using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using Pf2e.Common;
using Pf2e.Database;
using Pf2e.Scrapper.Helpers;
using Pf2e.Scrapper.WPF.EntityViewer.EntityViewStructure;
using Pf2e.Scrapper.WPF.EntityViewer.Stores;
using Pf2e.WPF.EntityViewer.EntityViewStructure;
using Pf2e.WPF.EntityViewer.Stores;

namespace Pf2e.WPF.EntityViewer.ViewModel;

internal class ViewViewModel : ViewModelBase
{
    public Pf2eDbContext Context { get; }
    public SelectedEntityStore SelectedEntityStore { get; }

    public FullEntity? CurrentEntityView
    {
        get => _currentEntityView;
        set
        {
            _currentEntityView = value;
            OnPropertyChanged();
        }
    }
    private FullEntity? _currentEntityView;

    public ObservableCollection<StructureRow> Rows
    {
        get => _rows;
        set
        {
            _rows = value;
            OnPropertyChanged();
        }
    }
    private ObservableCollection<StructureRow> _rows = [];

    private readonly List<StructureField> _fields = [];

    private readonly List<StructureRow> _allRows = [];

    public ViewViewModel(Pf2eDbContext context, SelectedEntityStore selectedEntityStore)
    {
        Context = context;
        SelectedEntityStore = selectedEntityStore;

        SelectedEntityStore.SelectedEntityChanged += SelectedEntityStore_SelectedEntityTypeChanged;
    }

    ~ViewViewModel()
    {
        SelectedEntityStore.SelectedEntityChanged -= SelectedEntityStore_SelectedEntityTypeChanged;
    }

    private void SelectedEntityStore_SelectedEntityTypeChanged(Database.Model.Base.Entity? entity)
    {
        if (entity is null)
        {
            CurrentEntityView = null;
            return;
        }

        CurrentEntityView = new(Context, entity.Type, entity.Id);

        if (CurrentEntityView.Entity is null)
        {
            CurrentEntityView = null;
            return;
        }

        StructureBuilder builder = new();

        _fields.Clear();
        _fields.Add(builder.Create("Entity", CurrentEntityView.Entity));

        if (CurrentEntityView.SubEntity is not null)
        {
            string typeName = CurrentEntityView.SubEntity.GetType().Name;

            _fields.Add(builder.Create(typeName, CurrentEntityView.SubEntity));
        }

        _allRows.Clear();
        _allRows.AddRange(
            _fields.SelectMany(field =>
                field.GetRows(structureField => new StructureRow(structureField))
            )
        );

        Rows.Clear();
        foreach (StructureRow row in _allRows)
        {
            Rows.Add(row);

            row.OnChange += Row_OnChange;
        }

        BuildLadder();

        OnPropertyChanged(nameof(Rows));
    }

    private void Row_OnChange(StructureRow row, StructureField field)
    {
        OnPropertyChanged(nameof(Rows));
    }

    /// <summary>
    /// Построение лестницы для строк полей структуры.
    /// </summary>
    private void BuildLadder()
    {
        List<LadderType> lastLadder = [];

        for (int i = Rows.Count - 1; i >= 0; i--)
        {
            StructureRow row = Rows[i];
            List<LadderType> ladder;

            if (row.Depth == 0)
            {
                ladder = [];
            }
            else if (row.Depth < lastLadder.Count)
            {
                ladder =
                [
                    .. lastLadder[..(row.Depth - 1)],
                    lastLadder[row.Depth - 1] == LadderType.Empty
                        ? LadderType.Last
                        : LadderType.Through,
                ];
            }
            else if (row.Depth == lastLadder.Count)
            {
                ladder = lastLadder;
            }
            else
            {
                ladder =
                [
                    .. lastLadder,
                    .. Enumerable.Repeat(LadderType.Empty, row.Depth - lastLadder.Count - 1),
                    LadderType.Last,
                ];
            }

            row.Ladder = ladder;

            lastLadder = ladder.Select(l => l == LadderType.Last ? LadderType.Through : l).ToList();
        }
    }
}