//
// Copyright 2020 Electronic Arts Inc.
//
// The Command & Conquer Map Editor and corresponding source code 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.

// The Command & Conquer Map Editor and corresponding source code is distributed 
// in the hope that it will be useful, but with permitted additional restrictions 
// under Section 7 of the GPL. See the GNU General Public License in LICENSE.TXT 
// distributed with this program. You should have received a copy of the 
// GNU General Public License along with permitted additional restrictions 
// with this program. If not, see https://github.com/electronicarts/CnC_Remastered_Collection
using MobiusEditor.Interface;
using System;
using System.Collections;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;

namespace MobiusEditor.Model
{
    public class OccupierAddedEventArgs<T> : EventArgs
    {
        public readonly int Cell;

        public readonly Point Location;

        public readonly T Occupier;

        public OccupierAddedEventArgs(CellMetrics metrics, int cell, T occupier)
        {
            Cell = cell;
            metrics.GetLocation(cell, out Location);
            Occupier = occupier;
        }

        public OccupierAddedEventArgs(CellMetrics metrics, Point location, T occupier)
        {
            Location = location;
            metrics.GetCell(location, out Cell);
            Occupier = occupier;
        }
    }

    public class OccupierRemovedEventArgs<T> : EventArgs
    {
        public readonly int Cell;

        public readonly Point Location;

        public readonly T Occupier;

        public OccupierRemovedEventArgs(CellMetrics metrics, int cell, T occupier)
        {
            Cell = cell;
            metrics.GetLocation(cell, out Location);
            Occupier = occupier;
        }

        public OccupierRemovedEventArgs(CellMetrics metrics, Point location, T occupier)
        {
            Location = location;
            metrics.GetCell(location, out Cell);
            Occupier = occupier;
        }
    }

    public class OccupierSet<T> : IEnumerable<(Point Location, T Occupier)>, IEnumerable where T : class, ICellOccupier
    {
        private readonly CellMetrics metrics;
        private readonly Dictionary<T, Point> occupiers = new Dictionary<T, Point>();
        private readonly T[,] occupierCells;

        public T this[Point location] => this[location.X, location.Y];

        public T this[int x, int y] => Contains(x, y) ? occupierCells[y, x] : null;

        public T this[int cell] => metrics.GetLocation(cell, out Point location) ? this[location] : null;

        public Point? this[T occupier] => occupiers.ContainsKey(occupier) ? occupiers[occupier] : default;

        public IEnumerable<T> Occupiers => occupiers.Keys;

        public event EventHandler<OccupierAddedEventArgs<T>> OccupierAdded;
        public event EventHandler<OccupierRemovedEventArgs<T>> OccupierRemoved;
        public event EventHandler<EventArgs> Cleared;

        public OccupierSet(CellMetrics metrics)
        {
            this.metrics = metrics;
            occupierCells = new T[metrics.Height, metrics.Width];
        }

        public bool CanAdd(Point location, T occupier, bool[,] occupyMask)
        {
            if ((occupier == null) || Contains(occupier))
            {
                return false;
            }

            var occupyPoints = GetOccupyPoints(location, occupyMask).ToArray();
            return !occupyPoints.Any(p => !Contains(p) || (this[p] != null));
        }

        public bool CanAdd(int x, int y, T occupier, bool[,] occupyMask) => CanAdd(new Point(x, y), occupier, occupyMask);

        public bool CanAdd(int cell, T occupier, bool[,] occupyMask) => metrics.GetLocation(cell, out Point location) ? CanAdd(location, occupier, occupyMask) : false;

        public bool CanAdd(Point location, T occupier) => (occupier != null) ? CanAdd(location, occupier, occupier.OccupyMask) : false;

        public bool CanAdd(int x, int y, T occupier) => (occupier != null) ? CanAdd(x, y, occupier, occupier.OccupyMask) : false;

        public bool CanAdd(int cell, T occupier) => (occupier != null) ? CanAdd(cell, occupier, occupier.OccupyMask) : false;

        public bool Add(Point location, T occupier, bool[,] occupyMask)
        {
            if (!DoAdd(location, occupier, occupyMask))
            {
                return false;
            }

            OnOccupierAdded(new OccupierAddedEventArgs<T>(metrics, location, occupier));
            return true;
        }

        public bool Add(int x, int y, T occupier, bool[,] occupyMask) => Add(new Point(x, y), occupier, occupyMask);

        public bool Add(int cell, T occupier, bool[,] occupyMask) => metrics.GetLocation(cell, out Point location) ? Add(location, occupier, occupyMask) : false;

        public bool Add(Point location, T occupier) => (occupier != null) ? Add(location, occupier, occupier.OccupyMask) : false;

        public bool Add(int x, int y, T occupier) => (occupier != null) ? Add(x, y, occupier, occupier.OccupyMask) : false;

        public bool Add(int cell, T occupier) => (occupier != null) ? Add(cell, occupier, occupier.OccupyMask) : false;

        public void Clear()
        {
            occupiers.Clear();
            Array.Clear(occupierCells, 0, occupierCells.Length);
            OnCleared();
        }

        public bool Contains(int x, int y) => ((x >= 0) && (x < occupierCells.GetLength(1)) && (y >= 0) && (y < occupierCells.GetLength(0)));

        public bool Contains(Point location) => Contains(location.X, location.Y);

        public bool Contains(int cell) => metrics.GetLocation(cell, out Point location) ? Contains(location) : false;

        public bool Contains(T occupier) => occupiers.ContainsKey(occupier);

        public IEnumerator<(Point Location, T Occupier)> GetEnumerator() => occupiers.Select(kv => (kv.Value, kv.Key)).GetEnumerator();

        public bool Remove(T occupier)
        {
            var oldLocation = this[occupier];
            if (!DoRemove(occupier))
            {
                return false;
            }

            OnOccupierRemoved(new OccupierRemovedEventArgs<T>(metrics, oldLocation.Value, occupier));
            return true;
        }

        public bool Remove(Point location) => Remove(this[location]);

        public bool Remove(int x, int y) => Remove(new Point(x, y));

        public bool Remove(int cell) => metrics.GetLocation(cell, out Point location) ? Remove(location) : false;

        public IEnumerable<(Point Location, U Occupier)> OfType<U>() where U : T => this.Where(i => i.Occupier is U).Select(i => (i.Location, (U)i.Occupier));

        protected virtual void OnOccupierAdded(OccupierAddedEventArgs<T> e)
        {
            OccupierAdded?.Invoke(this, e);
        }

        protected virtual void OnOccupierRemoved(OccupierRemovedEventArgs<T> e)
        {
            OccupierRemoved?.Invoke(this, e);
        }

        protected virtual void OnCleared()
        {
            Cleared?.Invoke(this, new EventArgs());
        }

        IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();

        private bool DoAdd(Point location, T occupier, bool[,] occupyMask)
        {
            if ((occupier == null) || Contains(occupier))
            {
                return false;
            }

            var occupyPoints = GetOccupyPoints(location, occupyMask).ToArray();
            if (occupyPoints.Any(p => !Contains(p) || (this[p] != null)))
            {
                return false;
            }

            occupiers[occupier] = location;
            foreach (var p in occupyPoints)
            {
                occupierCells[p.Y, p.X] = occupier;
            }
            return true;
        }

        private bool DoRemove(T occupier)
        {
            if ((occupier == null) || !occupiers.TryGetValue(occupier, out Point location))
            {
                return false;
            }

            occupiers.Remove(occupier);
            for (var y = location.Y; y < metrics.Height; ++y)
            {
                for (var x = location.X; x < metrics.Width; ++x)
                {
                    if (occupierCells[y, x] == occupier)
                    {
                        occupierCells[y, x] = null;
                    }
                }
            }
            return true;
        }

        private static IEnumerable<Point> GetOccupyPoints(Point location, bool[,] occupyMask)
        {
            for (var y = 0; y < occupyMask.GetLength(0); ++y)
            {
                for (var x = 0; x < occupyMask.GetLength(1); ++x)
                {
                    if (occupyMask[y, x])
                    {
                        yield return location + new Size(x, y);
                    }
                }
            }
        }

        private static IEnumerable<Point> GetOccupyPoints(Point location, T occupier) => GetOccupyPoints(location, occupier.OccupyMask);
    }
}