Go board

go.test.ts

import { Board } from "./go";

describe("go", () => {
  test("creates 19 x 19 board", () => {
    const board = new Board();

    for (let i = 0; i < 19; i++) {
      for (let j = 0; j < 19; j++) {
        const space = board.getSpace(i, j);
        expect([space.row, space.col]).toEqual([i, j]);
        expect(space.color).toBeUndefined();
      }
    }
  });

  test("creates adjacent references", () => {
    const board = new Board();

    const nwCornerSpace = board.getSpace(0, 0);
    const neCornerSpace = board.getSpace(0, 18);
    const swCornerSpace = board.getSpace(18, 0);
    const seCornerSpace = board.getSpace(18, 18);
    const nEdgeSpace = board.getSpace(0, 5);
    const eEdgeSpace = board.getSpace(5, 18);
    const sEdgeSpace = board.getSpace(18, 5);
    const wEdgeSpace = board.getSpace(5, 0);
    const middleSpace = board.getSpace(5, 5);

    expect(nwCornerSpace.adjacents).toHaveLength(2);
    expect(neCornerSpace.adjacents).toHaveLength(2);
    expect(swCornerSpace.adjacents).toHaveLength(2);
    expect(seCornerSpace.adjacents).toHaveLength(2);
    expect(nEdgeSpace.adjacents).toHaveLength(3);
    expect(eEdgeSpace.adjacents).toHaveLength(3);
    expect(sEdgeSpace.adjacents).toHaveLength(3);
    expect(wEdgeSpace.adjacents).toHaveLength(3);
    expect(middleSpace.adjacents).toHaveLength(4);
  });

  test("assigns color", () => {
    const board = new Board();
    const space = board.getSpace(5, 5);

    space.place("white");
    expect(space.color).toBe("white");
  });

  test("determines if space is free (not trapped)", () => {
    // trap a white stone in NW corner
    const board = new Board();

    board.getSpace(0, 0).place("white");
    expect(board.getSpace(0, 0).isFree()).toBe(true);

    board.getSpace(0, 1).place("black");
    expect(board.getSpace(0, 0).isFree()).toBe(true);

    board.getSpace(1, 0).place("black");
    expect(board.getSpace(0, 0).isFree()).toBe(false);

    // trap a white stone in the center
    board.getSpace(5, 5).place("white");
    expect(board.getSpace(5, 5).isFree()).toBe(true);

    board.getSpace(4, 5).place("black");
    board.getSpace(6, 5).place("black");
    board.getSpace(5, 4).place("black");
    board.getSpace(5, 6).place("black");
    expect(board.getSpace(5, 5).isFree()).toBe(false);

    // trap a 3x3 set of white stones in the center
    board.getSpace(10, 10).place("white");
    board.getSpace(10, 11).place("white");
    board.getSpace(10, 12).place("white");
    board.getSpace(11, 10).place("white");
    board.getSpace(11, 11).place("white");
    board.getSpace(11, 12).place("white");
    board.getSpace(12, 10).place("white");
    board.getSpace(12, 11).place("white");
    board.getSpace(12, 12).place("white");
    expect(board.getSpace(11, 11).isFree()).toBe(true);

    board.getSpace(9, 9).place("black");
    board.getSpace(9, 10).place("black");
    board.getSpace(9, 11).place("black");
    board.getSpace(9, 12).place("black");
    board.getSpace(9, 13).place("black");
    board.getSpace(10, 9).place("black");
    board.getSpace(10, 13).place("black");
    board.getSpace(11, 9).place("black");
    board.getSpace(11, 13).place("black");
    board.getSpace(12, 9).place("black");
    board.getSpace(12, 13).place("black");
    board.getSpace(13, 9).place("black");
    board.getSpace(13, 10).place("black");
    board.getSpace(13, 11).place("black");
    board.getSpace(13, 12).place("black");
    board.getSpace(13, 13).place("black");
    expect(board.getSpace(11, 11).isFree()).toBe(false);
  });
});

go.ts

export type Color = "white" | "black";

export class Board {
  private spaces: Space[][] = [];

  constructor() {
    for (let i = 0; i < 19; i++) {
      this.spaces.push([]);

      for (let j = 0; j < 19; j++) {
        this.spaces[i].push(new Space(i, j));
      }
    }

    this.spaces.flat().forEach((space) => {
      space.adjacents = this.setAdjacents(space);
    });
  }

  private setAdjacents(space: Space): Space[] {
    const [row, col] = [space.row, space.col];
    const spaces = [];

    if (row > 0) {
      spaces.push(this.spaces[row - 1][col]);
    }
    if (row < 19 - 1) {
      spaces.push(this.spaces[row + 1][col]);
    }
    if (col > 0) {
      spaces.push(this.spaces[row][col - 1]);
    }
    if (col < 19 - 1) {
      spaces.push(this.spaces[row][col + 1]);
    }

    return spaces;
  }

  public getSpace(row: number, col: number): Space {
    return this.spaces[row][col];
  }
}

export class Space {
  public row: number;
  public col: number;
  public color?: Color;
  public adjacents: Space[];

  constructor(row: number, col: number) {
    this.row = row;
    this.col = col;
    this.adjacents = [];
  }

  public place(color: Color) {
    this.color = color;
  }

  public isFree(evaluated: string[] = []): boolean {
    const id = this.id();

    const adjacents = this.adjacents.filter((space) => {
      return !evaluated.includes(space.id());
    });
    
    return adjacents.some((space) => {
      if (space.color === undefined) {
        return true;
      }
      else if (space.color === this.color) {
        evaluated.push(id);
        return space.isFree(evaluated);
      }

      return false;
    });
  }

  id() {
    return [this.row, this.col].toString();
  }
}