using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Shapes;
using System.Windows.Threading;

namespace x01.Tetris
{
    public enum BlockType
    {
        Straight, T, Square, Bent
    }

    public struct Square
    {
        public int Row, Col;
    }

    public partial class MainWindow : Window
    {
        const int MaxRow = 20;
        const int MaxCol = 11;
        double size = 0;
        static bool isStarted = false;
        int top = 0, down = 0;
        Random rand = new Random();
        DispatcherTimer timer = new DispatcherTimer();
        Rectangle[,] rects = new Rectangle[MaxRow, MaxCol];
        Square[] current = new Square[4];
        List<Square> backup = new List<Square>();
        BlockType blockType = BlockType.T;

        public MainWindow()
        {
            InitializeComponent();
            Init();

            timer.Tick += Timer_Tick;
            timer.Interval = TimeSpan.FromSeconds(0.5);
            timer.Start();
        }

        bool isPressing = false;
        protected override void OnKeyDown(KeyEventArgs e)
        {
            base.OnKeyDown(e);

            if (e.Key == Key.Escape) {
                for (int r = 0; r < MaxRow; r++) {
                    for (int c = 0; c < MaxCol; c++) {
                        rects[r, c].Visibility = Visibility.Hidden;
                    }
                }
                isStarted = false;
                isStarting = false;
            }

            if (!isStarted) return;

            isPressing = true;

            if (e.Key == Key.Left) {
                for (int i = 0; i < 4; i++) {
                    var c = current[i];
                    if (HasSquare(c.Row, c.Col - 1) || !InRange(c.Row, c.Col - 1)) {
                        isPressing = false;
                        return;
                    }
                }
                backup.AddRange(current);
                for (int i = 0; i < 4; i++) {
                    current[i].Col--;
                }
            } else if (e.Key == Key.Right) {
                for (int i = 0; i < 4; i++) {
                    var c = current[i];
                    if (HasSquare(c.Row, c.Col + 1) || !InRange(c.Row, c.Col + 1)) {
                        isPressing = false;
                        return;
                    }
                }
                backup.AddRange(current);
                for (int i = 0; i < 4; i++) {
                    current[i].Col++;
                }
            } else if (e.Key == Key.Up) {
                Rotate();
            } else if (e.Key == Key.Down) {
                for (int i = 0; i < 5; i++) {
                    Down();
                    ReDraw();
                }
            }

            isPressing = false;
        }

        bool HasSquare(int row, int col)
        {
            return InRange(row, col) && !current.Any(s => s.Row == row && s.Col == col)
                && rects[row, col].Visibility == Visibility.Visible;
        }

        int rotateCount = 0;
        Square[] rotateBack = null;
        private void Rotate()
        {
            rotateBack = (Square[])current.Clone();

            switch (blockType) {
                case BlockType.Straight:
                    if (rotateCount % 4 == 0 || rotateCount % 4 == 2) {
                        for (int i = 0; i < 4; i++) {
                            rotateBack[i].Row = top;
                            rotateBack[i].Col += i;
                        }
                    } else if (rotateCount % 4 == 1 || rotateCount % 4 == 3) {
                        for (int i = 0; i < 4; i++) {
                            rotateBack[i].Row += i;
                            rotateBack[i].Col = rotateBack[0].Col;
                        }
                    }
                    break;
                case BlockType.T:
                    if (rotateCount % 4 == 0) {
                        rotateBack[0].Row--;
                        rotateBack[0].Col++;
                        rotateBack[1].Row++;
                        rotateBack[1].Col++;
                        rotateBack[3].Row--;
                        rotateBack[3].Col--;
                    } else if (rotateCount % 4 == 1) {
                        rotateBack[0].Row--;
                        rotateBack[0].Col--;
                        rotateBack[1].Row--;
                        rotateBack[1].Col++;
                        rotateBack[3].Row++;
                        rotateBack[3].Col--;
                    } else if (rotateCount % 4 == 2) {
                        rotateBack[0].Row++;
                        rotateBack[0].Col--;
                        rotateBack[1].Row--;
                        rotateBack[1].Col--;
                        rotateBack[3].Row++;
                        rotateBack[3].Col++;
                    } else if (rotateCount % 4 == 3) {
                        rotateBack[0].Row++;
                        rotateBack[0].Col++;
                        rotateBack[1].Row++;
                        rotateBack[1].Col--;
                        rotateBack[3].Row--;
                        rotateBack[3].Col++;
                    }
                    break;
                case BlockType.Square:
                    break;
                case BlockType.Bent:
                    if (rotateCount % 4 == 0 || rotateCount % 4 == 2) {
                        rotateBack[2].Col += 2;
                        rotateBack[1].Row -= 2;
                    } else if (rotateCount % 4 == 1 || rotateCount % 4 == 3) {
                        rotateBack[2].Col -= 2;
                        rotateBack[1].Row += 2;
                    }
                    break;
                default:
                    break;
            }

            for (int i = 0; i < 4; i++) {
                var r = rotateBack[i];
                if (HasSquare(r.Row, r.Col) || !InRange(r.Row, r.Col)) {
                    return;
                }
            }

            current = (Square[])rotateBack.Clone();
            backup.AddRange(current);
            rotateCount++;
            if (rotateCount == 4) rotateCount = 0;
        }

        private void Timer_Tick(object sender, EventArgs e)
        {
            if (isPressing) return;
            if (isStarting) return;

            if (isStarted == false)
                Start();

            Down();
            ReDraw();
        }

        private void Down()
        {
            if (isStarted == false) return;
            if (current.Any(s => s.Row + 1 == MaxRow)) return;

            foreach (var b in backup) {
                if (InRange(b.Row, b.Col))
                    rects[b.Row, b.Col].Visibility = Visibility.Hidden;
            }

            backup.Clear();
            top = down = current[0].Row;
            for (int i = 0; i < 4; i++) {
                int row = ++current[i].Row;
                int col = current[i].Col;
                if (InRange(row, col)) {
                    rects[row, col].Visibility = Visibility.Visible;
                }

                if (top > row) top = row;
                if (down < row) down = row;
            }

            backup.AddRange(current);
        }

        bool InRange(int row, int col)
        {
            return row >= 0 && row < MaxRow && col >= 0 && col < MaxCol;
        }

        bool isStarting = false;
        private void Start()
        {
            isStarting = true;

            if (isStarted) return;
            isStarted = true;

            for (int i = 0; i < 4; i++) {
                current[i].Row = current[i].Col = 0;
            }
            rotateCount = 0;

            blockType = (BlockType)rand.Next(4);
            switch (blockType) {
                case BlockType.Straight:
                    for (int i = 0; i < 4; i++) {
                        current[i].Col = (MaxCol - 1) / 2;
                        current[i].Row = -i;
                    }
                    break;
                case BlockType.T:
                    for (int i = 0; i < 4; i++) {
                        current[0].Row = 0;
                        current[0].Col = (MaxCol - 1) / 2;
                        if (i > 0) {
                            current[i].Row = -1;
                            current[i].Col = (MaxCol - 1) / 2 + (i - 2);
                        }
                    }
                    break;
                case BlockType.Square:
                    for (int i = 0; i < 4; i++) {
                        if (i <= 1) {
                            current[i].Row = 0;
                            current[i].Col = (MaxCol - 1) / 2 + i;
                        } else {
                            current[i].Row = -1;
                            current[i].Col = (MaxCol - 1) / 2 + (i - 2);
                        }
                    }
                    break;
                case BlockType.Bent:
                    for (int i = 0; i < 4; i++) {
                        if (i <= 1) {
                            current[i].Row = 0;
                            current[i].Col = (MaxCol - 1) / 2 + i;
                        } else {
                            current[i].Row = -1;
                            current[i].Col = (MaxCol - 1) / 2 + (i - 3);
                        }
                    }
                    break;
            }

            isStarting = false;
        }

        private void Init()
        {
            size = (Height - 50) / MaxRow;
            canvas.Width = size * MaxCol;
            canvas.Height = size * MaxRow;

            for (int r = 0; r < MaxRow; r++) {
                for (int c = 0; c < MaxCol; c++) {
                    rects[r, c] = new Rectangle();
                    rects[r, c].Width = rects[r, c].Height = size;
                    rects[r, c].Fill = Brushes.Gray;
                    rects[r, c].Stroke = Brushes.LightGray;
                    rects[r, c].Visibility = Visibility.Hidden;
                    canvas.Children.Add(rects[r, c]);
                    Canvas.SetLeft(rects[r, c], c * size);
                    Canvas.SetTop(rects[r, c], r * size);
                }
            }

            for (int i = 0; i < 4; i++) {
                current[i].Col = current[i].Row = 0;
            }
        }

        protected override void OnRender(DrawingContext drawingContext)
        {
            base.OnRender(drawingContext);

            size = (ActualHeight - 50) / MaxRow;
            canvas.Width = size * MaxCol;
            canvas.Height = size * MaxRow;
            ReDraw();
        }

        private void ReDraw()
        {
            if (isStarted == false) return;

            for (int r = 0; r < MaxRow; r++) {
                for (int c = 0; c < MaxCol; c++) {
                    rects[r, c].Width = rects[r, c].Height = size;
                    Canvas.SetLeft(rects[r, c], c * size);
                    Canvas.SetTop(rects[r, c], r * size);

                    bool hasSquare = current.Any(s => s.Col == c && s.Row + 1 == r
                        && rects[r, c].Visibility == Visibility.Visible)
                        && !current.Any(s => s.Row == r && s.Col == c);
                    if (down == MaxRow - 1 || hasSquare) {
                        top = down = 0;
                        isStarted = false;
                        backup.Clear();
                        ClearLines();
                        return;
                    }
                }
            }
        }

        List<int> cols = new List<int>();
        List<int> rows = new List<int>();
        void ClearLines()
        {
            cols.Clear();
            rows.Clear();

            bool isClear;
            for (int r = 0; r < MaxRow; r++) {
                for (int c = 0; c < MaxCol; c++) {
                    cols.Add(c);
                    if (c == MaxCol - 1) {
                        isClear = true;
                        foreach (var col in cols) {
                            if (rects[r, col].Visibility != Visibility.Visible) {
                                isClear = false;
                                break;
                            }
                        }
                        cols.Clear();
                        if (isClear) rows.Add(r);
                    }
                }
            }

            foreach (var r in rows) {
                for (int c = 0; c < MaxCol; c++) {
                    rects[r, c].Visibility = Visibility.Hidden;
                }
            }

            foreach (var r in rows) {
                for (int i = r - 1; i >= 0; i--) {
                    for (int j = 0; j < MaxCol; j++) {
                        rects[i + 1, j].Visibility = rects[i, j].Visibility;
                    }
                }
            }
        }
    }
}