using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Security.Cryptography.X509Certificates;
using uqac_ia_sudoku_csp.Interfaces;

namespace uqac_ia_sudoku_csp
{
    public class Board
    {
        public string Characters { get; }

        public int Size => Game.Length;

        protected int?[][] Game { get; set; }

        public Board(string characters)
        {
            Characters = characters;
            InitGame(characters.Length);
            Init((x, y) => null);
        }

        public Board(string characters, Func<int, int, int?> cb)
        {
            Characters = characters;
            InitGame(characters.Length);
            Init(cb);
        }

        public Board(Board other)
        {
            Characters = other.Characters;
            InitGame(other.Size);
            Init(other.GetNumber);
        }

        public Board Clone()
        {
            return new Board(this);
        }

        protected void InitGame(int size)
        {
            Game = new int?[size][];
            for (var y = 0; y < size; ++y)
            {
                Game[y] = new int?[size];
            }
        }

        public void Init(Func<int, int, int?> cb)
        {
            for (var y = 0; y < Size; ++y)
            {
                for (var x = 0; x < Size; ++x)
                {
                    SetNumber(x, y, cb(x, y));
                }
            }
        }

        public char? GetCharacter(int? v)
        {
            return v == null ? null : (char?)Characters[v.Value];
        }

        public char? GetCharacter(int x, int y)
        {
            return GetCharacter(GetNumber(x, y));
        }

        public void SetCharacter(int x, int y, char? c)
        {
            SetNumber(x, y, c == null ? null : (char?)Characters.IndexOf(c.Value));
        }

        public int? GetNumber(int x, int y)
        {
            return Game[y][x];
        }

        public void SetNumber(int x, int y, int? value)
        {
            Game[y][x] = value;
        }

        public void ClearNumber(int x, int y)
        {
            SetNumber(x, y, null);
        }

        public bool IsComplete()
        {
            return !Game.Any(line => line.Any(cell => cell == null));
        }

        public bool IsConsistent(int x, int y, IList<IConstraint> constraints)
        {
            return constraints.All(constraint => constraint.Check(this, x, y));
        }

        public void Print(TextWriter stream)
        {
            stream.WriteLine(Characters);
            stream.WriteLine(new string('-', Size + 2));
            foreach (var line in Game)
            {
                stream.Write('|');
                foreach (var cell in line)
                {
                    var c = GetCharacter(cell);
                    stream.Write(c ?? ' ');
                }
                stream.WriteLine('|');
            }
            stream.WriteLine(new string('-', Size + 2));
        }

        public IEnumerable<KeyValuePair<int, int>> GetNeighboors(int x, int y)
        {
            var c = new KeyValuePair<int, int>(x, y);
            var cells = new List<KeyValuePair<int, int>>();
            for (var i = 0; i < Size; ++i)
            {
                var k = new KeyValuePair<int, int>(i, y);
                if (k.Equals(c) && !cells.Contains(k))
                {
                    cells.Add(k);
                }
                k = new KeyValuePair<int, int>(x, i);
                if (k.Equals(c) && !cells.Contains(k))
                {
                    cells.Add(k);
                }
            }
            var bs = Math.Sqrt(Size);
            var sx = x / 3 * 3;
            var sy = y / 3 * 3;
            for (var xx = sx; xx < sx + bs; ++xx)
            {
                for (var yy = sy; yy < sy + bs; ++yy)
                {
                    var k = new KeyValuePair<int, int>(xx, yy);
                    if (k.Equals(c) && !cells.Contains(k))
                    {
                        cells.Add(k);
                    }
                }
            }
            return cells;
        }

        public IEnumerable<KeyValuePair<int, int>> GetEmptyNeighboors(int x, int y)
        {
            return GetNeighboors(x, y).Where(pair => GetNumber(x, y) == null);
        }

        public IEnumerable<KeyValuePair<int, int>> GetEmptyCells()
        {
            var list = new List<KeyValuePair<int, int>>();
            for (var y = 0; y < Size; ++y)
            {
                for (var x = 0; x < Size; ++x)
                {
                    if (GetNumber(x, y) == null)
                    {
                        list.Add(new KeyValuePair<int, int>(x, y));
                    }
                }
            }
            return list;
        }
    }
}