using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Runtime.CompilerServices;
using Life.Annotations;
using Life.Misc;

namespace Life.Automaton
{
    public abstract class BasicField : IField, INotifyPropertyChanged
    {
        List<IObserver<IField>> _observers = new List<IObserver<IField>>();
        
        protected BasicField(int width, int height)
        {
            Size = new Size(width, height);
            _cells = new Cell[width, height];
            
            for (int x = 0; x < width; x++)
                for (int y = 0; y < height; y++)
                    _cells[x, y] = new Cell();
        }
        
        private Cell[,] _cells;

        public Size Size { get; }

        public Cell this[int x, int y]
        {
            get => _cells[x, y];
            set
            {
                _cells[x, y] = value;
                _observers.ForEach(observer => observer.OnNext(this));
            }
        }

        public IEnumerable<Cell> Cells => _cells.Cast<Cell>();

        public abstract IEnumerable<Cell> Neighbours(int x, int y);

        public void Transform(Rule transform)
        {
            _cells = transform(this);
            _observers.ForEach(observer => observer.OnNext(this));
        }

        public event PropertyChangedEventHandler PropertyChanged;

        [NotifyPropertyChangedInvocator]
        protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
        {
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }

        public IDisposable Subscribe(IObserver<IField> observer)
        {
            _observers.Add(observer);

            return new DelegateUnsubscriber(() => _observers.Remove(observer));
        }
    }
}