using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace SimplePuzzle
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        private Button[,] _puzzleButtons;
        private Random _random = new Random();

        public MainWindow()
        {
            InitializeComponent();
            InitPuzzle();
        }

        private void InitPuzzle()
        {
            _puzzleButtons = new Button[3, 3];
            int counter = 1;
            for (int row = 0; row < 3; row++)
            {
                for (int col = 0; col < 3; col++)
                {
                    Button button = new Button
                    {
                        Content = counter == 9 ? "" : counter.ToString(),
                        Width = 50,
                        Height = 50
                    };
                    button.Click += PuzzleButton_Click;

                    _puzzleButtons[row, col] = button;
                    Grid.SetRow(button, row);
                    Grid.SetColumn(button, col);
                    PuzzleGrid.Children.Add(button);

                    counter++;
                }
            }

            ShufflePuzzle();
        }

        private void ShufflePuzzle()
        {
            int n = 3 * 3;
            while (n > 1)
            {
                n--;
                int k = _random.Next(n + 1);
                int row1 = n / 3;
                int col1 = n % 3;
                int row2 = k / 3;
                int col2 = k % 3;

                Button temp = _puzzleButtons[row1, col1];
                _puzzleButtons[row1, col1] = _puzzleButtons[row2, col2];
                _puzzleButtons[row2, col2] = temp;

                Grid.SetRow(_puzzleButtons[row1, col1], row1);
                Grid.SetColumn(_puzzleButtons[row1, col1], col1);
                Grid.SetRow(_puzzleButtons[row2, col2], row2);
                Grid.SetColumn(_puzzleButtons[row2, col2], col2);
            }
        }

        private void PuzzleButton_Click(object sender, RoutedEventArgs e)
        {
            Button clickedButton = sender as Button;
            if (clickedButton == null)
                return;

            int row = Grid.GetRow(clickedButton);
            int col = Grid.GetColumn(clickedButton);

            if (!CheckMoveValidation(row, col))
                return;

            Button emptyButton = FindEmptyButton();
            SwapButton(clickedButton, emptyButton);

            if (IsPuzzleSolved())
                MessageBox.Show("🎊 Congratulations!! 🎊");
        }

        private bool CheckMoveValidation(int row, int col)
        {
            return (Math.Abs(row - FindEmptyButtonRow()) + Math.Abs(col - FindEmptyButtonCol()) == 1);
        }

        private Button FindEmptyButton()
        {
            for (int row = 0; row < 3; row++)
            {
                for (int col = 0; col < 3; col++)
                {
                    if (string.IsNullOrEmpty(_puzzleButtons[row, col].Content.ToString()))
                        return _puzzleButtons[row, col];
                }
            }

            return null;
        }

        private int FindEmptyButtonRow()
        {
            return Grid.GetRow(FindEmptyButton());
        }

        private int FindEmptyButtonCol()
        {
            return Grid.GetColumn(FindEmptyButton());
        }

        private void SwapButton(Button button1, Button button2)
        {
            int row1 = Grid.GetRow(button1);
            int col1 = Grid.GetColumn(button1);
            int row2 = Grid.GetRow(button2);
            int col2 = Grid.GetColumn(button2);

            _puzzleButtons[row1, col1] = button2;
            _puzzleButtons[row2, col2] = button1;

            Grid.SetRow(button1, row2);
            Grid.SetColumn(button1, col2);
            Grid.SetRow(button2, row1);
            Grid.SetColumn(button2, col1);
        }

        private bool IsPuzzleSolved()
        {
            int counter = 1;
            for (int row = 0; row < 3; row++)
            {
                for (int col = 0; col < 3; col++)
                {
                    if (row == 2 && col == 2)
                        return string.IsNullOrEmpty(_puzzleButtons[row, col].Content.ToString());

                    if (_puzzleButtons[row, col].Content.ToString() != counter.ToString())
                        return false;

                    counter++;
                }
            }

            return true;
        }
    }
}