gomoku/src/game/GameInstance.ts

import { v4 as uuidv4 } from 'uuid';

type PlayerColor = 'black' | 'white';
type GameStatus = 'waiting' | 'playing' | 'finished';
type BoardCell = null | 'black' | 'white';

export class GameInstance {
  public readonly id: string;
  public readonly board: BoardCell[][];
  public currentPlayer: PlayerColor | null;
  public status: GameStatus;
  public winner: null | PlayerColor | 'draw';
  public players: { black?: string; white?: string };

  private readonly boardSize = 15;
  private moveCount = 0;

  constructor(id?: string) {
    this.id = id || uuidv4();
    this.board = Array.from({ length: this.boardSize }, () =>
      Array(this.boardSize).fill(null),
    );
    this.currentPlayer = null;
    this.status = 'waiting';
    this.winner = null;
    this.players = {};
  }

  public getPlayerCount(): number {
    return Object.values(this.players).filter(Boolean).length;
  }

  public addPlayer(playerId: string): boolean {
    // If game is full, prevent new players from joining.
    if (this.getPlayerCount() >= 2) {
      return false;
    }

    // If player is already in the game, return true.
    if (Object.values(this.players).includes(playerId)) {
      return true;
    }

    // Assign black if available, otherwise white
    if (!this.players.black) {
      this.players.black = playerId;
    } else if (!this.players.white) {
      this.players.white = playerId;
    } else {
      return false; // Should not happen if getPlayerCount() check is correct
    }

    // If both players have joined, start the game.
    if (this.players.black && this.players.white) {
      this.currentPlayer = 'black';
      this.status = 'playing';
    }
    return true;
  }

  public makeMove(
    playerId: string,
    row: number,
    col: number,
  ): { success: boolean; error?: string } {
    // Find player's color
    let playerColor: PlayerColor | null = null;
    for (const [color, id] of Object.entries(this.players)) {
      if (id === playerId) {
        playerColor = color as PlayerColor;
        break;
      }
    }

    if (!playerColor) {
      return { success: false, error: 'Player not in this game' };
    }

    // Validate it's the player's turn
    if (this.currentPlayer !== playerColor) {
      return { success: false, error: 'Not your turn' };
    }

    // Validate move is within bounds
    if (row < 0 || row >= this.boardSize || col < 0 || col >= this.boardSize) {
      return { success: false, error: 'Move out of bounds' };
    }

    // Validate cell is empty
    if (this.board[row][col] !== null) {
      return { success: false, error: 'Cell already occupied' };
    }

    // Make the move
    this.board[row][col] = playerColor;
    this.moveCount++;

    // Check for win condition
    if (this.checkWin(row, col, playerColor)) {
      this.winner = playerColor;
      this.status = 'finished';
      this.currentPlayer = null;
      return { success: true };
    }

    // Check for draw condition
    if (this.moveCount === this.boardSize * this.boardSize) {
      this.winner = 'draw';
      this.status = 'finished';
      this.currentPlayer = null;
      return { success: true };
    }

    // Switch turns
    this.currentPlayer = playerColor === 'black' ? 'white' : 'black';

    return { success: true };
  }

  private checkWin(row: number, col: number, color: PlayerColor): boolean {
    const directions = [
      [1, 0], // vertical
      [0, 1], // horizontal
      [1, 1], // diagonal down-right
      [1, -1], // diagonal down-left
    ];

    for (const [dx, dy] of directions) {
      let count = 1;

      // Check in positive direction
      for (let i = 1; i < 5; i++) {
        const newRow = row + dx * i;
        const newCol = col + dy * i;
        if (
          newRow < 0 ||
          newRow >= this.boardSize ||
          newCol < 0 ||
          newCol >= this.boardSize
        ) {
          break;
        }
        if (this.board[newRow][newCol] === color) {
          count++;
        } else {
          break;
        }
      }

      // Check in negative direction
      for (let i = 1; i < 5; i++) {
        const newRow = row - dx * i;
        const newCol = col - dy * i;
        if (
          newRow < 0 ||
          newRow >= this.boardSize ||
          newCol < 0 ||
          newCol >= this.boardSize
        ) {
          break;
        }
        if (this.board[newRow][newCol] === color) {
          count++;
        } else {
          break;
        }
      }

      if (count >= 5) {
        return true;
      }
    }

    return false;
  }
}