.Virtual when list.Id == "virtual:review"  => all.Where(t => t.Status == TaskStatus.Done && t.Worktree?.State == WorktreeState.Active),
                ListKind.User  => all.Where(t => $"user:{t.ListId}" == list.Id),
                _              => Enumerable.Empty<TaskEntity>(),
            };

            foreach (var t in filtered)
                Items.Add(TaskRowViewModel.FromEntity(t));

            Regroup();
            UpdateSubtitle();
        }
        catch (OperationCanceledException) { }
    }

    private void Regroup()
    {
        OverdueItems.Clear();
        OpenItems.Clear();
        CompletedItems.Clear();

        var today = DateTime.Today;
        foreach (var r in Items)
        {
            if (r.Done)
                CompletedItems.Add(r);
            else if (r.ScheduledFor is { } d && d.Date < today)
                OverdueItems.Add(r);
            else
                OpenItems.Add(r);
        }

        HasOverdue     = OverdueItems.Count > 0;
        HasOpen        = OpenItems.Count > 0;
        HasCompleted   = CompletedItems.Count > 0;
        ShowOpenLabel  = HasOpen && HasOverdue;
        CompletedHeader = $"COMPLETED · {CompletedItems.Count}";
    }

    private void UpdateSubtitle()
    {
        var now     = DateTime.Now;
        var open    = Items.Count(i => !i.Done);
        var running = Items.Count(i => i.Status == TaskStatus.Running);
        var review  = Items.Count(i => i.Status == TaskStatus.Done && i.Branch != null);

        Subtitle = open == 1 ? "1 open task" : $"{open} open tasks";

        if (running > 0 || review > 0)
        {
            StatusPill    = $"{running} running · {review} review";
            HasStatusPill = true;
        }
        else
        {
            StatusPill    = "";
            HasStatusPill = false;
        }
    }

    [RelayCommand]
    private async Task AddAsync()
    {
        if (string.IsNullOrWhiteSpace(NewTaskTitle) || _currentList?.Kind != ListKind.User) return;
        var listId = _currentList.Id["user:".Length..];
        var entity = new TaskEntity
        {
            Id        = Guid.NewGuid().ToString("N"),
            ListId    = listId,
            Title     = NewTaskTitle.Trim(),
            CreatedAt = DateTime.UtcNow,
        };
        await using var db = await _dbFactory.CreateDbContextAsync();
        db.Tasks.Add(entity);
        await db.SaveChangesAsync();
        var row = TaskRowViewModel.FromEntity(entity);
        Items.Insert(0, row);
        Regroup();
        NewTaskTitle = "";
        UpdateSubtitle();
    }

    [RelayCommand]
    private async Task ToggleDoneAsync(TaskRowViewModel row)
    {
        row.Done = !row.Done;
        await using var db = await _dbFactory.CreateDbContextAsync();
        var entity = await db.Tasks.FirstOrDefaultAsync(t => t.Id == row.Id);
        if (entity != null)
        {
            entity.Status = row.Done ? TaskStatus.Done : TaskStatus.Manual;
            row.Status = entity.Status;
            await db.SaveChangesAsync();
        }
        Regroup();
        UpdateSubtitle();
    }

    [RelayCommand]
    private async Task ToggleStarAsync(TaskRowViewModel row)
    {
        row.IsStarred = !row.IsStarred;
        await using var db = await _dbFactory.CreateDbContextAsync();
        var entity = await db.Tasks.FirstOrDefaultAsync(t => t.Id == row.Id);
        if (entity != null)
        {
            entity.IsStarred = row.IsStarred;
            await db.SaveChangesAsync();
        }
    }

    [RelayCommand]
    private void Select(TaskRowViewModel row) => SelectedTask = row;

    [RelayCommand]
    private void ToggleShowCompleted() => IsShowingCompleted = !IsShowingCompleted;

    [RelayCommand]
    private void Sort() { /* placeholder — UI-only */ }

    [RelayCommand]
    private void More() { /* placeholder — UI-only */ }

    partial void OnSelectedTaskChanged(TaskRowViewModel? value)
    {
        foreach (var i in Items) i.IsSelected = ReferenceEquals(i, value);
        SelectionChanged?.Invoke(this, EventArgs.Empty);
    }
}