Screen screen;
 
PFont headingFont;
PFont textFont;
 
void setup() {
  size(500, 500);
 
  headingFont = createFont("Liberation Sans Bold", 32);
  textFont = createFont("Liberation Sans", 16);
 
  rectMode(CENTER);
  ellipseMode(CENTER);
  textAlign(CENTER, CENTER);
 
  screen = new SplashScreen();
}
 
void draw() {
  screen.draw();
}
 
void keyPressed() {  
  screen.keyPressed();
}
 
void mouseClicked() {
  screen.mouseClicked();
}
 
void setScreen(Screen newScreen) {
  screen = newScreen;
}

interface Screen {
  public void draw();
 
  public void keyPressed();
 
  public void mouseClicked();
}

interface Player {
  void draw(int x, int y, int xOffset, int yOffset, int cellSize);
  boolean isSame(Player player);
}
 
class Cross implements Player {
  void draw(int x, int y, int xOffset, int yOffset, int cellSize) {
    line(xOffset + x * cellSize + cellSize / 6, yOffset + y * cellSize + cellSize / 6, xOffset + (x + 1) * cellSize - cellSize / 6, yOffset + (y + 1) * cellSize - cellSize / 6);
    line(xOffset + (x + 1) * cellSize - cellSize / 6, yOffset + y * cellSize + cellSize / 6, xOffset + x * cellSize + cellSize / 6, yOffset + (y + 1) * cellSize - cellSize / 6);
  }
 
  boolean isSame(Player player) {
    return player != null && player instanceof Cross;
  }
}
 
class Circle implements Player {
  void draw(int x, int y, int xOffset, int yOffset, int cellSize) {
    ellipse(xOffset + x * cellSize + cellSize / 2, yOffset + y * cellSize + cellSize / 2, 2*cellSize / 3, 2*cellSize / 3);
  }
 
  boolean isSame(Player player) {
    return player != null && player instanceof Circle;
  }
}

class PlayingScreen implements Screen {
  final int[][] WINNING_COMBINATIONS = { 
    { 0, 1, 2 }, // first row
    { 3, 4, 5 }, // second row
    { 6, 7, 8 }, // third row
    { 0, 3, 6 }, // first column
    { 1, 4, 7 }, // second column
    { 2, 5, 8 }, // third column
    { 0, 4, 8 }, // first diagonal
    { 2, 4, 6 }  // second diagonal
  };
  Player[] game = {
    null, null, null, 
    null, null, null, 
    null, null, null
  };
  Player currentPlayer = null;
  int[] winnerIndices = null;
  boolean gameIsDraw = false;
  String highScoreText = "";
  int size;
  int xOffset;
  int yOffset;
  int cellSize;
 
  public PlayingScreen() {
    size = min(width, height);
    xOffset = (width - size) / 2;
    yOffset = (height - size) / 2;  
    cellSize = size / 3;    
 
    gameIsDraw = false;
    currentPlayer = null;
    game = new Player[] {
      null, null, null, 
      null, null, null, 
      null, null, null
    };
    winnerIndices = null;
  }
 
  public void draw() {
    background(#CCCCCC);
 
    drawWinnerIndices();
    drawBoard();
    drawPlayerMarkers();
  }
 
  public void keyPressed() { }
 
  public void mouseClicked() {
    int x = (mouseX - xOffset) / cellSize;
    int y = (mouseY - yOffset) / cellSize;
    int idx = y * 3 + x;
 
    if (game[idx] != null) return;
 
    if (currentPlayer == null || currentPlayer instanceof Circle) {
      currentPlayer = new Cross();
    } else {
      currentPlayer = new Circle();
    }
 
    game[idx] = currentPlayer;
 
    checkWinner();
  }
 
  void drawBoard() {
    stroke(#000000);
    strokeWeight(5);
 
    line(xOffset + cellSize, yOffset, xOffset + cellSize, height - yOffset);
    line(xOffset + 2*cellSize, yOffset, xOffset + 2*cellSize, height - yOffset);
    line(xOffset, yOffset + cellSize, width - xOffset, yOffset + cellSize);
    line(xOffset, yOffset + 2*cellSize, width - xOffset, yOffset + 2*cellSize);
  }
 
  void drawWinnerIndices() {
    if (winnerIndices == null || winnerIndices.length <= 0) return;
 
    for (int i = 0; i < winnerIndices.length; i++) {
      int x = winnerIndices[i] % 3;
      int y = winnerIndices[i] / 3;
 
      noStroke();
      fill(#AACCEE);
      rect(xOffset + x * cellSize + cellSize / 2, yOffset + y * cellSize + cellSize / 2, cellSize, cellSize);
    }
  }
 
  void drawPlayerMarkers() {
    for (int i = 0; i < game.length; i++) {
      int x = i % 3;
      int y = i / 3;
 
      Player marker = game[i];
 
      noFill();
      strokeWeight(5);
      stroke(#000000);
 
      if (marker != null) {
        marker.draw(x, y, xOffset, yOffset, cellSize);
      }
    }
  }
 
  void checkWinner() {
    for (int[] indices : WINNING_COMBINATIONS) {
      Player firstMarker = game[indices[0]];
      boolean failed = false;
 
      if (firstMarker == null) continue;
 
      for (int i = 1; i < indices.length; i++) {
        Player marker = game[indices[i]];
 
        if (!firstMarker.isSame(marker)) {
          failed = true;
        }
      }
 
      if ((firstMarker instanceof Cross || firstMarker instanceof Circle) && !failed) {
        endGame(indices, firstMarker, false);
        return;
      }
    }
 
    int usedCells = 0;
 
    for (int i = 0; i < game.length; i++) {
      if (game[i] != null) {
        usedCells++;
      }
    }
 
    if (usedCells == game.length) {
      endGame(null, null, true);
    }
  }
 
  void endGame(int[] indices, Player marker, boolean isDraw) {
    winnerIndices = indices;
    gameIsDraw = isDraw;
 
    StringList highScores = new StringList();
 
    if (dataFile("highscores.txt").isFile()) {
      highScores.append(loadStrings("data/highscores.txt"));
    }
 
    String date = nf(year(), 4) + "-" + nf(month(), 2) + "-" + nf(day(), 2) + " " + nf(hour(), 2) + ":" + nf(minute(), 2) + ":" + nf(second(), 2);
    String text = isDraw
      ? "draw"
      : ((marker instanceof Cross ? "cross" : "circle") + "@" + join(nf(indices, 1), ","));
 
    highScores.append(date + " / " + text);
 
    saveStrings("data/highscores.txt", highScores.array());
 
    if (highScores.size() > 0) {
      int crossWins = 0;
      int circleWins = 0;
      int draw = 0;
 
      for (String s : highScores) {
        String winner = s.substring(22);
 
        if (winner.indexOf("@") > 0) {
          winner = winner.substring(0, winner.indexOf("@"));
        }
 
        if (winner.equals("cross")) crossWins++;
        else if (winner.equals("circle")) circleWins++;
        else if (winner.equals("draw")) draw++;
      }
 
      highScoreText = "\n\nHighScores:\nCross: " + crossWins + "\nCircle: " + circleWins + "\nDraw: " + draw;
 
      setScreen(new GameOverScreen(this));
    }
  }
}

class GameOverScreen implements Screen {
  private PlayingScreen playingScreen;
 
  public GameOverScreen(PlayingScreen playingScreen) {
    this.playingScreen = playingScreen;
  }
 
  public void draw() {
      background(#CCCCCC);
 
      playingScreen.draw();
 
      fill(#77000000);
      noStroke();
      rect(playingScreen.xOffset, playingScreen.yOffset, 6 * playingScreen.cellSize, 6 * playingScreen.cellSize);
 
      fill(#FFFFFF);
      textFont(headingFont);
      text("Game Over", width / 2, height / 4);
 
      textFont(textFont);
      String text = "The player using " + (playingScreen.currentPlayer instanceof Cross ? "crosses" : "circles") + " has won the game.";
 
      if (playingScreen.gameIsDraw) {
        text = "The game is a draw.";
      }
 
      text(text + "\n\nPress any key or click anywhere to play again." + playingScreen.highScoreText, width / 2, height / 2);
  }
 
  public void keyPressed() {
    setScreen(new PlayingScreen());
  }
 
  public void mouseClicked() {
    setScreen(new PlayingScreen());
  }
}

class SplashScreen implements Screen {
  public void draw() {
    background(#000000);
 
    fill(#FFFFFF);
 
    textFont(headingFont);
    text("TikTakToe", width / 2, height / 4);
 
    textFont(textFont);
    text("A two-player game\n\nPress any key or click anywhere to start playing\n\n© 2022 Christian Weber", width / 2, height / 2);
  }
 
  public void keyPressed() {
    setScreen(new PlayingScreen());
  }
 
  public void mouseClicked() {
    setScreen(new PlayingScreen());
  }
}