using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using GameOfLife.Entities;

namespace GameOfLife
{
    public static class Neighborhood
    {
        public static Tuple<Cell, short>[] GetNeighborField(IEnumerable<Cell> world)
        {
            var neighbors = new List<Cell>();

            Parallel.ForEach(
                world,
                () => new List<Cell>(),
                (cell, loop, localNeighbors) =>
                {
                    localNeighbors.AddRange(cell.NeighborCells);
                    return localNeighbors;
                },
                globalNeighbors =>
                {
                    lock(neighbors)
                        neighbors.AddRange(globalNeighbors);
                });

            var neighborCount =
                    neighbors
                        .GroupBy(n => n)
                        .Select(n => Tuple.Create(n.Key, (short)n.Count()))
                        .ToArray();

            return neighborCount;
        }

        public static Tuple<Cell, short>[] GetNeighborField_Serial(IEnumerable<Cell> world)
        {
            var neighborCount = new Dictionary<Cell, short>();

            foreach (var cell in world)
            {
                foreach (var neighbor in cell.NeighborCells)
                {
                    if (!neighborCount.ContainsKey(neighbor))
                        neighborCount[neighbor] = 1;
                    else
                        neighborCount[neighbor] += 1;
                }
            }

            return neighborCount.Select(pair => Tuple.Create(pair.Key, pair.Value)).ToArray();
        }
    }
}