/*************************************************************************
 * ModernUO                                                              *
 * Copyright 2019-2025 - ModernUO Development Team                       *
 * Email: hi@modernuo.com                                                *
 * File: Map.MultiEnumerator.cs                                          *
 *                                                                       *
 * This program is free software: you can redistribute it and/or modify  *
 * it under the terms of the GNU General Public License as published by  *
 * the Free Software Foundation, either version 3 of the License, or     *
 * (at your option) any later version.                                   *
 *                                                                       *
 * You should have received a copy of the GNU General Public License     *
 * along with this program.  If not, see <http://www.gnu.org/licenses/>. *
 *************************************************************************/

using System;
using System.Collections.Generic;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using Server.Collections;
using Server.Items;

namespace Server;

public partial class Map
{
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public MultiSectorEnumerable<BaseMulti> GetMultisInSector(Point3D p) => GetMultisInSector<BaseMulti>(p);

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public MultiSectorEnumerable<BaseMulti> GetMultisInSector(Point2D p) => GetMultisInSector<BaseMulti>(p);

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public MultiSectorEnumerable<BaseMulti> GetMultisInSector(int x, int y) => GetMultisInSector<BaseMulti>(x, y);

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public MultiSectorEnumerable<T> GetMultisInSector<T>(Point3D p) where T : BaseMulti =>
        new(this, new Point2D(p.X, p.Y));

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public MultiSectorEnumerable<T> GetMultisInSector<T>(Point2D p) where T : BaseMulti => new(this, p);

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public MultiSectorEnumerable<T> GetMultisInSector<T>(int x, int y) where T : BaseMulti => new(this, new Point2D(x, y));

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public MultiBoundsEnumerable<BaseMulti> GetMultisInRange(Point3D p) => GetMultisInRange<BaseMulti>(p);

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public MultiBoundsEnumerable<BaseMulti> GetMultisInRange(Point3D p, int range) => GetMultisInRange<BaseMulti>(p, range);

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public MultiBoundsEnumerable<T> GetMultisInRange<T>(Point3D p) where T : BaseMulti => GetMultisInRange<T>(p, Core.GlobalMaxUpdateRange);

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public MultiBoundsEnumerable<T> GetMultisInRange<T>(Point3D p, int range) where T : BaseMulti =>
        GetMultisInRange<T>(p.m_X, p.m_Y, range);

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public MultiBoundsEnumerable<BaseMulti> GetMultisInRange(Point2D p) => GetMultisInRange<BaseMulti>(p);

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public MultiBoundsEnumerable<BaseMulti> GetMultisInRange(Point2D p, int range) => GetMultisInRange<BaseMulti>(p, range);

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public MultiBoundsEnumerable<T> GetMultisInRange<T>(Point2D p) where T : BaseMulti => GetMultisInRange<T>(p, Core.GlobalMaxUpdateRange);

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public MultiBoundsEnumerable<T> GetMultisInRange<T>(Point2D p, int range) where T : BaseMulti =>
        GetMultisInRange<T>(p.m_X, p.m_Y, range);

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public MultiBoundsEnumerable<T> GetMultisInRange<T>(int x, int y, int range) where T : BaseMulti
    {
        var clampedRange = Math.Max(0, range);
        var edge = clampedRange * 2 + 1;
        return GetMultisInBounds<T>(new Rectangle2D(x - clampedRange, y - clampedRange, edge, edge));
    }

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public MultiBoundsEnumerable<BaseMulti> GetMultisInBounds(Rectangle2D bounds, bool makeBoundsInclusive = false) =>
        GetMultisInBounds<BaseMulti>(bounds, makeBoundsInclusive);

    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public MultiBoundsEnumerable<T> GetMultisInBounds<T>(Rectangle2D bounds, bool makeBoundsInclusive = false) where T : BaseMulti =>
        new(this, bounds, makeBoundsInclusive);

    private static readonly HashSet<Serial> _sharedDupes = [];

    public ref struct MultiSectorEnumerable<T>(Map map, Point2D loc) where T : BaseMulti
    {
        public static MultiSectorEnumerable<T> Empty
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get => new();
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public MultiSectorEnumerator<T> GetEnumerator() => new(map, loc);
    }

    public ref struct MultiSectorEnumerator<T> where T : BaseMulti
    {
        private readonly Span<BaseMulti> _list;
        private readonly int _version;
        private readonly Sector _sector;
        private int _index;
        private T _current;

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public MultiSectorEnumerator(Map map, Point2D loc)
        {
            if (map == null)
            {
                _list = Span<BaseMulti>.Empty;
                _sector = null;
                _version = 0;
            }
            else
            {
                _sector = map.GetSector(loc.m_X, loc.m_Y);
                _list = CollectionsMarshal.AsSpan(_sector.Multis);
                _version = _sector.MultisVersion;
            }

            _index = -1;
            _current = null;
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public bool MoveNext()
        {
            if (_sector != null && _version != _sector.MultisVersion)
            {
                throw new InvalidOperationException(CollectionThrowStrings.InvalidOperation_EnumFailedVersion);
            }

            while (++_index < _list.Length)
            {
                if (_list[_index] is T { Deleted: false } o)
                {
                    _current = o;
                    return true;
                }
            }

            return false;
        }

        public T Current
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get => _current;
        }
    }

    public ref struct MultiBoundsEnumerable<T> where T : BaseMulti
    {
        public static MultiBoundsEnumerable<T> Empty
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get => new(null, Rectangle2D.Empty, false);
        }

        private Map _map;
        private Rectangle2D _bounds;
        private bool _makeBoundsInclusive;

        public MultiBoundsEnumerable(Map map, Rectangle2D bounds, bool makeBoundsInclusive)
        {
            _map = map;
            _bounds = bounds;
            _makeBoundsInclusive = makeBoundsInclusive;
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public MultiBoundsEnumerator<T> GetEnumerator() => new(_map, _bounds, _makeBoundsInclusive);
    }

    public ref struct MultiBoundsEnumerator<T> where T : BaseMulti
    {
        private Map _map;
        private int _sectorStartX;
        private int _sectorEndX;
        private int _sectorEndY;
        private Rectangle2D _bounds;

        private int _currentSectorX;
        private int _currentSectorY;

        private Span<BaseMulti> _currentList;
        private int _currentIndex;
        private int _currentVersion;
        private Sector _currentSector;
        private T _current;


        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public MultiBoundsEnumerator(Map map, Rectangle2D bounds, bool makeBoundsInclusive)
        {
            _sharedDupes.Clear();

            _map = map;
            _bounds = bounds;

            if (makeBoundsInclusive)
            {
                ++bounds.Width;
                ++bounds.Height;
            }

            _bounds = bounds;

            if (map != null)
            {
                map.CalculateSectors(bounds, out _sectorStartX, out var _sectorStartY, out _sectorEndX, out _sectorEndY);

                // We start the X sector one short because it gets incremented immediately in MoveNext()
                _currentSectorX = _sectorStartX - 1;
                _currentSectorY = _sectorStartY;
            }

            _currentList = default;
            _currentIndex = -1;
            _currentVersion = 0;
            _currentSector = null;
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public bool MoveNext()
        {
            var map = _map;

            if (map == null)
            {
                return false;
            }

            ref var bounds = ref _bounds;
            var currentSectorX = _currentSectorX;
            var currentSectorY = _currentSectorY;
            var sectorEndX = _sectorEndX;
            var sectorEndY = _sectorEndY;

            while (true)
            {
                // Try to advance in the current list
                if (_currentList.Length > 0)
                {
                    if (_currentVersion != _currentSector.MultisVersion)
                    {
                        throw new InvalidOperationException(CollectionThrowStrings.InvalidOperation_EnumFailedVersion);
                    }

                    while (++_currentIndex < _currentList.Length)
                    {
                        var item = _currentList[_currentIndex];
                        if (item is T { Deleted: false } o && bounds.Contains(o.Location))
                        {
                            // Multis can span multiple sectors, so we need to deduplicate
                            if (_sharedDupes.Add(o.Serial))
                            {
                                _current = o;
                                return true;
                            }
                        }
                    }
                }

                // Move to next sector
                if (currentSectorX < sectorEndX)
                {
                    _currentSectorX = ++currentSectorX;
                }
                else if (currentSectorY < sectorEndY)
                {
                    _currentSectorX = currentSectorX = _sectorStartX;
                    _currentSectorY = ++currentSectorY;
                }
                else
                {
                    // Ran out of sectors
                    return false;
                }

                _currentSector = map.GetRealSector(currentSectorX, currentSectorY);
                _currentList = CollectionsMarshal.AsSpan(_currentSector.Multis);
                _currentVersion = _currentSector.MultisVersion;
                _currentIndex = -1;
            }
        }

        public T Current
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get => _current;
        }
    }
}